LCOV - code coverage report
Current view: top level - src/backend/storage/buffer - bufmgr.c (source / functions) Hit Total Coverage
Test: PostgreSQL 19devel Lines: 1674 1833 91.3 %
Date: 2025-09-10 22:18:18 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   129663440 : ReservePrivateRefCountEntry(void)
     260             : {
     261             :     /* Already reserved (or freed), nothing to do */
     262   129663440 :     if (ReservedRefCountEntry != NULL)
     263   121445710 :         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    20964130 :         for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
     273             :         {
     274             :             PrivateRefCountEntry *res;
     275             : 
     276    20624922 :             res = &PrivateRefCountArray[i];
     277             : 
     278    20624922 :             if (res->buffer == InvalidBuffer)
     279             :             {
     280     7878522 :                 ReservedRefCountEntry = res;
     281     7878522 :                 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      339208 :         ReservedRefCountEntry =
     300      339208 :             &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      339208 :         hashent = hash_search(PrivateRefCountHash,
     307      339208 :                               &(ReservedRefCountEntry->buffer),
     308             :                               HASH_ENTER,
     309             :                               &found);
     310             :         Assert(!found);
     311      339208 :         hashent->refcount = ReservedRefCountEntry->refcount;
     312             : 
     313             :         /* clear the now free array slot */
     314      339208 :         ReservedRefCountEntry->buffer = InvalidBuffer;
     315      339208 :         ReservedRefCountEntry->refcount = 0;
     316             : 
     317      339208 :         PrivateRefCountOverflowed++;
     318             :     }
     319             : }
     320             : 
     321             : /*
     322             :  * Fill a previously reserved refcount entry.
     323             :  */
     324             : static PrivateRefCountEntry *
     325   118057786 : 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   118057786 :     res = ReservedRefCountEntry;
     334   118057786 :     ReservedRefCountEntry = NULL;
     335             : 
     336             :     /* and fill it */
     337   118057786 :     res->buffer = buffer;
     338   118057786 :     res->refcount = 0;
     339             : 
     340   118057786 :     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   291873992 : 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  1372758422 :     for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
     364             :     {
     365  1258748676 :         res = &PrivateRefCountArray[i];
     366             : 
     367  1258748676 :         if (res->buffer == buffer)
     368   177864246 :             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   114009746 :     if (PrivateRefCountOverflowed == 0)
     379   113206274 :         return NULL;
     380             : 
     381      803472 :     res = hash_search(PrivateRefCountHash, &buffer, HASH_FIND, NULL);
     382             : 
     383      803472 :     if (res == NULL)
     384      459708 :         return NULL;
     385      343764 :     else if (!do_move)
     386             :     {
     387             :         /* caller doesn't want us to move the hash entry into the array */
     388      302218 :         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       41546 :         ReservePrivateRefCountEntry();
     398             : 
     399             :         /* Use up the reserved slot */
     400             :         Assert(ReservedRefCountEntry != NULL);
     401       41546 :         free = ReservedRefCountEntry;
     402       41546 :         ReservedRefCountEntry = NULL;
     403             :         Assert(free->buffer == InvalidBuffer);
     404             : 
     405             :         /* and fill it */
     406       41546 :         free->buffer = buffer;
     407       41546 :         free->refcount = res->refcount;
     408             : 
     409             :         /* delete from hashtable */
     410       41546 :         hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
     411             :         Assert(found);
     412             :         Assert(PrivateRefCountOverflowed > 0);
     413       41546 :         PrivateRefCountOverflowed--;
     414             : 
     415       41546 :         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     6404312 : 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     6404312 :     ref = GetPrivateRefCountEntry(buffer, false);
     437             : 
     438     6404312 :     if (ref == NULL)
     439        8936 :         return 0;
     440     6395376 :     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   118057786 : ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref)
     449             : {
     450             :     Assert(ref->refcount == 0);
     451             : 
     452   118057786 :     if (ref >= &PrivateRefCountArray[0] &&
     453             :         ref < &PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES])
     454             :     {
     455   117760124 :         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   117760124 :         ReservedRefCountEntry = ref;
     463             :     }
     464             :     else
     465             :     {
     466             :         bool        found;
     467      297662 :         Buffer      buffer = ref->buffer;
     468             : 
     469      297662 :         hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
     470             :         Assert(found);
     471             :         Assert(PrivateRefCountOverflowed > 0);
     472      297662 :         PrivateRefCountOverflowed--;
     473             :     }
     474   118057786 : }
     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       60976 : PrefetchSharedBuffer(SMgrRelation smgr_reln,
     562             :                      ForkNumber forkNum,
     563             :                      BlockNumber blockNum)
     564             : {
     565       60976 :     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       60976 :     InitBufferTag(&newTag, &smgr_reln->smgr_rlocator.locator,
     575             :                   forkNum, blockNum);
     576             : 
     577             :     /* determine its hash code and partition lock ID */
     578       60976 :     newHash = BufTableHashCode(&newTag);
     579       60976 :     newPartitionLock = BufMappingPartitionLock(newHash);
     580             : 
     581             :     /* see if the block is in the buffer pool already */
     582       60976 :     LWLockAcquire(newPartitionLock, LW_SHARED);
     583       60976 :     buf_id = BufTableLookup(&newTag, newHash);
     584       60976 :     LWLockRelease(newPartitionLock);
     585             : 
     586             :     /* If not in buffers, initiate prefetch */
     587       60976 :     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       34888 :         if ((io_direct_flags & IO_DIRECT_DATA) == 0 &&
     595       17220 :             smgrprefetch(smgr_reln, forkNum, blockNum, 1))
     596             :         {
     597       17220 :             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       43308 :         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       60976 :     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       39786 : PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
     652             : {
     653             :     Assert(RelationIsValid(reln));
     654             :     Assert(BlockNumberIsValid(blockNum));
     655             : 
     656       39786 :     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       38220 :         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        8950 : 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        8950 :     ResourceOwnerEnlarge(CurrentResourceOwner);
     693        8950 :     ReservePrivateRefCountEntry();
     694        8950 :     InitBufferTag(&tag, &rlocator, forkNum, blockNum);
     695             : 
     696        8950 :     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        8886 :         bufHdr = GetBufferDescriptor(recent_buffer - 1);
     716        8886 :         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        8886 :         if (have_private_ref)
     724           0 :             buf_state = pg_atomic_read_u32(&bufHdr->state);
     725             :         else
     726        8886 :             buf_state = LockBufHdr(bufHdr);
     727             : 
     728        8886 :         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        8768 :             if (have_private_ref)
     736           0 :                 PinBuffer(bufHdr, NULL);    /* bump pin count */
     737             :             else
     738        8768 :                 PinBuffer_Locked(bufHdr);   /* pin for first time */
     739             : 
     740        8768 :             pgBufferUsage.shared_blks_hit++;
     741             : 
     742        8768 :             return true;
     743             :         }
     744             : 
     745             :         /* If we locked the header above, now unlock. */
     746         118 :         if (!have_private_ref)
     747         118 :             UnlockBufHdr(bufHdr, buf_state);
     748             :     }
     749             : 
     750         118 :     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    86116118 : ReadBuffer(Relation reln, BlockNumber blockNum)
     759             : {
     760    86116118 :     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   104171442 : 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   104171442 :     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   104171442 :     buf = ReadBuffer_common(reln, RelationGetSmgr(reln), 0,
     825             :                             forkNum, blockNum, mode, strategy);
     826             : 
     827   104171396 :     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    11343910 : ReadBufferWithoutRelcache(RelFileLocator rlocator, ForkNumber forkNum,
     843             :                           BlockNumber blockNum, ReadBufferMode mode,
     844             :                           BufferAccessStrategy strategy, bool permanent)
     845             : {
     846    11343910 :     SMgrRelation smgr = smgropen(rlocator, INVALID_PROC_NUMBER);
     847             : 
     848    11343910 :     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       90422 : ExtendBufferedRel(BufferManagerRelation bmr,
     859             :                   ForkNumber forkNum,
     860             :                   BufferAccessStrategy strategy,
     861             :                   uint32 flags)
     862             : {
     863             :     Buffer      buf;
     864       90422 :     uint32      extend_by = 1;
     865             : 
     866       90422 :     ExtendBufferedRelBy(bmr, forkNum, strategy, flags, extend_by,
     867             :                         &buf, &extend_by);
     868             : 
     869       90422 :     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      317774 : 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      317774 :     if (bmr.smgr == NULL)
     903             :     {
     904      317774 :         bmr.smgr = RelationGetSmgr(bmr.rel);
     905      317774 :         bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
     906             :     }
     907             : 
     908      317774 :     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      102528 : 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      102528 :     uint32      extended_by = 0;
     931      102528 :     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      102528 :     if (bmr.smgr == NULL)
     939             :     {
     940       14024 :         bmr.smgr = RelationGetSmgr(bmr.rel);
     941       14024 :         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      102528 :     if ((flags & EB_CREATE_FORK_IF_NEEDED) &&
     950       14024 :         (bmr.smgr->smgr_cached_nblocks[fork] == 0 ||
     951          34 :          bmr.smgr->smgr_cached_nblocks[fork] == InvalidBlockNumber) &&
     952       13990 :         !smgrexists(bmr.smgr, fork))
     953             :     {
     954       13964 :         LockRelationForExtension(bmr.rel, ExclusiveLock);
     955             : 
     956             :         /* recheck, fork might have been created concurrently */
     957       13964 :         if (!smgrexists(bmr.smgr, fork))
     958       13960 :             smgrcreate(bmr.smgr, fork, flags & EB_PERFORMING_RECOVERY);
     959             : 
     960       13964 :         UnlockRelationForExtension(bmr.rel, ExclusiveLock);
     961             :     }
     962             : 
     963             :     /*
     964             :      * If requested, invalidate size cache, so that smgrnblocks asks the
     965             :      * kernel.
     966             :      */
     967      102528 :     if (flags & EB_CLEAR_SIZE_CACHE)
     968       14024 :         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      102528 :     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      102528 :     if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
     983       87772 :         flags |= EB_LOCK_TARGET;
     984             : 
     985      209042 :     while (current_size < extend_to)
     986             :     {
     987      106514 :         uint32      num_pages = lengthof(buffers);
     988             :         BlockNumber first_block;
     989             : 
     990      106514 :         if ((uint64) current_size + num_pages > extend_to)
     991      106512 :             num_pages = extend_to - current_size;
     992             : 
     993      106514 :         first_block = ExtendBufferedRelCommon(bmr, fork, strategy, flags,
     994             :                                               num_pages, extend_to,
     995             :                                               buffers, &extended_by);
     996             : 
     997      106514 :         current_size = first_block + extended_by;
     998             :         Assert(num_pages != 0 || current_size >= extend_to);
     999             : 
    1000      227342 :         for (uint32 i = 0; i < extended_by; i++)
    1001             :         {
    1002      120828 :             if (first_block + i != extend_to - 1)
    1003       18314 :                 ReleaseBuffer(buffers[i]);
    1004             :             else
    1005      102514 :                 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      102528 :     if (buffer == InvalidBuffer)
    1016             :     {
    1017             :         Assert(extended_by == 0);
    1018          14 :         buffer = ReadBuffer_common(bmr.rel, bmr.smgr, bmr.relpersistence,
    1019             :                                    fork, extend_to - 1, mode, strategy);
    1020             :     }
    1021             : 
    1022      102528 :     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      631866 : ZeroAndLockBuffer(Buffer buffer, ReadBufferMode mode, bool already_valid)
    1032             : {
    1033             :     BufferDesc *bufHdr;
    1034             :     bool        need_to_zero;
    1035      631866 :     bool        isLocalBuf = BufferIsLocal(buffer);
    1036             : 
    1037             :     Assert(mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK);
    1038             : 
    1039      631866 :     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       74336 :         need_to_zero = false;
    1046             :     }
    1047      557530 :     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      557482 :         bufHdr = GetBufferDescriptor(buffer - 1);
    1064      557482 :         need_to_zero = StartBufferIO(bufHdr, true, false);
    1065             :     }
    1066             : 
    1067      631866 :     if (need_to_zero)
    1068             :     {
    1069      557530 :         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      557530 :         if (!isLocalBuf)
    1083      557482 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_EXCLUSIVE);
    1084             : 
    1085             :         /* Set BM_VALID, terminate IO, and wake up any waiters */
    1086      557530 :         if (isLocalBuf)
    1087          48 :             TerminateLocalBufferIO(bufHdr, false, BM_VALID, false);
    1088             :         else
    1089      557482 :             TerminateBufferIO(bufHdr, false, BM_VALID, true, false);
    1090             :     }
    1091       74336 :     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       74296 :         if (mode == RBM_ZERO_AND_LOCK)
    1098       74198 :             LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
    1099             :         else
    1100          98 :             LockBufferForCleanup(buffer);
    1101             :     }
    1102      631866 : }
    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   123859044 : 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   123859044 :     if (persistence == RELPERSISTENCE_TEMP)
    1130             :     {
    1131     2554082 :         io_context = IOCONTEXT_NORMAL;
    1132     2554082 :         io_object = IOOBJECT_TEMP_RELATION;
    1133             :     }
    1134             :     else
    1135             :     {
    1136   121304962 :         io_context = IOContextForStrategy(strategy);
    1137   121304962 :         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   123859044 :     if (persistence == RELPERSISTENCE_TEMP)
    1147             :     {
    1148     2554082 :         bufHdr = LocalBufferAlloc(smgr, forkNum, blockNum, foundPtr);
    1149     2554070 :         if (*foundPtr)
    1150     2537294 :             pgBufferUsage.local_blks_hit++;
    1151             :     }
    1152             :     else
    1153             :     {
    1154   121304962 :         bufHdr = BufferAlloc(smgr, persistence, forkNum, blockNum,
    1155             :                              strategy, foundPtr, io_context);
    1156   121304962 :         if (*foundPtr)
    1157   117954104 :             pgBufferUsage.shared_blks_hit++;
    1158             :     }
    1159   123859032 :     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   112052406 :         pgstat_count_buffer_read(rel);
    1167   112052406 :         if (*foundPtr)
    1168   109601116 :             pgstat_count_buffer_hit(rel);
    1169             :     }
    1170   123859032 :     if (*foundPtr)
    1171             :     {
    1172   120491398 :         pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
    1173   120491398 :         if (VacuumCostActive)
    1174     6670936 :             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   123859032 :     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   115515366 : 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   115515366 :     if (unlikely(blockNum == P_NEW))
    1209             :     {
    1210         520 :         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         520 :         if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
    1218           0 :             flags |= EB_LOCK_FIRST;
    1219             : 
    1220         520 :         return ExtendBufferedRel(BMR_REL(rel), forkNum, strategy, flags);
    1221             :     }
    1222             : 
    1223   115514846 :     if (rel)
    1224   104170936 :         persistence = rel->rd_rel->relpersistence;
    1225             :     else
    1226    11343910 :         persistence = smgr_persistence;
    1227             : 
    1228   115514846 :     if (unlikely(mode == RBM_ZERO_AND_CLEANUP_LOCK ||
    1229             :                  mode == RBM_ZERO_AND_LOCK))
    1230             :     {
    1231             :         bool        found;
    1232             : 
    1233      631866 :         buffer = PinBufferForBlock(rel, smgr, persistence,
    1234             :                                    forkNum, blockNum, strategy, &found);
    1235      631866 :         ZeroAndLockBuffer(buffer, mode, found);
    1236      631866 :         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   114882980 :     flags = READ_BUFFERS_SYNCHRONOUSLY;
    1245   114882980 :     if (mode == RBM_ZERO_ON_ERROR)
    1246     3199628 :         flags |= READ_BUFFERS_ZERO_ON_ERROR;
    1247   114882980 :     operation.smgr = smgr;
    1248   114882980 :     operation.rel = rel;
    1249   114882980 :     operation.persistence = persistence;
    1250   114882980 :     operation.forknum = forkNum;
    1251   114882980 :     operation.strategy = strategy;
    1252   114882980 :     if (StartReadBuffer(&operation,
    1253             :                         &buffer,
    1254             :                         blockNum,
    1255             :                         flags))
    1256     1374962 :         WaitReadBuffers(&operation);
    1257             : 
    1258   114882934 :     return buffer;
    1259             : }
    1260             : 
    1261             : static pg_attribute_always_inline bool
    1262   122897672 : StartReadBuffersImpl(ReadBuffersOperation *operation,
    1263             :                      Buffer *buffers,
    1264             :                      BlockNumber blockNum,
    1265             :                      int *nblocks,
    1266             :                      int flags,
    1267             :                      bool allow_forwarding)
    1268             : {
    1269   122897672 :     int         actual_nblocks = *nblocks;
    1270   122897672 :     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   125707776 :     for (int i = 0; i < actual_nblocks; ++i)
    1278             :     {
    1279             :         bool        found;
    1280             : 
    1281   123230018 :         if (allow_forwarding && buffers[i] != InvalidBuffer)
    1282        2840 :         {
    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        2840 :             if (BufferIsLocal(buffers[i]))
    1311           4 :                 bufHdr = GetLocalBufferDescriptor(-buffers[i] - 1);
    1312             :             else
    1313        2836 :                 bufHdr = GetBufferDescriptor(buffers[i] - 1);
    1314             :             Assert(pg_atomic_read_u32(&bufHdr->state) & BM_TAG_VALID);
    1315        2840 :             found = pg_atomic_read_u32(&bufHdr->state) & BM_VALID;
    1316             :         }
    1317             :         else
    1318             :         {
    1319   123227166 :             buffers[i] = PinBufferForBlock(operation->rel,
    1320   123227178 :                                            operation->smgr,
    1321   123227178 :                                            operation->persistence,
    1322             :                                            operation->forknum,
    1323             :                                            blockNum + i,
    1324             :                                            operation->strategy,
    1325             :                                            &found);
    1326             :         }
    1327             : 
    1328   123230006 :         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   120419902 :             if (i == 0)
    1337             :             {
    1338   120417058 :                 *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   120417058 :                 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        2844 :             actual_nblocks = i;
    1366        2844 :             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     2810104 :             if (i == 0 && actual_nblocks > 1)
    1375             :             {
    1376       66798 :                 maxcombine = smgrmaxcombine(operation->smgr,
    1377             :                                             operation->forknum,
    1378             :                                             blockNum);
    1379       66798 :                 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     2480602 :     *nblocks = actual_nblocks;
    1389             : 
    1390             :     /* Populate information needed for I/O. */
    1391     2480602 :     operation->buffers = buffers;
    1392     2480602 :     operation->blocknum = blockNum;
    1393     2480602 :     operation->flags = flags;
    1394     2480602 :     operation->nblocks = actual_nblocks;
    1395     2480602 :     operation->nblocks_done = 0;
    1396     2480602 :     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     2480602 :     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     2478442 :         did_start_io = AsyncReadBuffers(operation, nblocks);
    1429             : 
    1430     2478412 :         operation->nblocks = *nblocks;
    1431             :     }
    1432             :     else
    1433             :     {
    1434        2160 :         operation->flags |= READ_BUFFERS_SYNCHRONOUSLY;
    1435             : 
    1436        2160 :         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        2160 :         did_start_io = true;
    1458             :     }
    1459             : 
    1460     2480572 :     CheckReadBuffersOperation(operation, !did_start_io);
    1461             : 
    1462     2480572 :     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             : bool
    1489     3990428 : StartReadBuffers(ReadBuffersOperation *operation,
    1490             :                  Buffer *buffers,
    1491             :                  BlockNumber blockNum,
    1492             :                  int *nblocks,
    1493             :                  int flags)
    1494             : {
    1495     3990428 :     return StartReadBuffersImpl(operation, buffers, blockNum, nblocks, flags,
    1496             :                                 true /* expect forwarded buffers */ );
    1497             : }
    1498             : 
    1499             : /*
    1500             :  * Single block version of the StartReadBuffers().  This might save a few
    1501             :  * instructions when called from another translation unit, because it is
    1502             :  * specialized for nblocks == 1.
