LCOV - code coverage report
Current view: top level - src/backend/storage/buffer - bufmgr.c (source / functions) Hit Total Coverage
Test: PostgreSQL 18beta1 Lines: 1674 1839 91.0 %
Date: 2025-05-17 02:15:21 Functions: 109 115 94.8 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * bufmgr.c
       4             :  *    buffer manager interface routines
       5             :  *
       6             :  * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  *
      10             :  * IDENTIFICATION
      11             :  *    src/backend/storage/buffer/bufmgr.c
      12             :  *
      13             :  *-------------------------------------------------------------------------
      14             :  */
      15             : /*
      16             :  * Principal entry points:
      17             :  *
      18             :  * ReadBuffer() -- find or create a buffer holding the requested page,
      19             :  *      and pin it so that no one can destroy it while this process
      20             :  *      is using it.
      21             :  *
      22             :  * StartReadBuffer() -- as above, with separate wait step
      23             :  * StartReadBuffers() -- multiple block version
      24             :  * WaitReadBuffers() -- second step of above
      25             :  *
      26             :  * ReleaseBuffer() -- unpin a buffer
      27             :  *
      28             :  * MarkBufferDirty() -- mark a pinned buffer's contents as "dirty".
      29             :  *      The disk write is delayed until buffer replacement or checkpoint.
      30             :  *
      31             :  * See also these files:
      32             :  *      freelist.c -- chooses victim for buffer replacement
      33             :  *      buf_table.c -- manages the buffer lookup table
      34             :  */
      35             : #include "postgres.h"
      36             : 
      37             : #include <sys/file.h>
      38             : #include <unistd.h>
      39             : 
      40             : #include "access/tableam.h"
      41             : #include "access/xloginsert.h"
      42             : #include "access/xlogutils.h"
      43             : #ifdef USE_ASSERT_CHECKING
      44             : #include "catalog/pg_tablespace_d.h"
      45             : #endif
      46             : #include "catalog/storage.h"
      47             : #include "catalog/storage_xlog.h"
      48             : #include "executor/instrument.h"
      49             : #include "lib/binaryheap.h"
      50             : #include "miscadmin.h"
      51             : #include "pg_trace.h"
      52             : #include "pgstat.h"
      53             : #include "postmaster/bgwriter.h"
      54             : #include "storage/aio.h"
      55             : #include "storage/buf_internals.h"
      56             : #include "storage/bufmgr.h"
      57             : #include "storage/fd.h"
      58             : #include "storage/ipc.h"
      59             : #include "storage/lmgr.h"
      60             : #include "storage/proc.h"
      61             : #include "storage/read_stream.h"
      62             : #include "storage/smgr.h"
      63             : #include "storage/standby.h"
      64             : #include "utils/memdebug.h"
      65             : #include "utils/ps_status.h"
      66             : #include "utils/rel.h"
      67             : #include "utils/resowner.h"
      68             : #include "utils/timestamp.h"
      69             : 
      70             : 
      71             : /* Note: these two macros only work on shared buffers, not local ones! */
      72             : #define BufHdrGetBlock(bufHdr)  ((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
      73             : #define BufferGetLSN(bufHdr)    (PageGetLSN(BufHdrGetBlock(bufHdr)))
      74             : 
      75             : /* Note: this macro only works on local buffers, not shared ones! */
      76             : #define LocalBufHdrGetBlock(bufHdr) \
      77             :     LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]
      78             : 
      79             : /* Bits in SyncOneBuffer's return value */
      80             : #define BUF_WRITTEN             0x01
      81             : #define BUF_REUSABLE            0x02
      82             : 
      83             : #define RELS_BSEARCH_THRESHOLD      20
      84             : 
      85             : /*
      86             :  * This is the size (in the number of blocks) above which we scan the
      87             :  * entire buffer pool to remove the buffers for all the pages of relation
      88             :  * being dropped. For the relations with size below this threshold, we find
      89             :  * the buffers by doing lookups in BufMapping table.
      90             :  */
      91             : #define BUF_DROP_FULL_SCAN_THRESHOLD        (uint64) (NBuffers / 32)
      92             : 
      93             : typedef struct PrivateRefCountEntry
      94             : {
      95             :     Buffer      buffer;
      96             :     int32       refcount;
      97             : } PrivateRefCountEntry;
      98             : 
      99             : /* 64 bytes, about the size of a cache line on common systems */
     100             : #define REFCOUNT_ARRAY_ENTRIES 8
     101             : 
     102             : /*
     103             :  * Status of buffers to checkpoint for a particular tablespace, used
     104             :  * internally in BufferSync.
     105             :  */
     106             : typedef struct CkptTsStatus
     107             : {
     108             :     /* oid of the tablespace */
     109             :     Oid         tsId;
     110             : 
     111             :     /*
     112             :      * Checkpoint progress for this tablespace. To make progress comparable
     113             :      * between tablespaces the progress is, for each tablespace, measured as a
     114             :      * number between 0 and the total number of to-be-checkpointed pages. Each
     115             :      * page checkpointed in this tablespace increments this space's progress
     116             :      * by progress_slice.
     117             :      */
     118             :     float8      progress;
     119             :     float8      progress_slice;
     120             : 
     121             :     /* number of to-be checkpointed pages in this tablespace */
     122             :     int         num_to_scan;
     123             :     /* already processed pages in this tablespace */
     124             :     int         num_scanned;
     125             : 
     126             :     /* current offset in CkptBufferIds for this tablespace */
     127             :     int         index;
     128             : } CkptTsStatus;
     129             : 
     130             : /*
     131             :  * Type for array used to sort SMgrRelations
     132             :  *
     133             :  * FlushRelationsAllBuffers shares the same comparator function with
     134             :  * DropRelationsAllBuffers. Pointer to this struct and RelFileLocator must be
     135             :  * compatible.
     136             :  */
     137             : typedef struct SMgrSortArray
     138             : {
     139             :     RelFileLocator rlocator;    /* This must be the first member */
     140             :     SMgrRelation srel;
     141             : } SMgrSortArray;
     142             : 
     143             : /* GUC variables */
     144             : bool        zero_damaged_pages = false;
     145             : int         bgwriter_lru_maxpages = 100;
     146             : double      bgwriter_lru_multiplier = 2.0;
     147             : bool        track_io_timing = false;
     148             : 
     149             : /*
     150             :  * How many buffers PrefetchBuffer callers should try to stay ahead of their
     151             :  * ReadBuffer calls by.  Zero means "never prefetch".  This value is only used
     152             :  * for buffers not belonging to tablespaces that have their
     153             :  * effective_io_concurrency parameter set.
     154             :  */
     155             : int         effective_io_concurrency = DEFAULT_EFFECTIVE_IO_CONCURRENCY;
     156             : 
     157             : /*
     158             :  * Like effective_io_concurrency, but used by maintenance code paths that might
     159             :  * benefit from a higher setting because they work on behalf of many sessions.
     160             :  * Overridden by the tablespace setting of the same name.
     161             :  */
     162             : int         maintenance_io_concurrency = DEFAULT_MAINTENANCE_IO_CONCURRENCY;
     163             : 
     164             : /*
     165             :  * Limit on how many blocks should be handled in single I/O operations.
     166             :  * StartReadBuffers() callers should respect it, as should other operations
     167             :  * that call smgr APIs directly.  It is computed as the minimum of underlying
     168             :  * GUCs io_combine_limit_guc and io_max_combine_limit.
     169             :  */
     170             : int         io_combine_limit = DEFAULT_IO_COMBINE_LIMIT;
     171             : int         io_combine_limit_guc = DEFAULT_IO_COMBINE_LIMIT;
     172             : int         io_max_combine_limit = DEFAULT_IO_COMBINE_LIMIT;
     173             : 
     174             : /*
     175             :  * GUC variables about triggering kernel writeback for buffers written; OS
     176             :  * dependent defaults are set via the GUC mechanism.
     177             :  */
     178             : int         checkpoint_flush_after = DEFAULT_CHECKPOINT_FLUSH_AFTER;
     179             : int         bgwriter_flush_after = DEFAULT_BGWRITER_FLUSH_AFTER;
     180             : int         backend_flush_after = DEFAULT_BACKEND_FLUSH_AFTER;
     181             : 
     182             : /* local state for LockBufferForCleanup */
     183             : static BufferDesc *PinCountWaitBuf = NULL;
     184             : 
     185             : /*
     186             :  * Backend-Private refcount management:
     187             :  *
     188             :  * Each buffer also has a private refcount that keeps track of the number of
     189             :  * times the buffer is pinned in the current process.  This is so that the
     190             :  * shared refcount needs to be modified only once if a buffer is pinned more
     191             :  * than once by an individual backend.  It's also used to check that no buffers
     192             :  * are still pinned at the end of transactions and when exiting.
     193             :  *
     194             :  *
     195             :  * To avoid - as we used to - requiring an array with NBuffers entries to keep
     196             :  * track of local buffers, we use a small sequentially searched array
     197             :  * (PrivateRefCountArray) and an overflow hash table (PrivateRefCountHash) to
     198             :  * keep track of backend local pins.
     199             :  *
     200             :  * Until no more than REFCOUNT_ARRAY_ENTRIES buffers are pinned at once, all
     201             :  * refcounts are kept track of in the array; after that, new array entries
     202             :  * displace old ones into the hash table. That way a frequently used entry
     203             :  * can't get "stuck" in the hashtable while infrequent ones clog the array.
     204             :  *
     205             :  * Note that in most scenarios the number of pinned buffers will not exceed
     206             :  * REFCOUNT_ARRAY_ENTRIES.
     207             :  *
     208             :  *
     209             :  * To enter a buffer into the refcount tracking mechanism first reserve a free
     210             :  * entry using ReservePrivateRefCountEntry() and then later, if necessary,
     211             :  * fill it with NewPrivateRefCountEntry(). That split lets us avoid doing
     212             :  * memory allocations in NewPrivateRefCountEntry() which can be important
     213             :  * because in some scenarios it's called with a spinlock held...
     214             :  */
     215             : static struct PrivateRefCountEntry PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES];
     216             : static HTAB *PrivateRefCountHash = NULL;
     217             : static int32 PrivateRefCountOverflowed = 0;
     218             : static uint32 PrivateRefCountClock = 0;
     219             : static PrivateRefCountEntry *ReservedRefCountEntry = NULL;
     220             : 
     221             : static uint32 MaxProportionalPins;
     222             : 
     223             : static void ReservePrivateRefCountEntry(void);
     224             : static PrivateRefCountEntry *NewPrivateRefCountEntry(Buffer buffer);
     225             : static PrivateRefCountEntry *GetPrivateRefCountEntry(Buffer buffer, bool do_move);
     226             : static inline int32 GetPrivateRefCount(Buffer buffer);
     227             : static void ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref);
     228             : 
     229             : /* ResourceOwner callbacks to hold in-progress I/Os and buffer pins */
     230             : static void ResOwnerReleaseBufferIO(Datum res);
     231             : static char *ResOwnerPrintBufferIO(Datum res);
     232             : static void ResOwnerReleaseBufferPin(Datum res);
     233             : static char *ResOwnerPrintBufferPin(Datum res);
     234             : 
     235             : const ResourceOwnerDesc buffer_io_resowner_desc =
     236             : {
     237             :     .name = "buffer io",
     238             :     .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
     239             :     .release_priority = RELEASE_PRIO_BUFFER_IOS,
     240             :     .ReleaseResource = ResOwnerReleaseBufferIO,
     241             :     .DebugPrint = ResOwnerPrintBufferIO
     242             : };
     243             : 
     244             : const ResourceOwnerDesc buffer_pin_resowner_desc =
     245             : {
     246             :     .name = "buffer pin",
     247             :     .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
     248             :     .release_priority = RELEASE_PRIO_BUFFER_PINS,
     249             :     .ReleaseResource = ResOwnerReleaseBufferPin,
     250             :     .DebugPrint = ResOwnerPrintBufferPin
     251             : };
     252             : 
     253             : /*
     254             :  * Ensure that the PrivateRefCountArray has sufficient space to store one more
     255             :  * entry. This has to be called before using NewPrivateRefCountEntry() to fill
     256             :  * a new entry - but it's perfectly fine to not use a reserved entry.
     257             :  */
     258             : static void
     259   126137772 : ReservePrivateRefCountEntry(void)
     260             : {
     261             :     /* Already reserved (or freed), nothing to do */
     262   126137772 :     if (ReservedRefCountEntry != NULL)
     263   117874102 :         return;
     264             : 
     265             :     /*
     266             :      * First search for a free entry the array, that'll be sufficient in the
     267             :      * majority of cases.
     268             :      */
     269             :     {
     270             :         int         i;
     271             : 
     272    21151888 :         for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
     273             :         {
     274             :             PrivateRefCountEntry *res;
     275             : 
     276    20805700 :             res = &PrivateRefCountArray[i];
     277             : 
     278    20805700 :             if (res->buffer == InvalidBuffer)
     279             :             {
     280     7917482 :                 ReservedRefCountEntry = res;
     281     7917482 :                 return;
     282             :             }
     283             :         }
     284             :     }
     285             : 
     286             :     /*
     287             :      * No luck. All array entries are full. Move one array entry into the hash
     288             :      * table.
     289             :      */
     290             :     {
     291             :         /*
     292             :          * Move entry from the current clock position in the array into the
     293             :          * hashtable. Use that slot.
     294             :          */
     295             :         PrivateRefCountEntry *hashent;
     296             :         bool        found;
     297             : 
     298             :         /* select victim slot */
     299      346188 :         ReservedRefCountEntry =
     300      346188 :             &PrivateRefCountArray[PrivateRefCountClock++ % REFCOUNT_ARRAY_ENTRIES];
     301             : 
     302             :         /* Better be used, otherwise we shouldn't get here. */
     303             :         Assert(ReservedRefCountEntry->buffer != InvalidBuffer);
     304             : 
     305             :         /* enter victim array entry into hashtable */
     306      346188 :         hashent = hash_search(PrivateRefCountHash,
     307      346188 :                               &(ReservedRefCountEntry->buffer),
     308             :                               HASH_ENTER,
     309             :                               &found);
     310             :         Assert(!found);
     311      346188 :         hashent->refcount = ReservedRefCountEntry->refcount;
     312             : 
     313             :         /* clear the now free array slot */
     314      346188 :         ReservedRefCountEntry->buffer = InvalidBuffer;
     315      346188 :         ReservedRefCountEntry->refcount = 0;
     316             : 
     317      346188 :         PrivateRefCountOverflowed++;
     318             :     }
     319             : }
     320             : 
     321             : /*
     322             :  * Fill a previously reserved refcount entry.
     323             :  */
     324             : static PrivateRefCountEntry *
     325   114690728 : NewPrivateRefCountEntry(Buffer buffer)
     326             : {
     327             :     PrivateRefCountEntry *res;
     328             : 
     329             :     /* only allowed to be called when a reservation has been made */
     330             :     Assert(ReservedRefCountEntry != NULL);
     331             : 
     332             :     /* use up the reserved entry */
     333   114690728 :     res = ReservedRefCountEntry;
     334   114690728 :     ReservedRefCountEntry = NULL;
     335             : 
     336             :     /* and fill it */
     337   114690728 :     res->buffer = buffer;
     338   114690728 :     res->refcount = 0;
     339             : 
     340   114690728 :     return res;
     341             : }
     342             : 
     343             : /*
     344             :  * Return the PrivateRefCount entry for the passed buffer.
     345             :  *
     346             :  * Returns NULL if a buffer doesn't have a refcount entry. Otherwise, if
     347             :  * do_move is true, and the entry resides in the hashtable the entry is
     348             :  * optimized for frequent access by moving it to the array.
     349             :  */
     350             : static PrivateRefCountEntry *
     351   282838540 : GetPrivateRefCountEntry(Buffer buffer, bool do_move)
     352             : {
     353             :     PrivateRefCountEntry *res;
     354             :     int         i;
     355             : 
     356             :     Assert(BufferIsValid(buffer));
     357             :     Assert(!BufferIsLocal(buffer));
     358             : 
     359             :     /*
     360             :      * First search for references in the array, that'll be sufficient in the
     361             :      * majority of cases.
     362             :      */
     363  1336538066 :     for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
     364             :     {
     365  1225894068 :         res = &PrivateRefCountArray[i];
     366             : 
     367  1225894068 :         if (res->buffer == buffer)
     368   172194542 :             return res;
     369             :     }
     370             : 
     371             :     /*
     372             :      * By here we know that the buffer, if already pinned, isn't residing in
     373             :      * the array.
     374             :      *
     375             :      * Only look up the buffer in the hashtable if we've previously overflowed
     376             :      * into it.
     377             :      */
     378   110643998 :     if (PrivateRefCountOverflowed == 0)
     379   109823430 :         return NULL;
     380             : 
     381      820568 :     res = hash_search(PrivateRefCountHash, &buffer, HASH_FIND, NULL);
     382             : 
     383      820568 :     if (res == NULL)
     384      470176 :         return NULL;
     385      350392 :     else if (!do_move)
     386             :     {
     387             :         /* caller doesn't want us to move the hash entry into the array */
     388      310226 :         return res;
     389             :     }
     390             :     else
     391             :     {
     392             :         /* move buffer from hashtable into the free array slot */
     393             :         bool        found;
     394             :         PrivateRefCountEntry *free;
     395             : 
     396             :         /* Ensure there's a free array slot */
     397       40166 :         ReservePrivateRefCountEntry();
     398             : 
     399             :         /* Use up the reserved slot */
     400             :         Assert(ReservedRefCountEntry != NULL);
     401       40166 :         free = ReservedRefCountEntry;
     402       40166 :         ReservedRefCountEntry = NULL;
     403             :         Assert(free->buffer == InvalidBuffer);
     404             : 
     405             :         /* and fill it */
     406       40166 :         free->buffer = buffer;
     407       40166 :         free->refcount = res->refcount;
     408             : 
     409             :         /* delete from hashtable */
     410       40166 :         hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
     411             :         Assert(found);
     412             :         Assert(PrivateRefCountOverflowed > 0);
     413       40166 :         PrivateRefCountOverflowed--;
     414             : 
     415       40166 :         return free;
     416             :     }
     417             : }
     418             : 
     419             : /*
     420             :  * Returns how many times the passed buffer is pinned by this backend.
     421             :  *
     422             :  * Only works for shared memory buffers!
     423             :  */
     424             : static inline int32
     425     5494994 : GetPrivateRefCount(Buffer buffer)
     426             : {
     427             :     PrivateRefCountEntry *ref;
     428             : 
     429             :     Assert(BufferIsValid(buffer));
     430             :     Assert(!BufferIsLocal(buffer));
     431             : 
     432             :     /*
     433             :      * Not moving the entry - that's ok for the current users, but we might
     434             :      * want to change this one day.
     435             :      */
     436     5494994 :     ref = GetPrivateRefCountEntry(buffer, false);
     437             : 
     438     5494994 :     if (ref == NULL)
     439        8440 :         return 0;
     440     5486554 :     return ref->refcount;
     441             : }
     442             : 
     443             : /*
     444             :  * Release resources used to track the reference count of a buffer which we no
     445             :  * longer have pinned and don't want to pin again immediately.
     446             :  */
     447             : static void
     448   114690728 : ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref)
     449             : {
     450             :     Assert(ref->refcount == 0);
     451             : 
     452   114690728 :     if (ref >= &PrivateRefCountArray[0] &&
     453             :         ref < &PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES])
     454             :     {
     455   114384706 :         ref->buffer = InvalidBuffer;
     456             : 
     457             :         /*
     458             :          * Mark the just used entry as reserved - in many scenarios that
     459             :          * allows us to avoid ever having to search the array/hash for free
     460             :          * entries.
     461             :          */
     462   114384706 :         ReservedRefCountEntry = ref;
     463             :     }
     464             :     else
     465             :     {
     466             :         bool        found;
     467      306022 :         Buffer      buffer = ref->buffer;
     468             : 
     469      306022 :         hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
     470             :         Assert(found);
     471             :         Assert(PrivateRefCountOverflowed > 0);
     472      306022 :         PrivateRefCountOverflowed--;
     473             :     }
     474   114690728 : }
     475             : 
     476             : /*
     477             :  * BufferIsPinned
     478             :  *      True iff the buffer is pinned (also checks for valid buffer number).
     479             :  *
     480             :  *      NOTE: what we check here is that *this* backend holds a pin on
     481             :  *      the buffer.  We do not care whether some other backend does.
     482             :  */
     483             : #define BufferIsPinned(bufnum) \
     484             : ( \
     485             :     !BufferIsValid(bufnum) ? \
     486             :         false \
     487             :     : \
     488             :         BufferIsLocal(bufnum) ? \
     489             :             (LocalRefCount[-(bufnum) - 1] > 0) \
     490             :         : \
     491             :     (GetPrivateRefCount(bufnum) > 0) \
     492             : )
     493             : 
     494             : 
     495             : static Buffer ReadBuffer_common(Relation rel,
     496             :                                 SMgrRelation smgr, char smgr_persistence,
     497             :                                 ForkNumber forkNum, BlockNumber blockNum,
     498             :                                 ReadBufferMode mode, BufferAccessStrategy strategy);
     499             : static BlockNumber ExtendBufferedRelCommon(BufferManagerRelation bmr,
     500             :                                            ForkNumber fork,
     501             :                                            BufferAccessStrategy strategy,
     502             :                                            uint32 flags,
     503             :                                            uint32 extend_by,
     504             :                                            BlockNumber extend_upto,
     505             :                                            Buffer *buffers,
     506             :                                            uint32 *extended_by);
     507             : static BlockNumber ExtendBufferedRelShared(BufferManagerRelation bmr,
     508             :                                            ForkNumber fork,
     509             :                                            BufferAccessStrategy strategy,
     510             :                                            uint32 flags,
     511             :                                            uint32 extend_by,
     512             :                                            BlockNumber extend_upto,
     513             :                                            Buffer *buffers,
     514             :                                            uint32 *extended_by);
     515             : static bool PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy);
     516             : static void PinBuffer_Locked(BufferDesc *buf);
     517             : static void UnpinBuffer(BufferDesc *buf);
     518             : static void UnpinBufferNoOwner(BufferDesc *buf);
     519             : static void BufferSync(int flags);
     520             : static uint32 WaitBufHdrUnlocked(BufferDesc *buf);
     521             : static int  SyncOneBuffer(int buf_id, bool skip_recently_used,
     522             :                           WritebackContext *wb_context);
     523             : static void WaitIO(BufferDesc *buf);
     524             : static void AbortBufferIO(Buffer buffer);
     525             : static void shared_buffer_write_error_callback(void *arg);
     526             : static void local_buffer_write_error_callback(void *arg);
     527             : static inline BufferDesc *BufferAlloc(SMgrRelation smgr,
     528             :                                       char relpersistence,
     529             :                                       ForkNumber forkNum,
     530             :                                       BlockNumber blockNum,
     531             :                                       BufferAccessStrategy strategy,
     532             :                                       bool *foundPtr, IOContext io_context);
     533             : static bool AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress);
     534             : static void CheckReadBuffersOperation(ReadBuffersOperation *operation, bool is_complete);
     535             : static Buffer GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context);
     536             : static void FlushBuffer(BufferDesc *buf, SMgrRelation reln,
     537             :                         IOObject io_object, IOContext io_context);
     538             : static void FindAndDropRelationBuffers(RelFileLocator rlocator,
     539             :                                        ForkNumber forkNum,
     540             :                                        BlockNumber nForkBlock,
     541             :                                        BlockNumber firstDelBlock);
     542             : static void RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
     543             :                                            RelFileLocator dstlocator,
     544             :                                            ForkNumber forkNum, bool permanent);
     545             : static void AtProcExit_Buffers(int code, Datum arg);
     546             : static void CheckForBufferLeaks(void);
     547             : #ifdef USE_ASSERT_CHECKING
     548             : static void AssertNotCatalogBufferLock(LWLock *lock, LWLockMode mode,
     549             :                                        void *unused_context);
     550             : #endif
     551             : static int  rlocator_comparator(const void *p1, const void *p2);
     552             : static inline int buffertag_comparator(const BufferTag *ba, const BufferTag *bb);
     553             : static inline int ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b);
     554             : static int  ts_ckpt_progress_comparator(Datum a, Datum b, void *arg);
     555             : 
     556             : 
     557             : /*
     558             :  * Implementation of PrefetchBuffer() for shared buffers.
     559             :  */
     560             : PrefetchBufferResult
     561       60836 : PrefetchSharedBuffer(SMgrRelation smgr_reln,
     562             :                      ForkNumber forkNum,
     563             :                      BlockNumber blockNum)
     564             : {
     565       60836 :     PrefetchBufferResult result = {InvalidBuffer, false};
     566             :     BufferTag   newTag;         /* identity of requested block */
     567             :     uint32      newHash;        /* hash value for newTag */
     568             :     LWLock     *newPartitionLock;   /* buffer partition lock for it */
     569             :     int         buf_id;
     570             : 
     571             :     Assert(BlockNumberIsValid(blockNum));
     572             : 
     573             :     /* create a tag so we can lookup the buffer */
     574       60836 :     InitBufferTag(&newTag, &smgr_reln->smgr_rlocator.locator,
     575             :                   forkNum, blockNum);
     576             : 
     577             :     /* determine its hash code and partition lock ID */
     578       60836 :     newHash = BufTableHashCode(&newTag);
     579       60836 :     newPartitionLock = BufMappingPartitionLock(newHash);
     580             : 
     581             :     /* see if the block is in the buffer pool already */
     582       60836 :     LWLockAcquire(newPartitionLock, LW_SHARED);
     583       60836 :     buf_id = BufTableLookup(&newTag, newHash);
     584       60836 :     LWLockRelease(newPartitionLock);
     585             : 
     586             :     /* If not in buffers, initiate prefetch */
     587       60836 :     if (buf_id < 0)
     588             :     {
     589             : #ifdef USE_PREFETCH
     590             :         /*
     591             :          * Try to initiate an asynchronous read.  This returns false in
     592             :          * recovery if the relation file doesn't exist.
     593             :          */
     594       33556 :         if ((io_direct_flags & IO_DIRECT_DATA) == 0 &&
     595       16556 :             smgrprefetch(smgr_reln, forkNum, blockNum, 1))
     596             :         {
     597       16556 :             result.initiated_io = true;
     598             :         }
     599             : #endif                          /* USE_PREFETCH */
     600             :     }
     601             :     else
     602             :     {
     603             :         /*
     604             :          * Report the buffer it was in at that time.  The caller may be able
     605             :          * to avoid a buffer table lookup, but it's not pinned and it must be
     606             :          * rechecked!
     607             :          */
     608       43836 :         result.recent_buffer = buf_id + 1;
     609             :     }
     610             : 
     611             :     /*
     612             :      * If the block *is* in buffers, we do nothing.  This is not really ideal:
     613             :      * the block might be just about to be evicted, which would be stupid
     614             :      * since we know we are going to need it soon.  But the only easy answer
     615             :      * is to bump the usage_count, which does not seem like a great solution:
     616             :      * when the caller does ultimately touch the block, usage_count would get
     617             :      * bumped again, resulting in too much favoritism for blocks that are
     618             :      * involved in a prefetch sequence. A real fix would involve some
     619             :      * additional per-buffer state, and it's not clear that there's enough of
     620             :      * a problem to justify that.
     621             :      */
     622             : 
     623       60836 :     return result;
     624             : }
     625             : 
     626             : /*
     627             :  * PrefetchBuffer -- initiate asynchronous read of a block of a relation
     628             :  *
     629             :  * This is named by analogy to ReadBuffer but doesn't actually allocate a
     630             :  * buffer.  Instead it tries to ensure that a future ReadBuffer for the given
     631             :  * block will not be delayed by the I/O.  Prefetching is optional.
     632             :  *
     633             :  * There are three possible outcomes:
     634             :  *
     635             :  * 1.  If the block is already cached, the result includes a valid buffer that
     636             :  * could be used by the caller to avoid the need for a later buffer lookup, but
     637             :  * it's not pinned, so the caller must recheck it.
     638             :  *
     639             :  * 2.  If the kernel has been asked to initiate I/O, the initiated_io member is
     640             :  * true.  Currently there is no way to know if the data was already cached by
     641             :  * the kernel and therefore didn't really initiate I/O, and no way to know when
     642             :  * the I/O completes other than using synchronous ReadBuffer().
     643             :  *
     644             :  * 3.  Otherwise, the buffer wasn't already cached by PostgreSQL, and
     645             :  * USE_PREFETCH is not defined (this build doesn't support prefetching due to
     646             :  * lack of a kernel facility), direct I/O is enabled, or the underlying
     647             :  * relation file wasn't found and we are in recovery.  (If the relation file
     648             :  * wasn't found and we are not in recovery, an error is raised).
     649             :  */
     650             : PrefetchBufferResult
     651       40514 : PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
     652             : {
     653             :     Assert(RelationIsValid(reln));
     654             :     Assert(BlockNumberIsValid(blockNum));
     655             : 
     656       40514 :     if (RelationUsesLocalBuffers(reln))
     657             :     {
     658             :         /* see comments in ReadBufferExtended */
     659        1566 :         if (RELATION_IS_OTHER_TEMP(reln))
     660           0 :             ereport(ERROR,
     661             :                     (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     662             :                      errmsg("cannot access temporary tables of other sessions")));
     663             : 
     664             :         /* pass it off to localbuf.c */
     665        1566 :         return PrefetchLocalBuffer(RelationGetSmgr(reln), forkNum, blockNum);
     666             :     }
     667             :     else
     668             :     {
     669             :         /* pass it to the shared buffer version */
     670       38948 :         return PrefetchSharedBuffer(RelationGetSmgr(reln), forkNum, blockNum);
     671             :     }
     672             : }
     673             : 
     674             : /*
     675             :  * ReadRecentBuffer -- try to pin a block in a recently observed buffer
     676             :  *
     677             :  * Compared to ReadBuffer(), this avoids a buffer mapping lookup when it's
     678             :  * successful.  Return true if the buffer is valid and still has the expected
     679             :  * tag.  In that case, the buffer is pinned and the usage count is bumped.
     680             :  */
     681             : bool
     682        8450 : ReadRecentBuffer(RelFileLocator rlocator, ForkNumber forkNum, BlockNumber blockNum,
     683             :                  Buffer recent_buffer)
     684             : {
     685             :     BufferDesc *bufHdr;
     686             :     BufferTag   tag;
     687             :     uint32      buf_state;
     688             :     bool        have_private_ref;
     689             : 
     690             :     Assert(BufferIsValid(recent_buffer));
     691             : 
     692        8450 :     ResourceOwnerEnlarge(CurrentResourceOwner);
     693        8450 :     ReservePrivateRefCountEntry();
     694        8450 :     InitBufferTag(&tag, &rlocator, forkNum, blockNum);
     695             : 
     696        8450 :     if (BufferIsLocal(recent_buffer))
     697             :     {
     698          64 :         int         b = -recent_buffer - 1;
     699             : 
     700          64 :         bufHdr = GetLocalBufferDescriptor(b);
     701          64 :         buf_state = pg_atomic_read_u32(&bufHdr->state);
     702             : 
     703             :         /* Is it still valid and holding the right tag? */
     704          64 :         if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
     705             :         {
     706          64 :             PinLocalBuffer(bufHdr, true);
     707             : 
     708          64 :             pgBufferUsage.local_blks_hit++;
     709             : 
     710          64 :             return true;
     711             :         }
     712             :     }
     713             :     else
     714             :     {
     715        8386 :         bufHdr = GetBufferDescriptor(recent_buffer - 1);
     716        8386 :         have_private_ref = GetPrivateRefCount(recent_buffer) > 0;
     717             : 
     718             :         /*
     719             :          * Do we already have this buffer pinned with a private reference?  If
     720             :          * so, it must be valid and it is safe to check the tag without
     721             :          * locking.  If not, we have to lock the header first and then check.
     722             :          */
     723        8386 :         if (have_private_ref)
     724           0 :             buf_state = pg_atomic_read_u32(&bufHdr->state);
     725             :         else
     726        8386 :             buf_state = LockBufHdr(bufHdr);
     727             : 
     728        8386 :         if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
     729             :         {
     730             :             /*
     731             :              * It's now safe to pin the buffer.  We can't pin first and ask
     732             :              * questions later, because it might confuse code paths like
     733             :              * InvalidateBuffer() if we pinned a random non-matching buffer.
     734             :              */
     735        8334 :             if (have_private_ref)
     736           0 :                 PinBuffer(bufHdr, NULL);    /* bump pin count */
     737             :             else
     738        8334 :                 PinBuffer_Locked(bufHdr);   /* pin for first time */
     739             : 
     740        8334 :             pgBufferUsage.shared_blks_hit++;
     741             : 
     742        8334 :             return true;
     743             :         }
     744             : 
     745             :         /* If we locked the header above, now unlock. */
     746          52 :         if (!have_private_ref)
     747          52 :             UnlockBufHdr(bufHdr, buf_state);
     748             :     }
     749             : 
     750          52 :     return false;
     751             : }
     752             : 
     753             : /*
     754             :  * ReadBuffer -- a shorthand for ReadBufferExtended, for reading from main
     755             :  *      fork with RBM_NORMAL mode and default strategy.
     756             :  */
     757             : Buffer
     758    84311680 : ReadBuffer(Relation reln, BlockNumber blockNum)
     759             : {
     760    84311680 :     return ReadBufferExtended(reln, MAIN_FORKNUM, blockNum, RBM_NORMAL, NULL);
     761             : }
     762             : 
     763             : /*
     764             :  * ReadBufferExtended -- returns a buffer containing the requested
     765             :  *      block of the requested relation.  If the blknum
     766             :  *      requested is P_NEW, extend the relation file and
     767             :  *      allocate a new block.  (Caller is responsible for
     768             :  *      ensuring that only one backend tries to extend a
     769             :  *      relation at the same time!)
     770             :  *
     771             :  * Returns: the buffer number for the buffer containing
     772             :  *      the block read.  The returned buffer has been pinned.
     773             :  *      Does not return on error --- elog's instead.
     774             :  *
     775             :  * Assume when this function is called, that reln has been opened already.
     776             :  *
     777             :  * In RBM_NORMAL mode, the page is read from disk, and the page header is
     778             :  * validated.  An error is thrown if the page header is not valid.  (But
     779             :  * note that an all-zero page is considered "valid"; see
     780             :  * PageIsVerified().)
     781             :  *
     782             :  * RBM_ZERO_ON_ERROR is like the normal mode, but if the page header is not
     783             :  * valid, the page is zeroed instead of throwing an error. This is intended
     784             :  * for non-critical data, where the caller is prepared to repair errors.
     785             :  *
     786             :  * In RBM_ZERO_AND_LOCK mode, if the page isn't in buffer cache already, it's
     787             :  * filled with zeros instead of reading it from disk.  Useful when the caller
     788             :  * is going to fill the page from scratch, since this saves I/O and avoids
     789             :  * unnecessary failure if the page-on-disk has corrupt page headers.
     790             :  * The page is returned locked to ensure that the caller has a chance to
     791             :  * initialize the page before it's made visible to others.
     792             :  * Caution: do not use this mode to read a page that is beyond the relation's
     793             :  * current physical EOF; that is likely to cause problems in md.c when
     794             :  * the page is modified and written out. P_NEW is OK, though.
     795             :  *
     796             :  * RBM_ZERO_AND_CLEANUP_LOCK is the same as RBM_ZERO_AND_LOCK, but acquires
     797             :  * a cleanup-strength lock on the page.
     798             :  *
     799             :  * RBM_NORMAL_NO_LOG mode is treated the same as RBM_NORMAL here.
     800             :  *
     801             :  * If strategy is not NULL, a nondefault buffer access strategy is used.
     802             :  * See buffer/README for details.
     803             :  */
     804             : inline Buffer
     805   101462322 : ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
     806             :                    ReadBufferMode mode, BufferAccessStrategy strategy)
     807             : {
     808             :     Buffer      buf;
     809             : 
     810             :     /*
     811             :      * Reject attempts to read non-local temporary relations; we would be
     812             :      * likely to get wrong data since we have no visibility into the owning
     813             :      * session's local buffers.
     814             :      */
     815   101462322 :     if (RELATION_IS_OTHER_TEMP(reln))
     816           0 :         ereport(ERROR,
     817             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     818             :                  errmsg("cannot access temporary tables of other sessions")));
     819             : 
     820             :     /*
     821             :      * Read the buffer, and update pgstat counters to reflect a cache hit or
     822             :      * miss.
     823             :      */
     824   101462322 :     buf = ReadBuffer_common(reln, RelationGetSmgr(reln), 0,
     825             :                             forkNum, blockNum, mode, strategy);
     826             : 
     827   101462276 :     return buf;
     828             : }
     829             : 
     830             : 
     831             : /*
     832             :  * ReadBufferWithoutRelcache -- like ReadBufferExtended, but doesn't require
     833             :  *      a relcache entry for the relation.
     834             :  *
     835             :  * Pass permanent = true for a RELPERSISTENCE_PERMANENT relation, and
     836             :  * permanent = false for a RELPERSISTENCE_UNLOGGED relation. This function
     837             :  * cannot be used for temporary relations (and making that work might be
     838             :  * difficult, unless we only want to read temporary relations for our own
     839             :  * ProcNumber).
     840             :  */
     841             : Buffer
     842    11246412 : ReadBufferWithoutRelcache(RelFileLocator rlocator, ForkNumber forkNum,
     843             :                           BlockNumber blockNum, ReadBufferMode mode,
     844             :                           BufferAccessStrategy strategy, bool permanent)
     845             : {
     846    11246412 :     SMgrRelation smgr = smgropen(rlocator, INVALID_PROC_NUMBER);
     847             : 
     848    11246412 :     return ReadBuffer_common(NULL, smgr,
     849             :                              permanent ? RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED,
     850             :                              forkNum, blockNum,
     851             :                              mode, strategy);
     852             : }
     853             : 
     854             : /*
     855             :  * Convenience wrapper around ExtendBufferedRelBy() extending by one block.
     856             :  */
     857             : Buffer
     858       92694 : ExtendBufferedRel(BufferManagerRelation bmr,
     859             :                   ForkNumber forkNum,
     860             :                   BufferAccessStrategy strategy,
     861             :                   uint32 flags)
     862             : {
     863             :     Buffer      buf;
     864       92694 :     uint32      extend_by = 1;
     865             : 
     866       92694 :     ExtendBufferedRelBy(bmr, forkNum, strategy, flags, extend_by,
     867             :                         &buf, &extend_by);
     868             : 
     869       92694 :     return buf;
     870             : }
     871             : 
     872             : /*
     873             :  * Extend relation by multiple blocks.
     874             :  *
     875             :  * Tries to extend the relation by extend_by blocks. Depending on the
     876             :  * availability of resources the relation may end up being extended by a
     877             :  * smaller number of pages (unless an error is thrown, always by at least one
     878             :  * page). *extended_by is updated to the number of pages the relation has been
     879             :  * extended to.
     880             :  *
     881             :  * buffers needs to be an array that is at least extend_by long. Upon
     882             :  * completion, the first extend_by array elements will point to a pinned
     883             :  * buffer.
     884             :  *
     885             :  * If EB_LOCK_FIRST is part of flags, the first returned buffer is
     886             :  * locked. This is useful for callers that want a buffer that is guaranteed to
     887             :  * be empty.
     888             :  */
     889             : BlockNumber
     890      319762 : ExtendBufferedRelBy(BufferManagerRelation bmr,
     891             :                     ForkNumber fork,
     892             :                     BufferAccessStrategy strategy,
     893             :                     uint32 flags,
     894             :                     uint32 extend_by,
     895             :                     Buffer *buffers,
     896             :                     uint32 *extended_by)
     897             : {
     898             :     Assert((bmr.rel != NULL) != (bmr.smgr != NULL));
     899             :     Assert(bmr.smgr == NULL || bmr.relpersistence != 0);
     900             :     Assert(extend_by > 0);
     901             : 
     902      319762 :     if (bmr.smgr == NULL)
     903             :     {
     904      319762 :         bmr.smgr = RelationGetSmgr(bmr.rel);
     905      319762 :         bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
     906             :     }
     907             : 
     908      319762 :     return ExtendBufferedRelCommon(bmr, fork, strategy, flags,
     909             :                                    extend_by, InvalidBlockNumber,
     910             :                                    buffers, extended_by);
     911             : }
     912             : 
     913             : /*
     914             :  * Extend the relation so it is at least extend_to blocks large, return buffer
     915             :  * (extend_to - 1).
     916             :  *
     917             :  * This is useful for callers that want to write a specific page, regardless
     918             :  * of the current size of the relation (e.g. useful for visibilitymap and for
     919             :  * crash recovery).
     920             :  */
     921             : Buffer
     922      101374 : ExtendBufferedRelTo(BufferManagerRelation bmr,
     923             :                     ForkNumber fork,
     924             :                     BufferAccessStrategy strategy,
     925             :                     uint32 flags,
     926             :                     BlockNumber extend_to,
     927             :                     ReadBufferMode mode)
     928             : {
     929             :     BlockNumber current_size;
     930      101374 :     uint32      extended_by = 0;
     931      101374 :     Buffer      buffer = InvalidBuffer;
     932             :     Buffer      buffers[64];
     933             : 
     934             :     Assert((bmr.rel != NULL) != (bmr.smgr != NULL));
     935             :     Assert(bmr.smgr == NULL || bmr.relpersistence != 0);
     936             :     Assert(extend_to != InvalidBlockNumber && extend_to > 0);
     937             : 
     938      101374 :     if (bmr.smgr == NULL)
     939             :     {
     940       13832 :         bmr.smgr = RelationGetSmgr(bmr.rel);
     941       13832 :         bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
     942             :     }
     943             : 
     944             :     /*
     945             :      * If desired, create the file if it doesn't exist.  If
     946             :      * smgr_cached_nblocks[fork] is positive then it must exist, no need for
     947             :      * an smgrexists call.
     948             :      */
     949      101374 :     if ((flags & EB_CREATE_FORK_IF_NEEDED) &&
     950       13832 :         (bmr.smgr->smgr_cached_nblocks[fork] == 0 ||
     951          40 :          bmr.smgr->smgr_cached_nblocks[fork] == InvalidBlockNumber) &&
     952       13792 :         !smgrexists(bmr.smgr, fork))
     953             :     {
     954       13770 :         LockRelationForExtension(bmr.rel, ExclusiveLock);
     955             : 
     956             :         /* recheck, fork might have been created concurrently */
     957       13770 :         if (!smgrexists(bmr.smgr, fork))
     958       13764 :             smgrcreate(bmr.smgr, fork, flags & EB_PERFORMING_RECOVERY);
     959             : 
     960       13770 :         UnlockRelationForExtension(bmr.rel, ExclusiveLock);
     961             :     }
     962             : 
     963             :     /*
     964             :      * If requested, invalidate size cache, so that smgrnblocks asks the
     965             :      * kernel.