    1503             :  *
    1504             :  * This version does not support "forwarded" buffers: they cannot be created
    1505             :  * by reading only one block and *buffer is ignored on entry.
    1506             :  */
    1507             : bool
    1508   118907244 : StartReadBuffer(ReadBuffersOperation *operation,
    1509             :                 Buffer *buffer,
    1510             :                 BlockNumber blocknum,
    1511             :                 int flags)
    1512             : {
    1513   118907244 :     int         nblocks = 1;
    1514             :     bool        result;
    1515             : 
    1516   118907244 :     result = StartReadBuffersImpl(operation, buffer, blocknum, &nblocks, flags,
    1517             :                                   false /* single block, no forwarding */ );
    1518             :     Assert(nblocks == 1);       /* single block can't be short */
    1519             : 
    1520   118907214 :     return result;
    1521             : }
    1522             : 
    1523             : /*
    1524             :  * Perform sanity checks on the ReadBuffersOperation.
    1525             :  */
    1526             : static void
    1527     7409898 : CheckReadBuffersOperation(ReadBuffersOperation *operation, bool is_complete)
    1528             : {
    1529             : #ifdef USE_ASSERT_CHECKING
    1530             :     Assert(operation->nblocks_done <= operation->nblocks);
    1531             :     Assert(!is_complete || operation->nblocks == operation->nblocks_done);
    1532             : 
    1533             :     for (int i = 0; i < operation->nblocks; i++)
    1534             :     {
    1535             :         Buffer      buffer = operation->buffers[i];
    1536             :         BufferDesc *buf_hdr = BufferIsLocal(buffer) ?
    1537             :             GetLocalBufferDescriptor(-buffer - 1) :
    1538             :             GetBufferDescriptor(buffer - 1);
    1539             : 
    1540             :         Assert(BufferGetBlockNumber(buffer) == operation->blocknum + i);
    1541             :         Assert(pg_atomic_read_u32(&buf_hdr->state) & BM_TAG_VALID);
    1542             : 
    1543             :         if (i < operation->nblocks_done)
    1544             :             Assert(pg_atomic_read_u32(&buf_hdr->state) & BM_VALID);
    1545             :     }
    1546             : #endif
    1547     7409898 : }
    1548             : 
    1549             : /* helper for ReadBuffersCanStartIO(), to avoid repetition */
    1550             : static inline bool
    1551     2810140 : ReadBuffersCanStartIOOnce(Buffer buffer, bool nowait)
    1552             : {
    1553     2810140 :     if (BufferIsLocal(buffer))
    1554       16728 :         return StartLocalBufferIO(GetLocalBufferDescriptor(-buffer - 1),
    1555             :                                   true, nowait);
    1556             :     else
    1557     2793412 :         return StartBufferIO(GetBufferDescriptor(buffer - 1), true, nowait);
    1558             : }
    1559             : 
    1560             : /*
    1561             :  * Helper for AsyncReadBuffers that tries to get the buffer ready for IO.
    1562             :  */
    1563             : static inline bool
    1564     2810140 : ReadBuffersCanStartIO(Buffer buffer, bool nowait)
    1565             : {
    1566             :     /*
    1567             :      * If this backend currently has staged IO, we need to submit the pending
    1568             :      * IO before waiting for the right to issue IO, to avoid the potential for
    1569             :      * deadlocks (and, more commonly, unnecessary delays for other backends).
    1570             :      */
    1571     2810140 :     if (!nowait && pgaio_have_staged())
    1572             :     {
    1573        1140 :         if (ReadBuffersCanStartIOOnce(buffer, true))
    1574        1140 :             return true;
    1575             : 
    1576             :         /*
    1577             :          * Unfortunately StartBufferIO() returning false doesn't allow to
    1578             :          * distinguish between the buffer already being valid and IO already
    1579             :          * being in progress. Since IO already being in progress is quite
    1580             :          * rare, this approach seems fine.
    1581             :          */
    1582           0 :         pgaio_submit_staged();
    1583             :     }
    1584             : 
    1585     2809000 :     return ReadBuffersCanStartIOOnce(buffer, nowait);
    1586             : }
    1587             : 
    1588             : /*
    1589             :  * Helper for WaitReadBuffers() that processes the results of a readv
    1590             :  * operation, raising an error if necessary.
    1591             :  */
    1592             : static void
    1593     2463622 : ProcessReadBuffersResult(ReadBuffersOperation *operation)
    1594             : {
    1595     2463622 :     PgAioReturn *aio_ret = &operation->io_return;
    1596     2463622 :     PgAioResultStatus rs = aio_ret->result.status;
    1597     2463622 :     int         newly_read_blocks = 0;
    1598             : 
    1599             :     Assert(pgaio_wref_valid(&operation->io_wref));
    1600             :     Assert(aio_ret->result.status != PGAIO_RS_UNKNOWN);
    1601             : 
    1602             :     /*
    1603             :      * SMGR reports the number of blocks successfully read as the result of
    1604             :      * the IO operation. Thus we can simply add that to ->nblocks_done.
    1605             :      */
    1606             : 
    1607     2463622 :     if (likely(rs != PGAIO_RS_ERROR))
    1608     2463564 :         newly_read_blocks = aio_ret->result.result;
    1609             : 
    1610     2463622 :     if (rs == PGAIO_RS_ERROR || rs == PGAIO_RS_WARNING)
    1611          90 :         pgaio_result_report(aio_ret->result, &aio_ret->target_data,
    1612             :                             rs == PGAIO_RS_ERROR ? ERROR : WARNING);
    1613     2463532 :     else if (aio_ret->result.status == PGAIO_RS_PARTIAL)
    1614             :     {
    1615             :         /*
    1616             :          * We'll retry, so we just emit a debug message to the server log (or
    1617             :          * not even that in prod scenarios).
    1618             :          */
    1619          20 :         pgaio_result_report(aio_ret->result, &aio_ret->target_data, DEBUG1);
    1620          20 :         elog(DEBUG3, "partial read, will retry");
    1621             :     }
    1622             : 
    1623             :     Assert(newly_read_blocks > 0);
    1624             :     Assert(newly_read_blocks <= MAX_IO_COMBINE_LIMIT);
    1625             : 
    1626     2463564 :     operation->nblocks_done += newly_read_blocks;
    1627             : 
    1628             :     Assert(operation->nblocks_done <= operation->nblocks);
    1629     2463564 : }
    1630             : 
    1631             : void
    1632     2463602 : WaitReadBuffers(ReadBuffersOperation *operation)
    1633             : {
    1634     2463602 :     PgAioReturn *aio_ret = &operation->io_return;
    1635             :     IOContext   io_context;
    1636             :     IOObject    io_object;
    1637             : 
    1638     2463602 :     if (operation->persistence == RELPERSISTENCE_TEMP)
    1639             :     {
    1640        2974 :         io_context = IOCONTEXT_NORMAL;
    1641        2974 :         io_object = IOOBJECT_TEMP_RELATION;
    1642             :     }
    1643             :     else
    1644             :     {
    1645     2460628 :         io_context = IOContextForStrategy(operation->strategy);
    1646     2460628 :         io_object = IOOBJECT_RELATION;
    1647             :     }
    1648             : 
    1649             :     /*
    1650             :      * If we get here without an IO operation having been issued, the
    1651             :      * io_method == IOMETHOD_SYNC path must have been used. Otherwise the
    1652             :      * caller should not have called WaitReadBuffers().
    1653             :      *
    1654             :      * In the case of IOMETHOD_SYNC, we start - as we used to before the
    1655             :      * introducing of AIO - the IO in WaitReadBuffers(). This is done as part
    1656             :      * of the retry logic below, no extra code is required.
    1657             :      *
    1658             :      * This path is expected to eventually go away.
    1659             :      */
    1660     2463602 :     if (!pgaio_wref_valid(&operation->io_wref) && io_method != IOMETHOD_SYNC)
    1661           0 :         elog(ERROR, "waiting for read operation that didn't read");
    1662             : 
    1663             :     /*
    1664             :      * To handle partial reads, and IOMETHOD_SYNC, we re-issue IO until we're
    1665             :      * done. We may need multiple retries, not just because we could get
    1666             :      * multiple partial reads, but also because some of the remaining
    1667             :      * to-be-read buffers may have been read in by other backends, limiting
    1668             :      * the IO size.
    1669             :      */
    1670             :     while (true)
    1671        2180 :     {
    1672             :         int         ignored_nblocks_progress;
    1673             : 
    1674     2465782 :         CheckReadBuffersOperation(operation, false);
    1675             : 
    1676             :         /*
    1677             :          * If there is an IO associated with the operation, we may need to
    1678             :          * wait for it.
    1679             :          */
    1680     2465782 :         if (pgaio_wref_valid(&operation->io_wref))
    1681             :         {
    1682             :             /*
    1683             :              * Track the time spent waiting for the IO to complete. As
    1684             :              * tracking a wait even if we don't actually need to wait
    1685             :              *
    1686             :              * a) is not cheap, due to the timestamping overhead
    1687             :              *
    1688             :              * b) reports some time as waiting, even if we never waited
    1689             :              *
    1690             :              * we first check if we already know the IO is complete.
    1691             :              */
    1692     2463622 :             if (aio_ret->result.status == PGAIO_RS_UNKNOWN &&
    1693     1072484 :                 !pgaio_wref_check_done(&operation->io_wref))
    1694             :             {
    1695      333288 :                 instr_time  io_start = pgstat_prepare_io_time(track_io_timing);
    1696             : 
    1697      333288 :                 pgaio_wref_wait(&operation->io_wref);
    1698             : 
    1699             :                 /*
    1700             :                  * The IO operation itself was already counted earlier, in
    1701             :                  * AsyncReadBuffers(), this just accounts for the wait time.
    1702             :                  */
    1703      333288 :                 pgstat_count_io_op_time(io_object, io_context, IOOP_READ,
    1704             :                                         io_start, 0, 0);
    1705             :             }
    1706             :             else
    1707             :             {
    1708             :                 Assert(pgaio_wref_check_done(&operation->io_wref));
    1709             :             }
    1710             : 
    1711             :             /*
    1712             :              * We now are sure the IO completed. Check the results. This
    1713             :              * includes reporting on errors if there were any.
    1714             :              */
    1715     2463622 :             ProcessReadBuffersResult(operation);
    1716             :         }
    1717             : 
    1718             :         /*
    1719             :          * Most of the time, the one IO we already started, will read in
    1720             :          * everything.  But we need to deal with partial reads and buffers not
    1721             :          * needing IO anymore.
    1722             :          */
    1723     2465724 :         if (operation->nblocks_done == operation->nblocks)
    1724     2463544 :             break;
    1725             : 
    1726        2180 :         CHECK_FOR_INTERRUPTS();
    1727             : 
    1728             :         /*
    1729             :          * This may only complete the IO partially, either because some
    1730             :          * buffers were already valid, or because of a partial read.
    1731             :          *
    1732             :          * NB: In contrast to after the AsyncReadBuffers() call in
    1733             :          * StartReadBuffers(), we do *not* reduce
    1734             :          * ReadBuffersOperation->nblocks here, callers expect the full
    1735             :          * operation to be completed at this point (as more operations may
    1736             :          * have been queued).
    1737             :          */
    1738        2180 :         AsyncReadBuffers(operation, &ignored_nblocks_progress);
    1739             :     }
    1740             : 
    1741     2463544 :     CheckReadBuffersOperation(operation, true);
    1742             : 
    1743             :     /* NB: READ_DONE tracepoint was already executed in completion callback */
    1744     2463544 : }
    1745             : 
    1746             : /*
    1747             :  * Initiate IO for the ReadBuffersOperation
    1748             :  *
    1749             :  * This function only starts a single IO at a time. The size of the IO may be
    1750             :  * limited to below the to-be-read blocks, if one of the buffers has
    1751             :  * concurrently been read in. If the first to-be-read buffer is already valid,
    1752             :  * no IO will be issued.
    1753             :  *
    1754             :  * To support retries after partial reads, the first operation->nblocks_done
    1755             :  * buffers are skipped.
    1756             :  *
    1757             :  * On return *nblocks_progress is updated to reflect the number of buffers
    1758             :  * affected by the call. If the first buffer is valid, *nblocks_progress is
    1759             :  * set to 1 and operation->nblocks_done is incremented.
    1760             :  *
    1761             :  * Returns true if IO was initiated, false if no IO was necessary.
    1762             :  */
    1763             : static bool
    1764     2480622 : AsyncReadBuffers(ReadBuffersOperation *operation, int *nblocks_progress)
    1765             : {
    1766     2480622 :     Buffer     *buffers = &operation->buffers[0];
    1767     2480622 :     int         flags = operation->flags;
    1768     2480622 :     BlockNumber blocknum = operation->blocknum;
    1769     2480622 :     ForkNumber  forknum = operation->forknum;
    1770     2480622 :     char        persistence = operation->persistence;
    1771     2480622 :     int16       nblocks_done = operation->nblocks_done;
    1772     2480622 :     Buffer     *io_buffers = &operation->buffers[nblocks_done];
    1773     2480622 :     int         io_buffers_len = 0;
    1774             :     PgAioHandle *ioh;
    1775     2480622 :     uint32      ioh_flags = 0;
    1776             :     void       *io_pages[MAX_IO_COMBINE_LIMIT];
    1777             :     IOContext   io_context;
    1778             :     IOObject    io_object;
    1779             :     bool        did_start_io;
    1780             : 
    1781             :     /*
    1782             :      * When this IO is executed synchronously, either because the caller will
    1783             :      * immediately block waiting for the IO or because IOMETHOD_SYNC is used,
    1784             :      * the AIO subsystem needs to know.
    1785             :      */
    1786     2480622 :     if (flags & READ_BUFFERS_SYNCHRONOUSLY)
    1787     1385794 :         ioh_flags |= PGAIO_HF_SYNCHRONOUS;
    1788             : 
    1789     2480622 :     if (persistence == RELPERSISTENCE_TEMP)
    1790             :     {
    1791        3562 :         io_context = IOCONTEXT_NORMAL;
    1792        3562 :         io_object = IOOBJECT_TEMP_RELATION;
    1793        3562 :         ioh_flags |= PGAIO_HF_REFERENCES_LOCAL;
    1794             :     }
    1795             :     else
    1796             :     {
    1797     2477060 :         io_context = IOContextForStrategy(operation->strategy);
    1798     2477060 :         io_object = IOOBJECT_RELATION;
    1799             :     }
    1800             : 
    1801             :     /*
    1802             :      * If zero_damaged_pages is enabled, add the READ_BUFFERS_ZERO_ON_ERROR
    1803             :      * flag. The reason for that is that, hopefully, zero_damaged_pages isn't
    1804             :      * set globally, but on a per-session basis. The completion callback,
    1805             :      * which may be run in other processes, e.g. in IO workers, may have a
    1806             :      * different value of the zero_damaged_pages GUC.
    1807             :      *
    1808             :      * XXX: We probably should eventually use a different flag for
    1809             :      * zero_damaged_pages, so we can report different log levels / error codes
    1810             :      * for zero_damaged_pages and ZERO_ON_ERROR.
    1811             :      */
    1812     2480622 :     if (zero_damaged_pages)
    1813          32 :         flags |= READ_BUFFERS_ZERO_ON_ERROR;
    1814             : 
    1815             :     /*
    1816             :      * For the same reason as with zero_damaged_pages we need to use this
    1817             :      * backend's ignore_checksum_failure value.
    1818             :      */
    1819     2480622 :     if (ignore_checksum_failure)
    1820          16 :         flags |= READ_BUFFERS_IGNORE_CHECKSUM_FAILURES;
    1821             : 
    1822             : 
    1823             :     /*
    1824             :      * To be allowed to report stats in the local completion callback we need
    1825             :      * to prepare to report stats now. This ensures we can safely report the
    1826             :      * checksum failure even in a critical section.
    1827             :      */
    1828     2480622 :     pgstat_prepare_report_checksum_failure(operation->smgr->smgr_rlocator.locator.dbOid);
    1829             : 
    1830             :     /*
    1831             :      * Get IO handle before ReadBuffersCanStartIO(), as pgaio_io_acquire()
    1832             :      * might block, which we don't want after setting IO_IN_PROGRESS.
    1833             :      *
    1834             :      * If we need to wait for IO before we can get a handle, submit
    1835             :      * already-staged IO first, so that other backends don't need to wait.
    1836             :      * There wouldn't be a deadlock risk, as pgaio_io_acquire() just needs to
    1837             :      * wait for already submitted IO, which doesn't require additional locks,
    1838             :      * but it could still cause undesirable waits.
    1839             :      *
    1840             :      * A secondary benefit is that this would allow us to measure the time in
    1841             :      * pgaio_io_acquire() without causing undue timer overhead in the common,
    1842             :      * non-blocking, case.  However, currently the pgstats infrastructure
    1843             :      * doesn't really allow that, as it a) asserts that an operation can't
    1844             :      * have time without operations b) doesn't have an API to report
    1845             :      * "accumulated" time.
    1846             :      */
    1847     2480622 :     ioh = pgaio_io_acquire_nb(CurrentResourceOwner, &operation->io_return);
    1848     2480622 :     if (unlikely(!ioh))
    1849             :     {
    1850        6706 :         pgaio_submit_staged();
    1851             : 
    1852        6706 :         ioh = pgaio_io_acquire(CurrentResourceOwner, &operation->io_return);
    1853             :     }
    1854             : 
    1855             :     /*
    1856             :      * Check if we can start IO on the first to-be-read buffer.
    1857             :      *
    1858             :      * If an I/O is already in progress in another backend, we want to wait
    1859             :      * for the outcome: either done, or something went wrong and we will
    1860             :      * retry.
    1861             :      */
    1862     2480622 :     if (!ReadBuffersCanStartIO(buffers[nblocks_done], false))
    1863             :     {
    1864             :         /*
    1865             :          * Someone else has already completed this block, we're done.
    1866             :          *
    1867             :          * When IO is necessary, ->nblocks_done is updated in
    1868             :          * ProcessReadBuffersResult(), but that is not called if no IO is
    1869             :          * necessary. Thus update here.
    1870             :          */
    1871       16376 :         operation->nblocks_done += 1;
    1872       16376 :         *nblocks_progress = 1;
    1873             : 
    1874       16376 :         pgaio_io_release(ioh);
    1875       16376 :         pgaio_wref_clear(&operation->io_wref);
    1876       16376 :         did_start_io = false;
    1877             : 
    1878             :         /*
    1879             :          * Report and track this as a 'hit' for this backend, even though it
    1880             :          * must have started out as a miss in PinBufferForBlock(). The other
    1881             :          * backend will track this as a 'read'.
    1882             :          */
    1883             :         TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, blocknum + operation->nblocks_done,
    1884             :                                           operation->smgr->smgr_rlocator.locator.spcOid,
    1885             :                                           operation->smgr->smgr_rlocator.locator.dbOid,
    1886             :                                           operation->smgr->smgr_rlocator.locator.relNumber,
    1887             :                                           operation->smgr->smgr_rlocator.backend,
    1888             :                                           true);
    1889             : 
    1890       16376 :         if (persistence == RELPERSISTENCE_TEMP)
    1891           0 :             pgBufferUsage.local_blks_hit += 1;
    1892             :         else
    1893       16376 :             pgBufferUsage.shared_blks_hit += 1;
    1894             : 
    1895       16376 :         if (operation->rel)
    1896       16376 :             pgstat_count_buffer_hit(operation->rel);
    1897             : 
    1898       16376 :         pgstat_count_io_op(io_object, io_context, IOOP_HIT, 1, 0);
    1899             : 
    1900       16376 :         if (VacuumCostActive)
    1901          22 :             VacuumCostBalance += VacuumCostPageHit;
    1902             :     }
    1903             :     else
    1904             :     {
    1905             :         instr_time  io_start;
    1906             : 
    1907             :         /* We found a buffer that we need to read in. */
    1908             :         Assert(io_buffers[0] == buffers[nblocks_done]);
    1909     2464246 :         io_pages[0] = BufferGetBlock(buffers[nblocks_done]);
    1910     2464246 :         io_buffers_len = 1;
    1911             : 
    1912             :         /*
    1913             :          * How many neighboring-on-disk blocks can we scatter-read into other
    1914             :          * buffers at the same time?  In this case we don't wait if we see an
    1915             :          * I/O already in progress.  We already set BM_IO_IN_PROGRESS for the
    1916             :          * head block, so we should get on with that I/O as soon as possible.
    1917             :          */
    1918     2793764 :         for (int i = nblocks_done + 1; i < operation->nblocks; i++)
    1919             :         {
    1920      329518 :             if (!ReadBuffersCanStartIO(buffers[i], true))
    1921           0 :                 break;
    1922             :             /* Must be consecutive block numbers. */
    1923             :             Assert(BufferGetBlockNumber(buffers[i - 1]) ==
    1924             :                    BufferGetBlockNumber(buffers[i]) - 1);
    1925             :             Assert(io_buffers[io_buffers_len] == buffers[i]);
    1926             : 
    1927      329518 :             io_pages[io_buffers_len++] = BufferGetBlock(buffers[i]);
    1928             :         }
    1929             : 
    1930             :         /* get a reference to wait for in WaitReadBuffers() */
    1931     2464246 :         pgaio_io_get_wref(ioh, &operation->io_wref);
    1932             : 
    1933             :         /* provide the list of buffers to the completion callbacks */
    1934     2464246 :         pgaio_io_set_handle_data_32(ioh, (uint32 *) io_buffers, io_buffers_len);
    1935             : 
    1936     2464246 :         pgaio_io_register_callbacks(ioh,
    1937             :                                     persistence == RELPERSISTENCE_TEMP ?
    1938             :                                     PGAIO_HCB_LOCAL_BUFFER_READV :
    1939             :                                     PGAIO_HCB_SHARED_BUFFER_READV,
    1940             :                                     flags);
    1941             : 
    1942     2464246 :         pgaio_io_set_flag(ioh, ioh_flags);
    1943             : 
    1944             :         /* ---
    1945             :          * Even though we're trying to issue IO asynchronously, track the time
    1946             :          * in smgrstartreadv():
    1947             :          * - if io_method == IOMETHOD_SYNC, we will always perform the IO
    1948             :          *   immediately
    1949             :          * - the io method might not support the IO (e.g. worker IO for a temp
    1950             :          *   table)
    1951             :          * ---
    1952             :          */
    1953     2464246 :         io_start = pgstat_prepare_io_time(track_io_timing);
    1954     2464246 :         smgrstartreadv(ioh, operation->smgr, forknum,
    1955             :                        blocknum + nblocks_done,
    1956             :                        io_pages, io_buffers_len);
    1957     2464216 :         pgstat_count_io_op_time(io_object, io_context, IOOP_READ,
    1958     2464216 :                                 io_start, 1, io_buffers_len * BLCKSZ);
    1959             : 
    1960     2464216 :         if (persistence == RELPERSISTENCE_TEMP)
    1961        3562 :             pgBufferUsage.local_blks_read += io_buffers_len;
    1962             :         else
    1963     2460654 :             pgBufferUsage.shared_blks_read += io_buffers_len;
    1964             : 
    1965             :         /*
    1966             :          * Track vacuum cost when issuing IO, not after waiting for it.
    1967             :          * Otherwise we could end up issuing a lot of IO in a short timespan,
    1968             :          * despite a low cost limit.
    1969             :          */
    1970     2464216 :         if (VacuumCostActive)
    1971       48782 :             VacuumCostBalance += VacuumCostPageMiss * io_buffers_len;
    1972             : 
    1973     2464216 :         *nblocks_progress = io_buffers_len;
    1974     2464216 :         did_start_io = true;
    1975             :     }
    1976             : 
    1977     2480592 :     return did_start_io;
    1978             : }
    1979             : 
    1980             : /*
    1981             :  * BufferAlloc -- subroutine for PinBufferForBlock.  Handles lookup of a shared
    1982             :  *      buffer.  If no buffer exists already, selects a replacement victim and
    1983             :  *      evicts the old page, but does NOT read in new page.
    1984             :  *
    1985             :  * "strategy" can be a buffer replacement strategy object, or NULL for
    1986             :  * the default strategy.  The selected buffer's usage_count is advanced when
    1987             :  * using the default strategy, but otherwise possibly not (see PinBuffer).
    1988             :  *
    1989             :  * The returned buffer is pinned and is already marked as holding the
    1990             :  * desired page.  If it already did have the desired page, *foundPtr is
    1991             :  * set true.  Otherwise, *foundPtr is set false.
    1992             :  *
    1993             :  * io_context is passed as an output parameter to avoid calling
    1994             :  * IOContextForStrategy() when there is a shared buffers hit and no IO
    1995             :  * statistics need be captured.
    1996             :  *
    1997             :  * No locks are held either at entry or exit.
    1998             :  */
    1999             : static pg_attribute_always_inline BufferDesc *
    2000   121304962 : BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
    2001             :             BlockNumber blockNum,
    2002             :             BufferAccessStrategy strategy,
    2003             :             bool *foundPtr, IOContext io_context)
    2004             : {
    2005             :     BufferTag   newTag;         /* identity of requested block */
    2006             :     uint32      newHash;        /* hash value for newTag */
    2007             :     LWLock     *newPartitionLock;   /* buffer partition lock for it */
    2008             :     int         existing_buf_id;
    2009             :     Buffer      victim_buffer;
    2010             :     BufferDesc *victim_buf_hdr;
    2011             :     uint32      victim_buf_state;
    2012             : 
    2013             :     /* Make sure we will have room to remember the buffer pin */
    2014   121304962 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    2015   121304962 :     ReservePrivateRefCountEntry();
    2016             : 
    2017             :     /* create a tag so we can lookup the buffer */
    2018   121304962 :     InitBufferTag(&newTag, &smgr->smgr_rlocator.locator, forkNum, blockNum);
    2019             : 
    2020             :     /* determine its hash code and partition lock ID */
    2021   121304962 :     newHash = BufTableHashCode(&newTag);
    2022   121304962 :     newPartitionLock = BufMappingPartitionLock(newHash);
    2023             : 
    2024             :     /* see if the block is in the buffer pool already */
    2025   121304962 :     LWLockAcquire(newPartitionLock, LW_SHARED);
    2026   121304962 :     existing_buf_id = BufTableLookup(&newTag, newHash);
    2027   121304962 :     if (existing_buf_id >= 0)
    2028             :     {
    2029             :         BufferDesc *buf;
    2030             :         bool        valid;
    2031             : 
    2032             :         /*
    2033             :          * Found it.  Now, pin the buffer so no one can steal it from the
    2034             :          * buffer pool, and check to see if the correct data has been loaded
    2035             :          * into the buffer.
    2036             :          */
    2037   117967368 :         buf = GetBufferDescriptor(existing_buf_id);
    2038             : 
    2039   117967368 :         valid = PinBuffer(buf, strategy);
    2040             : 
    2041             :         /* Can release the mapping lock as soon as we've pinned it */
    2042   117967368 :         LWLockRelease(newPartitionLock);
    2043             : 
    2044   117967368 :         *foundPtr = true;
    2045             : 
    2046   117967368 :         if (!valid)
    2047             :         {
    2048             :             /*
    2049             :              * We can only get here if (a) someone else is still reading in
    2050             :              * the page, (b) a previous read attempt failed, or (c) someone
    2051             :              * called StartReadBuffers() but not yet WaitReadBuffers().
    2052             :              */
    2053       14062 :             *foundPtr = false;
    2054             :         }
    2055             : 
    2056   117967368 :         return buf;
    2057             :     }
    2058             : 
    2059             :     /*
    2060             :      * Didn't find it in the buffer pool.  We'll have to initialize a new
    2061             :      * buffer.  Remember to unlock the mapping lock while doing the work.
    2062             :      */
    2063     3337594 :     LWLockRelease(newPartitionLock);
    2064             : 
    2065             :     /*
    2066             :      * Acquire a victim buffer. Somebody else might try to do the same, we
    2067             :      * don't hold any conflicting locks. If so we'll have to undo our work
    2068             :      * later.
    2069             :      */
    2070     3337594 :     victim_buffer = GetVictimBuffer(strategy, io_context);
    2071     3337594 :     victim_buf_hdr = GetBufferDescriptor(victim_buffer - 1);
    2072             : 
    2073             :     /*
    2074             :      * Try to make a hashtable entry for the buffer under its new tag. If
    2075             :      * somebody else inserted another buffer for the tag, we'll release the
    2076             :      * victim buffer we acquired and use the already inserted one.
    2077             :      */
    2078     3337594 :     LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
    2079     3337594 :     existing_buf_id = BufTableInsert(&newTag, newHash, victim_buf_hdr->buf_id);
    2080     3337594 :     if (existing_buf_id >= 0)
    2081             :     {
    2082             :         BufferDesc *existing_buf_hdr;
    2083             :         bool        valid;
    2084             : 
    2085             :         /*
    2086             :          * Got a collision. Someone has already done what we were about to do.
    2087             :          * We'll just handle this as if it were found in the buffer pool in
    2088             :          * the first place.  First, give up the buffer we were planning to
    2089             :          * use.
    2090             :          *
    2091             :          * We could do this after releasing the partition lock, but then we'd
    2092             :          * have to call ResourceOwnerEnlarge() & ReservePrivateRefCountEntry()
    2093             :          * before acquiring the lock, for the rare case of such a collision.
    2094             :          */
    2095        3208 :         UnpinBuffer(victim_buf_hdr);
    2096             : 
    2097             :         /* remaining code should match code at top of routine */
    2098             : 
    2099        3208 :         existing_buf_hdr = GetBufferDescriptor(existing_buf_id);
    2100             : 
    2101        3208 :         valid = PinBuffer(existing_buf_hdr, strategy);
    2102             : 
    2103             :         /* Can release the mapping lock as soon as we've pinned it */
    2104        3208 :         LWLockRelease(newPartitionLock);
    2105             : 
    2106        3208 :         *foundPtr = true;
    2107             : 
    2108        3208 :         if (!valid)
    2109             :         {
    2110             :             /*
    2111             :              * We can only get here if (a) someone else is still reading in
    2112             :              * the page, (b) a previous read attempt failed, or (c) someone
    2113             :              * called StartReadBuffers() but not yet WaitReadBuffers().
    2114             :              */
    2115        2410 :             *foundPtr = false;
    2116             :         }
    2117             : 
    2118        3208 :         return existing_buf_hdr;
    2119             :     }
    2120             : 
    2121             :     /*
    2122             :      * Need to lock the buffer header too in order to change its tag.
    2123             :      */
    2124     3334386 :     victim_buf_state = LockBufHdr(victim_buf_hdr);
    2125             : 
    2126             :     /* some sanity checks while we hold the buffer header lock */
    2127             :     Assert(BUF_STATE_GET_REFCOUNT(victim_buf_state) == 1);
    2128             :     Assert(!(victim_buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY | BM_IO_IN_PROGRESS)));
    2129             : 
    2130     3334386 :     victim_buf_hdr->tag = newTag;
    2131             : 
    2132             :     /*
    2133             :      * Make sure BM_PERMANENT is set for buffers that must be written at every
    2134             :      * checkpoint.  Unlogged buffers only need to be written at shutdown
    2135             :      * checkpoints, except for their "init" forks, which need to be treated
    2136             :      * just like permanent relations.
    2137             :      */
    2138     3334386 :     victim_buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
    2139     3334386 :     if (relpersistence == RELPERSISTENCE_PERMANENT || forkNum == INIT_FORKNUM)
    2140     3333702 :         victim_buf_state |= BM_PERMANENT;
    2141             : 
    2142     3334386 :     UnlockBufHdr(victim_buf_hdr, victim_buf_state);
    2143             : 
    2144     3334386 :     LWLockRelease(newPartitionLock);
    2145             : 
    2146             :     /*
    2147             :      * Buffer contents are currently invalid.
    2148             :      */
    2149     3334386 :     *foundPtr = false;
    2150             : 
    2151     3334386 :     return victim_buf_hdr;
    2152             : }
    2153             : 
    2154             : /*
    2155             :  * InvalidateBuffer -- mark a shared buffer invalid.
    2156             :  *
    2157             :  * The buffer header spinlock must be held at entry.  We drop it before
    2158             :  * returning.  (This is sane because the caller must have locked the
    2159             :  * buffer in order to be sure it should be dropped.)
    2160             :  *
    2161             :  * This is used only in contexts such as dropping a relation.  We assume
    2162             :  * that no other backend could possibly be interested in using the page,
    2163             :  * so the only reason the buffer might be pinned is if someone else is
    2164             :  * trying to write it out.  We have to let them finish before we can
    2165             :  * reclaim the buffer.
    2166             :  *
    2167             :  * The buffer could get reclaimed by someone else while we are waiting
    2168             :  * to acquire the necessary locks; if so, don't mess it up.
    2169             :  */
    2170             : static void
    2171      210392 : InvalidateBuffer(BufferDesc *buf)
    2172             : {
    2173             :     BufferTag   oldTag;
    2174             :     uint32      oldHash;        /* hash value for oldTag */
    2175             :     LWLock     *oldPartitionLock;   /* buffer partition lock for it */
    2176             :     uint32      oldFlags;
    2177             :     uint32      buf_state;
    2178             : 
    2179             :     /* Save the original buffer tag before dropping the spinlock */
    2180      210392 :     oldTag = buf->tag;
    2181             : 
    2182      210392 :     buf_state = pg_atomic_read_u32(&buf->state);
    2183             :     Assert(buf_state & BM_LOCKED);
    2184      210392 :     UnlockBufHdr(buf, buf_state);
    2185             : 
    2186             :     /*
    2187             :      * Need to compute the old tag's hashcode and partition lock ID. XXX is it
    2188             :      * worth storing the hashcode in BufferDesc so we need not recompute it
    2189             :      * here?  Probably not.
    2190             :      */
    2191      210392 :     oldHash = BufTableHashCode(&oldTag);
    2192      210392 :     oldPartitionLock = BufMappingPartitionLock(oldHash);
    2193             : 
    2194      210394 : retry:
    2195             : 
    2196             :     /*
    2197             :      * Acquire exclusive mapping lock in preparation for changing the buffer's
    2198             :      * association.