     966             :      */
     967      101374 :     if (flags & EB_CLEAR_SIZE_CACHE)
     968       13832 :         bmr.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
     969             : 
     970             :     /*
     971             :      * Estimate how many pages we'll need to extend by. This avoids acquiring
     972             :      * unnecessarily many victim buffers.
     973             :      */
     974      101374 :     current_size = smgrnblocks(bmr.smgr, fork);
     975             : 
     976             :     /*
     977             :      * Since no-one else can be looking at the page contents yet, there is no
     978             :      * difference between an exclusive lock and a cleanup-strength lock. Note
     979             :      * that we pass the original mode to ReadBuffer_common() below, when
     980             :      * falling back to reading the buffer to a concurrent relation extension.
     981             :      */
     982      101374 :     if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
     983       86814 :         flags |= EB_LOCK_TARGET;
     984             : 
     985      206832 :     while (current_size < extend_to)
     986             :     {
     987      105458 :         uint32      num_pages = lengthof(buffers);
     988             :         BlockNumber first_block;
     989             : 
     990      105458 :         if ((uint64) current_size + num_pages > extend_to)
     991      105326 :             num_pages = extend_to - current_size;
     992             : 
     993      105458 :         first_block = ExtendBufferedRelCommon(bmr, fork, strategy, flags,
     994             :                                               num_pages, extend_to,
     995             :                                               buffers, &extended_by);
     996             : 
     997      105458 :         current_size = first_block + extended_by;
     998             :         Assert(num_pages != 0 || current_size >= extend_to);
     999             : 
    1000      225086 :         for (uint32 i = 0; i < extended_by; i++)
    1001             :         {
    1002      119628 :             if (first_block + i != extend_to - 1)
    1003       18260 :                 ReleaseBuffer(buffers[i]);
    1004             :             else
    1005      101368 :                 buffer = buffers[i];
    1006             :         }
    1007             :     }
    1008             : 
    1009             :     /*
    1010             :      * It's possible that another backend concurrently extended the relation.
    1011             :      * In that case read the buffer.
    1012             :      *
    1013             :      * XXX: Should we control this via a flag?
    1014             :      */
    1015      101374 :     if (buffer == InvalidBuffer)
    1016             :     {
    1017             :         Assert(extended_by == 0);
    1018           6 :         buffer = ReadBuffer_common(bmr.rel, bmr.smgr, bmr.relpersistence,
    1019             :                                    fork, extend_to - 1, mode, strategy);
    1020             :     }
    1021             : 
    1022      101374 :     return buffer;
    1023             : }
    1024             : 
    1025             : /*
    1026             :  * Lock and optionally zero a buffer, as part of the implementation of
    1027             :  * RBM_ZERO_AND_LOCK or RBM_ZERO_AND_CLEANUP_LOCK.  The buffer must be already
    1028             :  * pinned.  If the buffer is not already valid, it is zeroed and made valid.
    1029             :  */
    1030             : static void
    1031      608502 : ZeroAndLockBuffer(Buffer buffer, ReadBufferMode mode, bool already_valid)
    1032             : {
    1033             :     BufferDesc *bufHdr;
    1034             :     bool        need_to_zero;
    1035      608502 :     bool        isLocalBuf = BufferIsLocal(buffer);
    1036             : 
    1037             :     Assert(mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK);
    1038             : 
    1039      608502 :     if (already_valid)
    1040             :     {
    1041             :         /*
    1042             :          * If the caller already knew the buffer was valid, we can skip some
    1043             :          * header interaction.  The caller just wants to lock the buffer.
    1044             :          */
    1045       74028 :         need_to_zero = false;
    1046             :     }
    1047      534474 :     else if (isLocalBuf)
    1048             :     {
    1049             :         /* Simple case for non-shared buffers. */
    1050          48 :         bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    1051          48 :         need_to_zero = StartLocalBufferIO(bufHdr, true, false);
    1052             :     }
    1053             :     else
    1054             :     {
    1055             :         /*
    1056             :          * Take BM_IO_IN_PROGRESS, or discover that BM_VALID has been set
    1057             :          * concurrently.  Even though we aren't doing I/O, that ensures that
    1058             :          * we don't zero a page that someone else has pinned.  An exclusive
    1059             :          * content lock wouldn't be enough, because readers are allowed to
    1060             :          * drop the content lock after determining that a tuple is visible
    1061             :          * (see buffer access rules in README).
    1062             :          */
    1063      534426 :         bufHdr = GetBufferDescriptor(buffer - 1);
    1064      534426 :         need_to_zero = StartBufferIO(bufHdr, true, false);
    1065             :     }
    1066             : 
    1067      608502 :     if (need_to_zero)
    1068             :     {
    1069      534474 :         memset(BufferGetPage(buffer), 0, BLCKSZ);
    1070             : 
    1071             :         /*
    1072             :          * Grab the buffer content lock before marking the page as valid, to
    1073             :          * make sure that no other backend sees the zeroed page before the
    1074             :          * caller has had a chance to initialize it.
    1075             :          *
    1076             :          * Since no-one else can be looking at the page contents yet, there is
    1077             :          * no difference between an exclusive lock and a cleanup-strength
    1078             :          * lock. (Note that we cannot use LockBuffer() or
    1079             :          * LockBufferForCleanup() here, because they assert that the buffer is
    1080             :          * already valid.)
    1081             :          */
    1082      534474 :         if (!isLocalBuf)
    1083      534426 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_EXCLUSIVE);
    1084             : 
    1085             :         /* Set BM_VALID, terminate IO, and wake up any waiters */
    1086      534474 :         if (isLocalBuf)
    1087          48 :             TerminateLocalBufferIO(bufHdr, false, BM_VALID, false);
    1088             :         else
    1089      534426 :             TerminateBufferIO(bufHdr, false, BM_VALID, true, false);
    1090             :     }
    1091       74028 :     else if (!isLocalBuf)
    1092             :     {
    1093             :         /*
    1094             :          * The buffer is valid, so we can't zero it.  The caller still expects
    1095             :          * the page to be locked on return.
    1096             :          */
    1097       73988 :         if (mode == RBM_ZERO_AND_LOCK)
    1098       73886 :             LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
    1099             :         else
    1100         102 :             LockBufferForCleanup(buffer);
    1101             :     }
    1102      608502 : }
    1103             : 
    1104             : /*
    1105             :  * Pin a buffer for a given block.  *foundPtr is set to true if the block was
    1106             :  * already present, or false if more work is required to either read it in or
    1107             :  * zero it.
    1108             :  */
    1109             : static pg_attribute_always_inline Buffer
    1110   120479010 : PinBufferForBlock(Relation rel,
    1111             :                   SMgrRelation smgr,
    1112             :                   char persistence,
    1113             :                   ForkNumber forkNum,
    1114             :                   BlockNumber blockNum,
    1115             :                   BufferAccessStrategy strategy,
    1116             :                   bool *foundPtr)
    1117             : {
    1118             :     BufferDesc *bufHdr;
    1119             :     IOContext   io_context;
    1120             :     IOObject    io_object;
    1121             : 
    1122             :     Assert(blockNum != P_NEW);
    1123             : 
    1124             :     /* Persistence should be set before */
    1125             :     Assert((persistence == RELPERSISTENCE_TEMP ||
    1126             :             persistence == RELPERSISTENCE_PERMANENT ||
    1127             :             persistence == RELPERSISTENCE_UNLOGGED));
    1128             : 
    1129   120479010 :     if (persistence == RELPERSISTENCE_TEMP)
    1130             :     {
    1131     2542452 :         io_context = IOCONTEXT_NORMAL;
    1132     2542452 :         io_object = IOOBJECT_TEMP_RELATION;
    1133             :     }
    1134             :     else
    1135             :     {
    1136   117936558 :         io_context = IOContextForStrategy(strategy);
    1137   117936558 :         io_object = IOOBJECT_RELATION;
    1138             :     }
    1139             : 
    1140             :     TRACE_POSTGRESQL_BUFFER_READ_START(forkNum, blockNum,
    1141             :                                        smgr->smgr_rlocator.locator.spcOid,
    1142             :                                        smgr->smgr_rlocator.locator.dbOid,
    1143             :                                        smgr->smgr_rlocator.locator.relNumber,
    1144             :                                        smgr->smgr_rlocator.backend);
    1145             : 
    1146   120479010 :     if (persistence == RELPERSISTENCE_TEMP)
    1147             :     {
    1148     2542452 :         bufHdr = LocalBufferAlloc(smgr, forkNum, blockNum, foundPtr);
    1149     2542440 :         if (*foundPtr)
    1150     2525688 :             pgBufferUsage.local_blks_hit++;
    1151             :     }
    1152             :     else
    1153             :     {
    1154   117936558 :         bufHdr = BufferAlloc(smgr, persistence, forkNum, blockNum,
    1155             :                              strategy, foundPtr, io_context);
    1156   117936558 :         if (*foundPtr)
    1157   114578076 :             pgBufferUsage.shared_blks_hit++;
    1158             :     }
    1159   120478998 :     if (rel)
    1160             :     {
    1161             :         /*
    1162             :          * While pgBufferUsage's "read" counter isn't bumped unless we reach
    1163             :          * WaitReadBuffers() (so, not for hits, and not for buffers that are
    1164             :          * zeroed instead), the per-relation stats always count them.
    1165             :          */
    1166   108776960 :         pgstat_count_buffer_read(rel);
    1167   108776960 :         if (*foundPtr)
    1168   106281214 :             pgstat_count_buffer_hit(rel);
    1169             :     }
    1170   120478998 :     if (*foundPtr)
    1171             :     {
    1172   117103764 :         pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
    1173   117103764 :         if (VacuumCostActive)
    1174     3296640 :             VacuumCostBalance += VacuumCostPageHit;
    1175             : 
    1176             :         TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
    1177             :                                           smgr->smgr_rlocator.locator.spcOid,
    1178             :                                           smgr->smgr_rlocator.locator.dbOid,
    1179             :                                           smgr->smgr_rlocator.locator.relNumber,
    1180             :                                           smgr->smgr_rlocator.backend,
    1181             :                                           true);
    1182             :     }
    1183             : 
    1184   120478998 :     return BufferDescriptorGetBuffer(bufHdr);
    1185             : }
    1186             : 
    1187             : /*
    1188             :  * ReadBuffer_common -- common logic for all ReadBuffer variants
    1189             :  *
    1190             :  * smgr is required, rel is optional unless using P_NEW.
    1191             :  */
    1192             : static pg_attribute_always_inline Buffer
    1193   112708740 : ReadBuffer_common(Relation rel, SMgrRelation smgr, char smgr_persistence,
    1194             :                   ForkNumber forkNum,
    1195             :                   BlockNumber blockNum, ReadBufferMode mode,
    1196             :                   BufferAccessStrategy strategy)
    1197             : {
    1198             :     ReadBuffersOperation operation;
    1199             :     Buffer      buffer;
    1200             :     int         flags;
    1201             :     char        persistence;
    1202             : 
    1203             :     /*
    1204             :      * Backward compatibility path, most code should use ExtendBufferedRel()
    1205             :      * instead, as acquiring the extension lock inside ExtendBufferedRel()
    1206             :      * scales a lot better.
    1207             :      */
    1208   112708740 :     if (unlikely(blockNum == P_NEW))
    1209             :     {
    1210         574 :         uint32      flags = EB_SKIP_EXTENSION_LOCK;
    1211             : 
    1212             :         /*
    1213             :          * Since no-one else can be looking at the page contents yet, there is
    1214             :          * no difference between an exclusive lock and a cleanup-strength
    1215             :          * lock.
    1216             :          */
    1217         574 :         if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
    1218           0 :             flags |= EB_LOCK_FIRST;
    1219             : 
    1220         574 :         return ExtendBufferedRel(BMR_REL(rel), forkNum, strategy, flags);
    1221             :     }
    1222             : 
    1223   112708166 :     if (rel)
    1224   101461754 :         persistence = rel->rd_rel->relpersistence;
    1225             :     else
    1226    11246412 :         persistence = smgr_persistence;
    1227             : 
    1228   112708166 :     if (unlikely(mode == RBM_ZERO_AND_CLEANUP_LOCK ||
    1229             :                  mode == RBM_ZERO_AND_LOCK))
    1230             :     {
    1231             :         bool        found;
    1232             : 
    1233      608502 :         buffer = PinBufferForBlock(rel, smgr, persistence,
    1234             :                                    forkNum, blockNum, strategy, &found);
    1235      608502 :         ZeroAndLockBuffer(buffer, mode, found);
    1236      608502 :         return buffer;
    1237             :     }
    1238             : 
    1239             :     /*
    1240             :      * Signal that we are going to immediately wait. If we're immediately
    1241             :      * waiting, there is no benefit in actually executing the IO
    1242             :      * asynchronously, it would just add dispatch overhead.
    1243             :      */
    1244   112099664 :     flags = READ_BUFFERS_SYNCHRONOUSLY;
    1245   112099664 :     if (mode == RBM_ZERO_ON_ERROR)
    1246     2354272 :         flags |= READ_BUFFERS_ZERO_ON_ERROR;
    1247   112099664 :     operation.smgr = smgr;
    1248   112099664 :     operation.rel = rel;
    1249   112099664 :     operation.persistence = persistence;
    1250   112099664 :     operation.forknum = forkNum;
    1251   112099664 :     operation.strategy = strategy;
    1252   112099664 :     if (StartReadBuffer(&operation,
    1253             :                         &buffer,
    1254             :                         blockNum,
    1255             :                         flags))
    1256     1304114 :         WaitReadBuffers(&operation);
    1257             : 
    1258   112099618 :     return buffer;
    1259             : }
    1260             : 
    1261             : static pg_attribute_always_inline bool
    1262   119545906 : StartReadBuffersImpl(ReadBuffersOperation *operation,
    1263             :                      Buffer *buffers,
    1264             :                      BlockNumber blockNum,
    1265             :                      int *nblocks,
    1266             :                      int flags,
    1267             :                      bool allow_forwarding)
    1268             : {
    1269   119545906 :     int         actual_nblocks = *nblocks;
    1270   119545906 :     int         maxcombine = 0;
    1271             :     bool        did_start_io;
    1272             : 
    1273             :     Assert(*nblocks == 1 || allow_forwarding);
    1274             :     Assert(*nblocks > 0);
    1275             :     Assert(*nblocks <= MAX_IO_COMBINE_LIMIT);
    1276             : 
    1277   122386666 :     for (int i = 0; i < actual_nblocks; ++i)
    1278             :     {
    1279             :         bool        found;
    1280             : 
    1281   119873264 :         if (allow_forwarding && buffers[i] != InvalidBuffer)
    1282        2756 :         {
    1283             :             BufferDesc *bufHdr;
    1284             : 
    1285             :             /*
    1286             :              * This is a buffer that was pinned by an earlier call to
    1287             :              * StartReadBuffers(), but couldn't be handled in one operation at
    1288             :              * that time.  The operation was split, and the caller has passed
    1289             :              * an already pinned buffer back to us to handle the rest of the
    1290             :              * operation.  It must continue at the expected block number.
    1291             :              */
    1292             :             Assert(BufferGetBlockNumber(buffers[i]) == blockNum + i);
    1293             : 
    1294             :             /*
    1295             :              * It might be an already valid buffer (a hit) that followed the
    1296             :              * final contiguous block of an earlier I/O (a miss) marking the
    1297             :              * end of it, or a buffer that some other backend has since made
    1298             :              * valid by performing the I/O for us, in which case we can handle
    1299             :              * it as a hit now.  It is safe to check for a BM_VALID flag with
    1300             :              * a relaxed load, because we got a fresh view of it while pinning
    1301             :              * it in the previous call.
    1302             :              *
    1303             :              * On the other hand if we don't see BM_VALID yet, it must be an
    1304             :              * I/O that was split by the previous call and we need to try to
    1305             :              * start a new I/O from this block.  We're also racing against any
    1306             :              * other backend that might start the I/O or even manage to mark
    1307             :              * it BM_VALID after this check, but StartBufferIO() will handle
    1308             :              * those cases.
    1309             :              */
    1310        2756 :             if (BufferIsLocal(buffers[i]))
    1311           4 :                 bufHdr = GetLocalBufferDescriptor(-buffers[i] - 1);
    1312             :             else
    1313        2752 :                 bufHdr = GetBufferDescriptor(buffers[i] - 1);
    1314             :             Assert(pg_atomic_read_u32(&bufHdr->state) & BM_TAG_VALID);
    1315        2756 :             found = pg_atomic_read_u32(&bufHdr->state) & BM_VALID;
    1316             :         }
    1317             :         else
    1318             :         {
    1319   119870496 :             buffers[i] = PinBufferForBlock(operation->rel,
    1320   119870508 :                                            operation->smgr,
    1321   119870508 :                                            operation->persistence,
    1322             :                                            operation->forknum,
    1323             :                                            blockNum + i,
    1324             :                                            operation->strategy,
    1325             :                                            &found);
    1326             :         }
    1327             : 
    1328   119873252 :         if (found)
    1329             :         {
    1330             :             /*
    1331             :              * We have a hit.  If it's the first block in the requested range,
    1332             :              * we can return it immediately and report that WaitReadBuffers()
    1333             :              * does not need to be called.  If the initial value of *nblocks
    1334             :              * was larger, the caller will have to call again for the rest.
    1335             :              */
    1336   117032492 :             if (i == 0)
    1337             :             {
    1338   117029732 :                 *nblocks = 1;
    1339             : 
    1340             : #ifdef USE_ASSERT_CHECKING
    1341             : 
    1342             :                 /*
    1343             :                  * Initialize enough of ReadBuffersOperation to make
    1344             :                  * CheckReadBuffersOperation() work. Outside of assertions
    1345             :                  * that's not necessary when no IO is issued.
    1346             :                  */
    1347             :                 operation->buffers = buffers;
    1348             :                 operation->blocknum = blockNum;
    1349             :                 operation->nblocks = 1;
    1350             :                 operation->nblocks_done = 1;
    1351             :                 CheckReadBuffersOperation(operation, true);
    1352             : #endif
    1353   117029732 :                 return false;
    1354             :             }
    1355             : 
    1356             :             /*
    1357             :              * Otherwise we already have an I/O to perform, but this block
    1358             :              * can't be included as it is already valid.  Split the I/O here.
    1359             :              * There may or may not be more blocks requiring I/O after this
    1360             :              * one, we haven't checked, but they can't be contiguous with this
    1361             :              * one in the way.  We'll leave this buffer pinned, forwarding it
    1362             :              * to the next call, avoiding the need to unpin it here and re-pin
    1363             :              * it in the next call.
    1364             :              */
    1365        2760 :             actual_nblocks = i;
    1366        2760 :             break;
    1367             :         }
    1368             :         else
    1369             :         {
    1370             :             /*
    1371             :              * Check how many blocks we can cover with the same IO. The smgr
    1372             :              * implementation might e.g. be limited due to a segment boundary.
    1373             :              */
    1374     2840760 :             if (i == 0 && actual_nblocks > 1)
    1375             :             {
    1376       66284 :                 maxcombine = smgrmaxcombine(operation->smgr,
    1377             :                                             operation->forknum,
    1378             :                                             blockNum);
    1379       66284 :                 if (unlikely(maxcombine < actual_nblocks))
    1380             :                 {
    1381           0 :                     elog(DEBUG2, "limiting nblocks at %u from %u to %u",
    1382             :                          blockNum, actual_nblocks, maxcombine);
    1383           0 :                     actual_nblocks = maxcombine;
    1384             :                 }
    1385             :             }
    1386             :         }
    1387             :     }
    1388     2516162 :     *nblocks = actual_nblocks;
    1389             : 
    1390             :     /* Populate information needed for I/O. */
    1391     2516162 :     operation->buffers = buffers;
    1392     2516162 :     operation->blocknum = blockNum;
    1393     2516162 :     operation->flags = flags;
    1394     2516162 :     operation->nblocks = actual_nblocks;
    1395     2516162 :     operation->nblocks_done = 0;
    1396     2516162 :     pgaio_wref_clear(&operation->io_wref);
    1397             : 
    1398             :     /*
    1399             :      * When using AIO, start the IO in the background. If not, issue prefetch
    1400             :      * requests if desired by the caller.
    1401             :      *
    1402             :      * The reason we have a dedicated path for IOMETHOD_SYNC here is to
    1403             :      * de-risk the introduction of AIO somewhat. It's a large architectural
    1404             :      * change, with lots of chances for unanticipated performance effects.
    1405             :      *
    1406             :      * Use of IOMETHOD_SYNC already leads to not actually performing IO
    1407             :      * asynchronously, but without the check here we'd execute IO earlier than
    1408             :      * we used to. Eventually this IOMETHOD_SYNC specific path should go away.
    1409             :      */
    1410     2516162 :     if (io_method != IOMETHOD_SYNC)
    1411             :     {
    1412             :         /*
    1413             :          * Try to start IO asynchronously. It's possible that no IO needs to
    1414             :          * be started, if another backend already performed the IO.
    1415             :          *
    1416             :          * Note that if an IO is started, it might not cover the entire
    1417             :          * requested range, e.g. because an intermediary block has been read
    1418             :          * in by another backend.  In that case any "trailing" buffers we
    1419             :          * already pinned above will be "forwarded" by read_stream.c to the
    1420             :          * next call to StartReadBuffers().
    1421             :          *
    1422             :          * This is signalled to the caller by decrementing *nblocks *and*
    1423             :          * reducing operation->nblocks. The latter is done here, but not below
    1424             :          * WaitReadBuffers(), as in WaitReadBuffers() we can't "shorten" the
    1425             :          * overall read size anymore, we need to retry until done in its
    1426             :          * entirety or until failed.
    1427             :          */
    1428     2513984 :         did_start_io = AsyncReadBuffers(operation, nblocks);
    1429             : 
    1430     2513954 :         operation->nblocks = *nblocks;
    1431             :     }
    1432             :     else
    1433             :     {
    1434        2178 :         operation->flags |= READ_BUFFERS_SYNCHRONOUSLY;
    1435             : 
    1436        2178 :         if (flags & READ_BUFFERS_ISSUE_ADVICE)
    1437             :         {
    1438             :             /*
    1439             :              * In theory we should only do this if PinBufferForBlock() had to
    1440             :              * allocate new buffers above.  That way, if two calls to
    1441             :              * StartReadBuffers() were made for the same blocks before
    1442             :              * WaitReadBuffers(), only the first would issue the advice.
    1443             :              * That'd be a better simulation of true asynchronous I/O, which
    1444             :              * would only start the I/O once, but isn't done here for
    1445             :              * simplicity.
    1446             :              */
    1447           4 :             smgrprefetch(operation->smgr,
    1448             :                          operation->forknum,
    1449             :                          blockNum,
    1450             :                          actual_nblocks);
    1451             :         }
    1452             : 
    1453             :         /*
    1454             :          * Indicate that WaitReadBuffers() should be called. WaitReadBuffers()
    1455             :          * will initiate the necessary IO.
    1456             :          */
    1457        2178 :         did_start_io = true;
    1458             :     }
    1459             : 
    1460     2516132 :     CheckReadBuffersOperation(operation, !did_start_io);
    1461             : 
    1462     2516132 :     return did_start_io;
    1463             : }
    1464             : 
    1465             : /*
    1466             :  * Begin reading a range of blocks beginning at blockNum and extending for
    1467             :  * *nblocks.  *nblocks and the buffers array are in/out parameters.  On entry,
    1468             :  * the buffers elements covered by *nblocks must hold either InvalidBuffer or
    1469             :  * buffers forwarded by an earlier call to StartReadBuffers() that was split
    1470             :  * and is now being continued.  On return, *nblocks holds the number of blocks
    1471             :  * accepted by this operation.  If it is less than the original number then
    1472             :  * this operation has been split, but buffer elements up to the original
    1473             :  * requested size may hold forwarded buffers to be used for a continuing
    1474             :  * operation.  The caller must either start a new I/O beginning at the block
    1475             :  * immediately following the blocks accepted by this call and pass those
    1476             :  * buffers back in, or release them if it chooses not to.  It shouldn't make
    1477             :  * any other use of or assumptions about forwarded buffers.
    1478             :  *
    1479             :  * If false is returned, no I/O is necessary and the buffers covered by
    1480             :  * *nblocks on exit are valid and ready to be accessed.  If true is returned,
    1481             :  * an I/O has been started, and WaitReadBuffers() must be called with the same
    1482             :  * operation object before the buffers covered by *nblocks on exit can be
    1483             :  * accessed.  Along with the operation object, the caller-supplied array of
    1484             :  * buffers must remain valid until WaitReadBuffers() is called, and any
    1485             :  * forwarded buffers must also be preserved for a continuing call unless
    1486             :  * they are explicitly released.
    1487             :  *
    1488             :  * Currently the I/O is only started with optional operating system advice if
    1489             :  * requested by the caller with READ_BUFFERS_ISSUE_ADVICE, and the real I/O
    1490             :  * happens synchronously in WaitReadBuffers().  In future work, true I/O could
    1491             :  * be initiated here.
    1492             :  */
    1493             : bool
    1494     3652992 : StartReadBuffers(ReadBuffersOperation *operation,
    1495             :                  Buffer *buffers,
    1496             :                  BlockNumber blockNum,
    1497             :                  int *nblocks,
    1498             :                  int flags)
    1499             : {
    1500     3652992 :     return StartReadBuffersImpl(operation, buffers, blockNum, nblocks, flags,
    1501             :                                 true /* expect forwarded buffers */ );
    1502             : }
    1503             : 
    1504             : /*
    1505             :  * Single block version of the StartReadBuffers().  This might save a few
    1506             :  * instructions when called from another translation unit, because it is
    1507             :  * specialized for nblocks == 1.
    1508             :  *
    1509             :  * This version does not support "forwarded" buffers: they cannot be created
    1510             :  * by reading only one block and *buffer is ignored on entry.
    1511             :  */
    1512             : bool
    1513   115892914 : StartReadBuffer(ReadBuffersOperation *operation,
    1514             :                 Buffer *buffer,
    1515             :                 BlockNumber blocknum,
    1516             :                 int flags)
    1517             : {
    1518   115892914 :     int         nblocks = 1;
    1519             :     bool        result;
    1520             : 
    1521   115892914 :     result = StartReadBuffersImpl(operation, buffer, blocknum, &nblocks, flags,
    1522             :                                   false /* single block, no forwarding */ );
    1523             :     Assert(nblocks == 1);       /* single block can't be short */
    1524             : 
    1525   115892884 :     return result;
    1526             : }
    1527             : 
    1528             : /*
    1529             :  * Perform sanity checks on the ReadBuffersOperation.
    1530             :  */
    1531             : static void
    1532     7540052 : CheckReadBuffersOperation(ReadBuffersOperation *operation, bool is_complete)
    1533             : {
    1534             : #ifdef USE_ASSERT_CHECKING
    1535             :     Assert(operation->nblocks_done <= operation->nblocks);
    1536             :     Assert(!is_complete || operation->nblocks == operation->nblocks_done);
    1537             : 
    1538             :     for (int i = 0; i < operation->nblocks; i++)
    1539             :     {
    1540             :         Buffer      buffer = operation->buffers[i];
    1541             :         BufferDesc *buf_hdr = BufferIsLocal(buffer) ?
    1542             :             GetLocalBufferDescriptor(-buffer - 1) :
    1543             :             GetBufferDescriptor(buffer - 1);
    1544             : 
    1545             :         Assert(BufferGetBlockNumber(buffer) == operation->blocknum + i);
    1546             :         Assert(pg_atomic_read_u32(&buf_hdr->state) & BM_TAG_VALID);
    1547             : 
    1548             :         if (i < operation->nblocks_done)
    1549             :             Assert(pg_atomic_read_u32(&buf_hdr->state) & BM_VALID);
    1550             :     }
    1551             : #endif
    1552     7540052 : }
    1553             : 
    1554             : /* helper for ReadBuffersCanStartIO(), to avoid repetition */
    1555             : static inline bool
    1556     2840796 : ReadBuffersCanStartIOOnce(Buffer buffer, bool nowait)
    1557             : {
    1558     2840796 :     if (BufferIsLocal(buffer))
    1559       16704 :         return StartLocalBufferIO(GetLocalBufferDescriptor(-buffer - 1),
    1560             :                                   true, nowait);
    1561             :     else
    1562     2824092 :         return StartBufferIO(GetBufferDescriptor(buffer - 1), true, nowait);
    1563             : }
    1564             : 
    1565             : /*
    1566             :  * Helper for AsyncReadBuffers that tries to get the buffer ready for IO.
    1567             :  */
    1568             : static inline bool
    1569     2840796 : ReadBuffersCanStartIO(Buffer buffer, bool nowait)
    1570             : {
    1571             :     /*
    1572             :      * If this backend currently has staged IO, we need to submit the pending
    1573             :      * IO before waiting for the right to issue IO, to avoid the potential for
    1574             :      * deadlocks (and, more commonly, unnecessary delays for other backends).
    1575             :      */
    1576     2840796 :     if (!nowait && pgaio_have_staged())
    1577             :     {
    1578        1134 :         if (ReadBuffersCanStartIOOnce(buffer, true))
    1579        1134 :             return true;
    1580             : 
    1581             :         /*
    1582             :          * Unfortunately StartBufferIO() returning false doesn't allow to
    1583             :          * distinguish between the buffer already being valid and IO already
    1584             :          * being in progress. Since IO already being in progress is quite
    1585             :          * rare, this approach seems fine.
    1586             :          */
    1587           0 :         pgaio_submit_staged();
    1588             :     }
    1589             : 
    1590     2839662 :     return ReadBuffersCanStartIOOnce(buffer, nowait);
    1591             : }
    1592             : 
    1593             : /*
    1594             :  * Helper for WaitReadBuffers() that processes the results of a readv
    1595             :  * operation, raising an error if necessary.
    1596             :  */
    1597             : static void
    1598     2510910 : ProcessReadBuffersResult(ReadBuffersOperation *operation)
    1599             : {
    1600     2510910 :     PgAioReturn *aio_ret = &operation->io_return;
    1601     2510910 :     PgAioResultStatus rs = aio_ret->result.status;
    1602     2510910 :     int         newly_read_blocks = 0;
    1603             : 
    1604             :     Assert(pgaio_wref_valid(&operation->io_wref));
    1605             :     Assert(aio_ret->result.status != PGAIO_RS_UNKNOWN);
    1606             : 
    1607             :     /*
    1608             :      * SMGR reports the number of blocks successfully read as the result of
    1609             :      * the IO operation. Thus we can simply add that to ->nblocks_done.
    1610             :      */
    1611             : 
    1612     2510910 :     if (likely(rs != PGAIO_RS_ERROR))
    1613     2510852 :         newly_read_blocks = aio_ret->result.result;
    1614             : 
    1615     2510910 :     if (rs == PGAIO_RS_ERROR || rs == PGAIO_RS_WARNING)
    1616          90 :         pgaio_result_report(aio_ret->result, &aio_ret->target_data,
    1617             :                             rs == PGAIO_RS_ERROR ? ERROR : WARNING);
    1618     2510820 :     else if (aio_ret->result.status == PGAIO_RS_PARTIAL)
    1619             :     {
    1620             :         /*
    1621             :          * We'll retry, so we just emit a debug message to the server log (or
    1622             :          * not even that in prod scenarios).
    1623             :          */
    1624          20 :         pgaio_result_report(aio_ret->result, &aio_ret->target_data, DEBUG1);
    1625          20 :         elog(DEBUG3, "partial read, will retry");
    1626             :     }
    1627             : 
    1628             :     Assert(newly_read_blocks > 0);
    1629             :     Assert(newly_read_blocks <= MAX_IO_COMBINE_LIMIT);
    1630             : 
    1631     2510852 :     operation->nblocks_done += newly_read_blocks;
    1632             : 
    1633             :     Assert(operation->nblocks_done <= operation->nblocks);
    1634     2510852 : }
    1635             : 
    1636             : void
    1637     2510890 : WaitReadBuffers(ReadBuffersOperation *operation)
    1638             : {
    1639     2510890 :     PgAioReturn *aio_ret = &operation->io_return;
    1640             :     IOContext   io_context;
    1641             :     IOObject    io_object;
    1642             : 
    1643     2510890 :     if (operation->persistence == RELPERSISTENCE_TEMP)
    1644             :     {
    1645        2950 :         io_context = IOCONTEXT_NORMAL;
    1646        2950 :         io_object = IOOBJECT_TEMP_RELATION;
    1647             :     }
    1648             :     else
    1649             :     {
    1650     2507940 :         io_context = IOContextForStrategy(operation->strategy);
    1651     2507940 :         io_object = IOOBJECT_RELATION;
    1652             :     }
    1653             : 
    1654             :     /*
    1655             :      * If we get here without an IO operation having been issued, the
    1656             :      * io_method == IOMETHOD_SYNC path must have been used. Otherwise the
    1657             :      * caller should not have called WaitReadBuffers().
    1658             :      *
    1659             :      * In the case of IOMETHOD_SYNC, we start - as we used to before the
    1660             :      * introducing of AIO - the IO in WaitReadBuffers(). This is done as part
    1661             :      * of the retry logic below, no extra code is required.
    1662             :      *
    1663             :      * This path is expected to eventually go away.
    1664             :      */
    1665     2510890 :     if (!pgaio_wref_valid(&operation->io_wref) && io_method != IOMETHOD_SYNC)
    1666           0 :         elog(ERROR, "waiting for read operation that didn't read");
    1667             : 
    1668             :     /*
    1669             :      * To handle partial reads, and IOMETHOD_SYNC, we re-issue IO until we're
    1670             :      * done. We may need multiple retries, not just because we could get
    1671             :      * multiple partial reads, but also because some of the remaining
    1672             :      * to-be-read buffers may have been read in by other backends, limiting
    1673             :      * the IO size.
    1674             :      */
    1675             :     while (true)
    1676        2198 :     {
    1677             :         int         ignored_nblocks_progress;
    1678             : 
    1679     2513088 :         CheckReadBuffersOperation(operation, false);
    1680             : 
    1681             :         /*
    1682             :          * If there is an IO associated with the operation, we may need to
    1683             :          * wait for it.
    1684             :          */
    1685     2513088 :         if (pgaio_wref_valid(&operation->io_wref))
    1686             :         {
    1687             :             /*
    1688             :              * Track the time spent waiting for the IO to complete. As
    1689             :              * tracking a wait even if we don't actually need to wait
    1690             :              *
    1691             :              * a) is not cheap, due to the timestamping overhead
    1692             :              *
    1693             :              * b) reports some time as waiting, even if we never waited
    1694             :              *
    1695             :              * we first check if we already know the IO is complete.
    1696             :              */
    1697     2510910 :             if (aio_ret->result.status == PGAIO_RS_UNKNOWN &&
    1698     1193606 :                 !pgaio_wref_check_done(&operation->io_wref))
    1699             :             {
    1700      544610 :                 instr_time  io_start = pgstat_prepare_io_time(track_io_timing);
    1701             : 
    1702      544610 :                 pgaio_wref_wait(&operation->io_wref);
    1703             : 
    1704             :                 /*
    1705             :                  * The IO operation itself was already counted earlier, in
    1706             :                  * AsyncReadBuffers(), this just accounts for the wait time.
    1707             :                  */
    1708      544610 :                 pgstat_count_io_op_time(io_object, io_context, IOOP_READ,
    1709             :                                         io_start, 0, 0);
    1710             :             }
    1711             :             else
    1712             :             {
    1713             :                 Assert(pgaio_wref_check_done(&operation->io_wref));
    1714             :             }
    1715             : 
    1716             :             /*
    1717             :              * We now are sure the IO completed. Check the results. This
    1718             :              * includes reporting on errors if there were any.
    1719             :              */
    1720     2510910 :             ProcessReadBuffersResult(operation);
    1721             :         }
    1722             : 
    1723             :         /*
    1724             :          * Most of the time, the one IO we already started, will read in
    1725             :          * everything.  But we need to deal with partial reads and buffers not
    1726             :          * needing IO anymore.
    1727             :          */
    1728     2513030 :         if (operation->nblocks_done == operation->nblocks)
    1729     2510832 :             break;
    1730             : 
    1731        2198 :         CHECK_FOR_INTERRUPTS();
    1732             : 
    1733             :         /*
    1734             :          * This may only complete the IO partially, either because some
    1735             :          * buffers were already valid, or because of a partial read.
    1736             :          *
    1737             :          * NB: In contrast to after the AsyncReadBuffers() call in
    1738             :          * StartReadBuffers(), we do *not* reduce
    1739             :          * ReadBuffersOperation->nblocks here, callers expect the full
    1740             :          * operation to be completed at this point (as more operations may
    1741             :          * have been queued).
    1742             :          */
    1743        2198 :         AsyncReadBuffers(operation, &ignored_nblocks_progress);
    1744             :     }
    1745             : 
    1746     2510832 :     CheckReadBuffersOperation(operation, true);
    1747             : 
    1748             :     /* NB: READ_DONE tracepoint was already executed in completion callback */
    1749     2510832 : }
    1750             : 
    1751             : /*
    1752             :  * Initiate IO for the ReadBuffersOperation
    1753             :  *
    1754             :  * This function only starts a single IO at a time. The size of the IO may be
    1755             :  * limited to below the to-be-read blocks, if one of the buffers has
    1756             :  * concurrently been read in. If the first to-be-read buffer is already valid,
    1757             :  * no IO will be issued.
    1758             :  *
    1759             :  * To support retries after partial reads, the first operation->nblocks_done
    1760             :  * buffers are skipped.
    1761             :  *
    1762             :  * On return *nblocks_progress is updated to reflect the number of buffers
    1763             :  * affected by the call. If the first buffer is valid, *nblocks_progress is
    1764             :  * set to 1 and operation->nblocks_done is incremented.
    1765             :  *
    1766             :  * Returns true if IO was initiated, false if no IO was necessary.
    1767             :  */
    1768             : static bool
    1769     2516182 : AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress)
    1770             : {
    1771     2516182 :     Buffer     *buffers = &operation->buffers[0];
    1772     2516182 :     int         flags = operation->flags;
    1773     2516182 :     BlockNumber blocknum = operation->blocknum;
    1774     2516182 :     ForkNumber  forknum = operation->forknum;
    1775     2516182 :     char        persistence = operation->persistence;
    1776     2516182 :     int16       nblocks_done = operation->nblocks_done;
    1777     2516182 :     Buffer     *io_buffers = &operation->buffers[nblocks_done];
    1778     2516182 :     int         io_buffers_len = 0;
    1779             :     PgAioHandle *ioh;
    1780     2516182 :     uint32      ioh_flags = 0;
    1781             :     void       *io_pages[MAX_IO_COMBINE_LIMIT];
    1782             :     IOContext   io_context;
    1783             :     IOObject    io_object;
    1784             :     bool        did_start_io;
    1785             : 
    1786             :     /*
    1787             :      * When this IO is executed synchronously, either because the caller will
    1788             :      * immediately block waiting for the IO or because IOMETHOD_SYNC is used,
    1789             :      * the AIO subsystem needs to know.
    1790             :      */
    1791     2516182 :     if (flags & READ_BUFFERS_SYNCHRONOUSLY)
    1792     1306052 :         ioh_flags |= PGAIO_HF_SYNCHRONOUS;
    1793             : 
    1794     2516182 :     if (persistence == RELPERSISTENCE_TEMP)
    1795             :     {
    1796        3538 :         io_context = IOCONTEXT_NORMAL;
    1797        3538 :         io_object = IOOBJECT_TEMP_RELATION;
    1798        3538 :         ioh_flags |= PGAIO_HF_REFERENCES_LOCAL;
    1799             :     }
    1800             :     else
    1801             :     {
    1802     2512644 :         io_context = IOContextForStrategy(operation->strategy);
    1803     2512644 :         io_object = IOOBJECT_RELATION;
    1804             :     }
    1805             : 
    1806             :     /*
    1807             :      * If zero_damaged_pages is enabled, add the READ_BUFFERS_ZERO_ON_ERROR
    1808             :      * flag. The reason for that is that, hopefully, zero_damaged_pages isn't
    1809             :      * set globally, but on a per-session basis. The completion callback,
    1810             :      * which may be run in other processes, e.g. in IO workers, may have a
    1811             :      * different value of the zero_damaged_pages GUC.
    1812             :      *
    1813             :      * XXX: We probably should eventually use a different flag for
    1814             :      * zero_damaged_pages, so we can report different log levels / error codes
    1815             :      * for zero_damaged_pages and ZERO_ON_ERROR.
    1816             :      */
    1817     2516182 :     if (zero_damaged_pages)
    1818          32 :         flags |= READ_BUFFERS_ZERO_ON_ERROR;
    1819             : 
    1820             :     /*
    1821             :      * For the same reason as with zero_damaged_pages we need to use this
    1822             :      * backend's ignore_checksum_failure value.
    1823             :      */
    1824     2516182 :     if (ignore_checksum_failure)
    1825          16 :         flags |= READ_BUFFERS_IGNORE_CHECKSUM_FAILURES;
    1826             : 
    1827             : 
    1828             :     /*
    1829             :      * To be allowed to report stats in the local completion callback we need
    1830             :      * to prepare to report stats now. This ensures we can safely report the
    1831             :      * checksum failure even in a critical section.
    1832             :      */
    1833     2516182 :     pgstat_prepare_report_checksum_failure(operation->smgr->smgr_rlocator.locator.dbOid);
    1834             : 
    1835             :     /*
    1836             :      * Get IO handle before ReadBuffersCanStartIO(), as pgaio_io_acquire()
    1837             :      * might block, which we don't want after setting IO_IN_PROGRESS.
    1838             :      *
    1839             :      * If we need to wait for IO before we can get a handle, submit
    1840             :      * already-staged IO first, so that other backends don't need to wait.
    1841             :      * There wouldn't be a deadlock risk, as pgaio_io_acquire() just needs to
    1842             :      * wait for already submitted IO, which doesn't require additional locks,
    1843             :      * but it could still cause undesirable waits.
    1844             :      *
    1845             :      * A secondary benefit is that this would allow us to measure the time in
    1846             :      * pgaio_io_acquire() without causing undue timer overhead in the common,
    1847             :      * non-blocking, case.  However, currently the pgstats infrastructure
    1848             :      * doesn't really allow that, as it a) asserts that an operation can't
    1849             :      * have time without operations b) doesn't have an API to report
    1850             :      * "accumulated" time.
    1851             :      */
    1852     2516182 :     ioh = pgaio_io_acquire_nb(CurrentResourceOwner, &operation->io_return);
    1853     2516182 :     if (unlikely(!ioh))
    1854             :     {
    1855        5098 :         pgaio_submit_staged();
    1856             : 
    1857        5098 :         ioh = pgaio_io_acquire(CurrentResourceOwner, &operation->io_return);
    1858             :     }
    1859             : 
    1860             :     /*
    1861             :      * Check if we can start IO on the first to-be-read buffer.
    1862             :      *
    1863             :      * If an I/O is already in progress in another backend, we want to wait
    1864             :      * for the outcome: either done, or something went wrong and we will
    1865             :      * retry.
    1866             :      */
    1867     2516182 :     if (!ReadBuffersCanStartIO(buffers[nblocks_done], false))
    1868             :     {
    1869             :         /*
    1870             :          * Someone else has already completed this block, we're done.
    1871             :          *
    1872             :          * When IO is necessary, ->nblocks_done is updated in
    1873             :          * ProcessReadBuffersResult(), but that is not called if no IO is
    1874             :          * necessary. Thus update here.
    1875             :          */
    1876        4650 :         operation->nblocks_done += 1;
    1877        4650 :         *nblocks_progress = 1;
    1878             : 
    1879        4650 :         pgaio_io_release(ioh);
    1880        4650 :         pgaio_wref_clear(&operation->io_wref);
    1881        4650 :         did_start_io = false;
    1882             : 
    1883             :         /*
    1884             :          * Report and track this as a 'hit' for this backend, even though it
    1885             :          * must have started out as a miss in PinBufferForBlock(). The other
    1886             :          * backend will track this as a 'read'.
    1887             :          */
    1888             :         TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, blocknum + operation->nblocks_done,
    1889             :                                           operation->smgr->smgr_rlocator.locator.spcOid,
    1890             :                                           operation->smgr->smgr_rlocator.locator.dbOid,
    1891             :                                           operation->smgr->smgr_rlocator.locator.relNumber,
    1892             :                                           operation->smgr->smgr_rlocator.backend,
    1893             :                                           true);
    1894             : 
    1895        4650 :         if (persistence == RELPERSISTENCE_TEMP)
    1896           0 :             pgBufferUsage.local_blks_hit += 1;
    1897             :         else
    1898        4650 :             pgBufferUsage.shared_blks_hit += 1;
    1899             : 
    1900        4650 :         if (operation->rel)
    1901        4650 :             pgstat_count_buffer_hit(operation->rel);
    1902             : 
    1903        4650 :         pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
    1904             : 
    1905        4650 :         if (VacuumCostActive)
    1906           0 :             VacuumCostBalance += VacuumCostPageHit;
    1907             :     }
    1908             :     else
    1909             :     {
    1910             :         instr_time  io_start;
    1911             : 
    1912             :         /* We found a buffer that we need to read in. */
    1913             :         Assert(io_buffers[0] == buffers[nblocks_done]);
    1914     2511532 :         io_pages[0] = BufferGetBlock(buffers[nblocks_done]);
    1915     2511532 :         io_buffers_len = 1;
    1916             : 
    1917             :         /*
    1918             :          * How many neighboring-on-disk blocks can we scatter-read into other
    1919             :          * buffers at the same time?  In this case we don't wait if we see an
    1920             :          * I/O already in progress.  We already set BM_IO_IN_PROGRESS for the
    1921             :          * head block, so we should get on with that I/O as soon as possible.
    1922             :          */
    1923     2836146 :         for (int i = nblocks_done + 1; i < operation->nblocks; i++)
    1924             :         {
    1925      324614 :             if (!ReadBuffersCanStartIO(buffers[i], true))
    1926           0 :                 break;
    1927             :             /* Must be consecutive block numbers. */
    1928             :             Assert(BufferGetBlockNumber(buffers[i - 1]) ==
    1929             :                    BufferGetBlockNumber(buffers[i]) - 1);
    1930             :             Assert(io_buffers[io_buffers_len] == buffers[i]);
    1931             : 
    1932      324614 :             io_pages[io_buffers_len++] = BufferGetBlock(buffers[i]);
    1933             :         }
    1934             : 
    1935             :         /* get a reference to wait for in WaitReadBuffers() */
    1936     2511532 :         pgaio_io_get_wref(ioh, &operation->io_wref);
    1937             : 
    1938             :         /* provide the list of buffers to the completion callbacks */
    1939     2511532 :         pgaio_io_set_handle_data_32(ioh, (uint32 *) io_buffers, io_buffers_len);
    1940             : 
    1941     2511532 :         pgaio_io_register_callbacks(ioh,
    1942             :                                     persistence == RELPERSISTENCE_TEMP ?
    1943             :                                     PGAIO_HCB_LOCAL_BUFFER_READV :
    1944             :                                     PGAIO_HCB_SHARED_BUFFER_READV,
    1945             :                                     flags);
    1946             : 
    1947     2511532 :         pgaio_io_set_flag(ioh, ioh_flags);
    1948             : 
    1949             :         /* ---
    1950             :          * Even though we're trying to issue IO asynchronously, track the time
    1951             :          * in smgrstartreadv():
    1952             :          * - if io_method == IOMETHOD_SYNC, we will always perform the IO
    1953             :          *   immediately
    1954             :          * - the io method might not support the IO (e.g. worker IO for a temp
    1955             :          *   table)
    1956             :          * ---
    1957             :          */
    1958     2511532 :         io_start = pgstat_prepare_io_time(track_io_timing);
    1959     2511532 :         smgrstartreadv(ioh, operation->smgr, forknum,
    1960             :                        blocknum + nblocks_done,
    1961             :                        io_pages, io_buffers_len);
    1962     2511502 :         pgstat_count_io_op_time(io_object, io_context, IOOP_READ,
    1963     2511502 :                                 io_start, 1, io_buffers_len * BLCKSZ);
    1964             : 
    1965     2511502 :         if (persistence == RELPERSISTENCE_TEMP)
    1966        3538 :             pgBufferUsage.local_blks_read += io_buffers_len;
    1967             :         else
    1968     2507964 :             pgBufferUsage.shared_blks_read += io_buffers_len;
    1969             : 
    1970             :         /*
    1971             :          * Track vacuum cost when issuing IO, not after waiting for it.
    1972             :          * Otherwise we could end up issuing a lot of IO in a short timespan,
    1973             :          * despite a low cost limit.
    1974             :          */
    1975     2511502 :         if (VacuumCostActive)
    1976        9300 :             VacuumCostBalance += VacuumCostPageMiss * io_buffers_len;
    1977             : 
    1978     2511502 :         *nblocks_progress = io_buffers_len;
    1979     2511502 :         did_start_io = true;
    1980             :     }
    1981             : 
    1982     2516152 :     return did_start_io;
    1983             : }
    1984             : 
    1985             : /*
    1986             :  * BufferAlloc -- subroutine for PinBufferForBlock.  Handles lookup of a shared
    1987             :  *      buffer.  If no buffer exists already, selects a replacement victim and
    1988             :  *      evicts the old page, but does NOT read in new page.
    1989             :  *
    1990             :  * "strategy" can be a buffer replacement strategy object, or NULL for
    1991             :  * the default strategy.  The selected buffer's usage_count is advanced when
    1992             :  * using the default strategy, but otherwise possibly not (see PinBuffer).
    1993             :  *
    1994             :  * The returned buffer is pinned and is already marked as holding the
    1995             :  * desired page.  If it already did have the desired page, *foundPtr is
    1996             :  * set true.  Otherwise, *foundPtr is set false.
    1997             :  *
    1998             :  * io_context is passed as an output parameter to avoid calling
    1999             :  * IOContextForStrategy() when there is a shared buffers hit and no IO
    2000             :  * statistics need be captured.
    2001             :  *
    2002             :  * No locks are held either at entry or exit.
    2003             :  */
    2004             : static pg_attribute_always_inline BufferDesc *
    2005   117936558 : BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
    2006             :             BlockNumber blockNum,
    2007             :             BufferAccessStrategy strategy,
    2008             :             bool *foundPtr, IOContext io_context)
    2009             : {
    2010             :     BufferTag   newTag;         /* identity of requested block */
    2011             :     uint32      newHash;        /* hash value for newTag */
    2012             :     LWLock     *newPartitionLock;   /* buffer partition lock for it */
    2013             :     int         existing_buf_id;
    2014             :     Buffer      victim_buffer;
    2015             :     BufferDesc *victim_buf_hdr;
    2016             :     uint32      victim_buf_state;
    2017             : 
    2018             :     /* Make sure we will have room to remember the buffer pin */
    2019   117936558 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    2020   117936558 :     ReservePrivateRefCountEntry();
    2021             : 
    2022             :     /* create a tag so we can lookup the buffer */
    2023   117936558 :     InitBufferTag(&newTag, &smgr->smgr_rlocator.locator, forkNum, blockNum);
    2024             : 
    2025             :     /* determine its hash code and partition lock ID */
    2026   117936558 :     newHash = BufTableHashCode(&newTag);
    2027   117936558 :     newPartitionLock = BufMappingPartitionLock(newHash);
    2028             : 
    2029             :     /* see if the block is in the buffer pool already */
    2030   117936558 :     LWLockAcquire(newPartitionLock, LW_SHARED);
    2031   117936558 :     existing_buf_id = BufTableLookup(&newTag, newHash);
    2032   117936558 :     if (existing_buf_id >= 0)
    2033             :     {
    2034             :         BufferDesc *buf;
    2035             :         bool        valid;
    2036             : 
    2037             :         /*
    2038             :          * Found it.  Now, pin the buffer so no one can steal it from the
    2039             :          * buffer pool, and check to see if the correct data has been loaded
    2040             :          * into the buffer.
    2041             :          */
    2042   114581892 :         buf = GetBufferDescriptor(existing_buf_id);
    2043             : 
    2044   114581892 :         valid = PinBuffer(buf, strategy);
    2045             : 
    2046             :         /* Can release the mapping lock as soon as we've pinned it */
    2047   114581892 :         LWLockRelease(newPartitionLock);
    2048             : 
    2049   114581892 :         *foundPtr = true;
    2050             : 
    2051   114581892 :         if (!valid)
    2052             :         {
    2053             :             /*
    2054             :              * We can only get here if (a) someone else is still reading in
    2055             :              * the page, (b) a previous read attempt failed, or (c) someone
    2056             :              * called StartReadBuffers() but not yet WaitReadBuffers().
    2057             :              */
    2058        4052 :             *foundPtr = false;
    2059             :         }
    2060             : 
    2061   114581892 :         return buf;
    2062             :     }
    2063             : 
    2064             :     /*
    2065             :      * Didn't find it in the buffer pool.  We'll have to initialize a new
    2066             :      * buffer.  Remember to unlock the mapping lock while doing the work.
    2067             :      */
    2068     3354666 :     LWLockRelease(newPartitionLock);
    2069             : 
    2070             :     /*
    2071             :      * Acquire a victim buffer. Somebody else might try to do the same, we
    2072             :      * don't hold any conflicting locks. If so we'll have to undo our work
    2073             :      * later.
    2074             :      */
    2075     3354666 :     victim_buffer = GetVictimBuffer(strategy, io_context);
    2076     3354666 :     victim_buf_hdr = GetBufferDescriptor(victim_buffer - 1);
    2077             : 
    2078             :     /*
    2079             :      * Try to make a hashtable entry for the buffer under its new tag. If
    2080             :      * somebody else inserted another buffer for the tag, we'll release the
    2081             :      * victim buffer we acquired and use the already inserted one.
    2082             :      */
    2083     3354666 :     LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
    2084     3354666 :     existing_buf_id = BufTableInsert(&newTag, newHash, victim_buf_hdr->buf_id);
    2085     3354666 :     if (existing_buf_id >= 0)
    2086             :     {
    2087             :         BufferDesc *existing_buf_hdr;
    2088             :         bool        valid;
    2089             : 
    2090             :         /*
    2091             :          * Got a collision. Someone has already done what we were about to do.
    2092             :          * We'll just handle this as if it were found in the buffer pool in
    2093             :          * the first place.  First, give up the buffer we were planning to
    2094             :          * use.
    2095             :          *
    2096             :          * We could do this after releasing the partition lock, but then we'd
    2097             :          * have to call ResourceOwnerEnlarge() & ReservePrivateRefCountEntry()
    2098             :          * before acquiring the lock, for the rare case of such a collision.
    2099             :          */
    2100         930 :         UnpinBuffer(victim_buf_hdr);
    2101             : 
    2102             :         /*
    2103             :          * The victim buffer we acquired previously is clean and unused, let
    2104             :          * it be found again quickly
    2105             :          */
    2106         930 :         StrategyFreeBuffer(victim_buf_hdr);
    2107             : 
    2108             :         /* remaining code should match code at top of routine */
    2109             : 
    2110         930 :         existing_buf_hdr = GetBufferDescriptor(existing_buf_id);
    2111             : 
    2112         930 :         valid = PinBuffer(existing_buf_hdr, strategy);
    2113             : 
    2114             :         /* Can release the mapping lock as soon as we've pinned it */
    2115         930 :         LWLockRelease(newPartitionLock);
    2116             : 
    2117         930 :         *foundPtr = true;
    2118             : 
    2119         930 :         if (!valid)
    2120             :         {
    2121             :             /*
    2122             :              * We can only get here if (a) someone else is still reading in
    2123             :              * the page, (b) a previous read attempt failed, or (c) someone
    2124             :              * called StartReadBuffers() but not yet WaitReadBuffers().
    2125             :              */
    2126         694 :             *foundPtr = false;
    2127             :         }
    2128             : 
    2129         930 :         return existing_buf_hdr;
    2130             :     }
    2131             : 
    2132             :     /*
    2133             :      * Need to lock the buffer header too in order to change its tag.
    2134             :      */
    2135     3353736 :     victim_buf_state = LockBufHdr(victim_buf_hdr);
    2136             : 
    2137             :     /* some sanity checks while we hold the buffer header lock */
    2138             :     Assert(BUF_STATE_GET_REFCOUNT(victim_buf_state) == 1);
    2139             :     Assert(!(victim_buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY | BM_IO_IN_PROGRESS)));
    2140             : 
    2141     3353736 :     victim_buf_hdr->tag = newTag;
    2142             : 
    2143             :     /*
    2144             :      * Make sure BM_PERMANENT is set for buffers that must be written at every
    2145             :      * checkpoint.  Unlogged buffers only need to be written at shutdown
    2146             :      * checkpoints, except for their "init" forks, which need to be treated
    2147             :      * just like permanent relations.
    2148             :      */
    2149     3353736 :     victim_buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
    2150     3353736 :     if (relpersistence == RELPERSISTENCE_PERMANENT || forkNum == INIT_FORKNUM)
    2151     3353056 :         victim_buf_state |= BM_PERMANENT;
    2152             : 
    2153     3353736 :     UnlockBufHdr(victim_buf_hdr, victim_buf_state);
    2154             : 
    2155     3353736 :     LWLockRelease(newPartitionLock);
    2156             : 
    2157             :     /*
    2158             :      * Buffer contents are currently invalid.
    2159             :      */
    2160     3353736 :     *foundPtr = false;
    2161             : 
    2162     3353736 :     return victim_buf_hdr;
    2163             : }
    2164             : 
    2165             : /*
    2166             :  * InvalidateBuffer -- mark a shared buffer invalid and return it to the
    2167             :  * freelist.
    2168             :  *
    2169             :  * The buffer header spinlock must be held at entry.  We drop it before
    2170             :  * returning.  (This is sane because the caller must have locked the
    2171             :  * buffer in order to be sure it should be dropped.)
    2172             :  *
    2173             :  * This is used only in contexts such as dropping a relation.  We assume
    2174             :  * that no other backend could possibly be interested in using the page,
    2175             :  * so the only reason the buffer might be pinned is if someone else is
    2176             :  * trying to write it out.  We have to let them finish before we can
    2177             :  * reclaim the buffer.
    2178             :  *
    2179             :  * The buffer could get reclaimed by someone else while we are waiting
    2180             :  * to acquire the necessary locks; if so, don't mess it up.
    2181             :  */
    2182             : static void
    2183      215014 : InvalidateBuffer(BufferDesc *buf)
    2184             : {
    2185             :     BufferTag   oldTag;
    2186             :     uint32      oldHash;        /* hash value for oldTag */
    2187             :     LWLock     *oldPartitionLock;   /* buffer partition lock for it */
    2188             :     uint32      oldFlags;
    2189             :     uint32      buf_state;
    2190             : 
    2191             :     /* Save the original buffer tag before dropping the spinlock */
    2192      215014 :     oldTag = buf->tag;
    2193             : 
    2194      215014 :     buf_state = pg_atomic_read_u32(&buf->state);
    2195             :     Assert(buf_state & BM_LOCKED);
    2196      215014 :     UnlockBufHdr(buf, buf_state);
    2197             : 
    2198             :     /*
    2199             :      * Need to compute the old tag's hashcode and partition lock ID. XXX is it
    2200             :      * worth storing the hashcode in BufferDesc so we need not recompute it
    2201             :      * here?  Probably not.
    2202             :      */
    2203      215014 :     oldHash = BufTableHashCode(&oldTag);
    2204      215014 :     oldPartitionLock = BufMappingPartitionLock(oldHash);
    2205             : 
    2206      215020 : retry:
    2207             : 
    2208             :     /*
    2209             :      * Acquire exclusive mapping lock in preparation for changing the buffer's
    2210             :      * association.
    2211             :      */
    2212      215020 :     LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
    2213             : 
    2214             :     /* Re-lock the buffer header */
    2215      215020 :     buf_state = LockBufHdr(buf);
    2216             : 
    2217             :     /* If it's changed while we were waiting for lock, do nothing */
    2218      215020 :     if (!BufferTagsEqual(&buf->tag, &oldTag))
    2219             :     {
    2220           6 :         UnlockBufHdr(buf, buf_state);
    2221           6 :         LWLockRelease(oldPartitionLock);
    2222           6 :         return;
    2223             :     }
    2224             : 
    2225             :     /*
    2226             :      * We assume the reason for it to be pinned is that either we were
    2227             :      * asynchronously reading the page in before erroring out or someone else
    2228             :      * is flushing the page out.  Wait for the IO to finish.  (This could be
    2229             :      * an infinite loop if the refcount is messed up... it would be nice to
    2230             :      * time out after awhile, but there seems no way to be sure how many loops
    2231             :      * may be needed.  Note that if the other guy has pinned the buffer but
    2232             :      * not yet done StartBufferIO, WaitIO will fall through and we'll
    2233             :      * effectively be busy-looping here.)
    2234             :      */
    2235      215014 :     if (BUF_STATE_GET_REFCOUNT(buf_state) != 0)
    2236             :     {
    2237           6 :         UnlockBufHdr(buf, buf_state);
    2238           6 :         LWLockRelease(oldPartitionLock);
    2239             :         /* safety check: should definitely not be our *own* pin */
    2240           6 :         if (GetPrivateRefCount(BufferDescriptorGetBuffer(buf)) > 0)
    2241           0 :             elog(ERROR, "buffer is pinned in InvalidateBuffer");
    2242           6 :         WaitIO(buf);
    2243           6 :         goto retry;
    2244             :     }
    2245             : 
    2246             :     /*
    2247             :      * Clear out the buffer's tag and flags.  We must do this to ensure that
    2248             :      * linear scans of the buffer array don't think the buffer is valid.
    2249             :      */
    2250      215008 :     oldFlags = buf_state & BUF_FLAG_MASK;
    2251      215008 :     ClearBufferTag(&buf->tag);
    2252      215008 :     buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
    2253      215008 :     UnlockBufHdr(buf, buf_state);
    2254             : 
    2255             :     /*
    2256             :      * Remove the buffer from the lookup hashtable, if it was in there.
    2257             :      */
    2258      215008 :     if (oldFlags & BM_TAG_VALID)
    2259      215008 :         BufTableDelete(&oldTag, oldHash);
    2260             : 
    2261             :     /*
    2262             :      * Done with mapping lock.
    2263             :      */
    2264      215008 :     LWLockRelease(oldPartitionLock);
    2265             : 
    2266             :     /*
    2267             :      * Insert the buffer at the head of the list of free buffers.
    2268             :      */
    2269      215008 :     StrategyFreeBuffer(buf);
    2270             : }
    2271             : 
    2272             : /*
    2273             :  * Helper routine for GetVictimBuffer()
    2274             :  *
    2275             :  * Needs to be called on a buffer with a valid tag, pinned, but without the
    2276             :  * buffer header spinlock held.
    2277             :  *
    2278             :  * Returns true if the buffer can be reused, in which case the buffer is only
    2279             :  * pinned by this backend and marked as invalid, false otherwise.
    2280             :  */
    2281             : static bool
    2282     2370980 : InvalidateVictimBuffer(BufferDesc *buf_hdr)
    2283             : {
    2284             :     uint32      buf_state;
    2285             :     uint32      hash;
    2286             :     LWLock     *partition_lock;
    2287             :     BufferTag   tag;
    2288             : 
    2289             :     Assert(GetPrivateRefCount(BufferDescriptorGetBuffer(buf_hdr)) == 1);
    2290             : 
    2291             :     /* have buffer pinned, so it's safe to read tag without lock */
    2292     2370980 :     tag = buf_hdr->tag;
    2293             : 
    2294     2370980 :     hash = BufTableHashCode(&tag);
    2295     2370980 :     partition_lock = BufMappingPartitionLock(hash);
    2296             : 
    2297     2370980 :     LWLockAcquire(partition_lock, LW_EXCLUSIVE);
    2298             : 
    2299             :     /* lock the buffer header */
    2300     2370980 :     buf_state = LockBufHdr(buf_hdr);
    2301             : 
    2302             :     /*
    2303             :      * We have the buffer pinned nobody else should have been able to unset
    2304             :      * this concurrently.
    2305             :      */
    2306             :     Assert(buf_state & BM_TAG_VALID);
    2307             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2308             :     Assert(BufferTagsEqual(&buf_hdr->tag, &tag));
    2309             : 
    2310             :     /*
    2311             :      * If somebody else pinned the buffer since, or even worse, dirtied it,
    2312             :      * give up on this buffer: It's clearly in use.
    2313             :      */
    2314     2370980 :     if (BUF_STATE_GET_REFCOUNT(buf_state) != 1 || (buf_state & BM_DIRTY))
    2315             :     {
    2316             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2317             : 
    2318         436 :         UnlockBufHdr(buf_hdr, buf_state);
    2319         436 :         LWLockRelease(partition_lock);
    2320             : 
    2321         436 :         return false;
    2322             :     }
    2323             : 
    2324             :     /*
    2325             :      * Clear out the buffer's tag and flags and usagecount.  This is not
    2326             :      * strictly required, as BM_TAG_VALID/BM_VALID needs to be checked before
    2327             :      * doing anything with the buffer. But currently it's beneficial, as the
    2328             :      * cheaper pre-check for several linear scans of shared buffers use the
    2329             :      * tag (see e.g. FlushDatabaseBuffers()).
    2330             :      */
    2331     2370544 :     ClearBufferTag(&buf_hdr->tag);
    2332     2370544 :     buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
    2333     2370544 :     UnlockBufHdr(buf_hdr, buf_state);
    2334             : 
    2335             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2336             : 
    2337             :     /* finally delete buffer from the buffer mapping table */
    2338     2370544 :     BufTableDelete(&tag, hash);
    2339             : 
    2340     2370544 :     LWLockRelease(partition_lock);
    2341             : 
    2342             :     Assert(!(buf_state & (BM_DIRTY | BM_VALID | BM_TAG_VALID)));
    2343             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2344             :     Assert(BUF_STATE_GET_REFCOUNT(pg_atomic_read_u32(&buf_hdr->state)) > 0);
    2345             : 
    2346     2370544 :     return true;
    2347             : }
    2348             : 
    2349             : static Buffer
    2350     3809082 : GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context)
    2351             : {
    2352             :     BufferDesc *buf_hdr;
    2353             :     Buffer      buf;
    2354             :     uint32      buf_state;
    2355             :     bool        from_ring;
    2356             : 
    2357             :     /*
    2358             :      * Ensure, while the spinlock's not yet held, that there's a free refcount
    2359             :      * entry, and a resource owner slot for the pin.
    2360             :      */
    2361     3809082 :     ReservePrivateRefCountEntry();
    2362     3809082 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    2363             : 
    2364             :     /* we return here if a prospective victim buffer gets used concurrently */
    2365     3822000 : again:
    2366             : 
    2367             :     /*
    2368             :      * Select a victim buffer.  The buffer is returned with its header
    2369             :      * spinlock still held!
    2370             :      */
    2371     3822000 :     buf_hdr = StrategyGetBuffer(strategy, &buf_state, &from_ring);
    2372     3822000 :     buf = BufferDescriptorGetBuffer(buf_hdr);
    2373             : 
    2374             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 0);
    2375             : 
    2376             :     /* Pin the buffer and then release the buffer spinlock */
    2377     3822000 :     PinBuffer_Locked(buf_hdr);
    2378             : 
    2379             :     /*
    2380             :      * We shouldn't have any other pins for this buffer.
    2381             :      */
    2382     3822000 :     CheckBufferIsPinnedOnce(buf);
    2383             : 
    2384             :     /*
    2385             :      * If the buffer was dirty, try to write it out.  There is a race
    2386             :      * condition here, in that someone might dirty it after we released the
    2387             :      * buffer header lock above, or even while we are writing it out (since
    2388             :      * our share-lock won't prevent hint-bit updates).  We will recheck the
    2389             :      * dirty bit after re-locking the buffer header.
    2390             :      */
    2391     3822000 :     if (buf_state & BM_DIRTY)
    2392             :     {
    2393             :         LWLock     *content_lock;
    2394             : 
    2395             :         Assert(buf_state & BM_TAG_VALID);
    2396             :         Assert(buf_state & BM_VALID);
    2397             : 
    2398             :         /*
    2399             :          * We need a share-lock on the buffer contents to write it out (else
    2400             :          * we might write invalid data, eg because someone else is compacting
    2401             :          * the page contents while we write).  We must use a conditional lock
    2402             :          * acquisition here to avoid deadlock.  Even though the buffer was not
    2403             :          * pinned (and therefore surely not locked) when StrategyGetBuffer
    2404             :          * returned it, someone else could have pinned and exclusive-locked it
    2405             :          * by the time we get here. If we try to get the lock unconditionally,
    2406             :          * we'd block waiting for them; if they later block waiting for us,
    2407             :          * deadlock ensues. (This has been observed to happen when two
    2408             :          * backends are both trying to split btree index pages, and the second
    2409             :          * one just happens to be trying to split the page the first one got
    2410             :          * from StrategyGetBuffer.)
    2411             :          */
    2412      482732 :         content_lock = BufferDescriptorGetContentLock(buf_hdr);
    2413      482732 :         if (!LWLockConditionalAcquire(content_lock, LW_SHARED))
    2414             :         {
    2415             :             /*
    2416             :              * Someone else has locked the buffer, so give it up and loop back
    2417             :              * to get another one.
    2418             :              */
    2419           0 :             UnpinBuffer(buf_hdr);
    2420           0 :             goto again;
    2421             :         }
    2422             : 
    2423             :         /*
    2424             :          * If using a nondefault strategy, and writing the buffer would
    2425             :          * require a WAL flush, let the strategy decide whether to go ahead
    2426             :          * and write/reuse the buffer or to choose another victim.  We need a
    2427             :          * lock to inspect the page LSN, so this can't be done inside
    2428             :          * StrategyGetBuffer.
    2429             :          */
    2430      482732 :         if (strategy != NULL)
    2431             :         {
    2432             :             XLogRecPtr  lsn;
    2433             : 
    2434             :             /* Read the LSN while holding buffer header lock */
    2435      140746 :             buf_state = LockBufHdr(buf_hdr);
    2436      140746 :             lsn = BufferGetLSN(buf_hdr);
    2437      140746 :             UnlockBufHdr(buf_hdr, buf_state);
    2438             : 
    2439      140746 :             if (XLogNeedsFlush(lsn)
    2440       17152 :                 && StrategyRejectBuffer(strategy, buf_hdr, from_ring))
    2441             :             {
    2442       12482 :                 LWLockRelease(content_lock);
    2443       12482 :                 UnpinBuffer(buf_hdr);
    2444       12482 :                 goto again;
    2445             :             }
    2446             :         }
    2447             : 
    2448             :         /* OK, do the I/O */
    2449      470250 :         FlushBuffer(buf_hdr, NULL, IOOBJECT_RELATION, io_context);
    2450      470250 :         LWLockRelease(content_lock);
    2451             : 
    2452      470250 :         ScheduleBufferTagForWriteback(&BackendWritebackContext, io_context,
    2453             :                                       &buf_hdr->tag);
    2454             :     }
    2455             : 
    2456             : 
    2457     3809518 :     if (buf_state & BM_VALID)
    2458             :     {
    2459             :         /*
    2460             :          * When a BufferAccessStrategy is in use, blocks evicted from shared
    2461             :          * buffers are counted as IOOP_EVICT in the corresponding context
    2462             :          * (e.g. IOCONTEXT_BULKWRITE). Shared buffers are evicted by a
    2463             :          * strategy in two cases: 1) while initially claiming buffers for the
    2464             :          * strategy ring 2) to replace an existing strategy ring buffer
    2465             :          * because it is pinned or in use and cannot be reused.
    2466             :          *
    2467             :          * Blocks evicted from buffers already in the strategy ring are
    2468             :          * counted as IOOP_REUSE in the corresponding strategy context.
    2469             :          *
    2470             :          * At this point, we can accurately count evictions and reuses,
    2471             :          * because we have successfully claimed the valid buffer. Previously,
    2472             :          * we may have been forced to release the buffer due to concurrent
    2473             :          * pinners or erroring out.
    2474             :          */
    2475     2366718 :         pgstat_count_io_op(IOOBJECT_RELATION, io_context,
    2476     2366718 :                            from_ring ? IOOP_REUSE : IOOP_EVICT, 1, 0);
    2477             :     }
    2478             : 
    2479             :     /*
    2480             :      * If the buffer has an entry in the buffer mapping table, delete it. This
    2481             :      * can fail because another backend could have pinned or dirtied the
    2482             :      * buffer.
    2483             :      */
    2484     3809518 :     if ((buf_state & BM_TAG_VALID) && !InvalidateVictimBuffer(buf_hdr))
    2485             :     {
    2486         436 :         UnpinBuffer(buf_hdr);
    2487         436 :         goto again;
    2488             :     }
    2489             : 
    2490             :     /* a final set of sanity checks */
    2491             : #ifdef USE_ASSERT_CHECKING
    2492             :     buf_state = pg_atomic_read_u32(&buf_hdr->state);
    2493             : 
    2494             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
    2495             :     Assert(!(buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY)));
    2496             : 
    2497             :     CheckBufferIsPinnedOnce(buf);
    2498             : #endif
    2499             : 
    2500     3809082 :     return buf;
    2501             : }
    2502             : 
    2503             : /*
    2504             :  * Return the maximum number of buffers that a backend should try to pin once,
    2505             :  * to avoid exceeding its fair share.  This is the highest value that
    2506             :  * GetAdditionalPinLimit() could ever return.  Note that it may be zero on a
    2507             :  * system with a very small buffer pool relative to max_connections.
    2508             :  */
    2509             : uint32
    2510     1147262 : GetPinLimit(void)
    2511             : {
    2512     1147262 :     return MaxProportionalPins;
    2513             : }
    2514             : 
    2515             : /*
    2516             :  * Return the maximum number of additional buffers that this backend should
    2517             :  * pin if it wants to stay under the per-backend limit, considering the number
    2518             :  * of buffers it has already pinned.  Unlike LimitAdditionalPins(), the limit
    2519             :  * return by this function can be zero.
    2520             :  */
    2521             : uint32
    2522     7283812 : GetAdditionalPinLimit(void)
    2523             : {
    2524             :     uint32      estimated_pins_held;
    2525             : 
    2526             :     /*
    2527             :      * We get the number of "overflowed" pins for free, but don't know the
    2528             :      * number of pins in PrivateRefCountArray.  The cost of calculating that
    2529             :      * exactly doesn't seem worth it, so just assume the max.
    2530             :      */
    2531     7283812 :     estimated_pins_held = PrivateRefCountOverflowed + REFCOUNT_ARRAY_ENTRIES;
    2532             : 
    2533             :     /* Is this backend already holding more than its fair share? */
    2534     7283812 :     if (estimated_pins_held > MaxProportionalPins)
    2535     2561960 :         return 0;
    2536             : 
    2537     4721852 :     return MaxProportionalPins - estimated_pins_held;
    2538             : }
    2539             : 
    2540             : /*
    2541             :  * Limit the number of pins a batch operation may additionally acquire, to
    2542             :  * avoid running out of pinnable buffers.
    2543             :  *
    2544             :  * One additional pin is always allowed, on the assumption that the operation
    2545             :  * requires at least one to make progress.
    2546             :  */
    2547             : void
    2548      402510 : LimitAdditionalPins(uint32 *additional_pins)
    2549             : {
    2550             :     uint32      limit;
    2551             : 
    2552      402510 :     if (*additional_pins <= 1)
    2553      382302 :         return;
    2554             : 
    2555       20208 :     limit = GetAdditionalPinLimit();
    2556       20208 :     limit = Max(limit, 1);
    2557       20208 :     if (limit < *additional_pins)
    2558       10828 :         *additional_pins = limit;
    2559             : }
    2560             : 
    2561             : /*
    2562             :  * Logic shared between ExtendBufferedRelBy(), ExtendBufferedRelTo(). Just to
    2563             :  * avoid duplicating the tracing and relpersistence related logic.
    2564             :  */
    2565             : static BlockNumber
    2566      425220 : ExtendBufferedRelCommon(BufferManagerRelation bmr,
    2567             :                         ForkNumber fork,
    2568             :                         BufferAccessStrategy strategy,
    2569             :                         uint32 flags,
    2570             :                         uint32 extend_by,
    2571             :                         BlockNumber extend_upto,
    2572             :                         Buffer *buffers,
    2573             :                         uint32 *extended_by)
    2574             : {
    2575             :     BlockNumber first_block;
    2576             : 
    2577             :     TRACE_POSTGRESQL_BUFFER_EXTEND_START(fork,
    2578             :                                          bmr.smgr->smgr_rlocator.locator.spcOid,
    2579             :                                          bmr.smgr->smgr_rlocator.locator.dbOid,
    2580             :                                          bmr.smgr->smgr_rlocator.locator.relNumber,
    2581             :                                          bmr.smgr->smgr_rlocator.backend,
    2582             :                                          extend_by);
    2583             : 
    2584      425220 :     if (bmr.relpersistence == RELPERSISTENCE_TEMP)
    2585       22710 :         first_block = ExtendBufferedRelLocal(bmr, fork, flags,
    2586             :                                              extend_by, extend_upto,
    2587             :                                              buffers, &extend_by);
    2588             :     else
    2589      402510 :         first_block = ExtendBufferedRelShared(bmr, fork, strategy, flags,
    2590             :                                               extend_by, extend_upto,
    2591             :                                               buffers, &extend_by);
    2592      425220 :     *extended_by = extend_by;
    2593             : 
    2594             :     TRACE_POSTGRESQL_BUFFER_EXTEND_DONE(fork,
    2595             :                                         bmr.smgr->smgr_rlocator.locator.spcOid,
    2596             :                                         bmr.smgr->smgr_rlocator.locator.dbOid,
    2597             :                                         bmr.smgr->smgr_rlocator.locator.relNumber,
    2598             :                                         bmr.smgr->smgr_rlocator.backend,
    2599             :                                         *extended_by,
    2600             :                                         first_block);
    2601             : 
    2602      425220 :     return first_block;
    2603             : }
    2604             : 
    2605             : /*
    2606             :  * Implementation of ExtendBufferedRelBy() and ExtendBufferedRelTo() for
    2607             :  * shared buffers.
    2608             :  */
    2609             : static BlockNumber
    2610      402510 : ExtendBufferedRelShared(BufferManagerRelation bmr,
    2611             :                         ForkNumber fork,
    2612             :                         BufferAccessStrategy strategy,
    2613             :                         uint32 flags,
    2614             :                         uint32 extend_by,
    2615             :                         BlockNumber extend_upto,
    2616             :                         Buffer *buffers,
    2617             :                         uint32 *extended_by)
    2618             : {
    2619             :     BlockNumber first_block;
    2620      402510 :     IOContext   io_context = IOContextForStrategy(strategy);
    2621             :     instr_time  io_start;
    2622             : 
    2623      402510 :     LimitAdditionalPins(&extend_by);
    2624             : 
    2625             :     /*
    2626             :      * Acquire victim buffers for extension without holding extension lock.
    2627             :      * Writing out victim buffers is the most expensive part of extending the
    2628             :      * relation, particularly when doing so requires WAL flushes. Zeroing out
    2629             :      * the buffers is also quite expensive, so do that before holding the
    2630             :      * extension lock as well.
    2631             :      *
    2632             :      * These pages are pinned by us and not valid. While we hold the pin they
    2633             :      * can't be acquired as victim buffers by another backend.
    2634             :      */
    2635      856926 :     for (uint32 i = 0; i < extend_by; i++)
    2636             :     {
    2637             :         Block       buf_block;
    2638             : 
    2639      454416 :         buffers[i] = GetVictimBuffer(strategy, io_context);
    2640      454416 :         buf_block = BufHdrGetBlock(GetBufferDescriptor(buffers[i] - 1));
    2641             : 
    2642             :         /* new buffers are zero-filled */
    2643      454416 :         MemSet(buf_block, 0, BLCKSZ);
    2644             :     }
    2645             : 
    2646             :     /*
    2647             :      * Lock relation against concurrent extensions, unless requested not to.
    2648             :      *
    2649             :      * We use the same extension lock for all forks. That's unnecessarily
    2650             :      * restrictive, but currently extensions for forks don't happen often
    2651             :      * enough to make it worth locking more granularly.
    2652             :      *
    2653             :      * Note that another backend might have extended the relation by the time
    2654             :      * we get the lock.
    2655             :      */
    2656      402510 :     if (!(flags & EB_SKIP_EXTENSION_LOCK))
    2657      299824 :         LockRelationForExtension(bmr.rel, ExclusiveLock);
    2658             : 
    2659             :     /*
    2660             :      * If requested, invalidate size cache, so that smgrnblocks asks the
    2661             :      * kernel.
    2662             :      */
    2663      402510 :     if (flags & EB_CLEAR_SIZE_CACHE)
    2664       15096 :         bmr.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
    2665             : 
    2666      402510 :     first_block = smgrnblocks(bmr.smgr, fork);
    2667             : 
    2668             :     /*
    2669             :      * Now that we have the accurate relation size, check if the caller wants
    2670             :      * us to extend to only up to a specific size. If there were concurrent
    2671             :      * extensions, we might have acquired too many buffers and need to release
    2672             :      * them.
    2673             :      */
    2674      402510 :     if (extend_upto != InvalidBlockNumber)
    2675             :     {
    2676      105134 :         uint32      orig_extend_by = extend_by;
    2677             : 
    2678      105134 :         if (first_block > extend_upto)
    2679           0 :             extend_by = 0;
    2680      105134 :         else if ((uint64) first_block + extend_by > extend_upto)
    2681           6 :             extend_by = extend_upto - first_block;
    2682             : 
    2683      105148 :         for (uint32 i = extend_by; i < orig_extend_by; i++)
    2684             :         {
    2685          14 :             BufferDesc *buf_hdr = GetBufferDescriptor(buffers[i] - 1);
    2686             : 
    2687             :             /*
    2688             :              * The victim buffer we acquired previously is clean and unused,
    2689             :              * let it be found again quickly
    2690             :              */
    2691          14 :             StrategyFreeBuffer(buf_hdr);
    2692          14 :             UnpinBuffer(buf_hdr);
    2693             :         }
    2694             : 
    2695      105134 :         if (extend_by == 0)
    2696             :         {
    2697           6 :             if (!(flags & EB_SKIP_EXTENSION_LOCK))
    2698           6 :                 UnlockRelationForExtension(bmr.rel, ExclusiveLock);
    2699           6 :             *extended_by = extend_by;
    2700           6 :             return first_block;
    2701             :         }
    2702             :     }
    2703             : 
    2704             :     /* Fail if relation is already at maximum possible length */
    2705      402504 :     if ((uint64) first_block + extend_by >= MaxBlockNumber)
    2706           0 :         ereport(ERROR,
    2707             :                 (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
    2708             :                  errmsg("cannot extend relation %s beyond %u blocks",
    2709             :                         relpath(bmr.smgr->smgr_rlocator, fork).str,
    2710             :                         MaxBlockNumber)));
    2711             : 
    2712             :     /*
    2713             :      * Insert buffers into buffer table, mark as IO_IN_PROGRESS.
    2714             :      *
    2715             :      * This needs to happen before we extend the relation, because as soon as
    2716             :      * we do, other backends can start to read in those pages.
    2717             :      */
    2718      856906 :     for (uint32 i = 0; i < extend_by; i++)
    2719             :     {
    2720      454402 :         Buffer      victim_buf = buffers[i];
    2721      454402 :         BufferDesc *victim_buf_hdr = GetBufferDescriptor(victim_buf - 1);
    2722             :         BufferTag   tag;
    2723             :         uint32      hash;
    2724             :         LWLock     *partition_lock;
    2725             :         int         existing_id;
    2726             : 
    2727             :         /* in case we need to pin an existing buffer below */
    2728      454402 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    2729      454402 :         ReservePrivateRefCountEntry();
    2730             : 
    2731      454402 :         InitBufferTag(&tag, &bmr.smgr->smgr_rlocator.locator, fork, first_block + i);
    2732      454402 :         hash = BufTableHashCode(&tag);
    2733      454402 :         partition_lock = BufMappingPartitionLock(hash);
    2734             : 
    2735      454402 :         LWLockAcquire(partition_lock, LW_EXCLUSIVE);
    2736             : 
    2737      454402 :         existing_id = BufTableInsert(&tag, hash, victim_buf_hdr->buf_id);
    2738             : 
    2739             :         /*
    2740             :          * We get here only in the corner case where we are trying to extend
    2741             :          * the relation but we found a pre-existing buffer. This can happen
    2742             :          * because a prior attempt at extending the relation failed, and
    2743             :          * because mdread doesn't complain about reads beyond EOF (when
    2744             :          * zero_damaged_pages is ON) and so a previous attempt to read a block
    2745             :          * beyond EOF could have left a "valid" zero-filled buffer.
    2746             :          * Unfortunately, we have also seen this case occurring because of
    2747             :          * buggy Linux kernels that sometimes return an lseek(SEEK_END) result
    2748             :          * that doesn't account for a recent write. In that situation, the
    2749             :          * pre-existing buffer would contain valid data that we don't want to
    2750             :          * overwrite.  Since the legitimate cases should always have left a
    2751             :          * zero-filled buffer, complain if not PageIsNew.