    2199             :      */
    2200      210394 :     LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
    2201             : 
    2202             :     /* Re-lock the buffer header */
    2203      210394 :     buf_state = LockBufHdr(buf);
    2204             : 
    2205             :     /* If it's changed while we were waiting for lock, do nothing */
    2206      210394 :     if (!BufferTagsEqual(&buf->tag, &oldTag))
    2207             :     {
    2208           2 :         UnlockBufHdr(buf, buf_state);
    2209           2 :         LWLockRelease(oldPartitionLock);
    2210           2 :         return;
    2211             :     }
    2212             : 
    2213             :     /*
    2214             :      * We assume the reason for it to be pinned is that either we were
    2215             :      * asynchronously reading the page in before erroring out or someone else
    2216             :      * is flushing the page out.  Wait for the IO to finish.  (This could be
    2217             :      * an infinite loop if the refcount is messed up... it would be nice to
    2218             :      * time out after awhile, but there seems no way to be sure how many loops
    2219             :      * may be needed.  Note that if the other guy has pinned the buffer but
    2220             :      * not yet done StartBufferIO, WaitIO will fall through and we'll
    2221             :      * effectively be busy-looping here.)
    2222             :      */
    2223      210392 :     if (BUF_STATE_GET_REFCOUNT(buf_state) != 0)
    2224             :     {
    2225           2 :         UnlockBufHdr(buf, buf_state);
    2226           2 :         LWLockRelease(oldPartitionLock);
    2227             :         /* safety check: should definitely not be our *own* pin */
    2228           2 :         if (GetPrivateRefCount(BufferDescriptorGetBuffer(buf)) > 0)
    2229           0 :             elog(ERROR, "buffer is pinned in InvalidateBuffer");
    2230           2 :         WaitIO(buf);
    2231           2 :         goto retry;
    2232             :     }
    2233             : 
    2234             :     /*
    2235             :      * Clear out the buffer's tag and flags.  We must do this to ensure that
    2236             :      * linear scans of the buffer array don't think the buffer is valid.
    2237             :      */
    2238      210390 :     oldFlags = buf_state & BUF_FLAG_MASK;
    2239      210390 :     ClearBufferTag(&buf->tag);
    2240      210390 :     buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
    2241      210390 :     UnlockBufHdr(buf, buf_state);
    2242             : 
    2243             :     /*
    2244             :      * Remove the buffer from the lookup hashtable, if it was in there.
    2245             :      */
    2246      210390 :     if (oldFlags & BM_TAG_VALID)
    2247      210390 :         BufTableDelete(&oldTag, oldHash);
    2248             : 
    2249             :     /*
    2250             :      * Done with mapping lock.
    2251             :      */
    2252      210390 :     LWLockRelease(oldPartitionLock);
    2253             : }
    2254             : 
    2255             : /*
    2256             :  * Helper routine for GetVictimBuffer()
    2257             :  *
    2258             :  * Needs to be called on a buffer with a valid tag, pinned, but without the
    2259             :  * buffer header spinlock held.
    2260             :  *
    2261             :  * Returns true if the buffer can be reused, in which case the buffer is only
    2262             :  * pinned by this backend and marked as invalid, false otherwise.
    2263             :  */
    2264             : static bool
    2265     2348824 : InvalidateVictimBuffer(BufferDesc *buf_hdr)
    2266             : {
    2267             :     uint32      buf_state;
    2268             :     uint32      hash;
    2269             :     LWLock     *partition_lock;
    2270             :     BufferTag   tag;
    2271             : 
    2272             :     Assert(GetPrivateRefCount(BufferDescriptorGetBuffer(buf_hdr)) == 1);
    2273             : 
    2274             :     /* have buffer pinned, so it's safe to read tag without lock */
    2275     2348824 :     tag = buf_hdr->tag;
    2276             : 
    2277     2348824 :     hash = BufTableHashCode(&tag);
    2278     2348824 :     partition_lock = BufMappingPartitionLock(hash);
    2279             : 
    2280     2348824 :     LWLockAcquire(partition_lock, LW_EXCLUSIVE);
    2281             : 
    2282             :     /* lock the buffer header */
    2283     2348824 :     buf_state = LockBufHdr(buf_hdr);
    2284             : 
    2285             :     /*
    2286             :      * We have the buffer pinned nobody else should have been able to unset
    2287             :      * this concurrently.
    2288             :      */
    2289             :     Assert(buf_state & BM_TAG_VALID);
    2290             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2291             :     Assert(BufferTagsEqual(&buf_hdr->tag, &tag));
    2292             : 
    2293             :     /*
    2294             :      * If somebody else pinned the buffer since, or even worse, dirtied it,
    2295             :      * give up on this buffer: It's clearly in use.
    2296             :      */
    2297     2348824 :     if (BUF_STATE_GET_REFCOUNT(buf_state) != 1 || (buf_state & BM_DIRTY))
    2298             :     {
    2299             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2300             : 
    2301         964 :         UnlockBufHdr(buf_hdr, buf_state);
    2302         964 :         LWLockRelease(partition_lock);
    2303             : 
    2304         964 :         return false;
    2305             :     }
    2306             : 
    2307             :     /*
    2308             :      * Clear out the buffer's tag and flags and usagecount.  This is not
    2309             :      * strictly required, as BM_TAG_VALID/BM_VALID needs to be checked before
    2310             :      * doing anything with the buffer. But currently it's beneficial, as the
    2311             :      * cheaper pre-check for several linear scans of shared buffers use the
    2312             :      * tag (see e.g. FlushDatabaseBuffers()).
    2313             :      */
    2314     2347860 :     ClearBufferTag(&buf_hdr->tag);
    2315     2347860 :     buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
    2316     2347860 :     UnlockBufHdr(buf_hdr, buf_state);
    2317             : 
    2318             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2319             : 
    2320             :     /* finally delete buffer from the buffer mapping table */
    2321     2347860 :     BufTableDelete(&tag, hash);
    2322             : 
    2323     2347860 :     LWLockRelease(partition_lock);
    2324             : 
    2325             :     Assert(!(buf_state & (BM_DIRTY | BM_VALID | BM_TAG_VALID)));
    2326             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2327             :     Assert(BUF_STATE_GET_REFCOUNT(pg_atomic_read_u32(&buf_hdr->state)) > 0);
    2328             : 
    2329     2347860 :     return true;
    2330             : }
    2331             : 
    2332             : static Buffer
    2333     3781342 : GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context)
    2334             : {
    2335             :     BufferDesc *buf_hdr;
    2336             :     Buffer      buf;
    2337             :     uint32      buf_state;
    2338             :     bool        from_ring;
    2339             : 
    2340             :     /*
    2341             :      * Ensure, while the spinlock's not yet held, that there's a free refcount
    2342             :      * entry, and a resource owner slot for the pin.
    2343             :      */
    2344     3781342 :     ReservePrivateRefCountEntry();
    2345     3781342 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    2346             : 
    2347             :     /* we return here if a prospective victim buffer gets used concurrently */
    2348       12424 : again:
    2349             : 
    2350             :     /*
    2351             :      * Select a victim buffer.  The buffer is returned with its header
    2352             :      * spinlock still held!
    2353             :      */
    2354     3793766 :     buf_hdr = StrategyGetBuffer(strategy, &buf_state, &from_ring);
    2355     3793766 :     buf = BufferDescriptorGetBuffer(buf_hdr);
    2356             : 
    2357             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 0);
    2358             : 
    2359             :     /* Pin the buffer and then release the buffer spinlock */
    2360     3793766 :     PinBuffer_Locked(buf_hdr);
    2361             : 
    2362             :     /*
    2363             :      * We shouldn't have any other pins for this buffer.
    2364             :      */
    2365     3793766 :     CheckBufferIsPinnedOnce(buf);
    2366             : 
    2367             :     /*
    2368             :      * If the buffer was dirty, try to write it out.  There is a race
    2369             :      * condition here, in that someone might dirty it after we released the
    2370             :      * buffer header lock above, or even while we are writing it out (since
    2371             :      * our share-lock won't prevent hint-bit updates).  We will recheck the
    2372             :      * dirty bit after re-locking the buffer header.
    2373             :      */
    2374     3793766 :     if (buf_state & BM_DIRTY)
    2375             :     {
    2376             :         LWLock     *content_lock;
    2377             : 
    2378             :         Assert(buf_state & BM_TAG_VALID);
    2379             :         Assert(buf_state & BM_VALID);
    2380             : 
    2381             :         /*
    2382             :          * We need a share-lock on the buffer contents to write it out (else
    2383             :          * we might write invalid data, eg because someone else is compacting
    2384             :          * the page contents while we write).  We must use a conditional lock
    2385             :          * acquisition here to avoid deadlock.  Even though the buffer was not
    2386             :          * pinned (and therefore surely not locked) when StrategyGetBuffer
    2387             :          * returned it, someone else could have pinned and exclusive-locked it
    2388             :          * by the time we get here. If we try to get the lock unconditionally,
    2389             :          * we'd block waiting for them; if they later block waiting for us,
    2390             :          * deadlock ensues. (This has been observed to happen when two
    2391             :          * backends are both trying to split btree index pages, and the second
    2392             :          * one just happens to be trying to split the page the first one got
    2393             :          * from StrategyGetBuffer.)
    2394             :          */
    2395      531570 :         content_lock = BufferDescriptorGetContentLock(buf_hdr);
    2396      531570 :         if (!LWLockConditionalAcquire(content_lock, LW_SHARED))
    2397             :         {
    2398             :             /*
    2399             :              * Someone else has locked the buffer, so give it up and loop back
    2400             :              * to get another one.
    2401             :              */
    2402           0 :             UnpinBuffer(buf_hdr);
    2403           0 :             goto again;
    2404             :         }
    2405             : 
    2406             :         /*
    2407             :          * If using a nondefault strategy, and writing the buffer would
    2408             :          * require a WAL flush, let the strategy decide whether to go ahead
    2409             :          * and write/reuse the buffer or to choose another victim.  We need a
    2410             :          * lock to inspect the page LSN, so this can't be done inside
    2411             :          * StrategyGetBuffer.
    2412             :          */
    2413      531570 :         if (strategy != NULL)
    2414             :         {
    2415             :             XLogRecPtr  lsn;
    2416             : 
    2417             :             /* Read the LSN while holding buffer header lock */
    2418      156364 :             buf_state = LockBufHdr(buf_hdr);
    2419      156364 :             lsn = BufferGetLSN(buf_hdr);
    2420      156364 :             UnlockBufHdr(buf_hdr, buf_state);
    2421             : 
    2422      156364 :             if (XLogNeedsFlush(lsn)
    2423       18178 :                 && StrategyRejectBuffer(strategy, buf_hdr, from_ring))
    2424             :             {
    2425       11460 :                 LWLockRelease(content_lock);
    2426       11460 :                 UnpinBuffer(buf_hdr);
    2427       11460 :                 goto again;
    2428             :             }
    2429             :         }
    2430             : 
    2431             :         /* OK, do the I/O */
    2432      520110 :         FlushBuffer(buf_hdr, NULL, IOOBJECT_RELATION, io_context);
    2433      520110 :         LWLockRelease(content_lock);
    2434             : 
    2435      520110 :         ScheduleBufferTagForWriteback(&BackendWritebackContext, io_context,
    2436             :                                       &buf_hdr->tag);
    2437             :     }
    2438             : 
    2439             : 
    2440     3782306 :     if (buf_state & BM_VALID)
    2441             :     {
    2442             :         /*
    2443             :          * When a BufferAccessStrategy is in use, blocks evicted from shared
    2444             :          * buffers are counted as IOOP_EVICT in the corresponding context
    2445             :          * (e.g. IOCONTEXT_BULKWRITE). Shared buffers are evicted by a
    2446             :          * strategy in two cases: 1) while initially claiming buffers for the
    2447             :          * strategy ring 2) to replace an existing strategy ring buffer
    2448             :          * because it is pinned or in use and cannot be reused.
    2449             :          *
    2450             :          * Blocks evicted from buffers already in the strategy ring are
    2451             :          * counted as IOOP_REUSE in the corresponding strategy context.
    2452             :          *
    2453             :          * At this point, we can accurately count evictions and reuses,
    2454             :          * because we have successfully claimed the valid buffer. Previously,
    2455             :          * we may have been forced to release the buffer due to concurrent
    2456             :          * pinners or erroring out.
    2457             :          */
    2458     2344548 :         pgstat_count_io_op(IOOBJECT_RELATION, io_context,
    2459     2344548 :                            from_ring ? IOOP_REUSE : IOOP_EVICT, 1, 0);
    2460             :     }
    2461             : 
    2462             :     /*
    2463             :      * If the buffer has an entry in the buffer mapping table, delete it. This
    2464             :      * can fail because another backend could have pinned or dirtied the
    2465             :      * buffer.
    2466             :      */
    2467     3782306 :     if ((buf_state & BM_TAG_VALID) && !InvalidateVictimBuffer(buf_hdr))
    2468             :     {
    2469         964 :         UnpinBuffer(buf_hdr);
    2470         964 :         goto again;
    2471             :     }
    2472             : 
    2473             :     /* a final set of sanity checks */
    2474             : #ifdef USE_ASSERT_CHECKING
    2475             :     buf_state = pg_atomic_read_u32(&buf_hdr->state);
    2476             : 
    2477             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
    2478             :     Assert(!(buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY)));
    2479             : 
    2480             :     CheckBufferIsPinnedOnce(buf);
    2481             : #endif
    2482             : 
    2483     3781342 :     return buf;
    2484             : }
    2485             : 
    2486             : /*
    2487             :  * Return the maximum number of buffers that a backend should try to pin once,
    2488             :  * to avoid exceeding its fair share.  This is the highest value that
    2489             :  * GetAdditionalPinLimit() could ever return.  Note that it may be zero on a
    2490             :  * system with a very small buffer pool relative to max_connections.
    2491             :  */
    2492             : uint32
    2493     1307342 : GetPinLimit(void)
    2494             : {
    2495     1307342 :     return MaxProportionalPins;
    2496             : }
    2497             : 
    2498             : /*
    2499             :  * Return the maximum number of additional buffers that this backend should
    2500             :  * pin if it wants to stay under the per-backend limit, considering the number
    2501             :  * of buffers it has already pinned.  Unlike LimitAdditionalPins(), the limit
    2502             :  * return by this function can be zero.
    2503             :  */
    2504             : uint32
    2505     7958136 : GetAdditionalPinLimit(void)
    2506             : {
    2507             :     uint32      estimated_pins_held;
    2508             : 
    2509             :     /*
    2510             :      * We get the number of "overflowed" pins for free, but don't know the
    2511             :      * number of pins in PrivateRefCountArray.  The cost of calculating that
    2512             :      * exactly doesn't seem worth it, so just assume the max.
    2513             :      */
    2514     7958136 :     estimated_pins_held = PrivateRefCountOverflowed + REFCOUNT_ARRAY_ENTRIES;
    2515             : 
    2516             :     /* Is this backend already holding more than its fair share? */
    2517     7958136 :     if (estimated_pins_held > MaxProportionalPins)
    2518     2368312 :         return 0;
    2519             : 
    2520     5589824 :     return MaxProportionalPins - estimated_pins_held;
    2521             : }
    2522             : 
    2523             : /*
    2524             :  * Limit the number of pins a batch operation may additionally acquire, to
    2525             :  * avoid running out of pinnable buffers.
    2526             :  *
    2527             :  * One additional pin is always allowed, on the assumption that the operation
    2528             :  * requires at least one to make progress.
    2529             :  */
    2530             : void
    2531      401478 : LimitAdditionalPins(uint32 *additional_pins)
    2532             : {
    2533             :     uint32      limit;
    2534             : 
    2535      401478 :     if (*additional_pins <= 1)
    2536      381886 :         return;
    2537             : 
    2538       19592 :     limit = GetAdditionalPinLimit();
    2539       19592 :     limit = Max(limit, 1);
    2540       19592 :     if (limit < *additional_pins)
    2541       10720 :         *additional_pins = limit;
    2542             : }
    2543             : 
    2544             : /*
    2545             :  * Logic shared between ExtendBufferedRelBy(), ExtendBufferedRelTo(). Just to
    2546             :  * avoid duplicating the tracing and relpersistence related logic.
    2547             :  */
    2548             : static BlockNumber
    2549      424288 : ExtendBufferedRelCommon(BufferManagerRelation bmr,
    2550             :                         ForkNumber fork,
    2551             :                         BufferAccessStrategy strategy,
    2552             :                         uint32 flags,
    2553             :                         uint32 extend_by,
    2554             :                         BlockNumber extend_upto,
    2555             :                         Buffer *buffers,
    2556             :                         uint32 *extended_by)
    2557             : {
    2558             :     BlockNumber first_block;
    2559             : 
    2560             :     TRACE_POSTGRESQL_BUFFER_EXTEND_START(fork,
    2561             :                                          bmr.smgr->smgr_rlocator.locator.spcOid,
    2562             :                                          bmr.smgr->smgr_rlocator.locator.dbOid,
    2563             :                                          bmr.smgr->smgr_rlocator.locator.relNumber,
    2564             :                                          bmr.smgr->smgr_rlocator.backend,
    2565             :                                          extend_by);
    2566             : 
    2567      424288 :     if (bmr.relpersistence == RELPERSISTENCE_TEMP)
    2568       22810 :         first_block = ExtendBufferedRelLocal(bmr, fork, flags,
    2569             :                                              extend_by, extend_upto,
    2570             :                                              buffers, &extend_by);
    2571             :     else
    2572      401478 :         first_block = ExtendBufferedRelShared(bmr, fork, strategy, flags,
    2573             :                                               extend_by, extend_upto,
    2574             :                                               buffers, &extend_by);
    2575      424288 :     *extended_by = extend_by;
    2576             : 
    2577             :     TRACE_POSTGRESQL_BUFFER_EXTEND_DONE(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             :                                         *extended_by,
    2583             :                                         first_block);
    2584             : 
    2585      424288 :     return first_block;
    2586             : }
    2587             : 
    2588             : /*
    2589             :  * Implementation of ExtendBufferedRelBy() and ExtendBufferedRelTo() for
    2590             :  * shared buffers.
    2591             :  */
    2592             : static BlockNumber
    2593      401478 : ExtendBufferedRelShared(BufferManagerRelation bmr,
    2594             :                         ForkNumber fork,
    2595             :                         BufferAccessStrategy strategy,
    2596             :                         uint32 flags,
    2597             :                         uint32 extend_by,
    2598             :                         BlockNumber extend_upto,
    2599             :                         Buffer *buffers,
    2600             :                         uint32 *extended_by)
    2601             : {
    2602             :     BlockNumber first_block;
    2603      401478 :     IOContext   io_context = IOContextForStrategy(strategy);
    2604             :     instr_time  io_start;
    2605             : 
    2606      401478 :     LimitAdditionalPins(&extend_by);
    2607             : 
    2608             :     /*
    2609             :      * Acquire victim buffers for extension without holding extension lock.
    2610             :      * Writing out victim buffers is the most expensive part of extending the
    2611             :      * relation, particularly when doing so requires WAL flushes. Zeroing out
    2612             :      * the buffers is also quite expensive, so do that before holding the
    2613             :      * extension lock as well.
    2614             :      *
    2615             :      * These pages are pinned by us and not valid. While we hold the pin they
    2616             :      * can't be acquired as victim buffers by another backend.
    2617             :      */
    2618      845226 :     for (uint32 i = 0; i < extend_by; i++)
    2619             :     {
    2620             :         Block       buf_block;
    2621             : 
    2622      443748 :         buffers[i] = GetVictimBuffer(strategy, io_context);
    2623      443748 :         buf_block = BufHdrGetBlock(GetBufferDescriptor(buffers[i] - 1));
    2624             : 
    2625             :         /* new buffers are zero-filled */
    2626      443748 :         MemSet(buf_block, 0, BLCKSZ);
    2627             :     }
    2628             : 
    2629             :     /*
    2630             :      * Lock relation against concurrent extensions, unless requested not to.
    2631             :      *
    2632             :      * We use the same extension lock for all forks. That's unnecessarily
    2633             :      * restrictive, but currently extensions for forks don't happen often
    2634             :      * enough to make it worth locking more granularly.
    2635             :      *
    2636             :      * Note that another backend might have extended the relation by the time
    2637             :      * we get the lock.
    2638             :      */
    2639      401478 :     if (!(flags & EB_SKIP_EXTENSION_LOCK))
    2640      298884 :         LockRelationForExtension(bmr.rel, ExclusiveLock);
    2641             : 
    2642             :     /*
    2643             :      * If requested, invalidate size cache, so that smgrnblocks asks the
    2644             :      * kernel.
    2645             :      */
    2646      401478 :     if (flags & EB_CLEAR_SIZE_CACHE)
    2647       15360 :         bmr.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
    2648             : 
    2649      401478 :     first_block = smgrnblocks(bmr.smgr, fork);
    2650             : 
    2651             :     /*
    2652             :      * Now that we have the accurate relation size, check if the caller wants
    2653             :      * us to extend to only up to a specific size. If there were concurrent
    2654             :      * extensions, we might have acquired too many buffers and need to release
    2655             :      * them.
    2656             :      */
    2657      401478 :     if (extend_upto != InvalidBlockNumber)
    2658             :     {
    2659      106182 :         uint32      orig_extend_by = extend_by;
    2660             : 
    2661      106182 :         if (first_block > extend_upto)
    2662           0 :             extend_by = 0;
    2663      106182 :         else if ((uint64) first_block + extend_by > extend_upto)
    2664          14 :             extend_by = extend_upto - first_block;
    2665             : 
    2666      106224 :         for (uint32 i = extend_by; i < orig_extend_by; i++)
    2667             :         {
    2668          42 :             BufferDesc *buf_hdr = GetBufferDescriptor(buffers[i] - 1);
    2669             : 
    2670          42 :             UnpinBuffer(buf_hdr);
    2671             :         }
    2672             : 
    2673      106182 :         if (extend_by == 0)
    2674             :         {
    2675          14 :             if (!(flags & EB_SKIP_EXTENSION_LOCK))
    2676          14 :                 UnlockRelationForExtension(bmr.rel, ExclusiveLock);
    2677          14 :             *extended_by = extend_by;
    2678          14 :             return first_block;
    2679             :         }
    2680             :     }
    2681             : 
    2682             :     /* Fail if relation is already at maximum possible length */
    2683      401464 :     if ((uint64) first_block + extend_by >= MaxBlockNumber)
    2684           0 :         ereport(ERROR,
    2685             :                 (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
    2686             :                  errmsg("cannot extend relation %s beyond %u blocks",
    2687             :                         relpath(bmr.smgr->smgr_rlocator, fork).str,
    2688             :                         MaxBlockNumber)));
    2689             : 
    2690             :     /*
    2691             :      * Insert buffers into buffer table, mark as IO_IN_PROGRESS.
    2692             :      *
    2693             :      * This needs to happen before we extend the relation, because as soon as
    2694             :      * we do, other backends can start to read in those pages.
    2695             :      */
    2696      845170 :     for (uint32 i = 0; i < extend_by; i++)
    2697             :     {
    2698      443706 :         Buffer      victim_buf = buffers[i];
    2699      443706 :         BufferDesc *victim_buf_hdr = GetBufferDescriptor(victim_buf - 1);
    2700             :         BufferTag   tag;
    2701             :         uint32      hash;
    2702             :         LWLock     *partition_lock;
    2703             :         int         existing_id;
    2704             : 
    2705             :         /* in case we need to pin an existing buffer below */
    2706      443706 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    2707      443706 :         ReservePrivateRefCountEntry();
    2708             : 
    2709      443706 :         InitBufferTag(&tag, &bmr.smgr->smgr_rlocator.locator, fork, first_block + i);
    2710      443706 :         hash = BufTableHashCode(&tag);
    2711      443706 :         partition_lock = BufMappingPartitionLock(hash);
    2712             : 
    2713      443706 :         LWLockAcquire(partition_lock, LW_EXCLUSIVE);
    2714             : 
    2715      443706 :         existing_id = BufTableInsert(&tag, hash, victim_buf_hdr->buf_id);
    2716             : 
    2717             :         /*
    2718             :          * We get here only in the corner case where we are trying to extend
    2719             :          * the relation but we found a pre-existing buffer. This can happen
    2720             :          * because a prior attempt at extending the relation failed, and
    2721             :          * because mdread doesn't complain about reads beyond EOF (when
    2722             :          * zero_damaged_pages is ON) and so a previous attempt to read a block
    2723             :          * beyond EOF could have left a "valid" zero-filled buffer.
    2724             :          *
    2725             :          * This has also been observed when relation was overwritten by
    2726             :          * external process. Since the legitimate cases should always have
    2727             :          * left a zero-filled buffer, complain if not PageIsNew.
    2728             :          */
    2729      443706 :         if (existing_id >= 0)
    2730             :         {
    2731           0 :             BufferDesc *existing_hdr = GetBufferDescriptor(existing_id);
    2732             :             Block       buf_block;
    2733             :             bool        valid;
    2734             : 
    2735             :             /*
    2736             :              * Pin the existing buffer before releasing the partition lock,
    2737             :              * preventing it from being evicted.
    2738             :              */
    2739           0 :             valid = PinBuffer(existing_hdr, strategy);
    2740             : 
    2741           0 :             LWLockRelease(partition_lock);
    2742           0 :             UnpinBuffer(victim_buf_hdr);
    2743             : 
    2744           0 :             buffers[i] = BufferDescriptorGetBuffer(existing_hdr);
    2745           0 :             buf_block = BufHdrGetBlock(existing_hdr);
    2746             : 
    2747           0 :             if (valid && !PageIsNew((Page) buf_block))
    2748           0 :                 ereport(ERROR,
    2749             :                         (errmsg("unexpected data beyond EOF in block %u of relation \"%s\"",
    2750             :                                 existing_hdr->tag.blockNum,
    2751             :                                 relpath(bmr.smgr->smgr_rlocator, fork).str)));
    2752             : 
    2753             :             /*
    2754             :              * We *must* do smgr[zero]extend before succeeding, else the page
    2755             :              * will not be reserved by the kernel, and the next P_NEW call
    2756             :              * will decide to return the same page.  Clear the BM_VALID bit,
    2757             :              * do StartBufferIO() and proceed.
    2758             :              *
    2759             :              * Loop to handle the very small possibility that someone re-sets
    2760             :              * BM_VALID between our clearing it and StartBufferIO inspecting
    2761             :              * it.
    2762             :              */
    2763             :             do
    2764             :             {
    2765           0 :                 uint32      buf_state = LockBufHdr(existing_hdr);
    2766             : 
    2767           0 :                 buf_state &= ~BM_VALID;
    2768           0 :                 UnlockBufHdr(existing_hdr, buf_state);
    2769           0 :             } while (!StartBufferIO(existing_hdr, true, false));
    2770             :         }
    2771             :         else
    2772             :         {
    2773             :             uint32      buf_state;
    2774             : 
    2775      443706 :             buf_state = LockBufHdr(victim_buf_hdr);
    2776             : 
    2777             :             /* some sanity checks while we hold the buffer header lock */
    2778             :             Assert(!(buf_state & (BM_VALID | BM_TAG_VALID | BM_DIRTY | BM_JUST_DIRTIED)));
    2779             :             Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
    2780             : 
    2781      443706 :             victim_buf_hdr->tag = tag;
    2782             : 
    2783      443706 :             buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
    2784      443706 :             if (bmr.relpersistence == RELPERSISTENCE_PERMANENT || fork == INIT_FORKNUM)
    2785      433156 :                 buf_state |= BM_PERMANENT;
    2786             : 
    2787      443706 :             UnlockBufHdr(victim_buf_hdr, buf_state);
    2788             : 
    2789      443706 :             LWLockRelease(partition_lock);
    2790             : 
    2791             :             /* XXX: could combine the locked operations in it with the above */
    2792      443706 :             StartBufferIO(victim_buf_hdr, true, false);
    2793             :         }
    2794             :     }
    2795             : 
    2796      401464 :     io_start = pgstat_prepare_io_time(track_io_timing);
    2797             : 
    2798             :     /*
    2799             :      * Note: if smgrzeroextend fails, we will end up with buffers that are
    2800             :      * allocated but not marked BM_VALID.  The next relation extension will
    2801             :      * still select the same block number (because the relation didn't get any
    2802             :      * longer on disk) and so future attempts to extend the relation will find
    2803             :      * the same buffers (if they have not been recycled) but come right back
    2804             :      * here to try smgrzeroextend again.
    2805             :      *
    2806             :      * We don't need to set checksum for all-zero pages.
    2807             :      */
    2808      401464 :     smgrzeroextend(bmr.smgr, fork, first_block, extend_by, false);
    2809             : 
    2810             :     /*
    2811             :      * Release the file-extension lock; it's now OK for someone else to extend
    2812             :      * the relation some more.
    2813             :      *
    2814             :      * We remove IO_IN_PROGRESS after this, as waking up waiting backends can
    2815             :      * take noticeable time.
    2816             :      */
    2817      401464 :     if (!(flags & EB_SKIP_EXTENSION_LOCK))
    2818      298870 :         UnlockRelationForExtension(bmr.rel, ExclusiveLock);
    2819             : 
    2820      401464 :     pgstat_count_io_op_time(IOOBJECT_RELATION, io_context, IOOP_EXTEND,
    2821      401464 :                             io_start, 1, extend_by * BLCKSZ);
    2822             : 
    2823             :     /* Set BM_VALID, terminate IO, and wake up any waiters */
    2824      845170 :     for (uint32 i = 0; i < extend_by; i++)
    2825             :     {
    2826      443706 :         Buffer      buf = buffers[i];
    2827      443706 :         BufferDesc *buf_hdr = GetBufferDescriptor(buf - 1);
    2828      443706 :         bool        lock = false;
    2829             : 
    2830      443706 :         if (flags & EB_LOCK_FIRST && i == 0)
    2831      294764 :             lock = true;
    2832      148942 :         else if (flags & EB_LOCK_TARGET)
    2833             :         {
    2834             :             Assert(extend_upto != InvalidBlockNumber);
    2835       88694 :             if (first_block + i + 1 == extend_upto)
    2836       87772 :                 lock = true;
    2837             :         }
    2838             : 
    2839      443706 :         if (lock)
    2840      382536 :             LWLockAcquire(BufferDescriptorGetContentLock(buf_hdr), LW_EXCLUSIVE);
    2841             : 
    2842      443706 :         TerminateBufferIO(buf_hdr, false, BM_VALID, true, false);
    2843             :     }
    2844             : 
    2845      401464 :     pgBufferUsage.shared_blks_written += extend_by;
    2846             : 
    2847      401464 :     *extended_by = extend_by;
    2848             : 
    2849      401464 :     return first_block;
    2850             : }
    2851             : 
    2852             : /*
    2853             :  * BufferIsExclusiveLocked
    2854             :  *
    2855             :  *      Checks if buffer is exclusive-locked.
    2856             :  *
    2857             :  * Buffer must be pinned.
    2858             :  */
    2859             : bool
    2860           0 : BufferIsExclusiveLocked(Buffer buffer)
    2861             : {
    2862             :     BufferDesc *bufHdr;
    2863             : 
    2864             :     Assert(BufferIsPinned(buffer));
    2865             : 
    2866           0 :     if (BufferIsLocal(buffer))
    2867             :     {
    2868             :         /* Content locks are not maintained for local buffers. */
    2869           0 :         return true;
    2870             :     }
    2871             :     else
    2872             :     {
    2873           0 :         bufHdr = GetBufferDescriptor(buffer - 1);
    2874           0 :         return LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    2875             :                                     LW_EXCLUSIVE);
    2876             :     }
    2877             : }
    2878             : 
    2879             : /*
    2880             :  * BufferIsDirty
    2881             :  *
    2882             :  *      Checks if buffer is already dirty.
    2883             :  *
    2884             :  * Buffer must be pinned and exclusive-locked.  (Without an exclusive lock,
    2885             :  * the result may be stale before it's returned.)
    2886             :  */
    2887             : bool
    2888           0 : BufferIsDirty(Buffer buffer)
    2889             : {
    2890             :     BufferDesc *bufHdr;
    2891             : 
    2892             :     Assert(BufferIsPinned(buffer));
    2893             : 
    2894           0 :     if (BufferIsLocal(buffer))
    2895             :     {
    2896           0 :         int         bufid = -buffer - 1;
    2897             : 
    2898           0 :         bufHdr = GetLocalBufferDescriptor(bufid);
    2899             :         /* Content locks are not maintained for local buffers. */
    2900             :     }
    2901             :     else
    2902             :     {
    2903           0 :         bufHdr = GetBufferDescriptor(buffer - 1);
    2904             :         Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    2905             :                                     LW_EXCLUSIVE));
    2906             :     }
    2907             : 
    2908           0 :     return pg_atomic_read_u32(&bufHdr->state) & BM_DIRTY;
    2909             : }
    2910             : 
    2911             : /*
    2912             :  * MarkBufferDirty
    2913             :  *
    2914             :  *      Marks buffer contents as dirty (actual write happens later).
    2915             :  *
    2916             :  * Buffer must be pinned and exclusive-locked.  (If caller does not hold
    2917             :  * exclusive lock, then somebody could be in process of writing the buffer,
    2918             :  * leading to risk of bad data written to disk.)
    2919             :  */
    2920             : void
    2921    42820912 : MarkBufferDirty(Buffer buffer)
    2922             : {
    2923             :     BufferDesc *bufHdr;
    2924             :     uint32      buf_state;
    2925             :     uint32      old_buf_state;
    2926             : 
    2927    42820912 :     if (!BufferIsValid(buffer))
    2928           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    2929             : 
    2930    42820912 :     if (BufferIsLocal(buffer))
    2931             :     {
    2932     2444464 :         MarkLocalBufferDirty(buffer);
    2933     2444464 :         return;
    2934             :     }
    2935             : 
    2936    40376448 :     bufHdr = GetBufferDescriptor(buffer - 1);
    2937             : 
    2938             :     Assert(BufferIsPinned(buffer));
    2939             :     Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    2940             :                                 LW_EXCLUSIVE));
    2941             : 
    2942    40376448 :     old_buf_state = pg_atomic_read_u32(&bufHdr->state);
    2943             :     for (;;)
    2944             :     {
    2945    40376734 :         if (old_buf_state & BM_LOCKED)
    2946          50 :             old_buf_state = WaitBufHdrUnlocked(bufHdr);
    2947             : 
    2948    40376734 :         buf_state = old_buf_state;
    2949             : 
    2950             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2951    40376734 :         buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
    2952             : 
    2953    40376734 :         if (pg_atomic_compare_exchange_u32(&bufHdr->state, &old_buf_state,
    2954             :                                            buf_state))
    2955    40376448 :             break;
    2956             :     }
    2957             : 
    2958             :     /*
    2959             :      * If the buffer was not dirty already, do vacuum accounting.
    2960             :      */
    2961    40376448 :     if (!(old_buf_state & BM_DIRTY))
    2962             :     {
    2963     1292434 :         pgBufferUsage.shared_blks_dirtied++;
    2964     1292434 :         if (VacuumCostActive)
    2965       13548 :             VacuumCostBalance += VacuumCostPageDirty;
    2966             :     }
    2967             : }
    2968             : 
    2969             : /*
    2970             :  * ReleaseAndReadBuffer -- combine ReleaseBuffer() and ReadBuffer()
    2971             :  *
    2972             :  * Formerly, this saved one cycle of acquiring/releasing the BufMgrLock
    2973             :  * compared to calling the two routines separately.  Now it's mainly just
    2974             :  * a convenience function.  However, if the passed buffer is valid and
    2975             :  * already contains the desired block, we just return it as-is; and that
    2976             :  * does save considerable work compared to a full release and reacquire.
    2977             :  *
    2978             :  * Note: it is OK to pass buffer == InvalidBuffer, indicating that no old
    2979             :  * buffer actually needs to be released.  This case is the same as ReadBuffer,
    2980             :  * but can save some tests in the caller.