    2752             :          */
    2753      454402 :         if (existing_id >= 0)
    2754             :         {
    2755           0 :             BufferDesc *existing_hdr = GetBufferDescriptor(existing_id);
    2756             :             Block       buf_block;
    2757             :             bool        valid;
    2758             : 
    2759             :             /*
    2760             :              * Pin the existing buffer before releasing the partition lock,
    2761             :              * preventing it from being evicted.
    2762             :              */
    2763           0 :             valid = PinBuffer(existing_hdr, strategy);
    2764             : 
    2765           0 :             LWLockRelease(partition_lock);
    2766             : 
    2767             :             /*
    2768             :              * The victim buffer we acquired previously is clean and unused,
    2769             :              * let it be found again quickly
    2770             :              */
    2771           0 :             StrategyFreeBuffer(victim_buf_hdr);
    2772           0 :             UnpinBuffer(victim_buf_hdr);
    2773             : 
    2774           0 :             buffers[i] = BufferDescriptorGetBuffer(existing_hdr);
    2775           0 :             buf_block = BufHdrGetBlock(existing_hdr);
    2776             : 
    2777           0 :             if (valid && !PageIsNew((Page) buf_block))
    2778           0 :                 ereport(ERROR,
    2779             :                         (errmsg("unexpected data beyond EOF in block %u of relation %s",
    2780             :                                 existing_hdr->tag.blockNum,
    2781             :                                 relpath(bmr.smgr->smgr_rlocator, fork).str),
    2782             :                          errhint("This has been seen to occur with buggy kernels; consider updating your system.")));
    2783             : 
    2784             :             /*
    2785             :              * We *must* do smgr[zero]extend before succeeding, else the page
    2786             :              * will not be reserved by the kernel, and the next P_NEW call
    2787             :              * will decide to return the same page.  Clear the BM_VALID bit,
    2788             :              * do StartBufferIO() and proceed.
    2789             :              *
    2790             :              * Loop to handle the very small possibility that someone re-sets
    2791             :              * BM_VALID between our clearing it and StartBufferIO inspecting
    2792             :              * it.
    2793             :              */
    2794             :             do
    2795             :             {
    2796           0 :                 uint32      buf_state = LockBufHdr(existing_hdr);
    2797             : 
    2798           0 :                 buf_state &= ~BM_VALID;
    2799           0 :                 UnlockBufHdr(existing_hdr, buf_state);
    2800           0 :             } while (!StartBufferIO(existing_hdr, true, false));
    2801             :         }
    2802             :         else
    2803             :         {
    2804             :             uint32      buf_state;
    2805             : 
    2806      454402 :             buf_state = LockBufHdr(victim_buf_hdr);
    2807             : 
    2808             :             /* some sanity checks while we hold the buffer header lock */
    2809             :             Assert(!(buf_state & (BM_VALID | BM_TAG_VALID | BM_DIRTY | BM_JUST_DIRTIED)));
    2810             :             Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
    2811             : 
    2812      454402 :             victim_buf_hdr->tag = tag;
    2813             : 
    2814      454402 :             buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
    2815      454402 :             if (bmr.relpersistence == RELPERSISTENCE_PERMANENT || fork == INIT_FORKNUM)
    2816      443832 :                 buf_state |= BM_PERMANENT;
    2817             : 
    2818      454402 :             UnlockBufHdr(victim_buf_hdr, buf_state);
    2819             : 
    2820      454402 :             LWLockRelease(partition_lock);
    2821             : 
    2822             :             /* XXX: could combine the locked operations in it with the above */
    2823      454402 :             StartBufferIO(victim_buf_hdr, true, false);
    2824             :         }
    2825             :     }
    2826             : 
    2827      402504 :     io_start = pgstat_prepare_io_time(track_io_timing);
    2828             : 
    2829             :     /*
    2830             :      * Note: if smgrzeroextend fails, we will end up with buffers that are
    2831             :      * allocated but not marked BM_VALID.  The next relation extension will
    2832             :      * still select the same block number (because the relation didn't get any
    2833             :      * longer on disk) and so future attempts to extend the relation will find
    2834             :      * the same buffers (if they have not been recycled) but come right back
    2835             :      * here to try smgrzeroextend again.
    2836             :      *
    2837             :      * We don't need to set checksum for all-zero pages.
    2838             :      */
    2839      402504 :     smgrzeroextend(bmr.smgr, fork, first_block, extend_by, false);
    2840             : 
    2841             :     /*
    2842             :      * Release the file-extension lock; it's now OK for someone else to extend
    2843             :      * the relation some more.
    2844             :      *
    2845             :      * We remove IO_IN_PROGRESS after this, as waking up waiting backends can
    2846             :      * take noticeable time.
    2847             :      */
    2848      402504 :     if (!(flags & EB_SKIP_EXTENSION_LOCK))
    2849      299818 :         UnlockRelationForExtension(bmr.rel, ExclusiveLock);
    2850             : 
    2851      402504 :     pgstat_count_io_op_time(IOOBJECT_RELATION, io_context, IOOP_EXTEND,
    2852      402504 :                             io_start, 1, extend_by * BLCKSZ);
    2853             : 
    2854             :     /* Set BM_VALID, terminate IO, and wake up any waiters */
    2855      856906 :     for (uint32 i = 0; i < extend_by; i++)
    2856             :     {
    2857      454402 :         Buffer      buf = buffers[i];
    2858      454402 :         BufferDesc *buf_hdr = GetBufferDescriptor(buf - 1);
    2859      454402 :         bool        lock = false;
    2860             : 
    2861      454402 :         if (flags & EB_LOCK_FIRST && i == 0)
    2862      296790 :             lock = true;
    2863      157612 :         else if (flags & EB_LOCK_TARGET)
    2864             :         {
    2865             :             Assert(extend_upto != InvalidBlockNumber);
    2866       87926 :             if (first_block + i + 1 == extend_upto)
    2867       86814 :                 lock = true;
    2868             :         }
    2869             : 
    2870      454402 :         if (lock)
    2871      383604 :             LWLockAcquire(BufferDescriptorGetContentLock(buf_hdr), LW_EXCLUSIVE);
    2872             : 
    2873      454402 :         TerminateBufferIO(buf_hdr, false, BM_VALID, true, false);
    2874             :     }
    2875             : 
    2876      402504 :     pgBufferUsage.shared_blks_written += extend_by;
    2877             : 
    2878      402504 :     *extended_by = extend_by;
    2879             : 
    2880      402504 :     return first_block;
    2881             : }
    2882             : 
    2883             : /*
    2884             :  * BufferIsExclusiveLocked
    2885             :  *
    2886             :  *      Checks if buffer is exclusive-locked.
    2887             :  *
    2888             :  * Buffer must be pinned.
    2889             :  */
    2890             : bool
    2891           0 : BufferIsExclusiveLocked(Buffer buffer)
    2892             : {
    2893             :     BufferDesc *bufHdr;
    2894             : 
    2895             :     Assert(BufferIsPinned(buffer));
    2896             : 
    2897           0 :     if (BufferIsLocal(buffer))
    2898             :     {
    2899             :         /* Content locks are not maintained for local buffers. */
    2900           0 :         return true;
    2901             :     }
    2902             :     else
    2903             :     {
    2904           0 :         bufHdr = GetBufferDescriptor(buffer - 1);
    2905           0 :         return LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    2906             :                                     LW_EXCLUSIVE);
    2907             :     }
    2908             : }
    2909             : 
    2910             : /*
    2911             :  * BufferIsDirty
    2912             :  *
    2913             :  *      Checks if buffer is already dirty.
    2914             :  *
    2915             :  * Buffer must be pinned and exclusive-locked.  (Without an exclusive lock,
    2916             :  * the result may be stale before it's returned.)
    2917             :  */
    2918             : bool
    2919           0 : BufferIsDirty(Buffer buffer)
    2920             : {
    2921             :     BufferDesc *bufHdr;
    2922             : 
    2923             :     Assert(BufferIsPinned(buffer));
    2924             : 
    2925           0 :     if (BufferIsLocal(buffer))
    2926             :     {
    2927           0 :         int         bufid = -buffer - 1;
    2928             : 
    2929           0 :         bufHdr = GetLocalBufferDescriptor(bufid);
    2930             :         /* Content locks are not maintained for local buffers. */
    2931             :     }
    2932             :     else
    2933             :     {
    2934           0 :         bufHdr = GetBufferDescriptor(buffer - 1);
    2935             :         Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    2936             :                                     LW_EXCLUSIVE));
    2937             :     }
    2938             : 
    2939           0 :     return pg_atomic_read_u32(&bufHdr->state) & BM_DIRTY;
    2940             : }
    2941             : 
    2942             : /*
    2943             :  * MarkBufferDirty
    2944             :  *
    2945             :  *      Marks buffer contents as dirty (actual write happens later).
    2946             :  *
    2947             :  * Buffer must be pinned and exclusive-locked.  (If caller does not hold
    2948             :  * exclusive lock, then somebody could be in process of writing the buffer,
    2949             :  * leading to risk of bad data written to disk.)
    2950             :  */
    2951             : void
    2952    43081882 : MarkBufferDirty(Buffer buffer)
    2953             : {
    2954             :     BufferDesc *bufHdr;
    2955             :     uint32      buf_state;
    2956             :     uint32      old_buf_state;
    2957             : 
    2958    43081882 :     if (!BufferIsValid(buffer))
    2959           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    2960             : 
    2961    43081882 :     if (BufferIsLocal(buffer))
    2962             :     {
    2963     2433224 :         MarkLocalBufferDirty(buffer);
    2964     2433224 :         return;
    2965             :     }
    2966             : 
    2967    40648658 :     bufHdr = GetBufferDescriptor(buffer - 1);
    2968             : 
    2969             :     Assert(BufferIsPinned(buffer));
    2970             :     Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    2971             :                                 LW_EXCLUSIVE));
    2972             : 
    2973    40648658 :     old_buf_state = pg_atomic_read_u32(&bufHdr->state);
    2974             :     for (;;)
    2975             :     {
    2976    40649054 :         if (old_buf_state & BM_LOCKED)
    2977          50 :             old_buf_state = WaitBufHdrUnlocked(bufHdr);
    2978             : 
    2979    40649054 :         buf_state = old_buf_state;
    2980             : 
    2981             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2982    40649054 :         buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
    2983             : 
    2984    40649054 :         if (pg_atomic_compare_exchange_u32(&bufHdr->state, &old_buf_state,
    2985             :                                            buf_state))
    2986    40648658 :             break;
    2987             :     }
    2988             : 
    2989             :     /*
    2990             :      * If the buffer was not dirty already, do vacuum accounting.
    2991             :      */
    2992    40648658 :     if (!(old_buf_state & BM_DIRTY))
    2993             :     {
    2994     1243192 :         pgBufferUsage.shared_blks_dirtied++;
    2995     1243192 :         if (VacuumCostActive)
    2996        2828 :             VacuumCostBalance += VacuumCostPageDirty;
    2997             :     }
    2998             : }
    2999             : 
    3000             : /*
    3001             :  * ReleaseAndReadBuffer -- combine ReleaseBuffer() and ReadBuffer()
    3002             :  *
    3003             :  * Formerly, this saved one cycle of acquiring/releasing the BufMgrLock
    3004             :  * compared to calling the two routines separately.  Now it's mainly just
    3005             :  * a convenience function.  However, if the passed buffer is valid and
    3006             :  * already contains the desired block, we just return it as-is; and that
    3007             :  * does save considerable work compared to a full release and reacquire.
    3008             :  *
    3009             :  * Note: it is OK to pass buffer == InvalidBuffer, indicating that no old
    3010             :  * buffer actually needs to be released.  This case is the same as ReadBuffer,
    3011             :  * but can save some tests in the caller.
    3012             :  */
    3013             : Buffer
    3014    55897256 : ReleaseAndReadBuffer(Buffer buffer,
    3015             :                      Relation relation,
    3016             :                      BlockNumber blockNum)
    3017             : {
    3018    55897256 :     ForkNumber  forkNum = MAIN_FORKNUM;
    3019             :     BufferDesc *bufHdr;
    3020             : 
    3021    55897256 :     if (BufferIsValid(buffer))
    3022             :     {
    3023             :         Assert(BufferIsPinned(buffer));
    3024    33636322 :         if (BufferIsLocal(buffer))
    3025             :         {
    3026       73722 :             bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    3027       80772 :             if (bufHdr->tag.blockNum == blockNum &&
    3028       14100 :                 BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
    3029        7050 :                 BufTagGetForkNum(&bufHdr->tag) == forkNum)
    3030        7050 :                 return buffer;
    3031       66672 :             UnpinLocalBuffer(buffer);
    3032             :         }
    3033             :         else
    3034             :         {
    3035    33562600 :             bufHdr = GetBufferDescriptor(buffer - 1);
    3036             :             /* we have pin, so it's ok to examine tag without spinlock */
    3037    45210776 :             if (bufHdr->tag.blockNum == blockNum &&
    3038    23296352 :                 BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
    3039    11648176 :                 BufTagGetForkNum(&bufHdr->tag) == forkNum)
    3040    11648176 :                 return buffer;
    3041    21914424 :             UnpinBuffer(bufHdr);
    3042             :         }
    3043             :     }
    3044             : 
    3045    44242030 :     return ReadBuffer(relation, blockNum);
    3046             : }
    3047             : 
    3048             : /*
    3049             :  * PinBuffer -- make buffer unavailable for replacement.
    3050             :  *
    3051             :  * For the default access strategy, the buffer's usage_count is incremented
    3052             :  * when we first pin it; for other strategies we just make sure the usage_count
    3053             :  * isn't zero.  (The idea of the latter is that we don't want synchronized
    3054             :  * heap scans to inflate the count, but we need it to not be zero to discourage
    3055             :  * other backends from stealing buffers from our ring.  As long as we cycle
    3056             :  * through the ring faster than the global clock-sweep cycles, buffers in
    3057             :  * our ring won't be chosen as victims for replacement by other backends.)
    3058             :  *
    3059             :  * This should be applied only to shared buffers, never local ones.
    3060             :  *
    3061             :  * Since buffers are pinned/unpinned very frequently, pin buffers without
    3062             :  * taking the buffer header lock; instead update the state variable in loop of
    3063             :  * CAS operations. Hopefully it's just a single CAS.
    3064             :  *
    3065             :  * Note that ResourceOwnerEnlarge() and ReservePrivateRefCountEntry()
    3066             :  * must have been done already.
    3067             :  *
    3068             :  * Returns true if buffer is BM_VALID, else false.  This provision allows
    3069             :  * some callers to avoid an extra spinlock cycle.
    3070             :  */
    3071             : static bool
    3072   114582822 : PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
    3073             : {
    3074   114582822 :     Buffer      b = BufferDescriptorGetBuffer(buf);
    3075             :     bool        result;
    3076             :     PrivateRefCountEntry *ref;
    3077             : 
    3078             :     Assert(!BufferIsLocal(b));
    3079             :     Assert(ReservedRefCountEntry != NULL);
    3080             : 
    3081   114582822 :     ref = GetPrivateRefCountEntry(b, true);
    3082             : 
    3083   114582822 :     if (ref == NULL)
    3084             :     {
    3085             :         uint32      buf_state;
    3086             :         uint32      old_buf_state;
    3087             : 
    3088   110285166 :         ref = NewPrivateRefCountEntry(b);
    3089             : 
    3090   110285166 :         old_buf_state = pg_atomic_read_u32(&buf->state);
    3091             :         for (;;)
    3092             :         {
    3093   110320724 :             if (old_buf_state & BM_LOCKED)
    3094        2994 :                 old_buf_state = WaitBufHdrUnlocked(buf);
    3095             : 
    3096   110320724 :             buf_state = old_buf_state;
    3097             : 
    3098             :             /* increase refcount */
    3099   110320724 :             buf_state += BUF_REFCOUNT_ONE;
    3100             : 
    3101   110320724 :             if (strategy == NULL)
    3102             :             {
    3103             :                 /* Default case: increase usagecount unless already max. */
    3104   108968554 :                 if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
    3105     6288804 :                     buf_state += BUF_USAGECOUNT_ONE;
    3106             :             }
    3107             :             else
    3108             :             {
    3109             :                 /*
    3110             :                  * Ring buffers shouldn't evict others from pool.  Thus we
    3111             :                  * don't make usagecount more than 1.
    3112             :                  */
    3113     1352170 :                 if (BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
    3114       76964 :                     buf_state += BUF_USAGECOUNT_ONE;
    3115             :             }
    3116             : 
    3117   110320724 :             if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
    3118             :                                                buf_state))
    3119             :             {
    3120   110285166 :                 result = (buf_state & BM_VALID) != 0;
    3121             : 
    3122             :                 /*
    3123             :                  * Assume that we acquired a buffer pin for the purposes of
    3124             :                  * Valgrind buffer client checks (even in !result case) to
    3125             :                  * keep things simple.  Buffers that are unsafe to access are
    3126             :                  * not generally guaranteed to be marked undefined or
    3127             :                  * non-accessible in any case.
    3128             :                  */
    3129             :                 VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
    3130   110285166 :                 break;
    3131             :             }
    3132             :         }
    3133             :     }
    3134             :     else
    3135             :     {
    3136             :         /*
    3137             :          * If we previously pinned the buffer, it is likely to be valid, but
    3138             :          * it may not be if StartReadBuffers() was called and
    3139             :          * WaitReadBuffers() hasn't been called yet.  We'll check by loading
    3140             :          * the flags without locking.  This is racy, but it's OK to return
    3141             :          * false spuriously: when WaitReadBuffers() calls StartBufferIO(),
    3142             :          * it'll see that it's now valid.
    3143             :          *
    3144             :          * Note: We deliberately avoid a Valgrind client request here.
    3145             :          * Individual access methods can optionally superimpose buffer page
    3146             :          * client requests on top of our client requests to enforce that
    3147             :          * buffers are only accessed while locked (and pinned).  It's possible
    3148             :          * that the buffer page is legitimately non-accessible here.  We
    3149             :          * cannot meddle with that.
    3150             :          */
    3151     4297656 :         result = (pg_atomic_read_u32(&buf->state) & BM_VALID) != 0;
    3152             :     }
    3153             : 
    3154   114582822 :     ref->refcount++;
    3155             :     Assert(ref->refcount > 0);
    3156   114582822 :     ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
    3157   114582822 :     return result;
    3158             : }
    3159             : 
    3160             : /*
    3161             :  * PinBuffer_Locked -- as above, but caller already locked the buffer header.
    3162             :  * The spinlock is released before return.
    3163             :  *
    3164             :  * As this function is called with the spinlock held, the caller has to
    3165             :  * previously call ReservePrivateRefCountEntry() and
    3166             :  * ResourceOwnerEnlarge(CurrentResourceOwner);
    3167             :  *
    3168             :  * Currently, no callers of this function want to modify the buffer's
    3169             :  * usage_count at all, so there's no need for a strategy parameter.
    3170             :  * Also we don't bother with a BM_VALID test (the caller could check that for
    3171             :  * itself).
    3172             :  *
    3173             :  * Also all callers only ever use this function when it's known that the
    3174             :  * buffer can't have a preexisting pin by this backend. That allows us to skip
    3175             :  * searching the private refcount array & hash, which is a boon, because the
    3176             :  * spinlock is still held.
    3177             :  *
    3178             :  * Note: use of this routine is frequently mandatory, not just an optimization
    3179             :  * to save a spin lock/unlock cycle, because we need to pin a buffer before
    3180             :  * its state can change under us.
    3181             :  */
    3182             : static void
    3183     4405562 : PinBuffer_Locked(BufferDesc *buf)
    3184             : {
    3185             :     Buffer      b;
    3186             :     PrivateRefCountEntry *ref;
    3187             :     uint32      buf_state;
    3188             : 
    3189             :     /*
    3190             :      * As explained, We don't expect any preexisting pins. That allows us to
    3191             :      * manipulate the PrivateRefCount after releasing the spinlock
    3192             :      */
    3193             :     Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
    3194             : 
    3195             :     /*
    3196             :      * Buffer can't have a preexisting pin, so mark its page as defined to
    3197             :      * Valgrind (this is similar to the PinBuffer() case where the backend
    3198             :      * doesn't already have a buffer pin)
    3199             :      */
    3200             :     VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
    3201             : 
    3202             :     /*
    3203             :      * Since we hold the buffer spinlock, we can update the buffer state and
    3204             :      * release the lock in one operation.
    3205             :      */
    3206     4405562 :     buf_state = pg_atomic_read_u32(&buf->state);
    3207             :     Assert(buf_state & BM_LOCKED);
    3208     4405562 :     buf_state += BUF_REFCOUNT_ONE;
    3209     4405562 :     UnlockBufHdr(buf, buf_state);
    3210             : 
    3211     4405562 :     b = BufferDescriptorGetBuffer(buf);
    3212             : 
    3213     4405562 :     ref = NewPrivateRefCountEntry(b);
    3214     4405562 :     ref->refcount++;
    3215             : 
    3216     4405562 :     ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
    3217     4405562 : }
    3218             : 
    3219             : /*
    3220             :  * Support for waking up another backend that is waiting for the cleanup lock
    3221             :  * to be released using BM_PIN_COUNT_WAITER.
    3222             :  *
    3223             :  * See LockBufferForCleanup().
    3224             :  *
    3225             :  * Expected to be called just after releasing a buffer pin (in a BufferDesc,
    3226             :  * not just reducing the backend-local pincount for the buffer).
    3227             :  */
    3228             : static void
    3229           4 : WakePinCountWaiter(BufferDesc *buf)
    3230             : {
    3231             :     /*
    3232             :      * Acquire the buffer header lock, re-check that there's a waiter. Another
    3233             :      * backend could have unpinned this buffer, and already woken up the
    3234             :      * waiter.
    3235             :      *
    3236             :      * There's no danger of the buffer being replaced after we unpinned it
    3237             :      * above, as it's pinned by the waiter. The waiter removes
    3238             :      * BM_PIN_COUNT_WAITER if it stops waiting for a reason other than this
    3239             :      * backend waking it up.
    3240             :      */
    3241           4 :     uint32      buf_state = LockBufHdr(buf);
    3242             : 
    3243           4 :     if ((buf_state & BM_PIN_COUNT_WAITER) &&
    3244           4 :         BUF_STATE_GET_REFCOUNT(buf_state) == 1)
    3245           4 :     {
    3246             :         /* we just released the last pin other than the waiter's */
    3247           4 :         int         wait_backend_pgprocno = buf->wait_backend_pgprocno;
    3248             : 
    3249           4 :         buf_state &= ~BM_PIN_COUNT_WAITER;
    3250           4 :         UnlockBufHdr(buf, buf_state);
    3251           4 :         ProcSendSignal(wait_backend_pgprocno);
    3252             :     }
    3253             :     else
    3254           0 :         UnlockBufHdr(buf, buf_state);
    3255           4 : }
    3256             : 
    3257             : /*
    3258             :  * UnpinBuffer -- make buffer available for replacement.
    3259             :  *
    3260             :  * This should be applied only to shared buffers, never local ones.  This
    3261             :  * always adjusts CurrentResourceOwner.
    3262             :  */
    3263             : static void
    3264   140865862 : UnpinBuffer(BufferDesc *buf)
    3265             : {
    3266   140865862 :     Buffer      b = BufferDescriptorGetBuffer(buf);
    3267             : 
    3268   140865862 :     ResourceOwnerForgetBuffer(CurrentResourceOwner, b);
    3269   140865862 :     UnpinBufferNoOwner(buf);
    3270   140865862 : }
    3271             : 
    3272             : static void
    3273   140874554 : UnpinBufferNoOwner(BufferDesc *buf)
    3274             : {
    3275             :     PrivateRefCountEntry *ref;
    3276   140874554 :     Buffer      b = BufferDescriptorGetBuffer(buf);
    3277             : 
    3278             :     Assert(!BufferIsLocal(b));
    3279             : 
    3280             :     /* not moving as we're likely deleting it soon anyway */
    3281   140874554 :     ref = GetPrivateRefCountEntry(b, false);
    3282             :     Assert(ref != NULL);
    3283             :     Assert(ref->refcount > 0);
    3284   140874554 :     ref->refcount--;
    3285   140874554 :     if (ref->refcount == 0)
    3286             :     {
    3287             :         uint32      buf_state;
    3288             :         uint32      old_buf_state;
    3289             : 
    3290             :         /*
    3291             :          * Mark buffer non-accessible to Valgrind.
    3292             :          *
    3293             :          * Note that the buffer may have already been marked non-accessible
    3294             :          * within access method code that enforces that buffers are only
    3295             :          * accessed while a buffer lock is held.
    3296             :          */
    3297             :         VALGRIND_MAKE_MEM_NOACCESS(BufHdrGetBlock(buf), BLCKSZ);
    3298             : 
    3299             :         /* I'd better not still hold the buffer content lock */
    3300             :         Assert(!LWLockHeldByMe(BufferDescriptorGetContentLock(buf)));
    3301             : 
    3302             :         /*
    3303             :          * Decrement the shared reference count.
    3304             :          *
    3305             :          * Since buffer spinlock holder can update status using just write,
    3306             :          * it's not safe to use atomic decrement here; thus use a CAS loop.
    3307             :          */
    3308   114690728 :         old_buf_state = pg_atomic_read_u32(&buf->state);
    3309             :         for (;;)
    3310             :         {
    3311   114723046 :             if (old_buf_state & BM_LOCKED)
    3312        2756 :                 old_buf_state = WaitBufHdrUnlocked(buf);
    3313             : 
    3314   114723046 :             buf_state = old_buf_state;
    3315             : 
    3316   114723046 :             buf_state -= BUF_REFCOUNT_ONE;
    3317             : 
    3318   114723046 :             if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
    3319             :                                                buf_state))
    3320   114690728 :                 break;
    3321             :         }
    3322             : 
    3323             :         /* Support LockBufferForCleanup() */
    3324   114690728 :         if (buf_state & BM_PIN_COUNT_WAITER)
    3325           4 :             WakePinCountWaiter(buf);
    3326             : 
    3327   114690728 :         ForgetPrivateRefCountEntry(ref);
    3328             :     }
    3329   140874554 : }
    3330             : 
    3331             : #define ST_SORT sort_checkpoint_bufferids
    3332             : #define ST_ELEMENT_TYPE CkptSortItem
    3333             : #define ST_COMPARE(a, b) ckpt_buforder_comparator(a, b)
    3334             : #define ST_SCOPE static
    3335             : #define ST_DEFINE
    3336             : #include "lib/sort_template.h"
    3337             : 
    3338             : /*
    3339             :  * BufferSync -- Write out all dirty buffers in the pool.
    3340             :  *
    3341             :  * This is called at checkpoint time to write out all dirty shared buffers.
    3342             :  * The checkpoint request flags should be passed in.  If CHECKPOINT_IMMEDIATE
    3343             :  * is set, we disable delays between writes; if CHECKPOINT_IS_SHUTDOWN,
    3344             :  * CHECKPOINT_END_OF_RECOVERY or CHECKPOINT_FLUSH_ALL is set, we write even
    3345             :  * unlogged buffers, which are otherwise skipped.  The remaining flags
    3346             :  * currently have no effect here.
    3347             :  */
    3348             : static void
    3349        3318 : BufferSync(int flags)
    3350             : {
    3351             :     uint32      buf_state;
    3352             :     int         buf_id;
    3353             :     int         num_to_scan;
    3354             :     int         num_spaces;
    3355             :     int         num_processed;
    3356             :     int         num_written;
    3357        3318 :     CkptTsStatus *per_ts_stat = NULL;
    3358             :     Oid         last_tsid;
    3359             :     binaryheap *ts_heap;
    3360             :     int         i;
    3361        3318 :     int         mask = BM_DIRTY;
    3362             :     WritebackContext wb_context;
    3363             : 
    3364             :     /*
    3365             :      * Unless this is a shutdown checkpoint or we have been explicitly told,
    3366             :      * we write only permanent, dirty buffers.  But at shutdown or end of
    3367             :      * recovery, we write all dirty buffers.
    3368             :      */
    3369        3318 :     if (!((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY |
    3370             :                     CHECKPOINT_FLUSH_ALL))))
    3371        1912 :         mask |= BM_PERMANENT;
    3372             : 
    3373             :     /*
    3374             :      * Loop over all buffers, and mark the ones that need to be written with
    3375             :      * BM_CHECKPOINT_NEEDED.  Count them as we go (num_to_scan), so that we
    3376             :      * can estimate how much work needs to be done.
    3377             :      *
    3378             :      * This allows us to write only those pages that were dirty when the
    3379             :      * checkpoint began, and not those that get dirtied while it proceeds.
    3380             :      * Whenever a page with BM_CHECKPOINT_NEEDED is written out, either by us
    3381             :      * later in this function, or by normal backends or the bgwriter cleaning
    3382             :      * scan, the flag is cleared.  Any buffer dirtied after this point won't
    3383             :      * have the flag set.
    3384             :      *
    3385             :      * Note that if we fail to write some buffer, we may leave buffers with
    3386             :      * BM_CHECKPOINT_NEEDED still set.  This is OK since any such buffer would
    3387             :      * certainly need to be written for the next checkpoint attempt, too.
    3388             :      */
    3389        3318 :     num_to_scan = 0;
    3390    23413398 :     for (buf_id = 0; buf_id < NBuffers; buf_id++)
    3391             :     {
    3392    23410080 :         BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
    3393             : 
    3394             :         /*
    3395             :          * Header spinlock is enough to examine BM_DIRTY, see comment in
    3396             :          * SyncOneBuffer.
    3397             :          */
    3398    23410080 :         buf_state = LockBufHdr(bufHdr);
    3399             : 
    3400    23410080 :         if ((buf_state & mask) == mask)
    3401             :         {
    3402             :             CkptSortItem *item;
    3403             : 
    3404      567952 :             buf_state |= BM_CHECKPOINT_NEEDED;
    3405             : 
    3406      567952 :             item = &CkptBufferIds[num_to_scan++];
    3407      567952 :             item->buf_id = buf_id;
    3408      567952 :             item->tsId = bufHdr->tag.spcOid;
    3409      567952 :             item->relNumber = BufTagGetRelNumber(&bufHdr->tag);
    3410      567952 :             item->forkNum = BufTagGetForkNum(&bufHdr->tag);
    3411      567952 :             item->blockNum = bufHdr->tag.blockNum;
    3412             :         }
    3413             : 
    3414    23410080 :         UnlockBufHdr(bufHdr, buf_state);
    3415             : 
    3416             :         /* Check for barrier events in case NBuffers is large. */
    3417    23410080 :         if (ProcSignalBarrierPending)
    3418           0 :             ProcessProcSignalBarrier();
    3419             :     }
    3420             : 
    3421        3318 :     if (num_to_scan == 0)
    3422        1268 :         return;                 /* nothing to do */
    3423             : 
    3424        2050 :     WritebackContextInit(&wb_context, &checkpoint_flush_after);
    3425             : 
    3426             :     TRACE_POSTGRESQL_BUFFER_SYNC_START(NBuffers, num_to_scan);
    3427             : 
    3428             :     /*
    3429             :      * Sort buffers that need to be written to reduce the likelihood of random
    3430             :      * IO. The sorting is also important for the implementation of balancing
    3431             :      * writes between tablespaces. Without balancing writes we'd potentially
    3432             :      * end up writing to the tablespaces one-by-one; possibly overloading the
    3433             :      * underlying system.
    3434             :      */
    3435        2050 :     sort_checkpoint_bufferids(CkptBufferIds, num_to_scan);
    3436             : 
    3437        2050 :     num_spaces = 0;
    3438             : 
    3439             :     /*
    3440             :      * Allocate progress status for each tablespace with buffers that need to
    3441             :      * be flushed. This requires the to-be-flushed array to be sorted.
    3442             :      */
    3443        2050 :     last_tsid = InvalidOid;
    3444      570002 :     for (i = 0; i < num_to_scan; i++)
    3445             :     {
    3446             :         CkptTsStatus *s;
    3447             :         Oid         cur_tsid;
    3448             : 
    3449      567952 :         cur_tsid = CkptBufferIds[i].tsId;
    3450             : 
    3451             :         /*
    3452             :          * Grow array of per-tablespace status structs, every time a new
    3453             :          * tablespace is found.
    3454             :          */
    3455      567952 :         if (last_tsid == InvalidOid || last_tsid != cur_tsid)
    3456        3050 :         {
    3457             :             Size        sz;
    3458             : 
    3459        3050 :             num_spaces++;
    3460             : 
    3461             :             /*
    3462             :              * Not worth adding grow-by-power-of-2 logic here - even with a
    3463             :              * few hundred tablespaces this should be fine.
    3464             :              */
    3465        3050 :             sz = sizeof(CkptTsStatus) * num_spaces;
    3466             : 
    3467        3050 :             if (per_ts_stat == NULL)
    3468        2050 :                 per_ts_stat = (CkptTsStatus *) palloc(sz);
    3469             :             else
    3470        1000 :                 per_ts_stat = (CkptTsStatus *) repalloc(per_ts_stat, sz);
    3471             : 
    3472        3050 :             s = &per_ts_stat[num_spaces - 1];
    3473        3050 :             memset(s, 0, sizeof(*s));
    3474        3050 :             s->tsId = cur_tsid;
    3475             : 
    3476             :             /*
    3477             :              * The first buffer in this tablespace. As CkptBufferIds is sorted
    3478             :              * by tablespace all (s->num_to_scan) buffers in this tablespace
    3479             :              * will follow afterwards.
    3480             :              */
    3481        3050 :             s->index = i;
    3482             : 
    3483             :             /*
    3484             :              * progress_slice will be determined once we know how many buffers
    3485             :              * are in each tablespace, i.e. after this loop.
    3486             :              */
    3487             : 
    3488        3050 :             last_tsid = cur_tsid;
    3489             :         }
    3490             :         else
    3491             :         {
    3492      564902 :             s = &per_ts_stat[num_spaces - 1];
    3493             :         }
    3494             : 
    3495      567952 :         s->num_to_scan++;
    3496             : 
    3497             :         /* Check for barrier events. */
    3498      567952 :         if (ProcSignalBarrierPending)
    3499           0 :             ProcessProcSignalBarrier();
    3500             :     }
    3501             : 
    3502             :     Assert(num_spaces > 0);
    3503             : 
    3504             :     /*
    3505             :      * Build a min-heap over the write-progress in the individual tablespaces,
    3506             :      * and compute how large a portion of the total progress a single
    3507             :      * processed buffer is.
    3508             :      */
    3509        2050 :     ts_heap = binaryheap_allocate(num_spaces,
    3510             :                                   ts_ckpt_progress_comparator,
    3511             :                                   NULL);
    3512             : 
    3513        5100 :     for (i = 0; i < num_spaces; i++)
    3514             :     {
    3515        3050 :         CkptTsStatus *ts_stat = &per_ts_stat[i];
    3516             : 
    3517        3050 :         ts_stat->progress_slice = (float8) num_to_scan / ts_stat->num_to_scan;
    3518             : 
    3519        3050 :         binaryheap_add_unordered(ts_heap, PointerGetDatum(ts_stat));
    3520             :     }
    3521             : 
    3522        2050 :     binaryheap_build(ts_heap);
    3523             : 
    3524             :     /*
    3525             :      * Iterate through to-be-checkpointed buffers and write the ones (still)
    3526             :      * marked with BM_CHECKPOINT_NEEDED. The writes are balanced between
    3527             :      * tablespaces; otherwise the sorting would lead to only one tablespace
    3528             :      * receiving writes at a time, making inefficient use of the hardware.
    3529             :      */
    3530        2050 :     num_processed = 0;
    3531        2050 :     num_written = 0;
    3532      570002 :     while (!binaryheap_empty(ts_heap))
    3533             :     {
    3534      567952 :         BufferDesc *bufHdr = NULL;
    3535             :         CkptTsStatus *ts_stat = (CkptTsStatus *)
    3536      567952 :             DatumGetPointer(binaryheap_first(ts_heap));
    3537             : 
    3538      567952 :         buf_id = CkptBufferIds[ts_stat->index].buf_id;
    3539             :         Assert(buf_id != -1);
    3540             : 
    3541      567952 :         bufHdr = GetBufferDescriptor(buf_id);
    3542             : 
    3543      567952 :         num_processed++;
    3544             : 
    3545             :         /*
    3546             :          * We don't need to acquire the lock here, because we're only looking
    3547             :          * at a single bit. It's possible that someone else writes the buffer
    3548             :          * and clears the flag right after we check, but that doesn't matter
    3549             :          * since SyncOneBuffer will then do nothing.  However, there is a
    3550             :          * further race condition: it's conceivable that between the time we
    3551             :          * examine the bit here and the time SyncOneBuffer acquires the lock,
    3552             :          * someone else not only wrote the buffer but replaced it with another
    3553             :          * page and dirtied it.  In that improbable case, SyncOneBuffer will
    3554             :          * write the buffer though we didn't need to.  It doesn't seem worth
    3555             :          * guarding against this, though.
    3556             :          */
    3557      567952 :         if (pg_atomic_read_u32(&bufHdr->state) & BM_CHECKPOINT_NEEDED)
    3558             :         {
    3559      529942 :             if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
    3560             :             {
    3561             :                 TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
    3562      529942 :                 PendingCheckpointerStats.buffers_written++;
    3563      529942 :                 num_written++;
    3564             :             }
    3565             :         }
    3566             : 
    3567             :         /*
    3568             :          * Measure progress independent of actually having to flush the buffer
    3569             :          * - otherwise writing become unbalanced.
    3570             :          */
    3571      567952 :         ts_stat->progress += ts_stat->progress_slice;
    3572      567952 :         ts_stat->num_scanned++;
    3573      567952 :         ts_stat->index++;
    3574             : 
    3575             :         /* Have all the buffers from the tablespace been processed? */
    3576      567952 :         if (ts_stat->num_scanned == ts_stat->num_to_scan)
    3577             :         {
    3578        3050 :             binaryheap_remove_first(ts_heap);
    3579             :         }
    3580             :         else
    3581             :         {
    3582             :             /* update heap with the new progress */
    3583      564902 :             binaryheap_replace_first(ts_heap, PointerGetDatum(ts_stat));
    3584             :         }
    3585             : 
    3586             :         /*
    3587             :          * Sleep to throttle our I/O rate.
    3588             :          *
    3589             :          * (This will check for barrier events even if it doesn't sleep.)
    3590             :          */
    3591      567952 :         CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
    3592             :     }
    3593             : 
    3594             :     /*
    3595             :      * Issue all pending flushes. Only checkpointer calls BufferSync(), so
    3596             :      * IOContext will always be IOCONTEXT_NORMAL.
    3597             :      */
    3598        2050 :     IssuePendingWritebacks(&wb_context, IOCONTEXT_NORMAL);
    3599             : 
    3600        2050 :     pfree(per_ts_stat);
    3601        2050 :     per_ts_stat = NULL;
    3602        2050 :     binaryheap_free(ts_heap);
    3603             : 
    3604             :     /*
    3605             :      * Update checkpoint statistics. As noted above, this doesn't include
    3606             :      * buffers written by other backends or bgwriter scan.
    3607             :      */
    3608        2050 :     CheckpointStats.ckpt_bufs_written += num_written;
    3609             : 
    3610             :     TRACE_POSTGRESQL_BUFFER_SYNC_DONE(NBuffers, num_written, num_to_scan);
    3611             : }
    3612             : 
    3613             : /*
    3614             :  * BgBufferSync -- Write out some dirty buffers in the pool.
    3615             :  *
    3616             :  * This is called periodically by the background writer process.
    3617             :  *
    3618             :  * Returns true if it's appropriate for the bgwriter process to go into
    3619             :  * low-power hibernation mode.  (This happens if the strategy clock sweep
    3620             :  * has been "lapped" and no buffer allocations have occurred recently,
    3621             :  * or if the bgwriter has been effectively disabled by setting
    3622             :  * bgwriter_lru_maxpages to 0.)
    3623             :  */
    3624             : bool
    3625       19596 : BgBufferSync(WritebackContext *wb_context)
    3626             : {
    3627             :     /* info obtained from freelist.c */
    3628             :     int         strategy_buf_id;
    3629             :     uint32      strategy_passes;
    3630             :     uint32      recent_alloc;
    3631             : 
    3632             :     /*
    3633             :      * Information saved between calls so we can determine the strategy
    3634             :      * point's advance rate and avoid scanning already-cleaned buffers.
    3635             :      */
    3636             :     static bool saved_info_valid = false;
    3637             :     static int  prev_strategy_buf_id;
    3638             :     static uint32 prev_strategy_passes;
    3639             :     static int  next_to_clean;
    3640             :     static uint32 next_passes;
    3641             : 
    3642             :     /* Moving averages of allocation rate and clean-buffer density */
    3643             :     static float smoothed_alloc = 0;
    3644             :     static float smoothed_density = 10.0;
    3645             : 
    3646             :     /* Potentially these could be tunables, but for now, not */
    3647       19596 :     float       smoothing_samples = 16;
    3648       19596 :     float       scan_whole_pool_milliseconds = 120000.0;
    3649             : 
    3650             :     /* Used to compute how far we scan ahead */
    3651             :     long        strategy_delta;
    3652             :     int         bufs_to_lap;
    3653             :     int         bufs_ahead;
    3654             :     float       scans_per_alloc;
    3655             :     int         reusable_buffers_est;
    3656             :     int         upcoming_alloc_est;
    3657             :     int         min_scan_buffers;
    3658             : 
    3659             :     /* Variables for the scanning loop proper */
    3660             :     int         num_to_scan;
    3661             :     int         num_written;
    3662             :     int         reusable_buffers;
    3663             : 
    3664             :     /* Variables for final smoothed_density update */
    3665             :     long        new_strategy_delta;
    3666             :     uint32      new_recent_alloc;
    3667             : 
    3668             :     /*
    3669             :      * Find out where the freelist clock sweep currently is, and how many
    3670             :      * buffer allocations have happened since our last call.
    3671             :      */
    3672       19596 :     strategy_buf_id = StrategySyncStart(&strategy_passes, &recent_alloc);
    3673             : 
    3674             :     /* Report buffer alloc counts to pgstat */
    3675       19596 :     PendingBgWriterStats.buf_alloc += recent_alloc;
    3676             : 
    3677             :     /*
    3678             :      * If we're not running the LRU scan, just stop after doing the stats
    3679             :      * stuff.  We mark the saved state invalid so that we can recover sanely
    3680             :      * if LRU scan is turned back on later.
    3681             :      */
    3682       19596 :     if (bgwriter_lru_maxpages <= 0)
    3683             :     {
    3684          38 :         saved_info_valid = false;
    3685          38 :         return true;
    3686             :     }
    3687             : 
    3688             :     /*
    3689             :      * Compute strategy_delta = how many buffers have been scanned by the
    3690             :      * clock sweep since last time.  If first time through, assume none. Then
    3691             :      * see if we are still ahead of the clock sweep, and if so, how many
    3692             :      * buffers we could scan before we'd catch up with it and "lap" it. Note:
    3693             :      * weird-looking coding of xxx_passes comparisons are to avoid bogus
    3694             :      * behavior when the passes counts wrap around.