    2981             :  */
    2982             : Buffer
    2983    57575568 : ReleaseAndReadBuffer(Buffer buffer,
    2984             :                      Relation relation,
    2985             :                      BlockNumber blockNum)
    2986             : {
    2987    57575568 :     ForkNumber  forkNum = MAIN_FORKNUM;
    2988             :     BufferDesc *bufHdr;
    2989             : 
    2990    57575568 :     if (BufferIsValid(buffer))
    2991             :     {
    2992             :         Assert(BufferIsPinned(buffer));
    2993    34376622 :         if (BufferIsLocal(buffer))
    2994             :         {
    2995       73728 :             bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    2996       80772 :             if (bufHdr->tag.blockNum == blockNum &&
    2997       14088 :                 BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
    2998        7044 :                 BufTagGetForkNum(&bufHdr->tag) == forkNum)
    2999        7044 :                 return buffer;
    3000       66684 :             UnpinLocalBuffer(buffer);
    3001             :         }
    3002             :         else
    3003             :         {
    3004    34302894 :             bufHdr = GetBufferDescriptor(buffer - 1);
    3005             :             /* we have pin, so it's ok to examine tag without spinlock */
    3006    46093648 :             if (bufHdr->tag.blockNum == blockNum &&
    3007    23581508 :                 BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
    3008    11790754 :                 BufTagGetForkNum(&bufHdr->tag) == forkNum)
    3009    11790754 :                 return buffer;
    3010    22512140 :             UnpinBuffer(bufHdr);
    3011             :         }
    3012             :     }
    3013             : 
    3014    45777770 :     return ReadBuffer(relation, blockNum);
    3015             : }
    3016             : 
    3017             : /*
    3018             :  * PinBuffer -- make buffer unavailable for replacement.
    3019             :  *
    3020             :  * For the default access strategy, the buffer's usage_count is incremented
    3021             :  * when we first pin it; for other strategies we just make sure the usage_count
    3022             :  * isn't zero.  (The idea of the latter is that we don't want synchronized
    3023             :  * heap scans to inflate the count, but we need it to not be zero to discourage
    3024             :  * other backends from stealing buffers from our ring.  As long as we cycle
    3025             :  * through the ring faster than the global clock-sweep cycles, buffers in
    3026             :  * our ring won't be chosen as victims for replacement by other backends.)
    3027             :  *
    3028             :  * This should be applied only to shared buffers, never local ones.
    3029             :  *
    3030             :  * Since buffers are pinned/unpinned very frequently, pin buffers without
    3031             :  * taking the buffer header lock; instead update the state variable in loop of
    3032             :  * CAS operations. Hopefully it's just a single CAS.
    3033             :  *
    3034             :  * Note that ResourceOwnerEnlarge() and ReservePrivateRefCountEntry()
    3035             :  * must have been done already.
    3036             :  *
    3037             :  * Returns true if buffer is BM_VALID, else false.  This provision allows
    3038             :  * some callers to avoid an extra spinlock cycle.
    3039             :  */
    3040             : static bool
    3041   117970576 : PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
    3042             : {
    3043   117970576 :     Buffer      b = BufferDescriptorGetBuffer(buf);
    3044             :     bool        result;
    3045             :     PrivateRefCountEntry *ref;
    3046             : 
    3047             :     Assert(!BufferIsLocal(b));
    3048             :     Assert(ReservedRefCountEntry != NULL);
    3049             : 
    3050   117970576 :     ref = GetPrivateRefCountEntry(b, true);
    3051             : 
    3052   117970576 :     if (ref == NULL)
    3053             :     {
    3054             :         uint32      buf_state;
    3055             :         uint32      old_buf_state;
    3056             : 
    3057   113657046 :         ref = NewPrivateRefCountEntry(b);
    3058             : 
    3059   113657046 :         old_buf_state = pg_atomic_read_u32(&buf->state);
    3060             :         for (;;)
    3061             :         {
    3062   113701608 :             if (old_buf_state & BM_LOCKED)
    3063        1750 :                 old_buf_state = WaitBufHdrUnlocked(buf);
    3064             : 
    3065   113701608 :             buf_state = old_buf_state;
    3066             : 
    3067             :             /* increase refcount */
    3068   113701608 :             buf_state += BUF_REFCOUNT_ONE;
    3069             : 
    3070   113701608 :             if (strategy == NULL)
    3071             :             {
    3072             :                 /* Default case: increase usagecount unless already max. */
    3073   112030192 :                 if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
    3074     6527450 :                     buf_state += BUF_USAGECOUNT_ONE;
    3075             :             }
    3076             :             else
    3077             :             {
    3078             :                 /*
    3079             :                  * Ring buffers shouldn't evict others from pool.  Thus we
    3080             :                  * don't make usagecount more than 1.
    3081             :                  */
    3082     1671416 :                 if (BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
    3083       68184 :                     buf_state += BUF_USAGECOUNT_ONE;
    3084             :             }
    3085             : 
    3086   113701608 :             if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
    3087             :                                                buf_state))
    3088             :             {
    3089   113657046 :                 result = (buf_state & BM_VALID) != 0;
    3090             : 
    3091             :                 /*
    3092             :                  * Assume that we acquired a buffer pin for the purposes of
    3093             :                  * Valgrind buffer client checks (even in !result case) to
    3094             :                  * keep things simple.  Buffers that are unsafe to access are
    3095             :                  * not generally guaranteed to be marked undefined or
    3096             :                  * non-accessible in any case.
    3097             :                  */
    3098             :                 VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
    3099   113657046 :                 break;
    3100             :             }
    3101             :         }
    3102             :     }
    3103             :     else
    3104             :     {
    3105             :         /*
    3106             :          * If we previously pinned the buffer, it is likely to be valid, but
    3107             :          * it may not be if StartReadBuffers() was called and
    3108             :          * WaitReadBuffers() hasn't been called yet.  We'll check by loading
    3109             :          * the flags without locking.  This is racy, but it's OK to return
    3110             :          * false spuriously: when WaitReadBuffers() calls StartBufferIO(),
    3111             :          * it'll see that it's now valid.
    3112             :          *
    3113             :          * Note: We deliberately avoid a Valgrind client request here.
    3114             :          * Individual access methods can optionally superimpose buffer page
    3115             :          * client requests on top of our client requests to enforce that
    3116             :          * buffers are only accessed while locked (and pinned).  It's possible
    3117             :          * that the buffer page is legitimately non-accessible here.  We
    3118             :          * cannot meddle with that.
    3119             :          */
    3120     4313530 :         result = (pg_atomic_read_u32(&buf->state) & BM_VALID) != 0;
    3121             :     }
    3122             : 
    3123   117970576 :     ref->refcount++;
    3124             :     Assert(ref->refcount > 0);
    3125   117970576 :     ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
    3126   117970576 :     return result;
    3127             : }
    3128             : 
    3129             : /*
    3130             :  * PinBuffer_Locked -- as above, but caller already locked the buffer header.
    3131             :  * The spinlock is released before return.
    3132             :  *
    3133             :  * As this function is called with the spinlock held, the caller has to
    3134             :  * previously call ReservePrivateRefCountEntry() and
    3135             :  * ResourceOwnerEnlarge(CurrentResourceOwner);
    3136             :  *
    3137             :  * Currently, no callers of this function want to modify the buffer's
    3138             :  * usage_count at all, so there's no need for a strategy parameter.
    3139             :  * Also we don't bother with a BM_VALID test (the caller could check that for
    3140             :  * itself).
    3141             :  *
    3142             :  * Also all callers only ever use this function when it's known that the
    3143             :  * buffer can't have a preexisting pin by this backend. That allows us to skip
    3144             :  * searching the private refcount array & hash, which is a boon, because the
    3145             :  * spinlock is still held.
    3146             :  *
    3147             :  * Note: use of this routine is frequently mandatory, not just an optimization
    3148             :  * to save a spin lock/unlock cycle, because we need to pin a buffer before
    3149             :  * its state can change under us.
    3150             :  */
    3151             : static void
    3152     4400740 : PinBuffer_Locked(BufferDesc *buf)
    3153             : {
    3154             :     Buffer      b;
    3155             :     PrivateRefCountEntry *ref;
    3156             :     uint32      buf_state;
    3157             : 
    3158             :     /*
    3159             :      * As explained, We don't expect any preexisting pins. That allows us to
    3160             :      * manipulate the PrivateRefCount after releasing the spinlock
    3161             :      */
    3162             :     Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
    3163             : 
    3164             :     /*
    3165             :      * Buffer can't have a preexisting pin, so mark its page as defined to
    3166             :      * Valgrind (this is similar to the PinBuffer() case where the backend
    3167             :      * doesn't already have a buffer pin)
    3168             :      */
    3169             :     VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
    3170             : 
    3171             :     /*
    3172             :      * Since we hold the buffer spinlock, we can update the buffer state and
    3173             :      * release the lock in one operation.
    3174             :      */
    3175     4400740 :     buf_state = pg_atomic_read_u32(&buf->state);
    3176             :     Assert(buf_state & BM_LOCKED);
    3177     4400740 :     buf_state += BUF_REFCOUNT_ONE;
    3178     4400740 :     UnlockBufHdr(buf, buf_state);
    3179             : 
    3180     4400740 :     b = BufferDescriptorGetBuffer(buf);
    3181             : 
    3182     4400740 :     ref = NewPrivateRefCountEntry(b);
    3183     4400740 :     ref->refcount++;
    3184             : 
    3185     4400740 :     ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
    3186     4400740 : }
    3187             : 
    3188             : /*
    3189             :  * Support for waking up another backend that is waiting for the cleanup lock
    3190             :  * to be released using BM_PIN_COUNT_WAITER.
    3191             :  *
    3192             :  * See LockBufferForCleanup().
    3193             :  *
    3194             :  * Expected to be called just after releasing a buffer pin (in a BufferDesc,
    3195             :  * not just reducing the backend-local pincount for the buffer).
    3196             :  */
    3197             : static void
    3198         106 : WakePinCountWaiter(BufferDesc *buf)
    3199             : {
    3200             :     /*
    3201             :      * Acquire the buffer header lock, re-check that there's a waiter. Another
    3202             :      * backend could have unpinned this buffer, and already woken up the
    3203             :      * waiter.
    3204             :      *
    3205             :      * There's no danger of the buffer being replaced after we unpinned it
    3206             :      * above, as it's pinned by the waiter. The waiter removes
    3207             :      * BM_PIN_COUNT_WAITER if it stops waiting for a reason other than this
    3208             :      * backend waking it up.
    3209             :      */
    3210         106 :     uint32      buf_state = LockBufHdr(buf);
    3211             : 
    3212         106 :     if ((buf_state & BM_PIN_COUNT_WAITER) &&
    3213         106 :         BUF_STATE_GET_REFCOUNT(buf_state) == 1)
    3214         106 :     {
    3215             :         /* we just released the last pin other than the waiter's */
    3216         106 :         int         wait_backend_pgprocno = buf->wait_backend_pgprocno;
    3217             : 
    3218         106 :         buf_state &= ~BM_PIN_COUNT_WAITER;
    3219         106 :         UnlockBufHdr(buf, buf_state);
    3220         106 :         ProcSendSignal(wait_backend_pgprocno);
    3221             :     }
    3222             :     else
    3223           0 :         UnlockBufHdr(buf, buf_state);
    3224         106 : }
    3225             : 
    3226             : /*
    3227             :  * UnpinBuffer -- make buffer available for replacement.
    3228             :  *
    3229             :  * This should be applied only to shared buffers, never local ones.  This
    3230             :  * always adjusts CurrentResourceOwner.
    3231             :  */
    3232             : static void
    3233   144926368 : UnpinBuffer(BufferDesc *buf)
    3234             : {
    3235   144926368 :     Buffer      b = BufferDescriptorGetBuffer(buf);
    3236             : 
    3237   144926368 :     ResourceOwnerForgetBuffer(CurrentResourceOwner, b);
    3238   144926368 :     UnpinBufferNoOwner(buf);
    3239   144926368 : }
    3240             : 
    3241             : static void
    3242   144935210 : UnpinBufferNoOwner(BufferDesc *buf)
    3243             : {
    3244             :     PrivateRefCountEntry *ref;
    3245   144935210 :     Buffer      b = BufferDescriptorGetBuffer(buf);
    3246             : 
    3247             :     Assert(!BufferIsLocal(b));
    3248             : 
    3249             :     /* not moving as we're likely deleting it soon anyway */
    3250   144935210 :     ref = GetPrivateRefCountEntry(b, false);
    3251             :     Assert(ref != NULL);
    3252             :     Assert(ref->refcount > 0);
    3253   144935210 :     ref->refcount--;
    3254   144935210 :     if (ref->refcount == 0)
    3255             :     {
    3256             :         uint32      buf_state;
    3257             :         uint32      old_buf_state;
    3258             : 
    3259             :         /*
    3260             :          * Mark buffer non-accessible to Valgrind.
    3261             :          *
    3262             :          * Note that the buffer may have already been marked non-accessible
    3263             :          * within access method code that enforces that buffers are only
    3264             :          * accessed while a buffer lock is held.
    3265             :          */
    3266             :         VALGRIND_MAKE_MEM_NOACCESS(BufHdrGetBlock(buf), BLCKSZ);
    3267             : 
    3268             :         /* I'd better not still hold the buffer content lock */
    3269             :         Assert(!LWLockHeldByMe(BufferDescriptorGetContentLock(buf)));
    3270             : 
    3271             :         /*
    3272             :          * Decrement the shared reference count.
    3273             :          *
    3274             :          * Since buffer spinlock holder can update status using just write,
    3275             :          * it's not safe to use atomic decrement here; thus use a CAS loop.
    3276             :          */
    3277   118057786 :         old_buf_state = pg_atomic_read_u32(&buf->state);
    3278             :         for (;;)
    3279             :         {
    3280   118095808 :             if (old_buf_state & BM_LOCKED)
    3281        1588 :                 old_buf_state = WaitBufHdrUnlocked(buf);
    3282             : 
    3283   118095808 :             buf_state = old_buf_state;
    3284             : 
    3285   118095808 :             buf_state -= BUF_REFCOUNT_ONE;
    3286             : 
    3287   118095808 :             if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
    3288             :                                                buf_state))
    3289   118057786 :                 break;
    3290             :         }
    3291             : 
    3292             :         /* Support LockBufferForCleanup() */
    3293   118057786 :         if (buf_state & BM_PIN_COUNT_WAITER)
    3294         106 :             WakePinCountWaiter(buf);
    3295             : 
    3296   118057786 :         ForgetPrivateRefCountEntry(ref);
    3297             :     }
    3298   144935210 : }
    3299             : 
    3300             : #define ST_SORT sort_checkpoint_bufferids
    3301             : #define ST_ELEMENT_TYPE CkptSortItem
    3302             : #define ST_COMPARE(a, b) ckpt_buforder_comparator(a, b)
    3303             : #define ST_SCOPE static
    3304             : #define ST_DEFINE
    3305             : #include "lib/sort_template.h"
    3306             : 
    3307             : /*
    3308             :  * BufferSync -- Write out all dirty buffers in the pool.
    3309             :  *
    3310             :  * This is called at checkpoint time to write out all dirty shared buffers.
    3311             :  * The checkpoint request flags should be passed in.  If CHECKPOINT_FAST is
    3312             :  * set, we disable delays between writes; if CHECKPOINT_IS_SHUTDOWN,
    3313             :  * CHECKPOINT_END_OF_RECOVERY or CHECKPOINT_FLUSH_UNLOGGED is set, we write
    3314             :  * even unlogged buffers, which are otherwise skipped.  The remaining flags
    3315             :  * currently have no effect here.
    3316             :  */
    3317             : static void
    3318        3414 : BufferSync(int flags)
    3319             : {
    3320             :     uint32      buf_state;
    3321             :     int         buf_id;
    3322             :     int         num_to_scan;
    3323             :     int         num_spaces;
    3324             :     int         num_processed;
    3325             :     int         num_written;
    3326        3414 :     CkptTsStatus *per_ts_stat = NULL;
    3327             :     Oid         last_tsid;
    3328             :     binaryheap *ts_heap;
    3329             :     int         i;
    3330        3414 :     int         mask = BM_DIRTY;
    3331             :     WritebackContext wb_context;
    3332             : 
    3333             :     /*
    3334             :      * Unless this is a shutdown checkpoint or we have been explicitly told,
    3335             :      * we write only permanent, dirty buffers.  But at shutdown or end of
    3336             :      * recovery, we write all dirty buffers.
    3337             :      */
    3338        3414 :     if (!((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY |
    3339             :                     CHECKPOINT_FLUSH_UNLOGGED))))
    3340        1918 :         mask |= BM_PERMANENT;
    3341             : 
    3342             :     /*
    3343             :      * Loop over all buffers, and mark the ones that need to be written with
    3344             :      * BM_CHECKPOINT_NEEDED.  Count them as we go (num_to_scan), so that we
    3345             :      * can estimate how much work needs to be done.
    3346             :      *
    3347             :      * This allows us to write only those pages that were dirty when the
    3348             :      * checkpoint began, and not those that get dirtied while it proceeds.
    3349             :      * Whenever a page with BM_CHECKPOINT_NEEDED is written out, either by us
    3350             :      * later in this function, or by normal backends or the bgwriter cleaning
    3351             :      * scan, the flag is cleared.  Any buffer dirtied after this point won't
    3352             :      * have the flag set.
    3353             :      *
    3354             :      * Note that if we fail to write some buffer, we may leave buffers with
    3355             :      * BM_CHECKPOINT_NEEDED still set.  This is OK since any such buffer would
    3356             :      * certainly need to be written for the next checkpoint attempt, too.
    3357             :      */
    3358        3414 :     num_to_scan = 0;
    3359    23783414 :     for (buf_id = 0; buf_id < NBuffers; buf_id++)
    3360             :     {
    3361    23780000 :         BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
    3362             : 
    3363             :         /*
    3364             :          * Header spinlock is enough to examine BM_DIRTY, see comment in
    3365             :          * SyncOneBuffer.