    3695             :      */
    3696       19558 :     if (saved_info_valid)
    3697             :     {
    3698       18564 :         int32       passes_delta = strategy_passes - prev_strategy_passes;
    3699             : 
    3700       18564 :         strategy_delta = strategy_buf_id - prev_strategy_buf_id;
    3701       18564 :         strategy_delta += (long) passes_delta * NBuffers;
    3702             : 
    3703             :         Assert(strategy_delta >= 0);
    3704             : 
    3705       18564 :         if ((int32) (next_passes - strategy_passes) > 0)
    3706             :         {
    3707             :             /* we're one pass ahead of the strategy point */
    3708        4044 :             bufs_to_lap = strategy_buf_id - next_to_clean;
    3709             : #ifdef BGW_DEBUG
    3710             :             elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
    3711             :                  next_passes, next_to_clean,
    3712             :                  strategy_passes, strategy_buf_id,
    3713             :                  strategy_delta, bufs_to_lap);
    3714             : #endif
    3715             :         }
    3716       14520 :         else if (next_passes == strategy_passes &&
    3717       11292 :                  next_to_clean >= strategy_buf_id)
    3718             :         {
    3719             :             /* on same pass, but ahead or at least not behind */
    3720       11062 :             bufs_to_lap = NBuffers - (next_to_clean - strategy_buf_id);
    3721             : #ifdef BGW_DEBUG
    3722             :             elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
    3723             :                  next_passes, next_to_clean,
    3724             :                  strategy_passes, strategy_buf_id,
    3725             :                  strategy_delta, bufs_to_lap);
    3726             : #endif
    3727             :         }
    3728             :         else
    3729             :         {
    3730             :             /*
    3731             :              * We're behind, so skip forward to the strategy point and start
    3732             :              * cleaning from there.
    3733             :              */
    3734             : #ifdef BGW_DEBUG
    3735             :             elog(DEBUG2, "bgwriter behind: bgw %u-%u strategy %u-%u delta=%ld",
    3736             :                  next_passes, next_to_clean,
    3737             :                  strategy_passes, strategy_buf_id,
    3738             :                  strategy_delta);
    3739             : #endif
    3740        3458 :             next_to_clean = strategy_buf_id;
    3741        3458 :             next_passes = strategy_passes;
    3742        3458 :             bufs_to_lap = NBuffers;
    3743             :         }
    3744             :     }
    3745             :     else
    3746             :     {
    3747             :         /*
    3748             :          * Initializing at startup or after LRU scanning had been off. Always
    3749             :          * start at the strategy point.
    3750             :          */
    3751             : #ifdef BGW_DEBUG
    3752             :         elog(DEBUG2, "bgwriter initializing: strategy %u-%u",
    3753             :              strategy_passes, strategy_buf_id);
    3754             : #endif
    3755         994 :         strategy_delta = 0;
    3756         994 :         next_to_clean = strategy_buf_id;
    3757         994 :         next_passes = strategy_passes;
    3758         994 :         bufs_to_lap = NBuffers;
    3759             :     }
    3760             : 
    3761             :     /* Update saved info for next time */
    3762       19558 :     prev_strategy_buf_id = strategy_buf_id;
    3763       19558 :     prev_strategy_passes = strategy_passes;
    3764       19558 :     saved_info_valid = true;
    3765             : 
    3766             :     /*
    3767             :      * Compute how many buffers had to be scanned for each new allocation, ie,
    3768             :      * 1/density of reusable buffers, and track a moving average of that.
    3769             :      *
    3770             :      * If the strategy point didn't move, we don't update the density estimate
    3771             :      */
    3772       19558 :     if (strategy_delta > 0 && recent_alloc > 0)
    3773             :     {
    3774        4268 :         scans_per_alloc = (float) strategy_delta / (float) recent_alloc;
    3775        4268 :         smoothed_density += (scans_per_alloc - smoothed_density) /
    3776             :             smoothing_samples;
    3777             :     }
    3778             : 
    3779             :     /*
    3780             :      * Estimate how many reusable buffers there are between the current
    3781             :      * strategy point and where we've scanned ahead to, based on the smoothed
    3782             :      * density estimate.
    3783             :      */
    3784       19558 :     bufs_ahead = NBuffers - bufs_to_lap;
    3785       19558 :     reusable_buffers_est = (float) bufs_ahead / smoothed_density;
    3786             : 
    3787             :     /*
    3788             :      * Track a moving average of recent buffer allocations.  Here, rather than
    3789             :      * a true average we want a fast-attack, slow-decline behavior: we
    3790             :      * immediately follow any increase.
    3791             :      */
    3792       19558 :     if (smoothed_alloc <= (float) recent_alloc)
    3793        5660 :         smoothed_alloc = recent_alloc;
    3794             :     else
    3795       13898 :         smoothed_alloc += ((float) recent_alloc - smoothed_alloc) /
    3796             :             smoothing_samples;
    3797             : 
    3798             :     /* Scale the estimate by a GUC to allow more aggressive tuning. */
    3799       19558 :     upcoming_alloc_est = (int) (smoothed_alloc * bgwriter_lru_multiplier);
    3800             : 
    3801             :     /*
    3802             :      * If recent_alloc remains at zero for many cycles, smoothed_alloc will
    3803             :      * eventually underflow to zero, and the underflows produce annoying
    3804             :      * kernel warnings on some platforms.  Once upcoming_alloc_est has gone to
    3805             :      * zero, there's no point in tracking smaller and smaller values of
    3806             :      * smoothed_alloc, so just reset it to exactly zero to avoid this
    3807             :      * syndrome.  It will pop back up as soon as recent_alloc increases.
    3808             :      */
    3809       19558 :     if (upcoming_alloc_est == 0)
    3810        3290 :         smoothed_alloc = 0;
    3811             : 
    3812             :     /*
    3813             :      * Even in cases where there's been little or no buffer allocation
    3814             :      * activity, we want to make a small amount of progress through the buffer
    3815             :      * cache so that as many reusable buffers as possible are clean after an
    3816             :      * idle period.
    3817             :      *
    3818             :      * (scan_whole_pool_milliseconds / BgWriterDelay) computes how many times
    3819             :      * the BGW will be called during the scan_whole_pool time; slice the
    3820             :      * buffer pool into that many sections.
    3821             :      */
    3822       19558 :     min_scan_buffers = (int) (NBuffers / (scan_whole_pool_milliseconds / BgWriterDelay));
    3823             : 
    3824       19558 :     if (upcoming_alloc_est < (min_scan_buffers + reusable_buffers_est))
    3825             :     {
    3826             : #ifdef BGW_DEBUG
    3827             :         elog(DEBUG2, "bgwriter: alloc_est=%d too small, using min=%d + reusable_est=%d",
    3828             :              upcoming_alloc_est, min_scan_buffers, reusable_buffers_est);
    3829             : #endif
    3830       10484 :         upcoming_alloc_est = min_scan_buffers + reusable_buffers_est;
    3831             :     }
    3832             : 
    3833             :     /*
    3834             :      * Now write out dirty reusable buffers, working forward from the
    3835             :      * next_to_clean point, until we have lapped the strategy scan, or cleaned
    3836             :      * enough buffers to match our estimate of the next cycle's allocation
    3837             :      * requirements, or hit the bgwriter_lru_maxpages limit.
    3838             :      */
    3839             : 
    3840       19558 :     num_to_scan = bufs_to_lap;
    3841       19558 :     num_written = 0;
    3842       19558 :     reusable_buffers = reusable_buffers_est;
    3843             : 
    3844             :     /* Execute the LRU scan */
    3845     3361992 :     while (num_to_scan > 0 && reusable_buffers < upcoming_alloc_est)
    3846             :     {
    3847     3342434 :         int         sync_state = SyncOneBuffer(next_to_clean, true,
    3848             :                                                wb_context);
    3849             : 
    3850     3342434 :         if (++next_to_clean >= NBuffers)
    3851             :         {
    3852        3916 :             next_to_clean = 0;
    3853        3916 :             next_passes++;
    3854             :         }
    3855     3342434 :         num_to_scan--;
    3856             : 
    3857     3342434 :         if (sync_state & BUF_WRITTEN)
    3858             :         {
    3859       30652 :             reusable_buffers++;
    3860       30652 :             if (++num_written >= bgwriter_lru_maxpages)
    3861             :             {
    3862           0 :                 PendingBgWriterStats.maxwritten_clean++;
    3863           0 :                 break;
    3864             :             }
    3865             :         }
    3866     3311782 :         else if (sync_state & BUF_REUSABLE)
    3867     2524920 :             reusable_buffers++;
    3868             :     }
    3869             : 
    3870       19558 :     PendingBgWriterStats.buf_written_clean += num_written;
    3871             : 
    3872             : #ifdef BGW_DEBUG
    3873             :     elog(DEBUG1, "bgwriter: recent_alloc=%u smoothed=%.2f delta=%ld ahead=%d density=%.2f reusable_est=%d upcoming_est=%d scanned=%d wrote=%d reusable=%d",
    3874             :          recent_alloc, smoothed_alloc, strategy_delta, bufs_ahead,
    3875             :          smoothed_density, reusable_buffers_est, upcoming_alloc_est,
    3876             :          bufs_to_lap - num_to_scan,
    3877             :          num_written,
    3878             :          reusable_buffers - reusable_buffers_est);
    3879             : #endif
    3880             : 
    3881             :     /*
    3882             :      * Consider the above scan as being like a new allocation scan.
    3883             :      * Characterize its density and update the smoothed one based on it. This
    3884             :      * effectively halves the moving average period in cases where both the
    3885             :      * strategy and the background writer are doing some useful scanning,
    3886             :      * which is helpful because a long memory isn't as desirable on the
    3887             :      * density estimates.
    3888             :      */
    3889       19558 :     new_strategy_delta = bufs_to_lap - num_to_scan;
    3890       19558 :     new_recent_alloc = reusable_buffers - reusable_buffers_est;
    3891       19558 :     if (new_strategy_delta > 0 && new_recent_alloc > 0)
    3892             :     {
    3893       15234 :         scans_per_alloc = (float) new_strategy_delta / (float) new_recent_alloc;
    3894       15234 :         smoothed_density += (scans_per_alloc - smoothed_density) /
    3895             :             smoothing_samples;
    3896             : 
    3897             : #ifdef BGW_DEBUG
    3898             :         elog(DEBUG2, "bgwriter: cleaner density alloc=%u scan=%ld density=%.2f new smoothed=%.2f",
    3899             :              new_recent_alloc, new_strategy_delta,
    3900             :              scans_per_alloc, smoothed_density);
    3901             : #endif
    3902             :     }
    3903             : 
    3904             :     /* Return true if OK to hibernate */
    3905       19558 :     return (bufs_to_lap == 0 && recent_alloc == 0);
    3906             : }
    3907             : 
    3908             : /*
    3909             :  * SyncOneBuffer -- process a single buffer during syncing.
    3910             :  *
    3911             :  * If skip_recently_used is true, we don't write currently-pinned buffers, nor
    3912             :  * buffers marked recently used, as these are not replacement candidates.
    3913             :  *
    3914             :  * Returns a bitmask containing the following flag bits:
    3915             :  *  BUF_WRITTEN: we wrote the buffer.
    3916             :  *  BUF_REUSABLE: buffer is available for replacement, ie, it has
    3917             :  *      pin count 0 and usage count 0.
    3918             :  *
    3919             :  * (BUF_WRITTEN could be set in error if FlushBuffer finds the buffer clean
    3920             :  * after locking it, but we don't care all that much.)
    3921             :  */
    3922             : static int
    3923     3872376 : SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
    3924             : {
    3925     3872376 :     BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
    3926     3872376 :     int         result = 0;
    3927             :     uint32      buf_state;
    3928             :     BufferTag   tag;
    3929             : 
    3930             :     /* Make sure we can handle the pin */
    3931     3872376 :     ReservePrivateRefCountEntry();
    3932     3872376 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    3933             : 
    3934             :     /*
    3935             :      * Check whether buffer needs writing.
    3936             :      *
    3937             :      * We can make this check without taking the buffer content lock so long
    3938             :      * as we mark pages dirty in access methods *before* logging changes with
    3939             :      * XLogInsert(): if someone marks the buffer dirty just after our check we
    3940             :      * don't worry because our checkpoint.redo points before log record for
    3941             :      * upcoming changes and so we are not required to write such dirty buffer.
    3942             :      */
    3943     3872376 :     buf_state = LockBufHdr(bufHdr);
    3944             : 
    3945     3872376 :     if (BUF_STATE_GET_REFCOUNT(buf_state) == 0 &&
    3946     3867034 :         BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
    3947             :     {
    3948     2559564 :         result |= BUF_REUSABLE;
    3949             :     }
    3950     1312812 :     else if (skip_recently_used)
    3951             :     {
    3952             :         /* Caller told us not to write recently-used buffers */
    3953      786862 :         UnlockBufHdr(bufHdr, buf_state);
    3954      786862 :         return result;
    3955             :     }
    3956             : 
    3957     3085514 :     if (!(buf_state & BM_VALID) || !(buf_state & BM_DIRTY))
    3958             :     {
    3959             :         /* It's clean, so nothing to do */
    3960     2524920 :         UnlockBufHdr(bufHdr, buf_state);
    3961     2524920 :         return result;
    3962             :     }
    3963             : 
    3964             :     /*
    3965             :      * Pin it, share-lock it, write it.  (FlushBuffer will do nothing if the
    3966             :      * buffer is clean by the time we've locked it.)
    3967             :      */
    3968      560594 :     PinBuffer_Locked(bufHdr);
    3969      560594 :     LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    3970             : 
    3971      560594 :     FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    3972             : 
    3973      560594 :     LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    3974             : 
    3975      560594 :     tag = bufHdr->tag;
    3976             : 
    3977      560594 :     UnpinBuffer(bufHdr);
    3978             : 
    3979             :     /*
    3980             :      * SyncOneBuffer() is only called by checkpointer and bgwriter, so
    3981             :      * IOContext will always be IOCONTEXT_NORMAL.
    3982             :      */
    3983      560594 :     ScheduleBufferTagForWriteback(wb_context, IOCONTEXT_NORMAL, &tag);
    3984             : 
    3985      560594 :     return result | BUF_WRITTEN;
    3986             : }
    3987             : 
    3988             : /*
    3989             :  *      AtEOXact_Buffers - clean up at end of transaction.
    3990             :  *
    3991             :  *      As of PostgreSQL 8.0, buffer pins should get released by the
    3992             :  *      ResourceOwner mechanism.  This routine is just a debugging
    3993             :  *      cross-check that no pins remain.
    3994             :  */
    3995             : void
    3996      854764 : AtEOXact_Buffers(bool isCommit)
    3997             : {
    3998      854764 :     CheckForBufferLeaks();
    3999             : 
    4000      854764 :     AtEOXact_LocalBuffers(isCommit);
    4001             : 
    4002             :     Assert(PrivateRefCountOverflowed == 0);
    4003      854764 : }
    4004             : 
    4005             : /*
    4006             :  * Initialize access to shared buffer pool
    4007             :  *
    4008             :  * This is called during backend startup (whether standalone or under the
    4009             :  * postmaster).  It sets up for this backend's access to the already-existing
    4010             :  * buffer pool.
    4011             :  */
    4012             : void
    4013       43218 : InitBufferManagerAccess(void)
    4014             : {
    4015             :     HASHCTL     hash_ctl;
    4016             : 
    4017             :     /*
    4018             :      * An advisory limit on the number of pins each backend should hold, based
    4019             :      * on shared_buffers and the maximum number of connections possible.
    4020             :      * That's very pessimistic, but outside toy-sized shared_buffers it should
    4021             :      * allow plenty of pins.  LimitAdditionalPins() and
    4022             :      * GetAdditionalPinLimit() can be used to check the remaining balance.
    4023             :      */
    4024       43218 :     MaxProportionalPins = NBuffers / (MaxBackends + NUM_AUXILIARY_PROCS);
    4025             : 
    4026       43218 :     memset(&PrivateRefCountArray, 0, sizeof(PrivateRefCountArray));
    4027             : 
    4028       43218 :     hash_ctl.keysize = sizeof(int32);
    4029       43218 :     hash_ctl.entrysize = sizeof(PrivateRefCountEntry);
    4030             : 
    4031       43218 :     PrivateRefCountHash = hash_create("PrivateRefCount", 100, &hash_ctl,
    4032             :                                       HASH_ELEM | HASH_BLOBS);
    4033             : 
    4034             :     /*
    4035             :      * AtProcExit_Buffers needs LWLock access, and thereby has to be called at
    4036             :      * the corresponding phase of backend shutdown.
    4037             :      */
    4038             :     Assert(MyProc != NULL);
    4039       43218 :     on_shmem_exit(AtProcExit_Buffers, 0);
    4040       43218 : }
    4041             : 
    4042             : /*
    4043             :  * During backend exit, ensure that we released all shared-buffer locks and
    4044             :  * assert that we have no remaining pins.
    4045             :  */
    4046             : static void
    4047       43218 : AtProcExit_Buffers(int code, Datum arg)
    4048             : {
    4049       43218 :     UnlockBuffers();
    4050             : 
    4051       43218 :     CheckForBufferLeaks();
    4052             : 
    4053             :     /* localbuf.c needs a chance too */
    4054       43218 :     AtProcExit_LocalBuffers();
    4055       43218 : }
    4056             : 
    4057             : /*
    4058             :  *      CheckForBufferLeaks - ensure this backend holds no buffer pins
    4059             :  *
    4060             :  *      As of PostgreSQL 8.0, buffer pins should get released by the
    4061             :  *      ResourceOwner mechanism.  This routine is just a debugging
    4062             :  *      cross-check that no pins remain.
    4063             :  */
    4064             : static void
    4065      897982 : CheckForBufferLeaks(void)
    4066             : {
    4067             : #ifdef USE_ASSERT_CHECKING
    4068             :     int         RefCountErrors = 0;
    4069             :     PrivateRefCountEntry *res;
    4070             :     int         i;
    4071             :     char       *s;
    4072             : 
    4073             :     /* check the array */
    4074             :     for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
    4075             :     {
    4076             :         res = &PrivateRefCountArray[i];
    4077             : 
    4078             :         if (res->buffer != InvalidBuffer)
    4079             :         {
    4080             :             s = DebugPrintBufferRefcount(res->buffer);
    4081             :             elog(WARNING, "buffer refcount leak: %s", s);
    4082             :             pfree(s);
    4083             : 
    4084             :             RefCountErrors++;
    4085             :         }
    4086             :     }
    4087             : 
    4088             :     /* if necessary search the hash */
    4089             :     if (PrivateRefCountOverflowed)
    4090             :     {
    4091             :         HASH_SEQ_STATUS hstat;
    4092             : 
    4093             :         hash_seq_init(&hstat, PrivateRefCountHash);
    4094             :         while ((res = (PrivateRefCountEntry *) hash_seq_search(&hstat)) != NULL)
    4095             :         {
    4096             :             s = DebugPrintBufferRefcount(res->buffer);
    4097             :             elog(WARNING, "buffer refcount leak: %s", s);
    4098             :             pfree(s);
    4099             :             RefCountErrors++;
    4100             :         }
    4101             :     }
    4102             : 
    4103             :     Assert(RefCountErrors == 0);
    4104             : #endif
    4105      897982 : }
    4106             : 
    4107             : #ifdef USE_ASSERT_CHECKING
    4108             : /*
    4109             :  * Check for exclusive-locked catalog buffers.  This is the core of
    4110             :  * AssertCouldGetRelation().
    4111             :  *
    4112             :  * A backend would self-deadlock on LWLocks if the catalog scan read the
    4113             :  * exclusive-locked buffer.  The main threat is exclusive-locked buffers of
    4114             :  * catalogs used in relcache, because a catcache search on any catalog may
    4115             :  * build that catalog's relcache entry.  We don't have an inventory of
    4116             :  * catalogs relcache uses, so just check buffers of most catalogs.
    4117             :  *
    4118             :  * It's better to minimize waits while holding an exclusive buffer lock, so it
    4119             :  * would be nice to broaden this check not to be catalog-specific.  However,
    4120             :  * bttextcmp() accesses pg_collation, and non-core opclasses might similarly
    4121             :  * read tables.  That is deadlock-free as long as there's no loop in the
    4122             :  * dependency graph: modifying table A may cause an opclass to read table B,
    4123             :  * but it must not cause a read of table A.
    4124             :  */
    4125             : void
    4126             : AssertBufferLocksPermitCatalogRead(void)
    4127             : {
    4128             :     ForEachLWLockHeldByMe(AssertNotCatalogBufferLock, NULL);
    4129             : }
    4130             : 
    4131             : static void
    4132             : AssertNotCatalogBufferLock(LWLock *lock, LWLockMode mode,
    4133             :                            void *unused_context)
    4134             : {
    4135             :     BufferDesc *bufHdr;
    4136             :     BufferTag   tag;
    4137             :     Oid         relid;
    4138             : 
    4139             :     if (mode != LW_EXCLUSIVE)
    4140             :         return;
    4141             : 
    4142             :     if (!((BufferDescPadded *) lock > BufferDescriptors &&
    4143             :           (BufferDescPadded *) lock < BufferDescriptors + NBuffers))
    4144             :         return;                 /* not a buffer lock */
    4145             : 
    4146             :     bufHdr = (BufferDesc *)
    4147             :         ((char *) lock - offsetof(BufferDesc, content_lock));
    4148             :     tag = bufHdr->tag;
    4149             : 
    4150             :     /*
    4151             :      * This relNumber==relid assumption holds until a catalog experiences
    4152             :      * VACUUM FULL or similar.  After a command like that, relNumber will be
    4153             :      * in the normal (non-catalog) range, and we lose the ability to detect
    4154             :      * hazardous access to that catalog.  Calling RelidByRelfilenumber() would
    4155             :      * close that gap, but RelidByRelfilenumber() might then deadlock with a
    4156             :      * held lock.
    4157             :      */
    4158             :     relid = tag.relNumber;
    4159             : 
    4160             :     if (IsCatalogTextUniqueIndexOid(relid)) /* see comments at the callee */
    4161             :         return;
    4162             : 
    4163             :     Assert(!IsCatalogRelationOid(relid));
    4164             : }
    4165             : #endif
    4166             : 
    4167             : 
    4168             : /*
    4169             :  * Helper routine to issue warnings when a buffer is unexpectedly pinned
    4170             :  */
    4171             : char *
    4172          80 : DebugPrintBufferRefcount(Buffer buffer)
    4173             : {
    4174             :     BufferDesc *buf;
    4175             :     int32       loccount;
    4176             :     char       *result;
    4177             :     ProcNumber  backend;
    4178             :     uint32      buf_state;
    4179             : 
    4180             :     Assert(BufferIsValid(buffer));
    4181          80 :     if (BufferIsLocal(buffer))
    4182             :     {
    4183          32 :         buf = GetLocalBufferDescriptor(-buffer - 1);
    4184          32 :         loccount = LocalRefCount[-buffer - 1];
    4185          32 :         backend = MyProcNumber;
    4186             :     }
    4187             :     else
    4188             :     {
    4189          48 :         buf = GetBufferDescriptor(buffer - 1);
    4190          48 :         loccount = GetPrivateRefCount(buffer);
    4191          48 :         backend = INVALID_PROC_NUMBER;
    4192             :     }
    4193             : 
    4194             :     /* theoretically we should lock the bufhdr here */
    4195          80 :     buf_state = pg_atomic_read_u32(&buf->state);
    4196             : 
    4197          80 :     result = psprintf("[%03d] (rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",
    4198             :                       buffer,
    4199          80 :                       relpathbackend(BufTagGetRelFileLocator(&buf->tag), backend,
    4200             :                                      BufTagGetForkNum(&buf->tag)).str,
    4201             :                       buf->tag.blockNum, buf_state & BUF_FLAG_MASK,
    4202             :                       BUF_STATE_GET_REFCOUNT(buf_state), loccount);
    4203          80 :     return result;
    4204             : }
    4205             : 
    4206             : /*
    4207             :  * CheckPointBuffers
    4208             :  *
    4209             :  * Flush all dirty blocks in buffer pool to disk at checkpoint time.
    4210             :  *
    4211             :  * Note: temporary relations do not participate in checkpoints, so they don't
    4212             :  * need to be flushed.
    4213             :  */
    4214             : void
    4215        3318 : CheckPointBuffers(int flags)
    4216             : {
    4217        3318 :     BufferSync(flags);
    4218        3318 : }
    4219             : 
    4220             : /*
    4221             :  * BufferGetBlockNumber
    4222             :  *      Returns the block number associated with a buffer.
    4223             :  *
    4224             :  * Note:
    4225             :  *      Assumes that the buffer is valid and pinned, else the
    4226             :  *      value may be obsolete immediately...
    4227             :  */
    4228             : BlockNumber
    4229    98454282 : BufferGetBlockNumber(Buffer buffer)
    4230             : {
    4231             :     BufferDesc *bufHdr;
    4232             : 
    4233             :     Assert(BufferIsPinned(buffer));
    4234             : 
    4235    98454282 :     if (BufferIsLocal(buffer))
    4236     3799068 :         bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    4237             :     else
    4238    94655214 :         bufHdr = GetBufferDescriptor(buffer - 1);
    4239             : 
    4240             :     /* pinned, so OK to read tag without spinlock */
    4241    98454282 :     return bufHdr->tag.blockNum;
    4242             : }
    4243             : 
    4244             : /*
    4245             :  * BufferGetTag
    4246             :  *      Returns the relfilelocator, fork number and block number associated with
    4247             :  *      a buffer.
    4248             :  */
    4249             : void
    4250    29934182 : BufferGetTag(Buffer buffer, RelFileLocator *rlocator, ForkNumber *forknum,
    4251             :              BlockNumber *blknum)
    4252             : {
    4253             :     BufferDesc *bufHdr;
    4254             : 
    4255             :     /* Do the same checks as BufferGetBlockNumber. */
    4256             :     Assert(BufferIsPinned(buffer));
    4257             : 
    4258    29934182 :     if (BufferIsLocal(buffer))
    4259           0 :         bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    4260             :     else
    4261    29934182 :         bufHdr = GetBufferDescriptor(buffer - 1);
    4262             : 
    4263             :     /* pinned, so OK to read tag without spinlock */
    4264    29934182 :     *rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
    4265    29934182 :     *forknum = BufTagGetForkNum(&bufHdr->tag);
    4266    29934182 :     *blknum = bufHdr->tag.blockNum;
    4267    29934182 : }
    4268             : 
    4269             : /*
    4270             :  * FlushBuffer
    4271             :  *      Physically write out a shared buffer.
    4272             :  *
    4273             :  * NOTE: this actually just passes the buffer contents to the kernel; the
    4274             :  * real write to disk won't happen until the kernel feels like it.  This
    4275             :  * is okay from our point of view since we can redo the changes from WAL.
    4276             :  * However, we will need to force the changes to disk via fsync before
    4277             :  * we can checkpoint WAL.
    4278             :  *
    4279             :  * The caller must hold a pin on the buffer and have share-locked the
    4280             :  * buffer contents.  (Note: a share-lock does not prevent updates of
    4281             :  * hint bits in the buffer, so the page could change while the write
    4282             :  * is in progress, but we assume that that will not invalidate the data
    4283             :  * written.)
    4284             :  *
    4285             :  * If the caller has an smgr reference for the buffer's relation, pass it
    4286             :  * as the second parameter.  If not, pass NULL.
    4287             :  */
    4288             : static void
    4289     1043306 : FlushBuffer(BufferDesc *buf, SMgrRelation reln, IOObject io_object,
    4290             :             IOContext io_context)
    4291             : {
    4292             :     XLogRecPtr  recptr;
    4293             :     ErrorContextCallback errcallback;
    4294             :     instr_time  io_start;
    4295             :     Block       bufBlock;
    4296             :     char       *bufToWrite;
    4297             :     uint32      buf_state;
    4298             : 
    4299             :     /*
    4300             :      * Try to start an I/O operation.  If StartBufferIO returns false, then
    4301             :      * someone else flushed the buffer before we could, so we need not do
    4302             :      * anything.
    4303             :      */
    4304     1043306 :     if (!StartBufferIO(buf, false, false))
    4305           8 :         return;
    4306             : 
    4307             :     /* Setup error traceback support for ereport() */
    4308     1043298 :     errcallback.callback = shared_buffer_write_error_callback;
    4309     1043298 :     errcallback.arg = buf;
    4310     1043298 :     errcallback.previous = error_context_stack;
    4311     1043298 :     error_context_stack = &errcallback;
    4312             : 
    4313             :     /* Find smgr relation for buffer */
    4314     1043298 :     if (reln == NULL)
    4315     1032926 :         reln = smgropen(BufTagGetRelFileLocator(&buf->tag), INVALID_PROC_NUMBER);
    4316             : 
    4317             :     TRACE_POSTGRESQL_BUFFER_FLUSH_START(BufTagGetForkNum(&buf->tag),
    4318             :                                         buf->tag.blockNum,
    4319             :                                         reln->smgr_rlocator.locator.spcOid,
    4320             :                                         reln->smgr_rlocator.locator.dbOid,
    4321             :                                         reln->smgr_rlocator.locator.relNumber);
    4322             : 
    4323     1043298 :     buf_state = LockBufHdr(buf);
    4324             : 
    4325             :     /*
    4326             :      * Run PageGetLSN while holding header lock, since we don't have the
    4327             :      * buffer locked exclusively in all cases.
    4328             :      */
    4329     1043298 :     recptr = BufferGetLSN(buf);
    4330             : 
    4331             :     /* To check if block content changes while flushing. - vadim 01/17/97 */
    4332     1043298 :     buf_state &= ~BM_JUST_DIRTIED;
    4333     1043298 :     UnlockBufHdr(buf, buf_state);
    4334             : 
    4335             :     /*
    4336             :      * Force XLOG flush up to buffer's LSN.  This implements the basic WAL
    4337             :      * rule that log updates must hit disk before any of the data-file changes
    4338             :      * they describe do.
    4339             :      *
    4340             :      * However, this rule does not apply to unlogged relations, which will be
    4341             :      * lost after a crash anyway.  Most unlogged relation pages do not bear
    4342             :      * LSNs since we never emit WAL records for them, and therefore flushing
    4343             :      * up through the buffer LSN would be useless, but harmless.  However,
    4344             :      * GiST indexes use LSNs internally to track page-splits, and therefore
    4345             :      * unlogged GiST pages bear "fake" LSNs generated by
    4346             :      * GetFakeLSNForUnloggedRel.  It is unlikely but possible that the fake
    4347             :      * LSN counter could advance past the WAL insertion point; and if it did
    4348             :      * happen, attempting to flush WAL through that location would fail, with
    4349             :      * disastrous system-wide consequences.  To make sure that can't happen,
    4350             :      * skip the flush if the buffer isn't permanent.
    4351             :      */
    4352     1043298 :     if (buf_state & BM_PERMANENT)
    4353     1039736 :         XLogFlush(recptr);
    4354             : 
    4355             :     /*
    4356             :      * Now it's safe to write the buffer to disk. Note that no one else should
    4357             :      * have been able to write it, while we were busy with log flushing,
    4358             :      * because we got the exclusive right to perform I/O by setting the
    4359             :      * BM_IO_IN_PROGRESS bit.
    4360             :      */
    4361     1043298 :     bufBlock = BufHdrGetBlock(buf);
    4362             : 
    4363             :     /*
    4364             :      * Update page checksum if desired.  Since we have only shared lock on the
    4365             :      * buffer, other processes might be updating hint bits in it, so we must
    4366             :      * copy the page to private storage if we do checksumming.
    4367             :      */
    4368     1043298 :     bufToWrite = PageSetChecksumCopy((Page) bufBlock, buf->tag.blockNum);
    4369             : 
    4370     1043298 :     io_start = pgstat_prepare_io_time(track_io_timing);
    4371             : 
    4372             :     /*
    4373             :      * bufToWrite is either the shared buffer or a copy, as appropriate.
    4374             :      */
    4375     1043298 :     smgrwrite(reln,
    4376     1043298 :               BufTagGetForkNum(&buf->tag),
    4377             :               buf->tag.blockNum,
    4378             :               bufToWrite,
    4379             :               false);
    4380             : 
    4381             :     /*
    4382             :      * When a strategy is in use, only flushes of dirty buffers already in the
    4383             :      * strategy ring are counted as strategy writes (IOCONTEXT
    4384             :      * [BULKREAD|BULKWRITE|VACUUM] IOOP_WRITE) for the purpose of IO
    4385             :      * statistics tracking.
    4386             :      *
    4387             :      * If a shared buffer initially added to the ring must be flushed before
    4388             :      * being used, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE.
    4389             :      *
    4390             :      * If a shared buffer which was added to the ring later because the
    4391             :      * current strategy buffer is pinned or in use or because all strategy
    4392             :      * buffers were dirty and rejected (for BAS_BULKREAD operations only)
    4393             :      * requires flushing, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE
    4394             :      * (from_ring will be false).
    4395             :      *
    4396             :      * When a strategy is not in use, the write can only be a "regular" write
    4397             :      * of a dirty shared buffer (IOCONTEXT_NORMAL IOOP_WRITE).
    4398             :      */
    4399     1043298 :     pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
    4400             :                             IOOP_WRITE, io_start, 1, BLCKSZ);
    4401             : 
    4402     1043298 :     pgBufferUsage.shared_blks_written++;
    4403             : 
    4404             :     /*
    4405             :      * Mark the buffer as clean (unless BM_JUST_DIRTIED has become set) and
    4406             :      * end the BM_IO_IN_PROGRESS state.
    4407             :      */
    4408     1043298 :     TerminateBufferIO(buf, true, 0, true, false);
    4409             : 
    4410             :     TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(BufTagGetForkNum(&buf->tag),
    4411             :                                        buf->tag.blockNum,
    4412             :                                        reln->smgr_rlocator.locator.spcOid,
    4413             :                                        reln->smgr_rlocator.locator.dbOid,
    4414             :                                        reln->smgr_rlocator.locator.relNumber);
    4415             : 
    4416             :     /* Pop the error context stack */
    4417     1043298 :     error_context_stack = errcallback.previous;
    4418             : }
    4419             : 
    4420             : /*
    4421             :  * RelationGetNumberOfBlocksInFork
    4422             :  *      Determines the current number of pages in the specified relation fork.
    4423             :  *
    4424             :  * Note that the accuracy of the result will depend on the details of the
    4425             :  * relation's storage. For builtin AMs it'll be accurate, but for external AMs
    4426             :  * it might not be.
    4427             :  */
    4428             : BlockNumber
    4429     3920982 : RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
    4430             : {
    4431     3920982 :     if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind))
    4432             :     {
    4433             :         /*
    4434             :          * Not every table AM uses BLCKSZ wide fixed size blocks. Therefore
    4435             :          * tableam returns the size in bytes - but for the purpose of this
    4436             :          * routine, we want the number of blocks. Therefore divide, rounding
    4437             :          * up.
    4438             :          */
    4439             :         uint64      szbytes;
    4440             : 
    4441     3017530 :         szbytes = table_relation_size(relation, forkNum);
    4442             : 
    4443     3017492 :         return (szbytes + (BLCKSZ - 1)) / BLCKSZ;
    4444             :     }
    4445      903452 :     else if (RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
    4446             :     {
    4447      903452 :         return smgrnblocks(RelationGetSmgr(relation), forkNum);
    4448             :     }
    4449             :     else
    4450             :         Assert(false);
    4451             : 
    4452           0 :     return 0;                   /* keep compiler quiet */
    4453             : }
    4454             : 
    4455             : /*
    4456             :  * BufferIsPermanent
    4457             :  *      Determines whether a buffer will potentially still be around after
    4458             :  *      a crash.  Caller must hold a buffer pin.
    4459             :  */
    4460             : bool
    4461    20204638 : BufferIsPermanent(Buffer buffer)
    4462             : {
    4463             :     BufferDesc *bufHdr;
    4464             : 
    4465             :     /* Local buffers are used only for temp relations. */
    4466    20204638 :     if (BufferIsLocal(buffer))
    4467     1248026 :         return false;
    4468             : 
    4469             :     /* Make sure we've got a real buffer, and that we hold a pin on it. */
    4470             :     Assert(BufferIsValid(buffer));
    4471             :     Assert(BufferIsPinned(buffer));
    4472             : 
    4473             :     /*
    4474             :      * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
    4475             :      * need not bother with the buffer header spinlock.  Even if someone else
    4476             :      * changes the buffer header state while we're doing this, the state is
    4477             :      * changed atomically, so we'll read the old value or the new value, but
    4478             :      * not random garbage.
    4479             :      */
    4480    18956612 :     bufHdr = GetBufferDescriptor(buffer - 1);
    4481    18956612 :     return (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT) != 0;
    4482             : }
    4483             : 
    4484             : /*
    4485             :  * BufferGetLSNAtomic
    4486             :  *      Retrieves the LSN of the buffer atomically using a buffer header lock.
    4487             :  *      This is necessary for some callers who may not have an exclusive lock
    4488             :  *      on the buffer.
    4489             :  */
    4490             : XLogRecPtr
    4491    17688556 : BufferGetLSNAtomic(Buffer buffer)
    4492             : {
    4493    17688556 :     char       *page = BufferGetPage(buffer);
    4494             :     BufferDesc *bufHdr;
    4495             :     XLogRecPtr  lsn;
    4496             :     uint32      buf_state;
    4497             : 
    4498             :     /*
    4499             :      * If we don't need locking for correctness, fastpath out.
    4500             :      */
    4501    17688556 :     if (!XLogHintBitIsNeeded() || BufferIsLocal(buffer))
    4502      569688 :         return PageGetLSN(page);
    4503             : 
    4504             :     /* Make sure we've got a real buffer, and that we hold a pin on it. */
    4505             :     Assert(BufferIsValid(buffer));
    4506             :     Assert(BufferIsPinned(buffer));
    4507             : 
    4508    17118868 :     bufHdr = GetBufferDescriptor(buffer - 1);
    4509    17118868 :     buf_state = LockBufHdr(bufHdr);
    4510    17118868 :     lsn = PageGetLSN(page);
    4511    17118868 :     UnlockBufHdr(bufHdr, buf_state);
    4512             : 
    4513    17118868 :     return lsn;
    4514             : }
    4515             : 
    4516             : /* ---------------------------------------------------------------------
    4517             :  *      DropRelationBuffers
    4518             :  *
    4519             :  *      This function removes from the buffer pool all the pages of the
    4520             :  *      specified relation forks that have block numbers >= firstDelBlock.
    4521             :  *      (In particular, with firstDelBlock = 0, all pages are removed.)
    4522             :  *      Dirty pages are simply dropped, without bothering to write them
    4523             :  *      out first.  Therefore, this is NOT rollback-able, and so should be
    4524             :  *      used only with extreme caution!
    4525             :  *
    4526             :  *      Currently, this is called only from smgr.c when the underlying file
    4527             :  *      is about to be deleted or truncated (firstDelBlock is needed for
    4528             :  *      the truncation case).  The data in the affected pages would therefore
    4529             :  *      be deleted momentarily anyway, and there is no point in writing it.
    4530             :  *      It is the responsibility of higher-level code to ensure that the
    4531             :  *      deletion or truncation does not lose any data that could be needed
    4532             :  *      later.  It is also the responsibility of higher-level code to ensure
    4533             :  *      that no other process could be trying to load more pages of the
    4534             :  *      relation into buffers.
    4535             :  * --------------------------------------------------------------------
    4536             :  */
    4537             : void
    4538        1266 : DropRelationBuffers(SMgrRelation smgr_reln, ForkNumber *forkNum,
    4539             :                     int nforks, BlockNumber *firstDelBlock)
    4540             : {
    4541             :     int         i;
    4542             :     int         j;
    4543             :     RelFileLocatorBackend rlocator;
    4544             :     BlockNumber nForkBlock[MAX_FORKNUM];
    4545        1266 :     uint64      nBlocksToInvalidate = 0;
    4546             : 
    4547        1266 :     rlocator = smgr_reln->smgr_rlocator;
    4548             : 
    4549             :     /* If it's a local relation, it's localbuf.c's problem. */
    4550        1266 :     if (RelFileLocatorBackendIsTemp(rlocator))
    4551             :     {
    4552         748 :         if (rlocator.backend == MyProcNumber)
    4553             :         {
    4554        1542 :             for (j = 0; j < nforks; j++)
    4555         794 :                 DropRelationLocalBuffers(rlocator.locator, forkNum[j],
    4556         794 :                                          firstDelBlock[j]);
    4557             :         }
    4558         832 :         return;
    4559             :     }
    4560             : 
    4561             :     /*
    4562             :      * To remove all the pages of the specified relation forks from the buffer
    4563             :      * pool, we need to scan the entire buffer pool but we can optimize it by
    4564             :      * finding the buffers from BufMapping table provided we know the exact
    4565             :      * size of each fork of the relation. The exact size is required to ensure
    4566             :      * that we don't leave any buffer for the relation being dropped as
    4567             :      * otherwise the background writer or checkpointer can lead to a PANIC
    4568             :      * error while flushing buffers corresponding to files that don't exist.
    4569             :      *
    4570             :      * To know the exact size, we rely on the size cached for each fork by us
    4571             :      * during recovery which limits the optimization to recovery and on
    4572             :      * standbys but we can easily extend it once we have shared cache for
    4573             :      * relation size.
    4574             :      *
    4575             :      * In recovery, we cache the value returned by the first lseek(SEEK_END)
    4576             :      * and the future writes keeps the cached value up-to-date. See
    4577             :      * smgrextend. It is possible that the value of the first lseek is smaller
    4578             :      * than the actual number of existing blocks in the file due to buggy
    4579             :      * Linux kernels that might not have accounted for the recent write. But
    4580             :      * that should be fine because there must not be any buffers after that
    4581             :      * file size.