    3366             :          */
    3367    23780000 :         buf_state = LockBufHdr(bufHdr);
    3368             : 
    3369    23780000 :         if ((buf_state & mask) == mask)
    3370             :         {
    3371             :             CkptSortItem *item;
    3372             : 
    3373      578296 :             buf_state |= BM_CHECKPOINT_NEEDED;
    3374             : 
    3375      578296 :             item = &CkptBufferIds[num_to_scan++];
    3376      578296 :             item->buf_id = buf_id;
    3377      578296 :             item->tsId = bufHdr->tag.spcOid;
    3378      578296 :             item->relNumber = BufTagGetRelNumber(&bufHdr->tag);
    3379      578296 :             item->forkNum = BufTagGetForkNum(&bufHdr->tag);
    3380      578296 :             item->blockNum = bufHdr->tag.blockNum;
    3381             :         }
    3382             : 
    3383    23780000 :         UnlockBufHdr(bufHdr, buf_state);
    3384             : 
    3385             :         /* Check for barrier events in case NBuffers is large. */
    3386    23780000 :         if (ProcSignalBarrierPending)
    3387           0 :             ProcessProcSignalBarrier();
    3388             :     }
    3389             : 
    3390        3414 :     if (num_to_scan == 0)
    3391        1328 :         return;                 /* nothing to do */
    3392             : 
    3393        2086 :     WritebackContextInit(&wb_context, &checkpoint_flush_after);
    3394             : 
    3395             :     TRACE_POSTGRESQL_BUFFER_SYNC_START(NBuffers, num_to_scan);
    3396             : 
    3397             :     /*
    3398             :      * Sort buffers that need to be written to reduce the likelihood of random
    3399             :      * IO. The sorting is also important for the implementation of balancing
    3400             :      * writes between tablespaces. Without balancing writes we'd potentially
    3401             :      * end up writing to the tablespaces one-by-one; possibly overloading the
    3402             :      * underlying system.
    3403             :      */
    3404        2086 :     sort_checkpoint_bufferids(CkptBufferIds, num_to_scan);
    3405             : 
    3406        2086 :     num_spaces = 0;
    3407             : 
    3408             :     /*
    3409             :      * Allocate progress status for each tablespace with buffers that need to
    3410             :      * be flushed. This requires the to-be-flushed array to be sorted.
    3411             :      */
    3412        2086 :     last_tsid = InvalidOid;
    3413      580382 :     for (i = 0; i < num_to_scan; i++)
    3414             :     {
    3415             :         CkptTsStatus *s;
    3416             :         Oid         cur_tsid;
    3417             : 
    3418      578296 :         cur_tsid = CkptBufferIds[i].tsId;
    3419             : 
    3420             :         /*
    3421             :          * Grow array of per-tablespace status structs, every time a new
    3422             :          * tablespace is found.
    3423             :          */
    3424      578296 :         if (last_tsid == InvalidOid || last_tsid != cur_tsid)
    3425        3132 :         {
    3426             :             Size        sz;
    3427             : 
    3428        3132 :             num_spaces++;
    3429             : 
    3430             :             /*
    3431             :              * Not worth adding grow-by-power-of-2 logic here - even with a
    3432             :              * few hundred tablespaces this should be fine.
    3433             :              */
    3434        3132 :             sz = sizeof(CkptTsStatus) * num_spaces;
    3435             : 
    3436        3132 :             if (per_ts_stat == NULL)
    3437        2086 :                 per_ts_stat = (CkptTsStatus *) palloc(sz);
    3438             :             else
    3439        1046 :                 per_ts_stat = (CkptTsStatus *) repalloc(per_ts_stat, sz);
    3440             : 
    3441        3132 :             s = &per_ts_stat[num_spaces - 1];
    3442        3132 :             memset(s, 0, sizeof(*s));
    3443        3132 :             s->tsId = cur_tsid;
    3444             : 
    3445             :             /*
    3446             :              * The first buffer in this tablespace. As CkptBufferIds is sorted
    3447             :              * by tablespace all (s->num_to_scan) buffers in this tablespace
    3448             :              * will follow afterwards.
    3449             :              */
    3450        3132 :             s->index = i;
    3451             : 
    3452             :             /*
    3453             :              * progress_slice will be determined once we know how many buffers
    3454             :              * are in each tablespace, i.e. after this loop.
    3455             :              */
    3456             : 
    3457        3132 :             last_tsid = cur_tsid;
    3458             :         }
    3459             :         else
    3460             :         {
    3461      575164 :             s = &per_ts_stat[num_spaces - 1];
    3462             :         }
    3463             : 
    3464      578296 :         s->num_to_scan++;
    3465             : 
    3466             :         /* Check for barrier events. */
    3467      578296 :         if (ProcSignalBarrierPending)
    3468           0 :             ProcessProcSignalBarrier();
    3469             :     }
    3470             : 
    3471             :     Assert(num_spaces > 0);
    3472             : 
    3473             :     /*
    3474             :      * Build a min-heap over the write-progress in the individual tablespaces,
    3475             :      * and compute how large a portion of the total progress a single
    3476             :      * processed buffer is.
    3477             :      */
    3478        2086 :     ts_heap = binaryheap_allocate(num_spaces,
    3479             :                                   ts_ckpt_progress_comparator,
    3480             :                                   NULL);
    3481             : 
    3482        5218 :     for (i = 0; i < num_spaces; i++)
    3483             :     {
    3484        3132 :         CkptTsStatus *ts_stat = &per_ts_stat[i];
    3485             : 
    3486        3132 :         ts_stat->progress_slice = (float8) num_to_scan / ts_stat->num_to_scan;
    3487             : 
    3488        3132 :         binaryheap_add_unordered(ts_heap, PointerGetDatum(ts_stat));
    3489             :     }
    3490             : 
    3491        2086 :     binaryheap_build(ts_heap);
    3492             : 
    3493             :     /*
    3494             :      * Iterate through to-be-checkpointed buffers and write the ones (still)
    3495             :      * marked with BM_CHECKPOINT_NEEDED. The writes are balanced between
    3496             :      * tablespaces; otherwise the sorting would lead to only one tablespace
    3497             :      * receiving writes at a time, making inefficient use of the hardware.
    3498             :      */
    3499        2086 :     num_processed = 0;
    3500        2086 :     num_written = 0;
    3501      580382 :     while (!binaryheap_empty(ts_heap))
    3502             :     {
    3503      578296 :         BufferDesc *bufHdr = NULL;
    3504             :         CkptTsStatus *ts_stat = (CkptTsStatus *)
    3505      578296 :             DatumGetPointer(binaryheap_first(ts_heap));
    3506             : 
    3507      578296 :         buf_id = CkptBufferIds[ts_stat->index].buf_id;
    3508             :         Assert(buf_id != -1);
    3509             : 
    3510      578296 :         bufHdr = GetBufferDescriptor(buf_id);
    3511             : 
    3512      578296 :         num_processed++;
    3513             : 
    3514             :         /*
    3515             :          * We don't need to acquire the lock here, because we're only looking
    3516             :          * at a single bit. It's possible that someone else writes the buffer
    3517             :          * and clears the flag right after we check, but that doesn't matter
    3518             :          * since SyncOneBuffer will then do nothing.  However, there is a
    3519             :          * further race condition: it's conceivable that between the time we
    3520             :          * examine the bit here and the time SyncOneBuffer acquires the lock,
    3521             :          * someone else not only wrote the buffer but replaced it with another
    3522             :          * page and dirtied it.  In that improbable case, SyncOneBuffer will
    3523             :          * write the buffer though we didn't need to.  It doesn't seem worth
    3524             :          * guarding against this, though.
    3525             :          */
    3526      578296 :         if (pg_atomic_read_u32(&bufHdr->state) & BM_CHECKPOINT_NEEDED)
    3527             :         {
    3528      539178 :             if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
    3529             :             {
    3530             :                 TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
    3531      539178 :                 PendingCheckpointerStats.buffers_written++;
    3532      539178 :                 num_written++;
    3533             :             }
    3534             :         }
    3535             : 
    3536             :         /*
    3537             :          * Measure progress independent of actually having to flush the buffer
    3538             :          * - otherwise writing become unbalanced.
    3539             :          */
    3540      578296 :         ts_stat->progress += ts_stat->progress_slice;
    3541      578296 :         ts_stat->num_scanned++;
    3542      578296 :         ts_stat->index++;
    3543             : 
    3544             :         /* Have all the buffers from the tablespace been processed? */
    3545      578296 :         if (ts_stat->num_scanned == ts_stat->num_to_scan)
    3546             :         {
    3547        3132 :             binaryheap_remove_first(ts_heap);
    3548             :         }
    3549             :         else
    3550             :         {
    3551             :             /* update heap with the new progress */
    3552      575164 :             binaryheap_replace_first(ts_heap, PointerGetDatum(ts_stat));
    3553             :         }
    3554             : 
    3555             :         /*
    3556             :          * Sleep to throttle our I/O rate.
    3557             :          *
    3558             :          * (This will check for barrier events even if it doesn't sleep.)
    3559             :          */
    3560      578296 :         CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
    3561             :     }
    3562             : 
    3563             :     /*
    3564             :      * Issue all pending flushes. Only checkpointer calls BufferSync(), so
    3565             :      * IOContext will always be IOCONTEXT_NORMAL.
    3566             :      */
    3567        2086 :     IssuePendingWritebacks(&wb_context, IOCONTEXT_NORMAL);
    3568             : 
    3569        2086 :     pfree(per_ts_stat);
    3570        2086 :     per_ts_stat = NULL;
    3571        2086 :     binaryheap_free(ts_heap);
    3572             : 
    3573             :     /*
    3574             :      * Update checkpoint statistics. As noted above, this doesn't include
    3575             :      * buffers written by other backends or bgwriter scan.
    3576             :      */
    3577        2086 :     CheckpointStats.ckpt_bufs_written += num_written;
    3578             : 
    3579             :     TRACE_POSTGRESQL_BUFFER_SYNC_DONE(NBuffers, num_written, num_to_scan);
    3580             : }
    3581             : 
    3582             : /*
    3583             :  * BgBufferSync -- Write out some dirty buffers in the pool.
    3584             :  *
    3585             :  * This is called periodically by the background writer process.
    3586             :  *
    3587             :  * Returns true if it's appropriate for the bgwriter process to go into
    3588             :  * low-power hibernation mode.  (This happens if the strategy clock-sweep
    3589             :  * has been "lapped" and no buffer allocations have occurred recently,
    3590             :  * or if the bgwriter has been effectively disabled by setting
    3591             :  * bgwriter_lru_maxpages to 0.)
    3592             :  */
    3593             : bool
    3594       24236 : BgBufferSync(WritebackContext *wb_context)
    3595             : {
    3596             :     /* info obtained from freelist.c */
    3597             :     int         strategy_buf_id;
    3598             :     uint32      strategy_passes;
    3599             :     uint32      recent_alloc;
    3600             : 
    3601             :     /*
    3602             :      * Information saved between calls so we can determine the strategy
    3603             :      * point's advance rate and avoid scanning already-cleaned buffers.
    3604             :      */
    3605             :     static bool saved_info_valid = false;
    3606             :     static int  prev_strategy_buf_id;
    3607             :     static uint32 prev_strategy_passes;
    3608             :     static int  next_to_clean;
    3609             :     static uint32 next_passes;
    3610             : 
    3611             :     /* Moving averages of allocation rate and clean-buffer density */
    3612             :     static float smoothed_alloc = 0;
    3613             :     static float smoothed_density = 10.0;
    3614             : 
    3615             :     /* Potentially these could be tunables, but for now, not */
    3616       24236 :     float       smoothing_samples = 16;
    3617       24236 :     float       scan_whole_pool_milliseconds = 120000.0;
    3618             : 
    3619             :     /* Used to compute how far we scan ahead */
    3620             :     long        strategy_delta;
    3621             :     int         bufs_to_lap;
    3622             :     int         bufs_ahead;
    3623             :     float       scans_per_alloc;
    3624             :     int         reusable_buffers_est;
    3625             :     int         upcoming_alloc_est;
    3626             :     int         min_scan_buffers;
    3627             : 
    3628             :     /* Variables for the scanning loop proper */
    3629             :     int         num_to_scan;
    3630             :     int         num_written;
    3631             :     int         reusable_buffers;
    3632             : 
    3633             :     /* Variables for final smoothed_density update */
    3634             :     long        new_strategy_delta;
    3635             :     uint32      new_recent_alloc;
    3636             : 
    3637             :     /*
    3638             :      * Find out where the clock-sweep currently is, and how many buffer
    3639             :      * allocations have happened since our last call.
    3640             :      */
    3641       24236 :     strategy_buf_id = StrategySyncStart(&strategy_passes, &recent_alloc);
    3642             : 
    3643             :     /* Report buffer alloc counts to pgstat */
    3644       24236 :     PendingBgWriterStats.buf_alloc += recent_alloc;
    3645             : 
    3646             :     /*
    3647             :      * If we're not running the LRU scan, just stop after doing the stats
    3648             :      * stuff.  We mark the saved state invalid so that we can recover sanely
    3649             :      * if LRU scan is turned back on later.
    3650             :      */
    3651       24236 :     if (bgwriter_lru_maxpages <= 0)
    3652             :     {
    3653          76 :         saved_info_valid = false;
    3654          76 :         return true;
    3655             :     }
    3656             : 
    3657             :     /*
    3658             :      * Compute strategy_delta = how many buffers have been scanned by the
    3659             :      * clock-sweep since last time.  If first time through, assume none. Then
    3660             :      * see if we are still ahead of the clock-sweep, and if so, how many
    3661             :      * buffers we could scan before we'd catch up with it and "lap" it. Note:
    3662             :      * weird-looking coding of xxx_passes comparisons are to avoid bogus
    3663             :      * behavior when the passes counts wrap around.
    3664             :      */
    3665       24160 :     if (saved_info_valid)
    3666             :     {
    3667       23108 :         int32       passes_delta = strategy_passes - prev_strategy_passes;
    3668             : 
    3669       23108 :         strategy_delta = strategy_buf_id - prev_strategy_buf_id;
    3670       23108 :         strategy_delta += (long) passes_delta * NBuffers;
    3671             : 
    3672             :         Assert(strategy_delta >= 0);
    3673             : 
    3674       23108 :         if ((int32) (next_passes - strategy_passes) > 0)
    3675             :         {
    3676             :             /* we're one pass ahead of the strategy point */
    3677        4520 :             bufs_to_lap = strategy_buf_id - next_to_clean;
    3678             : #ifdef BGW_DEBUG
    3679             :             elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
    3680             :                  next_passes, next_to_clean,
    3681             :                  strategy_passes, strategy_buf_id,
    3682             :                  strategy_delta, bufs_to_lap);
    3683             : #endif
    3684             :         }
    3685       18588 :         else if (next_passes == strategy_passes &&
    3686       14244 :                  next_to_clean >= strategy_buf_id)
    3687             :         {
    3688             :             /* on same pass, but ahead or at least not behind */
    3689       12794 :             bufs_to_lap = NBuffers - (next_to_clean - strategy_buf_id);
    3690             : #ifdef BGW_DEBUG
    3691             :             elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
    3692             :                  next_passes, next_to_clean,
    3693             :                  strategy_passes, strategy_buf_id,
    3694             :                  strategy_delta, bufs_to_lap);
    3695             : #endif
    3696             :         }
    3697             :         else
    3698             :         {
    3699             :             /*
    3700             :              * We're behind, so skip forward to the strategy point and start
    3701             :              * cleaning from there.
    3702             :              */
    3703             : #ifdef BGW_DEBUG
    3704             :             elog(DEBUG2, "bgwriter behind: bgw %u-%u strategy %u-%u delta=%ld",
    3705             :                  next_passes, next_to_clean,
    3706             :                  strategy_passes, strategy_buf_id,
    3707             :                  strategy_delta);
    3708             : #endif
    3709        5794 :             next_to_clean = strategy_buf_id;
    3710        5794 :             next_passes = strategy_passes;
    3711        5794 :             bufs_to_lap = NBuffers;
    3712             :         }
    3713             :     }
    3714             :     else
    3715             :     {
    3716             :         /*
    3717             :          * Initializing at startup or after LRU scanning had been off. Always
    3718             :          * start at the strategy point.
    3719             :          */
    3720             : #ifdef BGW_DEBUG
    3721             :         elog(DEBUG2, "bgwriter initializing: strategy %u-%u",
    3722             :              strategy_passes, strategy_buf_id);
    3723             : #endif
    3724        1052 :         strategy_delta = 0;
    3725        1052 :         next_to_clean = strategy_buf_id;
    3726        1052 :         next_passes = strategy_passes;
    3727        1052 :         bufs_to_lap = NBuffers;
    3728             :     }
    3729             : 
    3730             :     /* Update saved info for next time */
    3731       24160 :     prev_strategy_buf_id = strategy_buf_id;
    3732       24160 :     prev_strategy_passes = strategy_passes;
    3733       24160 :     saved_info_valid = true;
    3734             : 
    3735             :     /*
    3736             :      * Compute how many buffers had to be scanned for each new allocation, ie,
    3737             :      * 1/density of reusable buffers, and track a moving average of that.
    3738             :      *
    3739             :      * If the strategy point didn't move, we don't update the density estimate
    3740             :      */
    3741       24160 :     if (strategy_delta > 0 && recent_alloc > 0)
    3742             :     {
    3743       12924 :         scans_per_alloc = (float) strategy_delta / (float) recent_alloc;
    3744       12924 :         smoothed_density += (scans_per_alloc - smoothed_density) /
    3745             :             smoothing_samples;
    3746             :     }
    3747             : 
    3748             :     /*
    3749             :      * Estimate how many reusable buffers there are between the current
    3750             :      * strategy point and where we've scanned ahead to, based on the smoothed
    3751             :      * density estimate.
    3752             :      */
    3753       24160 :     bufs_ahead = NBuffers - bufs_to_lap;
    3754       24160 :     reusable_buffers_est = (float) bufs_ahead / smoothed_density;
    3755             : 
    3756             :     /*
    3757             :      * Track a moving average of recent buffer allocations.  Here, rather than
    3758             :      * a true average we want a fast-attack, slow-decline behavior: we
    3759             :      * immediately follow any increase.