    4582             :      */
    4583         708 :     for (i = 0; i < nforks; i++)
    4584             :     {
    4585             :         /* Get the number of blocks for a relation's fork */
    4586         606 :         nForkBlock[i] = smgrnblocks_cached(smgr_reln, forkNum[i]);
    4587             : 
    4588         606 :         if (nForkBlock[i] == InvalidBlockNumber)
    4589             :         {
    4590         416 :             nBlocksToInvalidate = InvalidBlockNumber;
    4591         416 :             break;
    4592             :         }
    4593             : 
    4594             :         /* calculate the number of blocks to be invalidated */
    4595         190 :         nBlocksToInvalidate += (nForkBlock[i] - firstDelBlock[i]);
    4596             :     }
    4597             : 
    4598             :     /*
    4599             :      * We apply the optimization iff the total number of blocks to invalidate
    4600             :      * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
    4601             :      */
    4602         518 :     if (BlockNumberIsValid(nBlocksToInvalidate) &&
    4603         102 :         nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
    4604             :     {
    4605         234 :         for (j = 0; j < nforks; j++)
    4606         150 :             FindAndDropRelationBuffers(rlocator.locator, forkNum[j],
    4607         150 :                                        nForkBlock[j], firstDelBlock[j]);
    4608          84 :         return;
    4609             :     }
    4610             : 
    4611     5778098 :     for (i = 0; i < NBuffers; i++)
    4612             :     {
    4613     5777664 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    4614             :         uint32      buf_state;
    4615             : 
    4616             :         /*
    4617             :          * We can make this a tad faster by prechecking the buffer tag before
    4618             :          * we attempt to lock the buffer; this saves a lot of lock
    4619             :          * acquisitions in typical cases.  It should be safe because the
    4620             :          * caller must have AccessExclusiveLock on the relation, or some other
    4621             :          * reason to be certain that no one is loading new pages of the rel
    4622             :          * into the buffer pool.  (Otherwise we might well miss such pages
    4623             :          * entirely.)  Therefore, while the tag might be changing while we
    4624             :          * look at it, it can't be changing *to* a value we care about, only
    4625             :          * *away* from such a value.  So false negatives are impossible, and
    4626             :          * false positives are safe because we'll recheck after getting the
    4627             :          * buffer lock.
    4628             :          *
    4629             :          * We could check forkNum and blockNum as well as the rlocator, but
    4630             :          * the incremental win from doing so seems small.
    4631             :          */
    4632     5777664 :         if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator))
    4633     5762226 :             continue;
    4634             : 
    4635       15438 :         buf_state = LockBufHdr(bufHdr);
    4636             : 
    4637       39370 :         for (j = 0; j < nforks; j++)
    4638             :         {
    4639       27660 :             if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator) &&
    4640       27660 :                 BufTagGetForkNum(&bufHdr->tag) == forkNum[j] &&
    4641       15244 :                 bufHdr->tag.blockNum >= firstDelBlock[j])
    4642             :             {
    4643        3728 :                 InvalidateBuffer(bufHdr);   /* releases spinlock */
    4644        3728 :                 break;
    4645             :             }
    4646             :         }
    4647       15438 :         if (j >= nforks)
    4648       11710 :             UnlockBufHdr(bufHdr, buf_state);
    4649             :     }
    4650             : }
    4651             : 
    4652             : /* ---------------------------------------------------------------------
    4653             :  *      DropRelationsAllBuffers
    4654             :  *
    4655             :  *      This function removes from the buffer pool all the pages of all
    4656             :  *      forks of the specified relations.  It's equivalent to calling
    4657             :  *      DropRelationBuffers once per fork per relation with firstDelBlock = 0.
    4658             :  *      --------------------------------------------------------------------
    4659             :  */
    4660             : void
    4661       28000 : DropRelationsAllBuffers(SMgrRelation *smgr_reln, int nlocators)
    4662             : {
    4663             :     int         i;
    4664       28000 :     int         n = 0;
    4665             :     SMgrRelation *rels;
    4666             :     BlockNumber (*block)[MAX_FORKNUM + 1];
    4667       28000 :     uint64      nBlocksToInvalidate = 0;
    4668             :     RelFileLocator *locators;
    4669       28000 :     bool        cached = true;
    4670             :     bool        use_bsearch;
    4671             : 
    4672       28000 :     if (nlocators == 0)
    4673           0 :         return;
    4674             : 
    4675       28000 :     rels = palloc(sizeof(SMgrRelation) * nlocators);    /* non-local relations */
    4676             : 
    4677             :     /* If it's a local relation, it's localbuf.c's problem. */
    4678      120674 :     for (i = 0; i < nlocators; i++)
    4679             :     {
    4680       92674 :         if (RelFileLocatorBackendIsTemp(smgr_reln[i]->smgr_rlocator))
    4681             :         {
    4682        6194 :             if (smgr_reln[i]->smgr_rlocator.backend == MyProcNumber)
    4683        6194 :                 DropRelationAllLocalBuffers(smgr_reln[i]->smgr_rlocator.locator);
    4684             :         }
    4685             :         else
    4686       86480 :             rels[n++] = smgr_reln[i];
    4687             :     }
    4688             : 
    4689             :     /*
    4690             :      * If there are no non-local relations, then we're done. Release the
    4691             :      * memory and return.
    4692             :      */
    4693       28000 :     if (n == 0)
    4694             :     {
    4695        1578 :         pfree(rels);
    4696        1578 :         return;
    4697             :     }
    4698             : 
    4699             :     /*
    4700             :      * This is used to remember the number of blocks for all the relations
    4701             :      * forks.
    4702             :      */
    4703             :     block = (BlockNumber (*)[MAX_FORKNUM + 1])
    4704       26422 :         palloc(sizeof(BlockNumber) * n * (MAX_FORKNUM + 1));
    4705             : 
    4706             :     /*
    4707             :      * We can avoid scanning the entire buffer pool if we know the exact size
    4708             :      * of each of the given relation forks. See DropRelationBuffers.
    4709             :      */
    4710       55498 :     for (i = 0; i < n && cached; i++)
    4711             :     {
    4712       46358 :         for (int j = 0; j <= MAX_FORKNUM; j++)
    4713             :         {
    4714             :             /* Get the number of blocks for a relation's fork. */
    4715       42060 :             block[i][j] = smgrnblocks_cached(rels[i], j);
    4716             : 
    4717             :             /* We need to only consider the relation forks that exists. */
    4718       42060 :             if (block[i][j] == InvalidBlockNumber)
    4719             :             {
    4720       37372 :                 if (!smgrexists(rels[i], j))
    4721       12594 :                     continue;
    4722       24778 :                 cached = false;
    4723       24778 :                 break;
    4724             :             }
    4725             : 
    4726             :             /* calculate the total number of blocks to be invalidated */
    4727        4688 :             nBlocksToInvalidate += block[i][j];
    4728             :         }
    4729             :     }
    4730             : 
    4731             :     /*
    4732             :      * We apply the optimization iff the total number of blocks to invalidate
    4733             :      * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
    4734             :      */
    4735       26422 :     if (cached && nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
    4736             :     {
    4737        2694 :         for (i = 0; i < n; i++)
    4738             :         {
    4739        7410 :             for (int j = 0; j <= MAX_FORKNUM; j++)
    4740             :             {
    4741             :                 /* ignore relation forks that doesn't exist */
    4742        5928 :                 if (!BlockNumberIsValid(block[i][j]))
    4743        4428 :                     continue;
    4744             : 
    4745             :                 /* drop all the buffers for a particular relation fork */
    4746        1500 :                 FindAndDropRelationBuffers(rels[i]->smgr_rlocator.locator,
    4747        1500 :                                            j, block[i][j], 0);
    4748             :             }
    4749             :         }
    4750             : 
    4751        1212 :         pfree(block);
    4752        1212 :         pfree(rels);
    4753        1212 :         return;
    4754             :     }
    4755             : 
    4756       25210 :     pfree(block);
    4757       25210 :     locators = palloc(sizeof(RelFileLocator) * n);  /* non-local relations */
    4758      110208 :     for (i = 0; i < n; i++)
    4759       84998 :         locators[i] = rels[i]->smgr_rlocator.locator;
    4760             : 
    4761             :     /*
    4762             :      * For low number of relations to drop just use a simple walk through, to
    4763             :      * save the bsearch overhead. The threshold to use is rather a guess than
    4764             :      * an exactly determined value, as it depends on many factors (CPU and RAM
    4765             :      * speeds, amount of shared buffers etc.).
    4766             :      */
    4767       25210 :     use_bsearch = n > RELS_BSEARCH_THRESHOLD;
    4768             : 
    4769             :     /* sort the list of rlocators if necessary */
    4770       25210 :     if (use_bsearch)
    4771         334 :         qsort(locators, n, sizeof(RelFileLocator), rlocator_comparator);
    4772             : 
    4773   281912442 :     for (i = 0; i < NBuffers; i++)
    4774             :     {
    4775   281887232 :         RelFileLocator *rlocator = NULL;
    4776   281887232 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    4777             :         uint32      buf_state;
    4778             : 
    4779             :         /*
    4780             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4781             :          * saves some cycles.
    4782             :          */
    4783             : 
    4784   281887232 :         if (!use_bsearch)
    4785             :         {
    4786             :             int         j;
    4787             : 
    4788  1098313156 :             for (j = 0; j < n; j++)
    4789             :             {
    4790   820125760 :                 if (BufTagMatchesRelFileLocator(&bufHdr->tag, &locators[j]))
    4791             :                 {
    4792      178300 :                     rlocator = &locators[j];
    4793      178300 :                     break;
    4794             :                 }
    4795             :             }
    4796             :         }
    4797             :         else
    4798             :         {
    4799             :             RelFileLocator locator;
    4800             : 
    4801     3521536 :             locator = BufTagGetRelFileLocator(&bufHdr->tag);
    4802     3521536 :             rlocator = bsearch(&locator,
    4803             :                                locators, n, sizeof(RelFileLocator),
    4804             :                                rlocator_comparator);
    4805             :         }
    4806             : 
    4807             :         /* buffer doesn't belong to any of the given relfilelocators; skip it */
    4808   281887232 :         if (rlocator == NULL)
    4809   281705448 :             continue;
    4810             : 
    4811      181784 :         buf_state = LockBufHdr(bufHdr);
    4812      181784 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, rlocator))
    4813      181782 :             InvalidateBuffer(bufHdr);   /* releases spinlock */
    4814             :         else
    4815           2 :             UnlockBufHdr(bufHdr, buf_state);
    4816             :     }
    4817             : 
    4818       25210 :     pfree(locators);
    4819       25210 :     pfree(rels);
    4820             : }
    4821             : 
    4822             : /* ---------------------------------------------------------------------
    4823             :  *      FindAndDropRelationBuffers
    4824             :  *
    4825             :  *      This function performs look up in BufMapping table and removes from the
    4826             :  *      buffer pool all the pages of the specified relation fork that has block
    4827             :  *      number >= firstDelBlock. (In particular, with firstDelBlock = 0, all
    4828             :  *      pages are removed.)
    4829             :  * --------------------------------------------------------------------
    4830             :  */
    4831             : static void
    4832        1650 : FindAndDropRelationBuffers(RelFileLocator rlocator, ForkNumber forkNum,
    4833             :                            BlockNumber nForkBlock,
    4834             :                            BlockNumber firstDelBlock)
    4835             : {
    4836             :     BlockNumber curBlock;
    4837             : 
    4838        3982 :     for (curBlock = firstDelBlock; curBlock < nForkBlock; curBlock++)
    4839             :     {
    4840             :         uint32      bufHash;    /* hash value for tag */
    4841             :         BufferTag   bufTag;     /* identity of requested block */
    4842             :         LWLock     *bufPartitionLock;   /* buffer partition lock for it */
    4843             :         int         buf_id;
    4844             :         BufferDesc *bufHdr;
    4845             :         uint32      buf_state;
    4846             : 
    4847             :         /* create a tag so we can lookup the buffer */
    4848        2332 :         InitBufferTag(&bufTag, &rlocator, forkNum, curBlock);
    4849             : 
    4850             :         /* determine its hash code and partition lock ID */
    4851        2332 :         bufHash = BufTableHashCode(&bufTag);
    4852        2332 :         bufPartitionLock = BufMappingPartitionLock(bufHash);
    4853             : 
    4854             :         /* Check that it is in the buffer pool. If not, do nothing. */
    4855        2332 :         LWLockAcquire(bufPartitionLock, LW_SHARED);
    4856        2332 :         buf_id = BufTableLookup(&bufTag, bufHash);
    4857        2332 :         LWLockRelease(bufPartitionLock);
    4858             : 
    4859        2332 :         if (buf_id < 0)
    4860         222 :             continue;
    4861             : 
    4862        2110 :         bufHdr = GetBufferDescriptor(buf_id);
    4863             : 
    4864             :         /*
    4865             :          * We need to lock the buffer header and recheck if the buffer is
    4866             :          * still associated with the same block because the buffer could be
    4867             :          * evicted by some other backend loading blocks for a different
    4868             :          * relation after we release lock on the BufMapping table.
    4869             :          */
    4870        2110 :         buf_state = LockBufHdr(bufHdr);
    4871             : 
    4872        4220 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator) &&
    4873        2110 :             BufTagGetForkNum(&bufHdr->tag) == forkNum &&
    4874        2110 :             bufHdr->tag.blockNum >= firstDelBlock)
    4875        2110 :             InvalidateBuffer(bufHdr);   /* releases spinlock */
    4876             :         else
    4877           0 :             UnlockBufHdr(bufHdr, buf_state);
    4878             :     }
    4879        1650 : }
    4880             : 
    4881             : /* ---------------------------------------------------------------------
    4882             :  *      DropDatabaseBuffers
    4883             :  *
    4884             :  *      This function removes all the buffers in the buffer cache for a
    4885             :  *      particular database.  Dirty pages are simply dropped, without
    4886             :  *      bothering to write them out first.  This is used when we destroy a
    4887             :  *      database, to avoid trying to flush data to disk when the directory
    4888             :  *      tree no longer exists.  Implementation is pretty similar to
    4889             :  *      DropRelationBuffers() which is for destroying just one relation.
    4890             :  * --------------------------------------------------------------------
    4891             :  */
    4892             : void
    4893         136 : DropDatabaseBuffers(Oid dbid)
    4894             : {
    4895             :     int         i;
    4896             : 
    4897             :     /*
    4898             :      * We needn't consider local buffers, since by assumption the target
    4899             :      * database isn't our own.
    4900             :      */
    4901             : 
    4902      992904 :     for (i = 0; i < NBuffers; i++)
    4903             :     {
    4904      992768 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    4905             :         uint32      buf_state;
    4906             : 
    4907             :         /*
    4908             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4909             :          * saves some cycles.
    4910             :          */
    4911      992768 :         if (bufHdr->tag.dbOid != dbid)
    4912      965374 :             continue;
    4913             : 
    4914       27394 :         buf_state = LockBufHdr(bufHdr);
    4915       27394 :         if (bufHdr->tag.dbOid == dbid)
    4916       27394 :             InvalidateBuffer(bufHdr);   /* releases spinlock */
    4917             :         else
    4918           0 :             UnlockBufHdr(bufHdr, buf_state);
    4919             :     }
    4920         136 : }
    4921             : 
    4922             : /* ---------------------------------------------------------------------
    4923             :  *      FlushRelationBuffers
    4924             :  *
    4925             :  *      This function writes all dirty pages of a relation out to disk
    4926             :  *      (or more accurately, out to kernel disk buffers), ensuring that the
    4927             :  *      kernel has an up-to-date view of the relation.
    4928             :  *
    4929             :  *      Generally, the caller should be holding AccessExclusiveLock on the
    4930             :  *      target relation to ensure that no other backend is busy dirtying
    4931             :  *      more blocks of the relation; the effects can't be expected to last
    4932             :  *      after the lock is released.
    4933             :  *
    4934             :  *      XXX currently it sequentially searches the buffer pool, should be
    4935             :  *      changed to more clever ways of searching.  This routine is not
    4936             :  *      used in any performance-critical code paths, so it's not worth
    4937             :  *      adding additional overhead to normal paths to make it go faster.
    4938             :  * --------------------------------------------------------------------
    4939             :  */
    4940             : void
    4941         286 : FlushRelationBuffers(Relation rel)
    4942             : {
    4943             :     int         i;
    4944             :     BufferDesc *bufHdr;
    4945         286 :     SMgrRelation srel = RelationGetSmgr(rel);
    4946             : 
    4947         286 :     if (RelationUsesLocalBuffers(rel))
    4948             :     {
    4949        1818 :         for (i = 0; i < NLocBuffer; i++)
    4950             :         {
    4951             :             uint32      buf_state;
    4952             : 
    4953        1800 :             bufHdr = GetLocalBufferDescriptor(i);
    4954        1800 :             if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
    4955         600 :                 ((buf_state = pg_atomic_read_u32(&bufHdr->state)) &
    4956             :                  (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    4957             :             {
    4958             :                 ErrorContextCallback errcallback;
    4959             : 
    4960             :                 /* Setup error traceback support for ereport() */
    4961         600 :                 errcallback.callback = local_buffer_write_error_callback;
    4962         600 :                 errcallback.arg = bufHdr;
    4963         600 :                 errcallback.previous = error_context_stack;
    4964         600 :                 error_context_stack = &errcallback;
    4965             : 
    4966             :                 /* Make sure we can handle the pin */
    4967         600 :                 ReservePrivateRefCountEntry();
    4968         600 :                 ResourceOwnerEnlarge(CurrentResourceOwner);
    4969             : 
    4970             :                 /*
    4971             :                  * Pin/unpin mostly to make valgrind work, but it also seems
    4972             :                  * like the right thing to do.
    4973             :                  */
    4974         600 :                 PinLocalBuffer(bufHdr, false);
    4975             : 
    4976             : 
    4977         600 :                 FlushLocalBuffer(bufHdr, srel);
    4978             : 
    4979         600 :                 UnpinLocalBuffer(BufferDescriptorGetBuffer(bufHdr));
    4980             : 
    4981             :                 /* Pop the error context stack */
    4982         600 :                 error_context_stack = errcallback.previous;
    4983             :             }
    4984             :         }
    4985             : 
    4986          18 :         return;
    4987             :     }
    4988             : 
    4989     3188236 :     for (i = 0; i < NBuffers; i++)
    4990             :     {
    4991             :         uint32      buf_state;
    4992             : 
    4993     3187968 :         bufHdr = GetBufferDescriptor(i);
    4994             : 
    4995             :         /*
    4996             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4997             :          * saves some cycles.
    4998             :          */
    4999     3187968 :         if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator))
    5000     3187502 :             continue;
    5001             : 
    5002             :         /* Make sure we can handle the pin */
    5003         466 :         ReservePrivateRefCountEntry();
    5004         466 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    5005             : 
    5006         466 :         buf_state = LockBufHdr(bufHdr);
    5007         466 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
    5008         466 :             (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    5009             :         {
    5010         380 :             PinBuffer_Locked(bufHdr);
    5011         380 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    5012         380 :             FlushBuffer(bufHdr, srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    5013         380 :             LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    5014         380 :             UnpinBuffer(bufHdr);
    5015             :         }
    5016             :         else
    5017          86 :             UnlockBufHdr(bufHdr, buf_state);
    5018             :     }
    5019             : }
    5020             : 
    5021             : /* ---------------------------------------------------------------------
    5022             :  *      FlushRelationsAllBuffers
    5023             :  *
    5024             :  *      This function flushes out of the buffer pool all the pages of all
    5025             :  *      forks of the specified smgr relations.  It's equivalent to calling
    5026             :  *      FlushRelationBuffers once per relation.  The relations are assumed not
    5027             :  *      to use local buffers.
    5028             :  * --------------------------------------------------------------------
    5029             :  */
    5030             : void
    5031          30 : FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
    5032             : {
    5033             :     int         i;
    5034             :     SMgrSortArray *srels;
    5035             :     bool        use_bsearch;
    5036             : 
    5037          30 :     if (nrels == 0)
    5038           0 :         return;
    5039             : 
    5040             :     /* fill-in array for qsort */
    5041          30 :     srels = palloc(sizeof(SMgrSortArray) * nrels);
    5042             : 
    5043          60 :     for (i = 0; i < nrels; i++)
    5044             :     {
    5045             :         Assert(!RelFileLocatorBackendIsTemp(smgrs[i]->smgr_rlocator));
    5046             : 
    5047          30 :         srels[i].rlocator = smgrs[i]->smgr_rlocator.locator;
    5048          30 :         srels[i].srel = smgrs[i];
    5049             :     }
    5050             : 
    5051             :     /*
    5052             :      * Save the bsearch overhead for low number of relations to sync. See
    5053             :      * DropRelationsAllBuffers for details.
    5054             :      */
    5055          30 :     use_bsearch = nrels > RELS_BSEARCH_THRESHOLD;
    5056             : 
    5057             :     /* sort the list of SMgrRelations if necessary */
    5058          30 :     if (use_bsearch)
    5059           0 :         qsort(srels, nrels, sizeof(SMgrSortArray), rlocator_comparator);
    5060             : 
    5061      491550 :     for (i = 0; i < NBuffers; i++)
    5062             :     {
    5063      491520 :         SMgrSortArray *srelent = NULL;
    5064      491520 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    5065             :         uint32      buf_state;
    5066             : 
    5067             :         /*
    5068             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    5069             :          * saves some cycles.
    5070             :          */
    5071             : 
    5072      491520 :         if (!use_bsearch)
    5073             :         {
    5074             :             int         j;
    5075             : 
    5076      971868 :             for (j = 0; j < nrels; j++)
    5077             :             {
    5078      491520 :                 if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srels[j].rlocator))
    5079             :                 {
    5080       11172 :                     srelent = &srels[j];
    5081       11172 :                     break;
    5082             :                 }
    5083             :             }
    5084             :         }
    5085             :         else
    5086             :         {
    5087             :             RelFileLocator rlocator;
    5088             : 
    5089           0 :             rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
    5090           0 :             srelent = bsearch(&rlocator,
    5091             :                               srels, nrels, sizeof(SMgrSortArray),
    5092             :                               rlocator_comparator);
    5093             :         }
    5094             : 
    5095             :         /* buffer doesn't belong to any of the given relfilelocators; skip it */
    5096      491520 :         if (srelent == NULL)
    5097      480348 :             continue;
    5098             : 
    5099             :         /* Make sure we can handle the pin */
    5100       11172 :         ReservePrivateRefCountEntry();
    5101       11172 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    5102             : 
    5103       11172 :         buf_state = LockBufHdr(bufHdr);
    5104       11172 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srelent->rlocator) &&
    5105       11172 :             (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    5106             :         {
    5107        9992 :             PinBuffer_Locked(bufHdr);
    5108        9992 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    5109        9992 :             FlushBuffer(bufHdr, srelent->srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    5110        9992 :             LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    5111        9992 :             UnpinBuffer(bufHdr);
    5112             :         }
    5113             :         else
    5114        1180 :             UnlockBufHdr(bufHdr, buf_state);
    5115             :     }
    5116             : 
    5117          30 :     pfree(srels);
    5118             : }
    5119             : 
    5120             : /* ---------------------------------------------------------------------
    5121             :  *      RelationCopyStorageUsingBuffer
    5122             :  *
    5123             :  *      Copy fork's data using bufmgr.  Same as RelationCopyStorage but instead
    5124             :  *      of using smgrread and smgrextend this will copy using bufmgr APIs.
    5125             :  *
    5126             :  *      Refer comments atop CreateAndCopyRelationData() for details about
    5127             :  *      'permanent' parameter.
    5128             :  * --------------------------------------------------------------------
    5129             :  */
    5130             : static void
    5131      144876 : RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
    5132             :                                RelFileLocator dstlocator,
    5133             :                                ForkNumber forkNum, bool permanent)
    5134             : {
    5135             :     Buffer      srcBuf;
    5136             :     Buffer      dstBuf;
    5137             :     Page        srcPage;
    5138             :     Page        dstPage;
    5139             :     bool        use_wal;
    5140             :     BlockNumber nblocks;
    5141             :     BlockNumber blkno;
    5142             :     PGIOAlignedBlock buf;
    5143             :     BufferAccessStrategy bstrategy_src;
    5144             :     BufferAccessStrategy bstrategy_dst;
    5145             :     BlockRangeReadStreamPrivate p;
    5146             :     ReadStream *src_stream;
    5147             :     SMgrRelation src_smgr;
    5148             : 
    5149             :     /*
    5150             :      * In general, we want to write WAL whenever wal_level > 'minimal', but we
    5151             :      * can skip it when copying any fork of an unlogged relation other than
    5152             :      * the init fork.
    5153             :      */
    5154      144876 :     use_wal = XLogIsNeeded() && (permanent || forkNum == INIT_FORKNUM);
    5155             : 
    5156             :     /* Get number of blocks in the source relation. */
    5157      144876 :     nblocks = smgrnblocks(smgropen(srclocator, INVALID_PROC_NUMBER),
    5158             :                           forkNum);
    5159             : 
    5160             :     /* Nothing to copy; just return. */
    5161      144876 :     if (nblocks == 0)
    5162       25270 :         return;
    5163             : 
    5164             :     /*
    5165             :      * Bulk extend the destination relation of the same size as the source
    5166             :      * relation before starting to copy block by block.
    5167             :      */
    5168      119606 :     memset(buf.data, 0, BLCKSZ);
    5169      119606 :     smgrextend(smgropen(dstlocator, INVALID_PROC_NUMBER), forkNum, nblocks - 1,
    5170             :                buf.data, true);
    5171             : 
    5172             :     /* This is a bulk operation, so use buffer access strategies. */
    5173      119606 :     bstrategy_src = GetAccessStrategy(BAS_BULKREAD);
    5174      119606 :     bstrategy_dst = GetAccessStrategy(BAS_BULKWRITE);
    5175             : 
    5176             :     /* Initialize streaming read */
    5177      119606 :     p.current_blocknum = 0;
    5178      119606 :     p.last_exclusive = nblocks;
    5179      119606 :     src_smgr = smgropen(srclocator, INVALID_PROC_NUMBER);
    5180             : 
    5181             :     /*
    5182             :      * It is safe to use batchmode as block_range_read_stream_cb takes no
    5183             :      * locks.
    5184             :      */
    5185      119606 :     src_stream = read_stream_begin_smgr_relation(READ_STREAM_FULL |
    5186             :                                                  READ_STREAM_USE_BATCHING,
    5187             :                                                  bstrategy_src,
    5188             :                                                  src_smgr,
    5189             :                                                  permanent ? RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED,
    5190             :                                                  forkNum,
    5191             :                                                  block_range_read_stream_cb,
    5192             :                                                  &p,
    5193             :                                                  0);
    5194             : 
    5195             :     /* Iterate over each block of the source relation file. */
    5196      575224 :     for (blkno = 0; blkno < nblocks; blkno++)
    5197             :     {
    5198      455622 :         CHECK_FOR_INTERRUPTS();
    5199             : 
    5200             :         /* Read block from source relation. */
    5201      455622 :         srcBuf = read_stream_next_buffer(src_stream, NULL);
    5202      455618 :         LockBuffer(srcBuf, BUFFER_LOCK_SHARE);
    5203      455618 :         srcPage = BufferGetPage(srcBuf);
    5204             : 
    5205      455618 :         dstBuf = ReadBufferWithoutRelcache(dstlocator, forkNum,
    5206             :                                            BufferGetBlockNumber(srcBuf),
    5207             :                                            RBM_ZERO_AND_LOCK, bstrategy_dst,
    5208             :                                            permanent);
    5209      455618 :         dstPage = BufferGetPage(dstBuf);
    5210             : 
    5211      455618 :         START_CRIT_SECTION();
    5212             : 
    5213             :         /* Copy page data from the source to the destination. */
    5214      455618 :         memcpy(dstPage, srcPage, BLCKSZ);
    5215      455618 :         MarkBufferDirty(dstBuf);
    5216             : 
    5217             :         /* WAL-log the copied page. */
    5218      455618 :         if (use_wal)
    5219      243804 :             log_newpage_buffer(dstBuf, true);
    5220             : 
    5221      455618 :         END_CRIT_SECTION();
    5222             : 
    5223      455618 :         UnlockReleaseBuffer(dstBuf);
    5224      455618 :         UnlockReleaseBuffer(srcBuf);
    5225             :     }
    5226             :     Assert(read_stream_next_buffer(src_stream, NULL) == InvalidBuffer);
    5227      119602 :     read_stream_end(src_stream);
    5228             : 
    5229      119602 :     FreeAccessStrategy(bstrategy_src);
    5230      119602 :     FreeAccessStrategy(bstrategy_dst);
    5231             : }
    5232             : 
    5233             : /* ---------------------------------------------------------------------
    5234             :  *      CreateAndCopyRelationData
    5235             :  *
    5236             :  *      Create destination relation storage and copy all forks from the
    5237             :  *      source relation to the destination.
    5238             :  *
    5239             :  *      Pass permanent as true for permanent relations and false for
    5240             :  *      unlogged relations.  Currently this API is not supported for
    5241             :  *      temporary relations.
    5242             :  * --------------------------------------------------------------------
    5243             :  */
    5244             : void
    5245      108904 : CreateAndCopyRelationData(RelFileLocator src_rlocator,
    5246             :                           RelFileLocator dst_rlocator, bool permanent)
    5247             : {
    5248             :     char        relpersistence;
    5249             :     SMgrRelation src_rel;
    5250             :     SMgrRelation dst_rel;
    5251             : 
    5252             :     /* Set the relpersistence. */
    5253      108904 :     relpersistence = permanent ?
    5254             :         RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED;
    5255             : 
    5256      108904 :     src_rel = smgropen(src_rlocator, INVALID_PROC_NUMBER);
    5257      108904 :     dst_rel = smgropen(dst_rlocator, INVALID_PROC_NUMBER);
    5258             : 
    5259             :     /*
    5260             :      * Create and copy all forks of the relation.  During create database we
    5261             :      * have a separate cleanup mechanism which deletes complete database
    5262             :      * directory.  Therefore, each individual relation doesn't need to be
    5263             :      * registered for cleanup.
    5264             :      */
    5265      108904 :     RelationCreateStorage(dst_rlocator, relpersistence, false);
    5266             : 
    5267             :     /* copy main fork. */
    5268      108904 :     RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, MAIN_FORKNUM,
    5269             :                                    permanent);
    5270             : 
    5271             :     /* copy those extra forks that exist */
    5272      435600 :     for (ForkNumber forkNum = MAIN_FORKNUM + 1;
    5273      326700 :          forkNum <= MAX_FORKNUM; forkNum++)
    5274             :     {
    5275      326700 :         if (smgrexists(src_rel, forkNum))
    5276             :         {
    5277       35972 :             smgrcreate(dst_rel, forkNum, false);
    5278             : 
    5279             :             /*
    5280             :              * WAL log creation if the relation is persistent, or this is the
    5281             :              * init fork of an unlogged relation.
    5282             :              */
    5283       35972 :             if (permanent || forkNum == INIT_FORKNUM)
    5284       35972 :                 log_smgrcreate(&dst_rlocator, forkNum);
    5285             : 
    5286             :             /* Copy a fork's data, block by block. */
    5287       35972 :             RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, forkNum,
    5288             :                                            permanent);
    5289             :         }
    5290             :     }
    5291      108900 : }
    5292             : 
    5293             : /* ---------------------------------------------------------------------
    5294             :  *      FlushDatabaseBuffers
    5295             :  *
    5296             :  *      This function writes all dirty pages of a database out to disk
    5297             :  *      (or more accurately, out to kernel disk buffers), ensuring that the
    5298             :  *      kernel has an up-to-date view of the database.
    5299             :  *
    5300             :  *      Generally, the caller should be holding an appropriate lock to ensure
    5301             :  *      no other backend is active in the target database; otherwise more
    5302             :  *      pages could get dirtied.
    5303             :  *
    5304             :  *      Note we don't worry about flushing any pages of temporary relations.
    5305             :  *      It's assumed these wouldn't be interesting.
    5306             :  * --------------------------------------------------------------------
    5307             :  */
    5308             : void
    5309           8 : FlushDatabaseBuffers(Oid dbid)
    5310             : {
    5311             :     int         i;
    5312             :     BufferDesc *bufHdr;
    5313             : 
    5314        1032 :     for (i = 0; i < NBuffers; i++)
    5315             :     {
    5316             :         uint32      buf_state;
    5317             : 
    5318        1024 :         bufHdr = GetBufferDescriptor(i);
    5319             : 
    5320             :         /*
    5321             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    5322             :          * saves some cycles.
    5323             :          */
    5324        1024 :         if (bufHdr->tag.dbOid != dbid)
    5325         786 :             continue;
    5326             : 
    5327             :         /* Make sure we can handle the pin */
    5328         238 :         ReservePrivateRefCountEntry();
    5329         238 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    5330             : 
    5331         238 :         buf_state = LockBufHdr(bufHdr);
    5332         238 :         if (bufHdr->tag.dbOid == dbid &&
    5333         238 :             (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    5334             :         {
    5335           0 :             PinBuffer_Locked(bufHdr);
    5336           0 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    5337           0 :             FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    5338           0 :             LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    5339           0 :             UnpinBuffer(bufHdr);
    5340             :         }
    5341             :         else
    5342         238 :             UnlockBufHdr(bufHdr, buf_state);
    5343             :     }
    5344           8 : }
    5345             : 
    5346             : /*
    5347             :  * Flush a previously, shared or exclusively, locked and pinned buffer to the
    5348             :  * OS.
    5349             :  */
    5350             : void
    5351         158 : FlushOneBuffer(Buffer buffer)
    5352             : {
    5353             :     BufferDesc *bufHdr;
    5354             : 
    5355             :     /* currently not needed, but no fundamental reason not to support */
    5356             :     Assert(!BufferIsLocal(buffer));
    5357             : 
    5358             :     Assert(BufferIsPinned(buffer));
    5359             : 
    5360         158 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5361             : 
    5362             :     Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
    5363             : 
    5364         158 :     FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    5365         158 : }
    5366             : 
    5367             : /*
    5368             :  * ReleaseBuffer -- release the pin on a buffer
    5369             :  */
    5370             : void
    5371   121570528 : ReleaseBuffer(Buffer buffer)
    5372             : {
    5373   121570528 :     if (!BufferIsValid(buffer))
    5374           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    5375             : 
    5376   121570528 :     if (BufferIsLocal(buffer))
    5377     3208180 :         UnpinLocalBuffer(buffer);
    5378             :     else
    5379   118362348 :         UnpinBuffer(GetBufferDescriptor(buffer - 1));
    5380   121570528 : }
    5381             : 
    5382             : /*
    5383             :  * UnlockReleaseBuffer -- release the content lock and pin on a buffer
    5384             :  *
    5385             :  * This is just a shorthand for a common combination.
    5386             :  */
    5387             : void
    5388    37536786 : UnlockReleaseBuffer(Buffer buffer)
    5389             : {
    5390    37536786 :     LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5391    37536786 :     ReleaseBuffer(buffer);
    5392    37536786 : }
    5393             : 
    5394             : /*
    5395             :  * IncrBufferRefCount
    5396             :  *      Increment the pin count on a buffer that we have *already* pinned
    5397             :  *      at least once.
    5398             :  *
    5399             :  *      This function cannot be used on a buffer we do not have pinned,
    5400             :  *      because it doesn't change the shared buffer state.
    5401             :  */
    5402             : void
    5403    22595214 : IncrBufferRefCount(Buffer buffer)
    5404             : {
    5405             :     Assert(BufferIsPinned(buffer));
    5406    22595214 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    5407    22595214 :     if (BufferIsLocal(buffer))
    5408      709044 :         LocalRefCount[-buffer - 1]++;
    5409             :     else
    5410             :     {
    5411             :         PrivateRefCountEntry *ref;
    5412             : 
    5413    21886170 :         ref = GetPrivateRefCountEntry(buffer, true);
    5414             :         Assert(ref != NULL);
    5415    21886170 :         ref->refcount++;
    5416             :     }
    5417    22595214 :     ResourceOwnerRememberBuffer(CurrentResourceOwner, buffer);
    5418    22595214 : }
    5419             : 
    5420             : /*
    5421             :  * MarkBufferDirtyHint
    5422             :  *
    5423             :  *  Mark a buffer dirty for non-critical changes.
    5424             :  *
    5425             :  * This is essentially the same as MarkBufferDirty, except:
    5426             :  *
    5427             :  * 1. The caller does not write WAL; so if checksums are enabled, we may need
    5428             :  *    to write an XLOG_FPI_FOR_HINT WAL record to protect against torn pages.
    5429             :  * 2. The caller might have only share-lock instead of exclusive-lock on the
    5430             :  *    buffer's content lock.
    5431             :  * 3. This function does not guarantee that the buffer is always marked dirty
    5432             :  *    (due to a race condition), so it cannot be used for important changes.
    5433             :  */
    5434             : void
    5435    21131300 : MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
    5436             : {
    5437             :     BufferDesc *bufHdr;
    5438    21131300 :     Page        page = BufferGetPage(buffer);
    5439             : 
    5440    21131300 :     if (!BufferIsValid(buffer))
    5441           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    5442             : 
    5443    21131300 :     if (BufferIsLocal(buffer))
    5444             :     {
    5445     1264370 :         MarkLocalBufferDirty(buffer);
    5446     1264370 :         return;
    5447             :     }
    5448             : 
    5449    19866930 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5450             : 
    5451             :     Assert(GetPrivateRefCount(buffer) > 0);
    5452             :     /* here, either share or exclusive lock is OK */
    5453             :     Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
    5454             : 
    5455             :     /*
    5456             :      * This routine might get called many times on the same page, if we are
    5457             :      * making the first scan after commit of an xact that added/deleted many
    5458             :      * tuples. So, be as quick as we can if the buffer is already dirty.  We
    5459             :      * do this by not acquiring spinlock if it looks like the status bits are
    5460             :      * already set.  Since we make this test unlocked, there's a chance we
    5461             :      * might fail to notice that the flags have just been cleared, and failed
    5462             :      * to reset them, due to memory-ordering issues.  But since this function
    5463             :      * is only intended to be used in cases where failing to write out the
    5464             :      * data would be harmless anyway, it doesn't really matter.
    5465             :      */
    5466    19866930 :     if ((pg_atomic_read_u32(&bufHdr->state) & (BM_DIRTY | BM_JUST_DIRTIED)) !=
    5467             :         (BM_DIRTY | BM_JUST_DIRTIED))
    5468             :     {
    5469     2228666 :         XLogRecPtr  lsn = InvalidXLogRecPtr;
    5470     2228666 :         bool        dirtied = false;
    5471     2228666 :         bool        delayChkptFlags = false;
    5472             :         uint32      buf_state;
    5473             : 
    5474             :         /*
    5475             :          * If we need to protect hint bit updates from torn writes, WAL-log a
    5476             :          * full page image of the page. This full page image is only necessary
    5477             :          * if the hint bit update is the first change to the page since the
    5478             :          * last checkpoint.
    5479             :          *
    5480             :          * We don't check full_page_writes here because that logic is included
    5481             :          * when we call XLogInsert() since the value changes dynamically.
    5482             :          */
    5483     4455546 :         if (XLogHintBitIsNeeded() &&
    5484     2226880 :             (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT))
    5485             :         {
    5486             :             /*
    5487             :              * If we must not write WAL, due to a relfilelocator-specific
    5488             :              * condition or being in recovery, don't dirty the page.  We can
    5489             :              * set the hint, just not dirty the page as a result so the hint
    5490             :              * is lost when we evict the page or shutdown.
    5491             :              *
    5492             :              * See src/backend/storage/page/README for longer discussion.
    5493             :              */
    5494     2347656 :             if (RecoveryInProgress() ||
    5495      120840 :                 RelFileLocatorSkippingWAL(BufTagGetRelFileLocator(&bufHdr->tag)))
    5496     2111986 :                 return;
    5497             : 
    5498             :             /*
    5499             :              * If the block is already dirty because we either made a change
    5500             :              * or set a hint already, then we don't need to write a full page
    5501             :              * image.  Note that aggressive cleaning of blocks dirtied by hint
    5502             :              * bit setting would increase the call rate. Bulk setting of hint
    5503             :              * bits would reduce the call rate...
    5504             :              *
    5505             :              * We must issue the WAL record before we mark the buffer dirty.
    5506             :              * Otherwise we might write the page before we write the WAL. That
    5507             :              * causes a race condition, since a checkpoint might occur between
    5508             :              * writing the WAL record and marking the buffer dirty. We solve
    5509             :              * that with a kluge, but one that is already in use during
    5510             :              * transaction commit to prevent race conditions. Basically, we
    5511             :              * simply prevent the checkpoint WAL record from being written
    5512             :              * until we have marked the buffer dirty. We don't start the
    5513             :              * checkpoint flush until we have marked dirty, so our checkpoint
    5514             :              * must flush the change to disk successfully or the checkpoint
    5515             :              * never gets written, so crash recovery will fix.
    5516             :              *
    5517             :              * It's possible we may enter here without an xid, so it is
    5518             :              * essential that CreateCheckPoint waits for virtual transactions
    5519             :              * rather than full transactionids.
    5520             :              */
    5521             :             Assert((MyProc->delayChkptFlags & DELAY_CHKPT_START) == 0);
    5522      114830 :             MyProc->delayChkptFlags |= DELAY_CHKPT_START;
    5523      114830 :             delayChkptFlags = true;
    5524      114830 :             lsn = XLogSaveBufferForHint(buffer, buffer_std);
    5525             :         }
    5526             : 
    5527      116680 :         buf_state = LockBufHdr(bufHdr);
    5528             : 
    5529             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    5530             : 
    5531      116680 :         if (!(buf_state & BM_DIRTY))
    5532             :         {
    5533      116636 :             dirtied = true;     /* Means "will be dirtied by this action" */
    5534             : 
    5535             :             /*
    5536             :              * Set the page LSN if we wrote a backup block. We aren't supposed
    5537             :              * to set this when only holding a share lock but as long as we
    5538             :              * serialise it somehow we're OK. We choose to set LSN while
    5539             :              * holding the buffer header lock, which causes any reader of an
    5540             :              * LSN who holds only a share lock to also obtain a buffer header
    5541             :              * lock before using PageGetLSN(), which is enforced in
    5542             :              * BufferGetLSNAtomic().
    5543             :              *
    5544             :              * If checksums are enabled, you might think we should reset the
    5545             :              * checksum here. That will happen when the page is written
    5546             :              * sometime later in this checkpoint cycle.
    5547             :              */
    5548      116636 :             if (!XLogRecPtrIsInvalid(lsn))
    5549       61948 :                 PageSetLSN(page, lsn);
    5550             :         }
    5551             : 
    5552      116680 :         buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
    5553      116680 :         UnlockBufHdr(bufHdr, buf_state);
    5554             : 
    5555      116680 :         if (delayChkptFlags)
    5556      114830 :             MyProc->delayChkptFlags &= ~DELAY_CHKPT_START;
    5557             : 
    5558      116680 :         if (dirtied)
    5559             :         {
    5560      116636 :             pgBufferUsage.shared_blks_dirtied++;
    5561      116636 :             if (VacuumCostActive)
    5562         658 :                 VacuumCostBalance += VacuumCostPageDirty;
    5563             :         }
    5564             :     }
    5565             : }
    5566             : 
    5567             : /*
    5568             :  * Release buffer content locks for shared buffers.
    5569             :  *
    5570             :  * Used to clean up after errors.
    5571             :  *
    5572             :  * Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
    5573             :  * of releasing buffer content locks per se; the only thing we need to deal
    5574             :  * with here is clearing any PIN_COUNT request that was in progress.
    5575             :  */
    5576             : void
    5577      101564 : UnlockBuffers(void)
    5578             : {
    5579      101564 :     BufferDesc *buf = PinCountWaitBuf;
    5580             : 
    5581      101564 :     if (buf)
    5582             :     {
    5583             :         uint32      buf_state;
    5584             : 
    5585           0 :         buf_state = LockBufHdr(buf);
    5586             : 
    5587             :         /*
    5588             :          * Don't complain if flag bit not set; it could have been reset but we
    5589             :          * got a cancel/die interrupt before getting the signal.
    5590             :          */
    5591           0 :         if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
    5592           0 :             buf->wait_backend_pgprocno == MyProcNumber)
    5593           0 :             buf_state &= ~BM_PIN_COUNT_WAITER;
    5594             : 
    5595           0 :         UnlockBufHdr(buf, buf_state);
    5596             : 
    5597           0 :         PinCountWaitBuf = NULL;
    5598             :     }
    5599      101564 : }
    5600             : 
    5601             : /*
    5602             :  * Acquire or release the content_lock for the buffer.
    5603             :  */
    5604             : void
    5605   341560616 : LockBuffer(Buffer buffer, int mode)
    5606             : {
    5607             :     BufferDesc *buf;
    5608             : 
    5609             :     Assert(BufferIsPinned(buffer));
    5610   341560616 :     if (BufferIsLocal(buffer))
    5611    19757948 :         return;                 /* local buffers need no lock */
    5612             : 
    5613   321802668 :     buf = GetBufferDescriptor(buffer - 1);
    5614             : 
    5615   321802668 :     if (mode == BUFFER_LOCK_UNLOCK)
    5616   162817112 :         LWLockRelease(BufferDescriptorGetContentLock(buf));
    5617   158985556 :     else if (mode == BUFFER_LOCK_SHARE)
    5618   112979392 :         LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_SHARED);
    5619    46006164 :     else if (mode == BUFFER_LOCK_EXCLUSIVE)
    5620    46006164 :         LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_EXCLUSIVE);
    5621             :     else
    5622           0 :         elog(ERROR, "unrecognized buffer lock mode: %d", mode);
    5623             : }
    5624             : 
    5625             : /*
    5626             :  * Acquire the content_lock for the buffer, but only if we don't have to wait.
    5627             :  *
    5628             :  * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode.
    5629             :  */
    5630             : bool
    5631     3044586 : ConditionalLockBuffer(Buffer buffer)
    5632             : {
    5633             :     BufferDesc *buf;
    5634             : 
    5635             :     Assert(BufferIsPinned(buffer));
    5636     3044586 :     if (BufferIsLocal(buffer))
    5637      129488 :         return true;            /* act as though we got it */
    5638             : 
    5639     2915098 :     buf = GetBufferDescriptor(buffer - 1);
    5640             : 
    5641     2915098 :     return LWLockConditionalAcquire(BufferDescriptorGetContentLock(buf),
    5642             :                                     LW_EXCLUSIVE);
    5643             : }
    5644             : 
    5645             : /*
    5646             :  * Verify that this backend is pinning the buffer exactly once.
    5647             :  *
    5648             :  * NOTE: Like in BufferIsPinned(), what we check here is that *this* backend
    5649             :  * holds a pin on the buffer.  We do not care whether some other backend does.
    5650             :  */
    5651             : void
    5652     4628740 : CheckBufferIsPinnedOnce(Buffer buffer)
    5653             : {
    5654     4628740 :     if (BufferIsLocal(buffer))
    5655             :     {
    5656        1578 :         if (LocalRefCount[-buffer - 1] != 1)
    5657           0 :             elog(ERROR, "incorrect local pin count: %d",
    5658             :                  LocalRefCount[-buffer - 1]);
    5659             :     }
    5660             :     else
    5661             :     {
    5662     4627162 :         if (GetPrivateRefCount(buffer) != 1)
    5663           0 :             elog(ERROR, "incorrect local pin count: %d",
    5664             :                  GetPrivateRefCount(buffer));
    5665             :     }
    5666     4628740 : }
    5667             : 
    5668             : /*
    5669             :  * LockBufferForCleanup - lock a buffer in preparation for deleting items
    5670             :  *
    5671             :  * Items may be deleted from a disk page only when the caller (a) holds an
    5672             :  * exclusive lock on the buffer and (b) has observed that no other backend
    5673             :  * holds a pin on the buffer.  If there is a pin, then the other backend
    5674             :  * might have a pointer into the buffer (for example, a heapscan reference
    5675             :  * to an item --- see README for more details).  It's OK if a pin is added
    5676             :  * after the cleanup starts, however; the newly-arrived backend will be
    5677             :  * unable to look at the page until we release the exclusive lock.
    5678             :  *
    5679             :  * To implement this protocol, a would-be deleter must pin the buffer and
    5680             :  * then call LockBufferForCleanup().  LockBufferForCleanup() is similar to
    5681             :  * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE), except that it loops until
    5682             :  * it has successfully observed pin count = 1.
    5683             :  */
    5684             : void
    5685       38644 : LockBufferForCleanup(Buffer buffer)
    5686             : {
    5687             :     BufferDesc *bufHdr;
    5688       38644 :     TimestampTz waitStart = 0;
    5689       38644 :     bool        waiting = false;
    5690       38644 :     bool        logged_recovery_conflict = false;
    5691             : 
    5692             :     Assert(BufferIsPinned(buffer));
    5693             :     Assert(PinCountWaitBuf == NULL);
    5694             : 
    5695       38644 :     CheckBufferIsPinnedOnce(buffer);
    5696             : 
    5697             :     /*
    5698             :      * We do not yet need to be worried about in-progress AIOs holding a pin,
    5699             :      * as we, so far, only support doing reads via AIO and this function can
    5700             :      * only be called once the buffer is valid (i.e. no read can be in
    5701             :      * flight).
    5702             :      */
    5703             : 
    5704             :     /* Nobody else to wait for */
    5705       38644 :     if (BufferIsLocal(buffer))
    5706          32 :         return;
    5707             : 
    5708       38612 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5709             : 
    5710             :     for (;;)
    5711          20 :     {
    5712             :         uint32      buf_state;
    5713             : 
    5714             :         /* Try to acquire lock */
    5715       38632 :         LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
    5716       38632 :         buf_state = LockBufHdr(bufHdr);
    5717             : 
    5718             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    5719       38632 :         if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
    5720             :         {
    5721             :             /* Successfully acquired exclusive lock with pincount 1 */
    5722       38612 :             UnlockBufHdr(bufHdr, buf_state);
    5723             : 
    5724             :             /*
    5725             :              * Emit the log message if recovery conflict on buffer pin was
    5726             :              * resolved but the startup process waited longer than
    5727             :              * deadlock_timeout for it.
    5728             :              */
    5729       38612 :             if (logged_recovery_conflict)
    5730           4 :                 LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
    5731             :                                     waitStart, GetCurrentTimestamp(),
    5732             :                                     NULL, false);
    5733             : 
    5734       38612 :             if (waiting)
    5735             :             {
    5736             :                 /* reset ps display to remove the suffix if we added one */
    5737           4 :                 set_ps_display_remove_suffix();
    5738           4 :                 waiting = false;
    5739             :             }
    5740       38612 :             return;
    5741             :         }
    5742             :         /* Failed, so mark myself as waiting for pincount 1 */
    5743          20 :         if (buf_state & BM_PIN_COUNT_WAITER)
    5744             :         {
    5745           0 :             UnlockBufHdr(bufHdr, buf_state);
    5746           0 :             LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5747           0 :             elog(ERROR, "multiple backends attempting to wait for pincount 1");
    5748             :         }
    5749          20 :         bufHdr->wait_backend_pgprocno = MyProcNumber;
    5750          20 :         PinCountWaitBuf = bufHdr;
    5751          20 :         buf_state |= BM_PIN_COUNT_WAITER;
    5752          20 :         UnlockBufHdr(bufHdr, buf_state);
    5753          20 :         LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5754             : 
    5755             :         /* Wait to be signaled by UnpinBuffer() */
    5756          20 :         if (InHotStandby)
    5757             :         {
    5758          20 :             if (!waiting)
    5759             :             {
    5760             :                 /* adjust the process title to indicate that it's waiting */
    5761           4 :                 set_ps_display_suffix("waiting");
    5762           4 :                 waiting = true;
    5763             :             }
    5764             : 
    5765             :             /*
    5766             :              * Emit the log message if the startup process is waiting longer
    5767             :              * than deadlock_timeout for recovery conflict on buffer pin.
    5768             :              *
    5769             :              * Skip this if first time through because the startup process has
    5770             :              * not started waiting yet in this case. So, the wait start
    5771             :              * timestamp is set after this logic.
    5772             :              */
    5773          20 :             if (waitStart != 0 && !logged_recovery_conflict)
    5774             :             {
    5775           6 :                 TimestampTz now = GetCurrentTimestamp();
    5776             : 
    5777           6 :                 if (TimestampDifferenceExceeds(waitStart, now,
    5778             :                                                DeadlockTimeout))
    5779             :                 {
    5780           4 :                     LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
    5781             :                                         waitStart, now, NULL, true);
    5782           4 :                     logged_recovery_conflict = true;
    5783             :                 }
    5784             :             }
    5785             : 
    5786             :             /*
    5787             :              * Set the wait start timestamp if logging is enabled and first
    5788             :              * time through.
    5789             :              */
    5790          20 :             if (log_recovery_conflict_waits && waitStart == 0)
    5791           4 :                 waitStart = GetCurrentTimestamp();
    5792             : 
    5793             :             /* Publish the bufid that Startup process waits on */
    5794          20 :             SetStartupBufferPinWaitBufId(buffer - 1);
    5795             :             /* Set alarm and then wait to be signaled by UnpinBuffer() */
    5796          20 :             ResolveRecoveryConflictWithBufferPin();
    5797             :             /* Reset the published bufid */
    5798          20 :             SetStartupBufferPinWaitBufId(-1);
    5799             :         }
    5800             :         else
    5801           0 :             ProcWaitForSignal(WAIT_EVENT_BUFFER_PIN);
    5802             : 
    5803             :         /*
    5804             :          * Remove flag marking us as waiter. Normally this will not be set
    5805             :          * anymore, but ProcWaitForSignal() can return for other signals as
    5806             :          * well.  We take care to only reset the flag if we're the waiter, as
    5807             :          * theoretically another backend could have started waiting. That's
    5808             :          * impossible with the current usages due to table level locking, but
    5809             :          * better be safe.
    5810             :          */
    5811          20 :         buf_state = LockBufHdr(bufHdr);
    5812          20 :         if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
    5813          16 :             bufHdr->wait_backend_pgprocno == MyProcNumber)
    5814          16 :             buf_state &= ~BM_PIN_COUNT_WAITER;
    5815          20 :         UnlockBufHdr(bufHdr, buf_state);
    5816             : 
    5817          20 :         PinCountWaitBuf = NULL;
    5818             :         /* Loop back and try again */
    5819             :     }
    5820             : }
    5821             : 
    5822             : /*
    5823             :  * Check called from ProcessRecoveryConflictInterrupts() when Startup process
    5824             :  * requests cancellation of all pin holders that are blocking it.
    5825             :  */
    5826             : bool
    5827           8 : HoldingBufferPinThatDelaysRecovery(void)
    5828             : {
    5829           8 :     int         bufid = GetStartupBufferPinWaitBufId();
    5830             : 
    5831             :     /*
    5832             :      * If we get woken slowly then it's possible that the Startup process was
    5833             :      * already woken by other backends before we got here. Also possible that
    5834             :      * we get here by multiple interrupts or interrupts at inappropriate
    5835             :      * times, so make sure we do nothing if the bufid is not set.
    5836             :      */
    5837           8 :     if (bufid < 0)
    5838           4 :         return false;
    5839             : 
    5840           4 :     if (GetPrivateRefCount(bufid + 1) > 0)
    5841           4 :         return true;
    5842             : 
    5843           0 :     return false;
    5844             : }
    5845             : 
    5846             : /*
    5847             :  * ConditionalLockBufferForCleanup - as above, but don't wait to get the lock
    5848             :  *
    5849             :  * We won't loop, but just check once to see if the pin count is OK.  If
    5850             :  * not, return false with no lock held.
    5851             :  */
    5852             : bool
    5853      856928 : ConditionalLockBufferForCleanup(Buffer buffer)
    5854             : {
    5855             :     BufferDesc *bufHdr;
    5856             :     uint32      buf_state,
    5857             :                 refcount;
    5858             : 
    5859             :     Assert(BufferIsValid(buffer));
    5860             : 
    5861             :     /* see AIO related comment in LockBufferForCleanup() */
    5862             : 
    5863      856928 :     if (BufferIsLocal(buffer))
    5864             :     {
    5865        1600 :         refcount = LocalRefCount[-buffer - 1];
    5866             :         /* There should be exactly one pin */
    5867             :         Assert(refcount > 0);
    5868        1600 :         if (refcount != 1)
    5869          42 :             return false;
    5870             :         /* Nobody else to wait for */
    5871        1558 :         return true;
    5872             :     }
    5873             : 
    5874             :     /* There should be exactly one local pin */
    5875      855328 :     refcount = GetPrivateRefCount(buffer);
    5876             :     Assert(refcount);
    5877      855328 :     if (refcount != 1)
    5878         422 :         return false;
    5879             : 
    5880             :     /* Try to acquire lock */
    5881      854906 :     if (!ConditionalLockBuffer(buffer))
    5882          50 :         return false;
    5883             : 
    5884      854856 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5885      854856 :     buf_state = LockBufHdr(bufHdr);
    5886      854856 :     refcount = BUF_STATE_GET_REFCOUNT(buf_state);
    5887             : 
    5888             :     Assert(refcount > 0);
    5889      854856 :     if (refcount == 1)
    5890             :     {
    5891             :         /* Successfully acquired exclusive lock with pincount 1 */
    5892      854754 :         UnlockBufHdr(bufHdr, buf_state);
    5893      854754 :         return true;
    5894             :     }
    5895             : 
    5896             :     /* Failed, so release the lock */
    5897         102 :     UnlockBufHdr(bufHdr, buf_state);
    5898         102 :     LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5899         102 :     return false;
    5900             : }
    5901             : 
    5902             : /*
    5903             :  * IsBufferCleanupOK - as above, but we already have the lock
    5904             :  *
    5905             :  * Check whether it's OK to perform cleanup on a buffer we've already
    5906             :  * locked.  If we observe that the pin count is 1, our exclusive lock
    5907             :  * happens to be a cleanup lock, and we can proceed with anything that
    5908             :  * would have been allowable had we sought a cleanup lock originally.
    5909             :  */
    5910             : bool
    5911        4060 : IsBufferCleanupOK(Buffer buffer)
    5912             : {
    5913             :     BufferDesc *bufHdr;
    5914             :     uint32      buf_state;
    5915             : 
    5916             :     Assert(BufferIsValid(buffer));
    5917             : 
    5918             :     /* see AIO related comment in LockBufferForCleanup() */
    5919             : 
    5920        4060 :     if (BufferIsLocal(buffer))
    5921             :     {
    5922             :         /* There should be exactly one pin */
    5923           0 :         if (LocalRefCount[-buffer - 1] != 1)
    5924           0 :             return false;
    5925             :         /* Nobody else to wait for */
    5926           0 :         return true;
    5927             :     }
    5928             : 
    5929             :     /* There should be exactly one local pin */
    5930        4060 :     if (GetPrivateRefCount(buffer) != 1)
    5931           0 :         return false;
    5932             : 
    5933        4060 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5934             : 
    5935             :     /* caller must hold exclusive lock on buffer */
    5936             :     Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    5937             :                                 LW_EXCLUSIVE));
    5938             : 
    5939        4060 :     buf_state = LockBufHdr(bufHdr);
    5940             : 
    5941             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    5942        4060 :     if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
    5943             :     {
    5944             :         /* pincount is OK. */
    5945        4060 :         UnlockBufHdr(bufHdr, buf_state);
    5946        4060 :         return true;
    5947             :     }
    5948             : 
    5949           0 :     UnlockBufHdr(bufHdr, buf_state);
    5950           0 :     return false;
    5951             : }
    5952             : 
    5953             : 
    5954             : /*
    5955             :  *  Functions for buffer I/O handling
    5956             :  *
    5957             :  *  Also note that these are used only for shared buffers, not local ones.
    5958             :  */
    5959             : 
    5960             : /*
    5961             :  * WaitIO -- Block until the IO_IN_PROGRESS flag on 'buf' is cleared.
    5962             :  */
    5963             : static void
    5964        4464 : WaitIO(BufferDesc *buf)
    5965             : {
    5966        4464 :     ConditionVariable *cv = BufferDescriptorGetIOCV(buf);
    5967             : 
    5968        4464 :     ConditionVariablePrepareToSleep(cv);
    5969             :     for (;;)
    5970        4446 :     {
    5971             :         uint32      buf_state;
    5972             :         PgAioWaitRef iow;
    5973             : 
    5974             :         /*
    5975             :          * It may not be necessary to acquire the spinlock to check the flag
    5976             :          * here, but since this test is essential for correctness, we'd better
    5977             :          * play it safe.
    5978             :          */
    5979        8910 :         buf_state = LockBufHdr(buf);
    5980             : 
    5981             :         /*
    5982             :          * Copy the wait reference while holding the spinlock. This protects
    5983             :          * against a concurrent TerminateBufferIO() in another backend from
    5984             :          * clearing the wref while it's being read.
    5985             :          */
    5986        8910 :         iow = buf->io_wref;
    5987        8910 :         UnlockBufHdr(buf, buf_state);
    5988             : 
    5989             :         /* no IO in progress, we don't need to wait */
    5990        8910 :         if (!(buf_state & BM_IO_IN_PROGRESS))
    5991        4464 :             break;
    5992             : 
    5993             :         /*
    5994             :          * The buffer has asynchronous IO in progress, wait for it to
    5995             :          * complete.
    5996             :          */
    5997        4446 :         if (pgaio_wref_valid(&iow))
    5998             :         {
    5999        4040 :             pgaio_wref_wait(&iow);
    6000             : 
    6001             :             /*
    6002             :              * The AIO subsystem internally uses condition variables and thus
    6003             :              * might remove this backend from the BufferDesc's CV. While that
    6004             :              * wouldn't cause a correctness issue (the first CV sleep just
    6005             :              * immediately returns if not already registered), it seems worth
    6006             :              * avoiding unnecessary loop iterations, given that we take care
    6007             :              * to do so at the start of the function.
    6008             :              */
    6009        4040 :             ConditionVariablePrepareToSleep(cv);
    6010        4040 :             continue;
    6011             :         }
    6012             : 
    6013             :         /* wait on BufferDesc->cv, e.g. for concurrent synchronous IO */
    6014         406 :         ConditionVariableSleep(cv, WAIT_EVENT_BUFFER_IO);
    6015             :     }
    6016        4464 :     ConditionVariableCancelSleep();
    6017        4464 : }
    6018             : 
    6019             : /*
    6020             :  * StartBufferIO: begin I/O on this buffer
    6021             :  *  (Assumptions)
    6022             :  *  My process is executing no IO on this buffer
    6023             :  *  The buffer is Pinned
    6024             :  *
    6025             :  * In some scenarios multiple backends could attempt the same I/O operation
    6026             :  * concurrently.  If someone else has already started I/O on this buffer then
    6027             :  * we will wait for completion of the IO using WaitIO().
    6028             :  *
    6029             :  * Input operations are only attempted on buffers that are not BM_VALID,
    6030             :  * and output operations only on buffers that are BM_VALID and BM_DIRTY,
    6031             :  * so we can always tell if the work is already done.
    6032             :  *
    6033             :  * Returns true if we successfully marked the buffer as I/O busy,
    6034             :  * false if someone else already did the work.
    6035             :  *
    6036             :  * If nowait is true, then we don't wait for an I/O to be finished by another
    6037             :  * backend.  In that case, false indicates either that the I/O was already
    6038             :  * finished, or is still in progress.  This is useful for callers that want to
    6039             :  * find out if they can perform the I/O as part of a larger operation, without
    6040             :  * waiting for the answer or distinguishing the reasons why not.
    6041             :  */
    6042             : bool
    6043     4856414 : StartBufferIO(BufferDesc *buf, bool forInput, bool nowait)
    6044             : {
    6045             :     uint32      buf_state;
    6046             : 
    6047     4856414 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    6048             : 
    6049             :     for (;;)
    6050             :     {
    6051     4860872 :         buf_state = LockBufHdr(buf);
    6052             : 
    6053     4860872 :         if (!(buf_state & BM_IO_IN_PROGRESS))
    6054     4856406 :             break;
    6055        4466 :         UnlockBufHdr(buf, buf_state);
    6056        4466 :         if (nowait)
    6057           8 :             return false;
    6058        4458 :         WaitIO(buf);
    6059             :     }
    6060             : 
    6061             :     /* Once we get here, there is definitely no I/O active on this buffer */
    6062             : 
    6063             :     /* Check if someone else already did the I/O */
    6064     4856406 :     if (forInput ? (buf_state & BM_VALID) : !(buf_state & BM_DIRTY))
    6065             :     {
    6066        4662 :         UnlockBufHdr(buf, buf_state);
    6067        4662 :         return false;
    6068             :     }
    6069             : 
    6070     4851744 :     buf_state |= BM_IO_IN_PROGRESS;
    6071     4851744 :     UnlockBufHdr(buf, buf_state);
    6072             : 
    6073     4851744 :     ResourceOwnerRememberBufferIO(CurrentResourceOwner,
    6074             :                                   BufferDescriptorGetBuffer(buf));
    6075             : 
    6076     4851744 :     return true;
    6077             : }
    6078             : 
    6079             : /*
    6080             :  * TerminateBufferIO: release a buffer we were doing I/O on
    6081             :  *  (Assumptions)
    6082             :  *  My process is executing IO for the buffer
    6083             :  *  BM_IO_IN_PROGRESS bit is set for the buffer
    6084             :  *  The buffer is Pinned
    6085             :  *
    6086             :  * If clear_dirty is true and BM_JUST_DIRTIED is not set, we clear the
    6087             :  * buffer's BM_DIRTY flag.  This is appropriate when terminating a
    6088             :  * successful write.  The check on BM_JUST_DIRTIED is necessary to avoid
    6089             :  * marking the buffer clean if it was re-dirtied while we were writing.
    6090             :  *
    6091             :  * set_flag_bits gets ORed into the buffer's flags.  It must include
    6092             :  * BM_IO_ERROR in a failure case.  For successful completion it could
    6093             :  * be 0, or BM_VALID if we just finished reading in the page.
    6094             :  *
    6095             :  * If forget_owner is true, we release the buffer I/O from the current
    6096             :  * resource owner. (forget_owner=false is used when the resource owner itself
    6097             :  * is being released)
    6098             :  */
    6099             : void
    6100     4574498 : TerminateBufferIO(BufferDesc *buf, bool clear_dirty, uint32 set_flag_bits,
    6101             :                   bool forget_owner, bool release_aio)
    6102             : {
    6103             :     uint32      buf_state;
    6104             : 
    6105     4574498 :     buf_state = LockBufHdr(buf);
    6106             : 
    6107             :     Assert(buf_state & BM_IO_IN_PROGRESS);
    6108     4574498 :     buf_state &= ~BM_IO_IN_PROGRESS;
    6109             : 
    6110             :     /* Clear earlier errors, if this IO failed, it'll be marked again */
    6111     4574498 :     buf_state &= ~BM_IO_ERROR;
    6112             : 
    6113     4574498 :     if (clear_dirty && !(buf_state & BM_JUST_DIRTIED))
    6114     1043264 :         buf_state &= ~(BM_DIRTY | BM_CHECKPOINT_NEEDED);
    6115             : 
    6116     4574498 :     if (release_aio)
    6117             :     {
    6118             :         /* release ownership by the AIO subsystem */
    6119             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    6120     2542330 :         buf_state -= BUF_REFCOUNT_ONE;
    6121     2542330 :         pgaio_wref_clear(&buf->io_wref);
    6122             :     }
    6123             : 
    6124     4574498 :     buf_state |= set_flag_bits;
    6125     4574498 :     UnlockBufHdr(buf, buf_state);
    6126             : 
    6127     4574498 :     if (forget_owner)
    6128     2032126 :         ResourceOwnerForgetBufferIO(CurrentResourceOwner,
    6129             :                                     BufferDescriptorGetBuffer(buf));
    6130             : 
    6131     4574498 :     ConditionVariableBroadcast(BufferDescriptorGetIOCV(buf));
    6132             : 
    6133             :     /*
    6134             :      * Support LockBufferForCleanup()
    6135             :      *
    6136             :      * We may have just released the last pin other than the waiter's. In most
    6137             :      * cases, this backend holds another pin on the buffer. But, if, for
    6138             :      * example, this backend is completing an IO issued by another backend, it
    6139             :      * may be time to wake the waiter.
    6140             :      */
    6141     4574498 :     if (release_aio && (buf_state & BM_PIN_COUNT_WAITER))
    6142           0 :         WakePinCountWaiter(buf);
    6143     4574498 : }
    6144             : 
    6145             : /*
    6146             :  * AbortBufferIO: Clean up active buffer I/O after an error.
    6147             :  *
    6148             :  *  All LWLocks we might have held have been released,
    6149             :  *  but we haven't yet released buffer pins, so the buffer is still pinned.
    6150             :  *
    6151             :  *  If I/O was in progress, we always set BM_IO_ERROR, even though it's
    6152             :  *  possible the error condition wasn't related to the I/O.
    6153             :  *
    6154             :  *  Note: this does not remove the buffer I/O from the resource owner.
    6155             :  *  That's correct when we're releasing the whole resource owner, but
    6156             :  *  beware if you use this in other contexts.
    6157             :  */
    6158             : static void
    6159          30 : AbortBufferIO(Buffer buffer)
    6160             : {
    6161          30 :     BufferDesc *buf_hdr = GetBufferDescriptor(buffer - 1);
    6162             :     uint32      buf_state;
    6163             : 
    6164          30 :     buf_state = LockBufHdr(buf_hdr);
    6165             :     Assert(buf_state & (BM_IO_IN_PROGRESS | BM_TAG_VALID));
    6166             : 
    6167          30 :     if (!(buf_state & BM_VALID))
    6168             :     {
    6169             :         Assert(!(buf_state & BM_DIRTY));
    6170          30 :         UnlockBufHdr(buf_hdr, buf_state);
    6171             :     }
    6172             :     else
    6173             :     {
    6174             :         Assert(buf_state & BM_DIRTY);
    6175           0 :         UnlockBufHdr(buf_hdr, buf_state);
    6176             : 
    6177             :         /* Issue notice if this is not the first failure... */
    6178           0 :         if (buf_state & BM_IO_ERROR)
    6179             :         {
    6180             :             /* Buffer is pinned, so we can read tag without spinlock */
    6181           0 :             ereport(WARNING,
    6182             :                     (errcode(ERRCODE_IO_ERROR),
    6183             :                      errmsg("could not write block %u of %s",
    6184             :                             buf_hdr->tag.blockNum,
    6185             :                             relpathperm(BufTagGetRelFileLocator(&buf_hdr->tag),
    6186             :                                         BufTagGetForkNum(&buf_hdr->tag)).str),
    6187             :                      errdetail("Multiple failures --- write error might be permanent.")));
    6188             :         }
    6189             :     }
    6190             : 
    6191          30 :     TerminateBufferIO(buf_hdr, false, BM_IO_ERROR, false, false);
    6192          30 : }
    6193             : 
    6194             : /*
    6195             :  * Error context callback for errors occurring during shared buffer writes.
    6196             :  */
    6197             : static void
    6198          76 : shared_buffer_write_error_callback(void *arg)
    6199             : {
    6200          76 :     BufferDesc *bufHdr = (BufferDesc *) arg;
    6201             : 
    6202             :     /* Buffer is pinned, so we can read the tag without locking the spinlock */
    6203          76 :     if (bufHdr != NULL)
    6204         152 :         errcontext("writing block %u of relation %s",
    6205             :                    bufHdr->tag.blockNum,
    6206          76 :                    relpathperm(BufTagGetRelFileLocator(&bufHdr->tag),
    6207             :                                BufTagGetForkNum(&bufHdr->tag)).str);
    6208          76 : }
    6209             : 
    6210             : /*
    6211             :  * Error context callback for errors occurring during local buffer writes.
    6212             :  */
    6213             : static void
    6214           0 : local_buffer_write_error_callback(void *arg)
    6215             : {
    6216           0 :     BufferDesc *bufHdr = (BufferDesc *) arg;
    6217             : 
    6218           0 :     if (bufHdr != NULL)
    6219           0 :         errcontext("writing block %u of relation %s",
    6220             :                    bufHdr->tag.blockNum,
    6221           0 :                    relpathbackend(BufTagGetRelFileLocator(&bufHdr->tag),
    6222             :                                   MyProcNumber,
    6223             :                                   BufTagGetForkNum(&bufHdr->tag)).str);
    6224           0 : }
    6225             : 
    6226             : /*
    6227             :  * RelFileLocator qsort/bsearch comparator; see RelFileLocatorEquals.
    6228             :  */
    6229             : static int
    6230    18430724 : rlocator_comparator(const void *p1, const void *p2)
    6231             : {
    6232    18430724 :     RelFileLocator n1 = *(const RelFileLocator *) p1;
    6233    18430724 :     RelFileLocator n2 = *(const RelFileLocator *) p2;
    6234             : 
    6235    18430724 :     if (n1.relNumber < n2.relNumber)
    6236    18349624 :         return -1;
    6237       81100 :     else if (n1.relNumber > n2.relNumber)
    6238       77616 :         return 1;
    6239             : 
    6240        3484 :     if (n1.dbOid < n2.dbOid)
    6241           0 :         return -1;
    6242        3484 :     else if (n1.dbOid > n2.dbOid)
    6243           0 :         return 1;
    6244             : 
    6245        3484 :     if (n1.spcOid < n2.spcOid)
    6246           0 :         return -1;
    6247        3484 :     else if (n1.spcOid > n2.spcOid)
    6248           0 :         return 1;
    6249             :     else
    6250        3484 :         return 0;
    6251             : }
    6252             : 
    6253             : /*
    6254             :  * Lock buffer header - set BM_LOCKED in buffer state.
    6255             :  */
    6256             : uint32
    6257    75278774 : LockBufHdr(BufferDesc *desc)
    6258             : {
    6259             :     SpinDelayStatus delayStatus;
    6260             :     uint32      old_buf_state;
    6261             : 
    6262             :     Assert(!BufferIsLocal(BufferDescriptorGetBuffer(desc)));
    6263             : 
    6264    75278774 :     init_local_spin_delay(&delayStatus);
    6265             : 
    6266             :     while (true)
    6267             :     {
    6268             :         /* set BM_LOCKED flag */
    6269    75312918 :         old_buf_state = pg_atomic_fetch_or_u32(&desc->state, BM_LOCKED);
    6270             :         /* if it wasn't set before we're OK */
    6271    75312918 :         if (!(old_buf_state & BM_LOCKED))
    6272    75278774 :             break;
    6273       34144 :         perform_spin_delay(&delayStatus);
    6274             :     }
    6275    75278774 :     finish_spin_delay(&delayStatus);
    6276    75278774 :     return old_buf_state | BM_LOCKED;
    6277             : }
    6278             : 
    6279             : /*
    6280             :  * Wait until the BM_LOCKED flag isn't set anymore and return the buffer's
    6281             :  * state at that point.
    6282             :  *
    6283             :  * Obviously the buffer could be locked by the time the value is returned, so
    6284             :  * this is primarily useful in CAS style loops.
    6285             :  */
    6286             : static uint32
    6287        5800 : WaitBufHdrUnlocked(BufferDesc *buf)
    6288             : {
    6289             :     SpinDelayStatus delayStatus;
    6290             :     uint32      buf_state;
    6291             : 
    6292        5800 :     init_local_spin_delay(&delayStatus);
    6293             : 
    6294        5800 :     buf_state = pg_atomic_read_u32(&buf->state);
    6295             : 
    6296       29966 :     while (buf_state & BM_LOCKED)
    6297             :     {
    6298       24166 :         perform_spin_delay(&delayStatus);
    6299       24166 :         buf_state = pg_atomic_read_u32(&buf->state);
    6300             :     }
    6301             : 
    6302        5800 :     finish_spin_delay(&delayStatus);
    6303             : 
    6304        5800 :     return buf_state;
    6305             : }
    6306             : 
    6307             : /*
    6308             :  * BufferTag comparator.
    6309             :  */
    6310             : static inline int
    6311           0 : buffertag_comparator(const BufferTag *ba, const BufferTag *bb)
    6312             : {
    6313             :     int         ret;
    6314             :     RelFileLocator rlocatora;
    6315             :     RelFileLocator rlocatorb;
    6316             : 
    6317           0 :     rlocatora = BufTagGetRelFileLocator(ba);
    6318           0 :     rlocatorb = BufTagGetRelFileLocator(bb);
    6319             : 
    6320           0 :     ret = rlocator_comparator(&rlocatora, &rlocatorb);
    6321             : 
    6322           0 :     if (ret != 0)
    6323           0 :         return ret;
    6324             : 
    6325           0 :     if (BufTagGetForkNum(ba) < BufTagGetForkNum(bb))
    6326           0 :         return -1;
    6327           0 :     if (BufTagGetForkNum(ba) > BufTagGetForkNum(bb))
    6328           0 :         return 1;
    6329             : 
    6330           0 :     if (ba->blockNum < bb->blockNum)
    6331           0 :         return -1;
    6332           0 :     if (ba->blockNum > bb->blockNum)
    6333           0 :         return 1;
    6334             : 
    6335           0 :     return 0;
    6336             : }
    6337             : 
    6338             : /*
    6339             :  * Comparator determining the writeout order in a checkpoint.
    6340             :  *
    6341             :  * It is important that tablespaces are compared first, the logic balancing
    6342             :  * writes between tablespaces relies on it.
    6343             :  */
    6344             : static inline int
    6345     5824340 : ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b)
    6346             : {
    6347             :     /* compare tablespace */
    6348     5824340 :     if (a->tsId < b->tsId)
    6349       12318 :         return -1;
    6350     5812022 :     else if (a->tsId > b->tsId)
    6351       36314 :         return 1;
    6352             :     /* compare relation */
    6353     5775708 :     if (a->relNumber < b->relNumber)
    6354     1619904 :         return -1;
    6355     4155804 :     else if (a->relNumber > b->relNumber)
    6356     1546320 :         return 1;
    6357             :     /* compare fork */
    6358     2609484 :     else if (a->forkNum < b->forkNum)
    6359      104892 :         return -1;
    6360     2504592 :     else if (a->forkNum > b->forkNum)
    6361      114912 :         return 1;
    6362             :     /* compare block number */
    6363     2389680 :     else if (a->blockNum < b->blockNum)
    6364     1168628 :         return -1;
    6365     1221052 :     else if (a->blockNum > b->blockNum)
    6366     1137122 :         return 1;
    6367             :     /* equal page IDs are unlikely, but not impossible */
    6368       83930 :     return 0;
    6369             : }
    6370             : 
    6371             : /*
    6372             :  * Comparator for a Min-Heap over the per-tablespace checkpoint completion
    6373             :  * progress.
    6374             :  */
    6375             : static int
    6376      449962 : ts_ckpt_progress_comparator(Datum a, Datum b, void *arg)
    6377             : {
    6378      449962 :     CkptTsStatus *sa = (CkptTsStatus *) a;
    6379      449962 :     CkptTsStatus *sb = (CkptTsStatus *) b;
    6380             : 
    6381             :     /* we want a min-heap, so return 1 for the a < b */
    6382      449962 :     if (sa->progress < sb->progress)
    6383      429180 :         return 1;
    6384       20782 :     else if (sa->progress == sb->progress)
    6385        1186 :         return 0;
    6386             :     else
    6387       19596 :         return -1;
    6388             : }
    6389             : 
    6390             : /*
    6391             :  * Initialize a writeback context, discarding potential previous state.
    6392             :  *
    6393             :  * *max_pending is a pointer instead of an immediate value, so the coalesce
    6394             :  * limits can easily changed by the GUC mechanism, and so calling code does
    6395             :  * not have to check the current configuration. A value of 0 means that no
    6396             :  * writeback control will be performed.
    6397             :  */
    6398             : void
    6399        5156 : WritebackContextInit(WritebackContext *context, int *max_pending)
    6400             : {
    6401             :     Assert(*max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
    6402             : 
    6403        5156 :     context->max_pending = max_pending;
    6404        5156 :     context->nr_pending = 0;
    6405        5156 : }
    6406             : 
    6407             : /*
    6408             :  * Add buffer to list of pending writeback requests.
    6409             :  */
    6410             : void
    6411     1030844 : ScheduleBufferTagForWriteback(WritebackContext *wb_context, IOContext io_context,
    6412             :                               BufferTag *tag)
    6413             : {
    6414             :     PendingWriteback *pending;
    6415             : 
    6416             :     /*
    6417             :      * As pg_flush_data() doesn't do anything with fsync disabled, there's no
    6418             :      * point in tracking in that case.
    6419             :      */
    6420     1030844 :     if (io_direct_flags & IO_DIRECT_DATA ||
    6421     1029808 :         !enableFsync)
    6422     1030842 :         return;
    6423             : 
    6424             :     /*
    6425             :      * Add buffer to the pending writeback array, unless writeback control is
    6426             :      * disabled.
    6427             :      */
    6428           2 :     if (*wb_context->max_pending > 0)
    6429             :     {
    6430             :         Assert(*wb_context->max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
    6431             : 
    6432           0 :         pending = &wb_context->pending_writebacks[wb_context->nr_pending++];
    6433             : 
    6434           0 :         pending->tag = *tag;
    6435             :     }
    6436             : 
    6437             :     /*
    6438             :      * Perform pending flushes if the writeback limit is exceeded. This
    6439             :      * includes the case where previously an item has been added, but control
    6440             :      * is now disabled.
    6441             :      */
    6442           2 :     if (wb_context->nr_pending >= *wb_context->max_pending)
    6443           2 :         IssuePendingWritebacks(wb_context, io_context);
    6444             : }
    6445             : 
    6446             : #define ST_SORT sort_pending_writebacks
    6447             : #define ST_ELEMENT_TYPE PendingWriteback
    6448             : #define ST_COMPARE(a, b) buffertag_comparator(&a->tag, &b->tag)
    6449             : #define ST_SCOPE static
    6450             : #define ST_DEFINE
    6451             : #include "lib/sort_template.h"
    6452             : 
    6453             : /*
    6454             :  * Issue all pending writeback requests, previously scheduled with
    6455             :  * ScheduleBufferTagForWriteback, to the OS.
    6456             :  *
    6457             :  * Because this is only used to improve the OSs IO scheduling we try to never
    6458             :  * error out - it's just a hint.
    6459             :  */
    6460             : void
    6461        2052 : IssuePendingWritebacks(WritebackContext *wb_context, IOContext io_context)
    6462             : {
    6463             :     instr_time  io_start;
    6464             :     int         i;
    6465             : 
    6466        2052 :     if (wb_context->nr_pending == 0)
    6467        2052 :         return;
    6468             : 
    6469             :     /*
    6470             :      * Executing the writes in-order can make them a lot faster, and allows to
    6471             :      * merge writeback requests to consecutive blocks into larger writebacks.
    6472             :      */
    6473           0 :     sort_pending_writebacks(wb_context->pending_writebacks,
    6474           0 :                             wb_context->nr_pending);
    6475             : 
    6476           0 :     io_start = pgstat_prepare_io_time(track_io_timing);
    6477             : 
    6478             :     /*
    6479             :      * Coalesce neighbouring writes, but nothing else. For that we iterate
    6480             :      * through the, now sorted, array of pending flushes, and look forward to
    6481             :      * find all neighbouring (or identical) writes.
    6482             :      */
    6483           0 :     for (i = 0; i < wb_context->nr_pending; i++)
    6484             :     {
    6485             :         PendingWriteback *cur;
    6486             :         PendingWriteback *next;
    6487             :         SMgrRelation reln;
    6488             :         int         ahead;
    6489             :         BufferTag   tag;
    6490             :         RelFileLocator currlocator;
    6491           0 :         Size        nblocks = 1;
    6492             : 
    6493           0 :         cur = &wb_context->pending_writebacks[i];
    6494           0 :         tag = cur->tag;
    6495           0 :         currlocator = BufTagGetRelFileLocator(&tag);
    6496             : 
    6497             :         /*
    6498             :          * Peek ahead, into following writeback requests, to see if they can
    6499             :          * be combined with the current one.
    6500             :          */
    6501           0 :         for (ahead = 0; i + ahead + 1 < wb_context->nr_pending; ahead++)
    6502             :         {
    6503             : 
    6504           0 :             next = &wb_context->pending_writebacks[i + ahead + 1];
    6505             : 
    6506             :             /* different file, stop */
    6507           0 :             if (!RelFileLocatorEquals(currlocator,
    6508           0 :                                       BufTagGetRelFileLocator(&next->tag)) ||
    6509           0 :                 BufTagGetForkNum(&cur->tag) != BufTagGetForkNum(&next->tag))
    6510             :                 break;
    6511             : 
    6512             :             /* ok, block queued twice, skip */
    6513           0 :             if (cur->tag.blockNum == next->tag.blockNum)
    6514           0 :                 continue;
    6515             : 
    6516             :             /* only merge consecutive writes */
    6517           0 :             if (cur->tag.blockNum + 1 != next->tag.blockNum)
    6518           0 :                 break;
    6519             : 
    6520           0 :             nblocks++;
    6521           0 :             cur = next;
    6522             :         }
    6523             : 
    6524           0 :         i += ahead;
    6525             : 
    6526             :         /* and finally tell the kernel to write the data to storage */
    6527           0 :         reln = smgropen(currlocator, INVALID_PROC_NUMBER);
    6528           0 :         smgrwriteback(reln, BufTagGetForkNum(&tag), tag.blockNum, nblocks);
    6529             :     }
    6530             : 
    6531             :     /*
    6532             :      * Assume that writeback requests are only issued for buffers containing
    6533             :      * blocks of permanent relations.
    6534             :      */
    6535           0 :     pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
    6536           0 :                             IOOP_WRITEBACK, io_start, wb_context->nr_pending, 0);
    6537             : 
    6538           0 :     wb_context->nr_pending = 0;
    6539             : }
    6540             : 
    6541             : /* ResourceOwner callbacks */
    6542             : 
    6543             : static void
    6544          30 : ResOwnerReleaseBufferIO(Datum res)
    6545             : {
    6546          30 :     Buffer      buffer = DatumGetInt32(res);
    6547             : 
    6548          30 :     AbortBufferIO(buffer);
    6549          30 : }
    6550             : 
    6551             : static char *
    6552           0 : ResOwnerPrintBufferIO(Datum res)
    6553             : {
    6554           0 :     Buffer      buffer = DatumGetInt32(res);
    6555             : 
    6556           0 :     return psprintf("lost track of buffer IO on buffer %d", buffer);
    6557             : }
    6558             : 
    6559             : static void
    6560       14662 : ResOwnerReleaseBufferPin(Datum res)
    6561             : {
    6562       14662 :     Buffer      buffer = DatumGetInt32(res);
    6563             : 
    6564             :     /* Like ReleaseBuffer, but don't call ResourceOwnerForgetBuffer */
    6565       14662 :     if (!BufferIsValid(buffer))
    6566           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    6567             : 
    6568       14662 :     if (BufferIsLocal(buffer))
    6569        5970 :         UnpinLocalBufferNoOwner(buffer);
    6570             :     else
    6571        8692 :         UnpinBufferNoOwner(GetBufferDescriptor(buffer - 1));
    6572       14662 : }
    6573             : 
    6574             : static char *
    6575           0 : ResOwnerPrintBufferPin(Datum res)
    6576             : {
    6577           0 :     return DebugPrintBufferRefcount(DatumGetInt32(res));
    6578             : }
    6579             : 
    6580             : /*
    6581             :  * Helper function to evict unpinned buffer whose buffer header lock is
    6582             :  * already acquired.
    6583             :  */
    6584             : static bool
    6585        4262 : EvictUnpinnedBufferInternal(BufferDesc *desc, bool *buffer_flushed)
    6586             : {
    6587             :     uint32      buf_state;
    6588             :     bool        result;
    6589             : 
    6590        4262 :     *buffer_flushed = false;
    6591             : 
    6592        4262 :     buf_state = pg_atomic_read_u32(&(desc->state));
    6593             :     Assert(buf_state & BM_LOCKED);
    6594             : 
    6595        4262 :     if ((buf_state & BM_VALID) == 0)
    6596             :     {
    6597           0 :         UnlockBufHdr(desc, buf_state);
    6598           0 :         return false;
    6599             :     }
    6600             : 
    6601             :     /* Check that it's not pinned already. */
    6602        4262 :     if (BUF_STATE_GET_REFCOUNT(buf_state) > 0)
    6603             :     {
    6604           0 :         UnlockBufHdr(desc, buf_state);
    6605           0 :         return false;
    6606             :     }
    6607             : 
    6608        4262 :     PinBuffer_Locked(desc);     /* releases spinlock */
    6609             : 
    6610             :     /* If it was dirty, try to clean it once. */
    6611        4262 :     if (buf_state & BM_DIRTY)
    6612             :     {
    6613        1932 :         LWLockAcquire(BufferDescriptorGetContentLock(desc), LW_SHARED);
    6614        1932 :         FlushBuffer(desc, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    6615        1932 :         *buffer_flushed = true;
    6616        1932 :         LWLockRelease(BufferDescriptorGetContentLock(desc));
    6617             :     }
    6618             : 
    6619             :     /* This will return false if it becomes dirty or someone else pins it. */
    6620        4262 :     result = InvalidateVictimBuffer(desc);
    6621             : 
    6622        4262 :     UnpinBuffer(desc);
    6623             : 
    6624        4262 :     return result;
    6625             : }
    6626             : 
    6627             : /*
    6628             :  * Try to evict the current block in a shared buffer.
    6629             :  *
    6630             :  * This function is intended for testing/development use only!
    6631             :  *
    6632             :  * To succeed, the buffer must not be pinned on entry, so if the caller had a
    6633             :  * particular block in mind, it might already have been replaced by some other
    6634             :  * block by the time this function runs.  It's also unpinned on return, so the
    6635             :  * buffer might be occupied again by the time control is returned, potentially
    6636             :  * even by the same block.  This inherent raciness without other interlocking
    6637             :  * makes the function unsuitable for non-testing usage.
    6638             :  *
    6639             :  * *buffer_flushed is set to true if the buffer was dirty and has been
    6640             :  * flushed, false otherwise.  However, *buffer_flushed=true does not
    6641             :  * necessarily mean that we flushed the buffer, it could have been flushed by
    6642             :  * someone else.
    6643             :  *
    6644             :  * Returns true if the buffer was valid and it has now been made invalid.
    6645             :  * Returns false if it wasn't valid, if it couldn't be evicted due to a pin,
    6646             :  * or if the buffer becomes dirty again while we're trying to write it out.
    6647             :  */
    6648             : bool
    6649         280 : EvictUnpinnedBuffer(Buffer buf, bool *buffer_flushed)
    6650             : {
    6651             :     BufferDesc *desc;
    6652             : 
    6653             :     Assert(BufferIsValid(buf) && !BufferIsLocal(buf));
    6654             : 
    6655             :     /* Make sure we can pin the buffer. */
    6656         280 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    6657         280 :     ReservePrivateRefCountEntry();
    6658             : 
    6659         280 :     desc = GetBufferDescriptor(buf - 1);
    6660         280 :     LockBufHdr(desc);
    6661             : 
    6662         280 :     return EvictUnpinnedBufferInternal(desc, buffer_flushed);
    6663             : }
    6664             : 
    6665             : /*
    6666             :  * Try to evict all the shared buffers.
    6667             :  *
    6668             :  * This function is intended for testing/development use only! See
    6669             :  * EvictUnpinnedBuffer().
    6670             :  *
    6671             :  * The buffers_* parameters are mandatory and indicate the total count of
    6672             :  * buffers that:
    6673             :  * - buffers_evicted - were evicted
    6674             :  * - buffers_flushed - were flushed
    6675             :  * - buffers_skipped - could not be evicted
    6676             :  */
    6677             : void
    6678           2 : EvictAllUnpinnedBuffers(int32 *buffers_evicted, int32 *buffers_flushed,
    6679             :                         int32 *buffers_skipped)
    6680             : {
    6681           2 :     *buffers_evicted = 0;
    6682           2 :     *buffers_skipped = 0;
    6683           2 :     *buffers_flushed = 0;
    6684             : 
    6685       32770 :     for (int buf = 1; buf <= NBuffers; buf++)
    6686             :     {
    6687       32768 :         BufferDesc *desc = GetBufferDescriptor(buf - 1);
    6688             :         uint32      buf_state;
    6689             :         bool        buffer_flushed;
    6690             : 
    6691       32768 :         buf_state = pg_atomic_read_u32(&desc->state);
    6692       32768 :         if (!(buf_state & BM_VALID))
    6693       28786 :             continue;
    6694             : 
    6695        3982 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    6696        3982 :         ReservePrivateRefCountEntry();
    6697             : 
    6698        3982 :         LockBufHdr(desc);
    6699             : 
    6700        3982 :         if (EvictUnpinnedBufferInternal(desc, &buffer_flushed))
    6701        3982 :             (*buffers_evicted)++;
    6702             :         else
    6703           0 :             (*buffers_skipped)++;
    6704             : 
    6705        3982 :         if (buffer_flushed)
    6706        1894 :             (*buffers_flushed)++;
    6707             :     }
    6708           2 : }
    6709             : 
    6710             : /*
    6711             :  * Try to evict all the shared buffers containing provided relation's pages.
    6712             :  *
    6713             :  * This function is intended for testing/development use only! See
    6714             :  * EvictUnpinnedBuffer().
    6715             :  *
    6716             :  * The caller must hold at least AccessShareLock on the relation to prevent
    6717             :  * the relation from being dropped.
    6718             :  *
    6719             :  * The buffers_* parameters are mandatory and indicate the total count of
    6720             :  * buffers that:
    6721             :  * - buffers_evicted - were evicted
    6722             :  * - buffers_flushed - were flushed
    6723             :  * - buffers_skipped - could not be evicted
    6724             :  */
    6725             : void
    6726           2 : EvictRelUnpinnedBuffers(Relation rel, int32 *buffers_evicted,
    6727             :                         int32 *buffers_flushed, int32 *buffers_skipped)
    6728             : {
    6729             :     Assert(!RelationUsesLocalBuffers(rel));
    6730             : 
    6731           2 :     *buffers_skipped = 0;
    6732           2 :     *buffers_evicted = 0;
    6733           2 :     *buffers_flushed = 0;
    6734             : 
    6735       32770 :     for (int buf = 1; buf <= NBuffers; buf++)
    6736             :     {
    6737       32768 :         BufferDesc *desc = GetBufferDescriptor(buf - 1);
    6738       32768 :         uint32      buf_state = pg_atomic_read_u32(&(desc->state));
    6739             :         bool        buffer_flushed;
    6740             : 
    6741             :         /* An unlocked precheck should be safe and saves some cycles. */
    6742       32768 :         if ((buf_state & BM_VALID) == 0 ||
    6743          56 :             !BufTagMatchesRelFileLocator(&desc->tag, &rel->rd_locator))
    6744       32768 :             continue;
    6745             : 
    6746             :         /* Make sure we can pin the buffer. */
    6747           0 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    6748           0 :         ReservePrivateRefCountEntry();
    6749             : 
    6750           0 :         buf_state = LockBufHdr(desc);
    6751             : 
    6752             :         /* recheck, could have changed without the lock */
    6753           0 :         if ((buf_state & BM_VALID) == 0 ||
    6754           0 :             !BufTagMatchesRelFileLocator(&desc->tag, &rel->rd_locator))
    6755             :         {
    6756           0 :             UnlockBufHdr(desc, buf_state);
    6757           0 :             continue;
    6758             :         }
    6759             : 
    6760           0 :         if (EvictUnpinnedBufferInternal(desc, &buffer_flushed))
    6761           0 :             (*buffers_evicted)++;
    6762             :         else
    6763           0 :             (*buffers_skipped)++;
    6764             : 
    6765           0 :         if (buffer_flushed)
    6766           0 :             (*buffers_flushed)++;
    6767             :     }
    6768           2 : }
    6769             : 
    6770             : /*
    6771             :  * Generic implementation of the AIO handle staging callback for readv/writev
    6772             :  * on local/shared buffers.
    6773             :  *
    6774             :  * Each readv/writev can target multiple buffers. The buffers have already
    6775             :  * been registered with the IO handle.
    6776             :  *
    6777             :  * To make the IO ready for execution ("staging"), we need to ensure that the
    6778             :  * targeted buffers are in an appropriate state while the IO is ongoing. For
    6779             :  * that the AIO subsystem needs to have its own buffer pin, otherwise an error
    6780             :  * in this backend could lead to this backend's buffer pin being released as
    6781             :  * part of error handling, which in turn could lead to the buffer being
    6782             :  * replaced while IO is ongoing.
    6783             :  */
    6784             : static pg_attribute_always_inline void
    6785     2511646 : buffer_stage_common(PgAioHandle *ioh, bool is_write, bool is_temp)
    6786             : {
    6787             :     uint64     *io_data;
    6788             :     uint8       handle_data_len;
    6789             :     PgAioWaitRef io_ref;
    6790     2511646 :     BufferTag   first PG_USED_FOR_ASSERTS_ONLY = {0};
    6791             : 
    6792     2511646 :     io_data = pgaio_io_get_handle_data(ioh, &handle_data_len);
    6793             : 
    6794     2511646 :     pgaio_io_get_wref(ioh, &io_ref);
    6795             : 
    6796             :     /* iterate over all buffers affected by the vectored readv/writev */
    6797     5348010 :     for (int i = 0; i < handle_data_len; i++)
    6798             :     {
    6799     2836364 :         Buffer      buffer = (Buffer) io_data[i];
    6800     2836364 :         BufferDesc *buf_hdr = is_temp ?
    6801       16788 :             GetLocalBufferDescriptor(-buffer - 1)
    6802     2836364 :             : GetBufferDescriptor(buffer - 1);
    6803             :         uint32      buf_state;
    6804             : 
    6805             :         /*
    6806             :          * Check that all the buffers are actually ones that could conceivably
    6807             :          * be done in one IO, i.e. are sequential. This is the last
    6808             :          * buffer-aware code before IO is actually executed and confusion
    6809             :          * about which buffers are targeted by IO can be hard to debug, making
    6810             :          * it worth doing extra-paranoid checks.
    6811             :          */
    6812     2836364 :         if (i == 0)
    6813     2511646 :             first = buf_hdr->tag;
    6814             :         else
    6815             :         {
    6816             :             Assert(buf_hdr->tag.relNumber == first.relNumber);
    6817             :             Assert(buf_hdr->tag.blockNum == first.blockNum + i);
    6818             :         }
    6819             : 
    6820     2836364 :         if (is_temp)
    6821       16788 :             buf_state = pg_atomic_read_u32(&buf_hdr->state);
    6822             :         else
    6823     2819576 :             buf_state = LockBufHdr(buf_hdr);
    6824             : 
    6825             :         /* verify the buffer is in the expected state */
    6826             :         Assert(buf_state & BM_TAG_VALID);
    6827             :         if (is_write)
    6828             :         {
    6829             :             Assert(buf_state & BM_VALID);
    6830             :             Assert(buf_state & BM_DIRTY);
    6831             :         }
    6832             :         else
    6833             :         {
    6834             :             Assert(!(buf_state & BM_VALID));
    6835             :             Assert(!(buf_state & BM_DIRTY));
    6836             :         }
    6837             : 
    6838             :         /* temp buffers don't use BM_IO_IN_PROGRESS */
    6839     2836364 :         if (!is_temp)
    6840             :             Assert(buf_state & BM_IO_IN_PROGRESS);
    6841             : 
    6842             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) >= 1);
    6843             : 
    6844             :         /*
    6845             :          * Reflect that the buffer is now owned by the AIO subsystem.
    6846             :          *
    6847             :          * For local buffers: This can't be done just via LocalRefCount, as
    6848             :          * one might initially think, as this backend could error out while
    6849             :          * AIO is still in progress, releasing all the pins by the backend
    6850             :          * itself.
    6851             :          *
    6852             :          * This pin is released again in TerminateBufferIO().
    6853             :          */
    6854     2836364 :         buf_state += BUF_REFCOUNT_ONE;
    6855     2836364 :         buf_hdr->io_wref = io_ref;
    6856             : 
    6857     2836364 :         if (is_temp)
    6858       16788 :             pg_atomic_unlocked_write_u32(&buf_hdr->state, buf_state);
    6859             :         else
    6860     2819576 :             UnlockBufHdr(buf_hdr, buf_state);
    6861             : 
    6862             :         /*
    6863             :          * Ensure the content lock that prevents buffer modifications while
    6864             :          * the buffer is being written out is not released early due to an
    6865             :          * error.
    6866             :          */
    6867     2836364 :         if (is_write && !is_temp)
    6868             :         {
    6869             :             LWLock     *content_lock;
    6870             : 
    6871           0 :             content_lock = BufferDescriptorGetContentLock(buf_hdr);
    6872             : 
    6873             :             Assert(LWLockHeldByMe(content_lock));
    6874             : 
    6875             :             /*
    6876             :              * Lock is now owned by AIO subsystem.
    6877             :              */
    6878           0 :             LWLockDisown(content_lock);
    6879             :         }
    6880             : 
    6881             :         /*
    6882             :          * Stop tracking this buffer via the resowner - the AIO system now
    6883             :          * keeps track.
    6884             :          */
    6885     2836364 :         if (!is_temp)
    6886     2819576 :             ResourceOwnerForgetBufferIO(CurrentResourceOwner, buffer);
    6887             :     }
    6888     2511646 : }
    6889             : 
    6890             : /*
    6891             :  * Decode readv errors as encoded by buffer_readv_encode_error().
    6892             :  */
    6893             : static inline void
    6894         698 : buffer_readv_decode_error(PgAioResult result,
    6895             :                           bool *zeroed_any,
    6896             :                           bool *ignored_any,
    6897             :                           uint8 *zeroed_or_error_count,
    6898             :                           uint8 *checkfail_count,
    6899             :                           uint8 *first_off)
    6900             : {
    6901         698 :     uint32      rem_error = result.error_data;
    6902             : 
    6903             :     /* see static asserts in buffer_readv_encode_error */
    6904             : #define READV_COUNT_BITS    7
    6905             : #define READV_COUNT_MASK    ((1 << READV_COUNT_BITS) - 1)
    6906             : 
    6907         698 :     *zeroed_any = rem_error & 1;
    6908         698 :     rem_error >>= 1;
    6909             : 
    6910         698 :     *ignored_any = rem_error & 1;
    6911         698 :     rem_error >>= 1;
    6912             : 
    6913         698 :     *zeroed_or_error_count = rem_error & READV_COUNT_MASK;
    6914         698 :     rem_error >>= READV_COUNT_BITS;
    6915             : 
    6916         698 :     *checkfail_count = rem_error & READV_COUNT_MASK;
    6917         698 :     rem_error >>= READV_COUNT_BITS;
    6918             : 
    6919         698 :     *first_off = rem_error & READV_COUNT_MASK;
    6920         698 :     rem_error >>= READV_COUNT_BITS;
    6921         698 : }
    6922             : 
    6923             : /*
    6924             :  * Helper to encode errors for buffer_readv_complete()
    6925             :  *
    6926             :  * Errors are encoded as follows:
    6927             :  * - bit 0 indicates whether any page was zeroed (1) or not (0)
    6928             :  * - bit 1 indicates whether any checksum failure was ignored (1) or not (0)
    6929             :  * - next READV_COUNT_BITS bits indicate the number of errored or zeroed pages
    6930             :  * - next READV_COUNT_BITS bits indicate the number of checksum failures
    6931             :  * - next READV_COUNT_BITS bits indicate the first offset of the first page
    6932             :  *   that was errored or zeroed or, if no errors/zeroes, the first ignored
    6933             :  *   checksum
    6934             :  */
    6935             : static inline void
    6936         384 : buffer_readv_encode_error(PgAioResult *result,
    6937             :                           bool is_temp,
    6938             :                           bool zeroed_any,
    6939             :                           bool ignored_any,
    6940             :                           uint8 error_count,
    6941             :                           uint8 zeroed_count,
    6942             :                           uint8 checkfail_count,
    6943             :                           uint8 first_error_off,
    6944             :                           uint8 first_zeroed_off,
    6945             :                           uint8 first_ignored_off)
    6946             : {
    6947             : 
    6948         384 :     uint8       shift = 0;
    6949         384 :     uint8       zeroed_or_error_count =
    6950             :         error_count > 0 ? error_count : zeroed_count;
    6951             :     uint8       first_off;
    6952             : 
    6953             :     StaticAssertStmt(PG_IOV_MAX <= 1 << READV_COUNT_BITS,
    6954             :                      "PG_IOV_MAX is bigger than reserved space for error data");
    6955             :     StaticAssertStmt((1 + 1 + 3 * READV_COUNT_BITS) <= PGAIO_RESULT_ERROR_BITS,
    6956             :                      "PGAIO_RESULT_ERROR_BITS is insufficient for buffer_readv");
    6957             : 
    6958             :     /*
    6959             :      * We only have space to encode one offset - but luckily that's good
    6960             :      * enough. If there is an error, the error is the interesting offset, same
    6961             :      * with a zeroed buffer vs an ignored buffer.
    6962             :      */
    6963         384 :     if (error_count > 0)
    6964         188 :         first_off = first_error_off;
    6965         196 :     else if (zeroed_count > 0)
    6966         160 :         first_off = first_zeroed_off;
    6967             :     else
    6968          36 :         first_off = first_ignored_off;
    6969             : 
    6970             :     Assert(!zeroed_any || error_count == 0);
    6971             : 
    6972         384 :     result->error_data = 0;
    6973             : 
    6974         384 :     result->error_data |= zeroed_any << shift;
    6975         384 :     shift += 1;
    6976             : 
    6977         384 :     result->error_data |= ignored_any << shift;
    6978         384 :     shift += 1;
    6979             : 
    6980         384 :     result->error_data |= ((uint32) zeroed_or_error_count) << shift;
    6981         384 :     shift += READV_COUNT_BITS;
    6982             : 
    6983         384 :     result->error_data |= ((uint32) checkfail_count) << shift;
    6984         384 :     shift += READV_COUNT_BITS;
    6985             : 
    6986         384 :     result->error_data |= ((uint32) first_off) << shift;
    6987         384 :     shift += READV_COUNT_BITS;
    6988             : 
    6989         384 :     result->id = is_temp ? PGAIO_HCB_LOCAL_BUFFER_READV :
    6990             :         PGAIO_HCB_SHARED_BUFFER_READV;
    6991             : 
    6992         384 :     if (error_count > 0)
    6993         188 :         result->status = PGAIO_RS_ERROR;
    6994             :     else
    6995         196 :         result->status = PGAIO_RS_WARNING;
    6996             : 
    6997             :     /*
    6998             :      * The encoding is complicated enough to warrant cross-checking it against
    6999             :      * the decode function.
    7000             :      */
    7001             : #ifdef USE_ASSERT_CHECKING
    7002             :     {
    7003             :         bool        zeroed_any_2,
    7004             :                     ignored_any_2;
    7005             :         uint8       zeroed_or_error_count_2,
    7006             :                     checkfail_count_2,
    7007             :                     first_off_2;
    7008             : 
    7009             :         buffer_readv_decode_error(*result,
    7010             :                                   &zeroed_any_2, &ignored_any_2,
    7011             :                                   &zeroed_or_error_count_2,
    7012             :                                   &checkfail_count_2,
    7013             :                                   &first_off_2);
    7014             :         Assert(zeroed_any == zeroed_any_2);
    7015             :         Assert(ignored_any == ignored_any_2);
    7016             :         Assert(zeroed_or_error_count == zeroed_or_error_count_2);
    7017             :         Assert(checkfail_count == checkfail_count_2);
    7018             :         Assert(first_off == first_off_2);
    7019             :     }
    7020             : #endif
    7021             : 
    7022             : #undef READV_COUNT_BITS
    7023             : #undef READV_COUNT_MASK
    7024         384 : }
    7025             : 
    7026             : /*
    7027             :  * Helper for AIO readv completion callbacks, supporting both shared and temp
    7028             :  * buffers. Gets called once for each buffer in a multi-page read.
    7029             :  */
    7030             : static pg_attribute_always_inline void
    7031     2559118 : buffer_readv_complete_one(PgAioTargetData *td, uint8 buf_off, Buffer buffer,
    7032             :                           uint8 flags, bool failed, bool is_temp,
    7033             :                           bool *buffer_invalid,
    7034             :                           bool *failed_checksum,
    7035             :                           bool *ignored_checksum,
    7036             :                           bool *zeroed_buffer)
    7037             : {
    7038     2559118 :     BufferDesc *buf_hdr = is_temp ?
    7039       16788 :         GetLocalBufferDescriptor(-buffer - 1)
    7040     2559118 :         : GetBufferDescriptor(buffer - 1);
    7041     2559118 :     BufferTag   tag = buf_hdr->tag;
    7042     2559118 :     char       *bufdata = BufferGetBlock(buffer);
    7043             :     uint32      set_flag_bits;
    7044             :     int         piv_flags;
    7045             : 
    7046             :     /* check that the buffer is in the expected state for a read */
    7047             : #ifdef USE_ASSERT_CHECKING
    7048             :     {
    7049             :         uint32      buf_state = pg_atomic_read_u32(&buf_hdr->state);
    7050             : 
    7051             :         Assert(buf_state & BM_TAG_VALID);
    7052             :         Assert(!(buf_state & BM_VALID));
    7053             :         /* temp buffers don't use BM_IO_IN_PROGRESS */
    7054             :         if (!is_temp)
    7055             :             Assert(buf_state & BM_IO_IN_PROGRESS);
    7056             :         Assert(!(buf_state & BM_DIRTY));
    7057             :     }
    7058             : #endif
    7059             : 
    7060     2559118 :     *buffer_invalid = false;
    7061     2559118 :     *failed_checksum = false;
    7062     2559118 :     *ignored_checksum = false;
    7063     2559118 :     *zeroed_buffer = false;
    7064             : 
    7065             :     /*
    7066             :      * We ask PageIsVerified() to only log the message about checksum errors,
    7067             :      * as the completion might be run in any backend (or IO workers). We will
    7068             :      * report checksum errors in buffer_readv_report().
    7069             :      */
    7070     2559118 :     piv_flags = PIV_LOG_LOG;
    7071             : 
    7072             :     /* the local zero_damaged_pages may differ from the definer's */
    7073     2559118 :     if (flags & READ_BUFFERS_IGNORE_CHECKSUM_FAILURES)
    7074          76 :         piv_flags |= PIV_IGNORE_CHECKSUM_FAILURE;
    7075             : 
    7076             :     /* Check for garbage data. */
    7077     2559118 :     if (!failed)
    7078             :     {
    7079             :         /*
    7080             :          * If the buffer is not currently pinned by this backend, e.g. because
    7081             :          * we're completing this IO after an error, the buffer data will have
    7082             :          * been marked as inaccessible when the buffer was unpinned. The AIO
    7083             :          * subsystem holds a pin, but that doesn't prevent the buffer from
    7084             :          * having been marked as inaccessible. The completion might also be
    7085             :          * executed in a different process.
    7086             :          */
    7087             : #ifdef USE_VALGRIND
    7088             :         if (!BufferIsPinned(buffer))
    7089             :             VALGRIND_MAKE_MEM_DEFINED(bufdata, BLCKSZ);
    7090             : #endif
    7091             : 
    7092     2559060 :         if (!PageIsVerified((Page) bufdata, tag.blockNum, piv_flags,
    7093             :                             failed_checksum))
    7094             :         {
    7095         192 :             if (flags & READ_BUFFERS_ZERO_ON_ERROR)
    7096             :             {
    7097          92 :                 memset(bufdata, 0, BLCKSZ);
    7098          92 :                 *zeroed_buffer = true;
    7099             :             }
    7100             :             else
    7101             :             {
    7102         100 :                 *buffer_invalid = true;
    7103             :                 /* mark buffer as having failed */
    7104         100 :                 failed = true;
    7105             :             }
    7106             :         }
    7107     2558868 :         else if (*failed_checksum)
    7108          24 :             *ignored_checksum = true;
    7109             : 
    7110             :         /* undo what we did above */
    7111             : #ifdef USE_VALGRIND
    7112             :         if (!BufferIsPinned(buffer))
    7113             :             VALGRIND_MAKE_MEM_NOACCESS(bufdata, BLCKSZ);
    7114             : #endif
    7115             : 
    7116             :         /*
    7117             :          * Immediately log a message about the invalid page, but only to the
    7118             :          * server log. The reason to do so immediately is that this may be
    7119             :          * executed in a different backend than the one that originated the
    7120             :          * request. The reason to do so immediately is that the originator
    7121             :          * might not process the query result immediately (because it is busy
    7122             :          * doing another part of query processing) or at all (e.g. if it was
    7123             :          * cancelled or errored out due to another IO also failing). The
    7124             :          * definer of the IO will emit an ERROR or WARNING when processing the
    7125             :          * IO's results
    7126             :          *
    7127             :          * To avoid duplicating the code to emit these log messages, we reuse
    7128             :          * buffer_readv_report().
    7129             :          */
    7130     2559060 :         if (*buffer_invalid || *failed_checksum || *zeroed_buffer)
    7131             :         {
    7132         216 :             PgAioResult result_one = {0};
    7133             : 
    7134         216 :             buffer_readv_encode_error(&result_one, is_temp,
    7135         216 :                                       *zeroed_buffer,
    7136         216 :                                       *ignored_checksum,
    7137         216 :                                       *buffer_invalid,
    7138         216 :                                       *zeroed_buffer ? 1 : 0,
    7139         216 :                                       *failed_checksum ? 1 : 0,
    7140             :                                       buf_off, buf_off, buf_off);
    7141         216 :             pgaio_result_report(result_one, td, LOG_SERVER_ONLY);
    7142             :         }
    7143             :     }
    7144             : 
    7145             :     /* Terminate I/O and set BM_VALID. */
    7146     2559118 :     set_flag_bits = failed ? BM_IO_ERROR : BM_VALID;
    7147     2559118 :     if (is_temp)
    7148       16788 :         TerminateLocalBufferIO(buf_hdr, false, set_flag_bits, true);
    7149             :     else
    7150     2542330 :         TerminateBufferIO(buf_hdr, false, set_flag_bits, false, true);
    7151             : 
    7152             :     /*
    7153             :      * Call the BUFFER_READ_DONE tracepoint in the callback, even though the
    7154             :      * callback may not be executed in the same backend that called
    7155             :      * BUFFER_READ_START. The alternative would be to defer calling the
    7156             :      * tracepoint to a later point (e.g. the local completion callback for
    7157             :      * shared buffer reads), which seems even less helpful.
    7158             :      */
    7159             :     TRACE_POSTGRESQL_BUFFER_READ_DONE(tag.forkNum,
    7160             :                                       tag.blockNum,
    7161             :                                       tag.spcOid,
    7162             :                                       tag.dbOid,
    7163             :                                       tag.relNumber,
    7164             :                                       is_temp ? MyProcNumber : INVALID_PROC_NUMBER,
    7165             :                                       false);
    7166     2559118 : }
    7167             : 
    7168             : /*
    7169             :  * Perform completion handling of a single AIO read. This read may cover
    7170             :  * multiple blocks / buffers.
    7171             :  *
    7172             :  * Shared between shared and local buffers, to reduce code duplication.
    7173             :  */
    7174             : static pg_attribute_always_inline PgAioResult
    7175     2301688 : buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
    7176             :                       uint8 cb_data, bool is_temp)
    7177             : {
    7178     2301688 :     PgAioResult result = prior_result;
    7179     2301688 :     PgAioTargetData *td = pgaio_io_get_target_data(ioh);
    7180     2301688 :     uint8       first_error_off = 0;
    7181     2301688 :     uint8       first_zeroed_off = 0;
    7182     2301688 :     uint8       first_ignored_off = 0;
    7183     2301688 :     uint8       error_count = 0;
    7184     2301688 :     uint8       zeroed_count = 0;
    7185     2301688 :     uint8       ignored_count = 0;
    7186     2301688 :     uint8       checkfail_count = 0;
    7187             :     uint64     *io_data;
    7188             :     uint8       handle_data_len;
    7189             : 
    7190             :     if (is_temp)
    7191             :     {
    7192             :         Assert(td->smgr.is_temp);
    7193             :         Assert(pgaio_io_get_owner(ioh) == MyProcNumber);
    7194             :     }
    7195             :     else
    7196             :         Assert(!td->smgr.is_temp);
    7197             : 
    7198             :     /*
    7199             :      * Iterate over all the buffers affected by this IO and call the
    7200             :      * per-buffer completion function for each buffer.
    7201             :      */
    7202     2301688 :     io_data = pgaio_io_get_handle_data(ioh, &handle_data_len);
    7203     4860806 :     for (uint8 buf_off = 0; buf_off < handle_data_len; buf_off++)
    7204             :     {
    7205     2559118 :         Buffer      buf = io_data[buf_off];
    7206             :         bool        failed;
    7207     2559118 :         bool        failed_verification = false;
    7208     2559118 :         bool        failed_checksum = false;
    7209     2559118 :         bool        zeroed_buffer = false;
    7210     2559118 :         bool        ignored_checksum = false;
    7211             : 
    7212             :         Assert(BufferIsValid(buf));
    7213             : 
    7214             :         /*
    7215             :          * If the entire I/O failed on a lower-level, each buffer needs to be
    7216             :          * marked as failed. In case of a partial read, the first few buffers
    7217             :          * may be ok.
    7218             :          */
    7219     2559118 :         failed =
    7220     2559118 :             prior_result.status == PGAIO_RS_ERROR
    7221     2559118 :             || prior_result.result <= buf_off;
    7222             : 
    7223     2559118 :         buffer_readv_complete_one(td, buf_off, buf, cb_data, failed, is_temp,
    7224             :                                   &failed_verification,
    7225             :                                   &failed_checksum,
    7226             :                                   &ignored_checksum,
    7227             :                                   &zeroed_buffer);
    7228             : 
    7229             :         /*
    7230             :          * Track information about the number of different kinds of error
    7231             :          * conditions across all pages, as there can be multiple pages failing
    7232             :          * verification as part of one IO.
    7233             :          */
    7234     2559118 :         if (failed_verification && !zeroed_buffer && error_count++ == 0)
    7235          88 :             first_error_off = buf_off;
    7236     2559118 :         if (zeroed_buffer && zeroed_count++ == 0)
    7237          68 :             first_zeroed_off = buf_off;
    7238     2559118 :         if (ignored_checksum && ignored_count++ == 0)
    7239          20 :             first_ignored_off = buf_off;
    7240     2559118 :         if (failed_checksum)
    7241          64 :             checkfail_count++;
    7242             :     }
    7243             : 
    7244             :     /*
    7245             :      * If the smgr read succeeded [partially] and page verification failed for
    7246             :      * some of the pages, adjust the IO's result state appropriately.
    7247             :      */
    7248     2301688 :     if (prior_result.status != PGAIO_RS_ERROR &&
    7249     2301582 :         (error_count > 0 || ignored_count > 0 || zeroed_count > 0))
    7250             :     {
    7251         168 :         buffer_readv_encode_error(&result, is_temp,
    7252             :                                   zeroed_count > 0, ignored_count > 0,
    7253             :                                   error_count, zeroed_count, checkfail_count,
    7254             :                                   first_error_off, first_zeroed_off,
    7255             :                                   first_ignored_off);
    7256         168 :         pgaio_result_report(result, td, DEBUG1);
    7257             :     }
    7258             : 
    7259             :     /*
    7260             :      * For shared relations this reporting is done in
    7261             :      * shared_buffer_readv_complete_local().
    7262             :      */
    7263     2301688 :     if (is_temp && checkfail_count > 0)
    7264           4 :         pgstat_report_checksum_failures_in_db(td->smgr.rlocator.dbOid,
    7265             :                                               checkfail_count);
    7266             : 
    7267     2301688 :     return result;
    7268             : }
    7269             : 
    7270             : /*
    7271             :  * AIO error reporting callback for aio_shared_buffer_readv_cb and
    7272             :  * aio_local_buffer_readv_cb.
    7273             :  *
    7274             :  * The error is encoded / decoded in buffer_readv_encode_error() /
    7275             :  * buffer_readv_decode_error().
    7276             :  */
    7277             : static void
    7278         544 : buffer_readv_report(PgAioResult result, const PgAioTargetData *td,
    7279             :                     int elevel)
    7280             : {
    7281         544 :     int         nblocks = td->smgr.nblocks;
    7282         544 :     BlockNumber first = td->smgr.blockNum;
    7283         544 :     BlockNumber last = first + nblocks - 1;
    7284         544 :     ProcNumber  errProc =
    7285         544 :         td->smgr.is_temp ? MyProcNumber : INVALID_PROC_NUMBER;
    7286             :     RelPathStr  rpath =
    7287         544 :         relpathbackend(td->smgr.rlocator, errProc, td->smgr.forkNum);
    7288             :     bool        zeroed_any,
    7289             :                 ignored_any;
    7290             :     uint8       zeroed_or_error_count,
    7291             :                 checkfail_count,
    7292             :                 first_off;
    7293             :     uint8       affected_count;
    7294             :     const char *msg_one,
    7295             :                *msg_mult,
    7296             :                *det_mult,
    7297             :                *hint_mult;
    7298             : 
    7299         544 :     buffer_readv_decode_error(result, &zeroed_any, &ignored_any,
    7300             :                               &zeroed_or_error_count,
    7301             :                               &checkfail_count,
    7302             :                               &first_off);
    7303             : 
    7304             :     /*
    7305             :      * Treat a read that had both zeroed buffers *and* ignored checksums as a
    7306             :      * special case, it's too irregular to be emitted the same way as the
    7307             :      * other cases.
    7308             :      */
    7309         544 :     if (zeroed_any && ignored_any)
    7310             :     {
    7311             :         Assert(zeroed_any && ignored_any);
    7312             :         Assert(nblocks > 1); /* same block can't be both zeroed and ignored */
    7313             :         Assert(result.status != PGAIO_RS_ERROR);
    7314           8 :         affected_count = zeroed_or_error_count;
    7315             : 
    7316           8 :         ereport(elevel,
    7317             :                 errcode(ERRCODE_DATA_CORRUPTED),
    7318             :                 errmsg("zeroing %u page(s) and ignoring %u checksum failure(s) among blocks %u..%u of relation %s",
    7319             :                        affected_count, checkfail_count, first, last, rpath.str),
    7320             :                 affected_count > 1 ?
    7321             :                 errdetail("Block %u held first zeroed page.",
    7322             :                           first + first_off) : 0,
    7323             :                 errhint("See server log for details about the other %u invalid block(s).",
    7324             :                         affected_count + checkfail_count - 1));
    7325           8 :         return;
    7326             :     }
    7327             : 
    7328             :     /*
    7329             :      * The other messages are highly repetitive. To avoid duplicating a long
    7330             :      * and complicated ereport(), gather the translated format strings
    7331             :      * separately and then do one common ereport.
    7332             :      */
    7333         536 :     if (result.status == PGAIO_RS_ERROR)
    7334             :     {
    7335             :         Assert(!zeroed_any);    /* can't have invalid pages when zeroing them */
    7336         272 :         affected_count = zeroed_or_error_count;
    7337         272 :         msg_one = _("invalid page in block %u of relation %s");
    7338         272 :         msg_mult = _("%u invalid pages among blocks %u..%u of relation %s");
    7339         272 :         det_mult = _("Block %u held first invalid page.");
    7340         272 :         hint_mult = _("See server log for the other %u invalid block(s).");
    7341             :     }
    7342         264 :     else if (zeroed_any && !ignored_any)
    7343             :     {
    7344         216 :         affected_count = zeroed_or_error_count;
    7345         216 :         msg_one = _("invalid page in block %u of relation %s; zeroing out page");
    7346         216 :         msg_mult = _("zeroing out %u invalid pages among blocks %u..%u of relation %s");
    7347         216 :         det_mult = _("Block %u held first zeroed page.");
    7348         216 :         hint_mult = _("See server log for the other %u zeroed block(s).");
    7349             :     }
    7350          48 :     else if (!zeroed_any && ignored_any)
    7351             :     {
    7352          48 :         affected_count = checkfail_count;
    7353          48 :         msg_one = _("ignoring checksum failure in block %u of relation %s");
    7354          48 :         msg_mult = _("ignoring %u checksum failures among blocks %u..%u of relation %s");
    7355          48 :         det_mult = _("Block %u held first ignored page.");
    7356          48 :         hint_mult = _("See server log for the other %u ignored block(s).");
    7357             :     }
    7358             :     else
    7359           0 :         pg_unreachable();
    7360             : 
    7361         536 :     ereport(elevel,
    7362             :             errcode(ERRCODE_DATA_CORRUPTED),
    7363             :             affected_count == 1 ?
    7364             :             errmsg_internal(msg_one, first + first_off, rpath.str) :
    7365             :             errmsg_internal(msg_mult, affected_count, first, last, rpath.str),
    7366             :             affected_count > 1 ? errdetail_internal(det_mult, first + first_off) : 0,
    7367             :             affected_count > 1 ? errhint_internal(hint_mult, affected_count - 1) : 0);
    7368             : }
    7369             : 
    7370             : static void
    7371     2508064 : shared_buffer_readv_stage(PgAioHandle *ioh, uint8 cb_data)
    7372             : {
    7373     2508064 :     buffer_stage_common(ioh, false, false);
    7374     2508064 : }
    7375             : 
    7376             : static PgAioResult
    7377     2298106 : shared_buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
    7378             :                              uint8 cb_data)
    7379             : {
    7380     2298106 :     return buffer_readv_complete(ioh, prior_result, cb_data, false);
    7381             : }
    7382             : 
    7383             : /*
    7384             :  * We need a backend-local completion callback for shared buffers, to be able
    7385             :  * to report checksum errors correctly. Unfortunately that can only safely
    7386             :  * happen if the reporting backend has previously called
    7387             :  * pgstat_prepare_report_checksum_failure(), which we can only guarantee in
    7388             :  * the backend that started the IO. Hence this callback.
    7389             :  */
    7390             : static PgAioResult
    7391     2508064 : shared_buffer_readv_complete_local(PgAioHandle *ioh, PgAioResult prior_result,
    7392             :                                    uint8 cb_data)
    7393             : {
    7394             :     bool        zeroed_any,
    7395             :                 ignored_any;
    7396             :     uint8       zeroed_or_error_count,
    7397             :                 checkfail_count,
    7398             :                 first_off;
    7399             : 
    7400     2508064 :     if (prior_result.status == PGAIO_RS_OK)
    7401     2507910 :         return prior_result;
    7402             : 
    7403         154 :     buffer_readv_decode_error(prior_result,
    7404             :                               &zeroed_any,
    7405             :                               &ignored_any,
    7406             :                               &zeroed_or_error_count,
    7407             :                               &checkfail_count,
    7408             :                               &first_off);
    7409             : 
    7410         154 :     if (checkfail_count)
    7411             :     {
    7412          48 :         PgAioTargetData *td = pgaio_io_get_target_data(ioh);
    7413             : 
    7414          48 :         pgstat_report_checksum_failures_in_db(td->smgr.rlocator.dbOid,
    7415             :                                               checkfail_count);
    7416             :     }
    7417             : 
    7418         154 :     return prior_result;
    7419             : }
    7420             : 
    7421             : static void
    7422        3582 : local_buffer_readv_stage(PgAioHandle *ioh, uint8 cb_data)
    7423             : {
    7424        3582 :     buffer_stage_common(ioh, false, true);
    7425        3582 : }
    7426             : 
    7427             : static PgAioResult
    7428        3582 : local_buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
    7429             :                             uint8 cb_data)
    7430             : {
    7431        3582 :     return buffer_readv_complete(ioh, prior_result, cb_data, true);
    7432             : }
    7433             : 
    7434             : /* readv callback is passed READ_BUFFERS_* flags as callback data */
    7435             : const PgAioHandleCallbacks aio_shared_buffer_readv_cb = {
    7436             :     .stage = shared_buffer_readv_stage,
    7437             :     .complete_shared = shared_buffer_readv_complete,
    7438             :     /* need a local callback to report checksum failures */
    7439             :     .complete_local = shared_buffer_readv_complete_local,
    7440             :     .report = buffer_readv_report,
    7441             : };
    7442             : 
    7443             : /* readv callback is passed READ_BUFFERS_* flags as callback data */
    7444             : const PgAioHandleCallbacks aio_local_buffer_readv_cb = {
    7445             :     .stage = local_buffer_readv_stage,
    7446             : 
    7447             :     /*
    7448             :      * Note that this, in contrast to the shared_buffers case, uses
    7449             :      * complete_local, as only the issuing backend has access to the required
    7450             :      * datastructures. This is important in case the IO completion may be
    7451             :      * consumed incidentally by another backend.
    7452             :      */
    7453             :     .complete_local = local_buffer_readv_complete,
    7454             :     .report = buffer_readv_report,
    7455             : };

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