    3760             :      */
    3761       24160 :     if (smoothed_alloc <= (float) recent_alloc)
    3762        6504 :         smoothed_alloc = recent_alloc;
    3763             :     else
    3764       17656 :         smoothed_alloc += ((float) recent_alloc - smoothed_alloc) /
    3765             :             smoothing_samples;
    3766             : 
    3767             :     /* Scale the estimate by a GUC to allow more aggressive tuning. */
    3768       24160 :     upcoming_alloc_est = (int) (smoothed_alloc * bgwriter_lru_multiplier);
    3769             : 
    3770             :     /*
    3771             :      * If recent_alloc remains at zero for many cycles, smoothed_alloc will
    3772             :      * eventually underflow to zero, and the underflows produce annoying
    3773             :      * kernel warnings on some platforms.  Once upcoming_alloc_est has gone to
    3774             :      * zero, there's no point in tracking smaller and smaller values of
    3775             :      * smoothed_alloc, so just reset it to exactly zero to avoid this
    3776             :      * syndrome.  It will pop back up as soon as recent_alloc increases.
    3777             :      */
    3778       24160 :     if (upcoming_alloc_est == 0)
    3779        3842 :         smoothed_alloc = 0;
    3780             : 
    3781             :     /*
    3782             :      * Even in cases where there's been little or no buffer allocation
    3783             :      * activity, we want to make a small amount of progress through the buffer
    3784             :      * cache so that as many reusable buffers as possible are clean after an
    3785             :      * idle period.
    3786             :      *
    3787             :      * (scan_whole_pool_milliseconds / BgWriterDelay) computes how many times
    3788             :      * the BGW will be called during the scan_whole_pool time; slice the
    3789             :      * buffer pool into that many sections.
    3790             :      */
    3791       24160 :     min_scan_buffers = (int) (NBuffers / (scan_whole_pool_milliseconds / BgWriterDelay));
    3792             : 
    3793       24160 :     if (upcoming_alloc_est < (min_scan_buffers + reusable_buffers_est))
    3794             :     {
    3795             : #ifdef BGW_DEBUG
    3796             :         elog(DEBUG2, "bgwriter: alloc_est=%d too small, using min=%d + reusable_est=%d",
    3797             :              upcoming_alloc_est, min_scan_buffers, reusable_buffers_est);
    3798             : #endif
    3799       10734 :         upcoming_alloc_est = min_scan_buffers + reusable_buffers_est;
    3800             :     }
    3801             : 
    3802             :     /*
    3803             :      * Now write out dirty reusable buffers, working forward from the
    3804             :      * next_to_clean point, until we have lapped the strategy scan, or cleaned
    3805             :      * enough buffers to match our estimate of the next cycle's allocation
    3806             :      * requirements, or hit the bgwriter_lru_maxpages limit.
    3807             :      */
    3808             : 
    3809       24160 :     num_to_scan = bufs_to_lap;
    3810       24160 :     num_written = 0;
    3811       24160 :     reusable_buffers = reusable_buffers_est;
    3812             : 
    3813             :     /* Execute the LRU scan */
    3814     3553460 :     while (num_to_scan > 0 && reusable_buffers < upcoming_alloc_est)
    3815             :     {
    3816     3529304 :         int         sync_state = SyncOneBuffer(next_to_clean, true,
    3817             :                                                wb_context);
    3818             : 
    3819     3529304 :         if (++next_to_clean >= NBuffers)
    3820             :         {
    3821        5466 :             next_to_clean = 0;
    3822        5466 :             next_passes++;
    3823             :         }
    3824     3529304 :         num_to_scan--;
    3825             : 
    3826     3529304 :         if (sync_state & BUF_WRITTEN)
    3827             :         {
    3828       46410 :             reusable_buffers++;
    3829       46410 :             if (++num_written >= bgwriter_lru_maxpages)
    3830             :             {
    3831           4 :                 PendingBgWriterStats.maxwritten_clean++;
    3832           4 :                 break;
    3833             :             }
    3834             :         }
    3835     3482894 :         else if (sync_state & BUF_REUSABLE)
    3836     2725620 :             reusable_buffers++;
    3837             :     }
    3838             : 
    3839       24160 :     PendingBgWriterStats.buf_written_clean += num_written;
    3840             : 
    3841             : #ifdef BGW_DEBUG
    3842             :     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",
    3843             :          recent_alloc, smoothed_alloc, strategy_delta, bufs_ahead,
    3844             :          smoothed_density, reusable_buffers_est, upcoming_alloc_est,
    3845             :          bufs_to_lap - num_to_scan,
    3846             :          num_written,
    3847             :          reusable_buffers - reusable_buffers_est);
    3848             : #endif
    3849             : 
    3850             :     /*
    3851             :      * Consider the above scan as being like a new allocation scan.
    3852             :      * Characterize its density and update the smoothed one based on it. This
    3853             :      * effectively halves the moving average period in cases where both the
    3854             :      * strategy and the background writer are doing some useful scanning,
    3855             :      * which is helpful because a long memory isn't as desirable on the
    3856             :      * density estimates.
    3857             :      */
    3858       24160 :     new_strategy_delta = bufs_to_lap - num_to_scan;
    3859       24160 :     new_recent_alloc = reusable_buffers - reusable_buffers_est;
    3860       24160 :     if (new_strategy_delta > 0 && new_recent_alloc > 0)
    3861             :     {
    3862       19694 :         scans_per_alloc = (float) new_strategy_delta / (float) new_recent_alloc;
    3863       19694 :         smoothed_density += (scans_per_alloc - smoothed_density) /
    3864             :             smoothing_samples;
    3865             : 
    3866             : #ifdef BGW_DEBUG
    3867             :         elog(DEBUG2, "bgwriter: cleaner density alloc=%u scan=%ld density=%.2f new smoothed=%.2f",
    3868             :              new_recent_alloc, new_strategy_delta,
    3869             :              scans_per_alloc, smoothed_density);
    3870             : #endif
    3871             :     }
    3872             : 
    3873             :     /* Return true if OK to hibernate */
    3874       24160 :     return (bufs_to_lap == 0 && recent_alloc == 0);
    3875             : }
    3876             : 
    3877             : /*
    3878             :  * SyncOneBuffer -- process a single buffer during syncing.
    3879             :  *
    3880             :  * If skip_recently_used is true, we don't write currently-pinned buffers, nor
    3881             :  * buffers marked recently used, as these are not replacement candidates.
    3882             :  *
    3883             :  * Returns a bitmask containing the following flag bits:
    3884             :  *  BUF_WRITTEN: we wrote the buffer.
    3885             :  *  BUF_REUSABLE: buffer is available for replacement, ie, it has
    3886             :  *      pin count 0 and usage count 0.
    3887             :  *
    3888             :  * (BUF_WRITTEN could be set in error if FlushBuffer finds the buffer clean
    3889             :  * after locking it, but we don't care all that much.)
    3890             :  */
    3891             : static int
    3892     4068482 : SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
    3893             : {
    3894     4068482 :     BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
    3895     4068482 :     int         result = 0;
    3896             :     uint32      buf_state;
    3897             :     BufferTag   tag;
    3898             : 
    3899             :     /* Make sure we can handle the pin */
    3900     4068482 :     ReservePrivateRefCountEntry();
    3901     4068482 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    3902             : 
    3903             :     /*
    3904             :      * Check whether buffer needs writing.
    3905             :      *
    3906             :      * We can make this check without taking the buffer content lock so long
    3907             :      * as we mark pages dirty in access methods *before* logging changes with
    3908             :      * XLogInsert(): if someone marks the buffer dirty just after our check we
    3909             :      * don't worry because our checkpoint.redo points before log record for
    3910             :      * upcoming changes and so we are not required to write such dirty buffer.
    3911             :      */
    3912     4068482 :     buf_state = LockBufHdr(bufHdr);
    3913             : 
    3914     4068482 :     if (BUF_STATE_GET_REFCOUNT(buf_state) == 0 &&
    3915     4059204 :         BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
    3916             :     {
    3917     2776142 :         result |= BUF_REUSABLE;
    3918             :     }
    3919     1292340 :     else if (skip_recently_used)
    3920             :     {
    3921             :         /* Caller told us not to write recently-used buffers */
    3922      757274 :         UnlockBufHdr(bufHdr, buf_state);
    3923      757274 :         return result;
    3924             :     }
    3925             : 
    3926     3311208 :     if (!(buf_state & BM_VALID) || !(buf_state & BM_DIRTY))
    3927             :     {
    3928             :         /* It's clean, so nothing to do */
    3929     2725620 :         UnlockBufHdr(bufHdr, buf_state);
    3930     2725620 :         return result;
    3931             :     }
    3932             : 
    3933             :     /*
    3934             :      * Pin it, share-lock it, write it.  (FlushBuffer will do nothing if the
    3935             :      * buffer is clean by the time we've locked it.)
    3936             :      */
    3937      585588 :     PinBuffer_Locked(bufHdr);
    3938      585588 :     LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    3939             : 
    3940      585588 :     FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    3941             : 
    3942      585588 :     LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    3943             : 
    3944      585588 :     tag = bufHdr->tag;
    3945             : 
    3946      585588 :     UnpinBuffer(bufHdr);
    3947             : 
    3948             :     /*
    3949             :      * SyncOneBuffer() is only called by checkpointer and bgwriter, so
    3950             :      * IOContext will always be IOCONTEXT_NORMAL.
    3951             :      */
    3952      585588 :     ScheduleBufferTagForWriteback(wb_context, IOCONTEXT_NORMAL, &tag);
    3953             : 
    3954      585588 :     return result | BUF_WRITTEN;
    3955             : }
    3956             : 
    3957             : /*
    3958             :  *      AtEOXact_Buffers - clean up at end of transaction.
    3959             :  *
    3960             :  *      As of PostgreSQL 8.0, buffer pins should get released by the
    3961             :  *      ResourceOwner mechanism.  This routine is just a debugging
    3962             :  *      cross-check that no pins remain.
    3963             :  */
    3964             : void
    3965     1142280 : AtEOXact_Buffers(bool isCommit)
    3966             : {
    3967     1142280 :     CheckForBufferLeaks();
    3968             : 
    3969     1142280 :     AtEOXact_LocalBuffers(isCommit);
    3970             : 
    3971             :     Assert(PrivateRefCountOverflowed == 0);
    3972     1142280 : }
    3973             : 
    3974             : /*
    3975             :  * Initialize access to shared buffer pool
    3976             :  *
    3977             :  * This is called during backend startup (whether standalone or under the
    3978             :  * postmaster).  It sets up for this backend's access to the already-existing
    3979             :  * buffer pool.
    3980             :  */
    3981             : void
    3982       44504 : InitBufferManagerAccess(void)
    3983             : {
    3984             :     HASHCTL     hash_ctl;
    3985             : 
    3986             :     /*
    3987             :      * An advisory limit on the number of pins each backend should hold, based
    3988             :      * on shared_buffers and the maximum number of connections possible.
    3989             :      * That's very pessimistic, but outside toy-sized shared_buffers it should
    3990             :      * allow plenty of pins.  LimitAdditionalPins() and
    3991             :      * GetAdditionalPinLimit() can be used to check the remaining balance.
    3992             :      */
    3993       44504 :     MaxProportionalPins = NBuffers / (MaxBackends + NUM_AUXILIARY_PROCS);
    3994             : 
    3995       44504 :     memset(&PrivateRefCountArray, 0, sizeof(PrivateRefCountArray));
    3996             : 
    3997       44504 :     hash_ctl.keysize = sizeof(int32);
    3998       44504 :     hash_ctl.entrysize = sizeof(PrivateRefCountEntry);
    3999             : 
    4000       44504 :     PrivateRefCountHash = hash_create("PrivateRefCount", 100, &hash_ctl,
    4001             :                                       HASH_ELEM | HASH_BLOBS);
    4002             : 
    4003             :     /*
    4004             :      * AtProcExit_Buffers needs LWLock access, and thereby has to be called at
    4005             :      * the corresponding phase of backend shutdown.
    4006             :      */
    4007             :     Assert(MyProc != NULL);
    4008       44504 :     on_shmem_exit(AtProcExit_Buffers, 0);
    4009       44504 : }
    4010             : 
    4011             : /*
    4012             :  * During backend exit, ensure that we released all shared-buffer locks and
    4013             :  * assert that we have no remaining pins.
    4014             :  */
    4015             : static void
    4016       44506 : AtProcExit_Buffers(int code, Datum arg)
    4017             : {
    4018       44506 :     UnlockBuffers();
    4019             : 
    4020       44506 :     CheckForBufferLeaks();
    4021             : 
    4022             :     /* localbuf.c needs a chance too */
    4023       44506 :     AtProcExit_LocalBuffers();
    4024       44506 : }
    4025             : 
    4026             : /*
    4027             :  *      CheckForBufferLeaks - ensure this backend holds no buffer pins
    4028             :  *
    4029             :  *      As of PostgreSQL 8.0, buffer pins should get released by the
    4030             :  *      ResourceOwner mechanism.  This routine is just a debugging
    4031             :  *      cross-check that no pins remain.
    4032             :  */
    4033             : static void
    4034     1186790 : CheckForBufferLeaks(void)
    4035             : {
    4036             : #ifdef USE_ASSERT_CHECKING
    4037             :     int         RefCountErrors = 0;
    4038             :     PrivateRefCountEntry *res;
    4039             :     int         i;
    4040             :     char       *s;
    4041             : 
    4042             :     /* check the array */
    4043             :     for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
    4044             :     {
    4045             :         res = &PrivateRefCountArray[i];
    4046             : 
    4047             :         if (res->buffer != InvalidBuffer)
    4048             :         {
    4049             :             s = DebugPrintBufferRefcount(res->buffer);
    4050             :             elog(WARNING, "buffer refcount leak: %s", s);
    4051             :             pfree(s);
    4052             : 
    4053             :             RefCountErrors++;
    4054             :         }
    4055             :     }
    4056             : 
    4057             :     /* if necessary search the hash */
    4058             :     if (PrivateRefCountOverflowed)
    4059             :     {
    4060             :         HASH_SEQ_STATUS hstat;
    4061             : 
    4062             :         hash_seq_init(&hstat, PrivateRefCountHash);
    4063             :         while ((res = (PrivateRefCountEntry *) hash_seq_search(&hstat)) != NULL)
    4064             :         {
    4065             :             s = DebugPrintBufferRefcount(res->buffer);
    4066             :             elog(WARNING, "buffer refcount leak: %s", s);
    4067             :             pfree(s);
    4068             :             RefCountErrors++;
    4069             :         }
    4070             :     }
    4071             : 
    4072             :     Assert(RefCountErrors == 0);
    4073             : #endif
    4074     1186790 : }
    4075             : 
    4076             : #ifdef USE_ASSERT_CHECKING
    4077             : /*
    4078             :  * Check for exclusive-locked catalog buffers.  This is the core of
    4079             :  * AssertCouldGetRelation().
    4080             :  *
    4081             :  * A backend would self-deadlock on LWLocks if the catalog scan read the
    4082             :  * exclusive-locked buffer.  The main threat is exclusive-locked buffers of
    4083             :  * catalogs used in relcache, because a catcache search on any catalog may
    4084             :  * build that catalog's relcache entry.  We don't have an inventory of
    4085             :  * catalogs relcache uses, so just check buffers of most catalogs.
    4086             :  *
    4087             :  * It's better to minimize waits while holding an exclusive buffer lock, so it
    4088             :  * would be nice to broaden this check not to be catalog-specific.  However,
    4089             :  * bttextcmp() accesses pg_collation, and non-core opclasses might similarly
    4090             :  * read tables.  That is deadlock-free as long as there's no loop in the
    4091             :  * dependency graph: modifying table A may cause an opclass to read table B,
    4092             :  * but it must not cause a read of table A.
    4093             :  */
    4094             : void
    4095             : AssertBufferLocksPermitCatalogRead(void)
    4096             : {
    4097             :     ForEachLWLockHeldByMe(AssertNotCatalogBufferLock, NULL);
    4098             : }
    4099             : 
    4100             : static void
    4101             : AssertNotCatalogBufferLock(LWLock *lock, LWLockMode mode,
    4102             :                            void *unused_context)
    4103             : {
    4104             :     BufferDesc *bufHdr;
    4105             :     BufferTag   tag;
    4106             :     Oid         relid;
    4107             : 
    4108             :     if (mode != LW_EXCLUSIVE)
    4109             :         return;
    4110             : 
    4111             :     if (!((BufferDescPadded *) lock > BufferDescriptors &&
    4112             :           (BufferDescPadded *) lock < BufferDescriptors + NBuffers))
    4113             :         return;                 /* not a buffer lock */
    4114             : 
    4115             :     bufHdr = (BufferDesc *)
    4116             :         ((char *) lock - offsetof(BufferDesc, content_lock));
    4117             :     tag = bufHdr->tag;
    4118             : 
    4119             :     /*
    4120             :      * This relNumber==relid assumption holds until a catalog experiences
    4121             :      * VACUUM FULL or similar.  After a command like that, relNumber will be
    4122             :      * in the normal (non-catalog) range, and we lose the ability to detect
    4123             :      * hazardous access to that catalog.  Calling RelidByRelfilenumber() would
    4124             :      * close that gap, but RelidByRelfilenumber() might then deadlock with a
    4125             :      * held lock.
    4126             :      */
    4127             :     relid = tag.relNumber;
    4128             : 
    4129             :     if (IsCatalogTextUniqueIndexOid(relid)) /* see comments at the callee */
    4130             :         return;
    4131             : 
    4132             :     Assert(!IsCatalogRelationOid(relid));
    4133             : }
    4134             : #endif
    4135             : 
    4136             : 
    4137             : /*
    4138             :  * Helper routine to issue warnings when a buffer is unexpectedly pinned
    4139             :  */
    4140             : char *
    4141          80 : DebugPrintBufferRefcount(Buffer buffer)
    4142             : {
    4143             :     BufferDesc *buf;
    4144             :     int32       loccount;
    4145             :     char       *result;
    4146             :     ProcNumber  backend;
    4147             :     uint32      buf_state;
    4148             : 
    4149             :     Assert(BufferIsValid(buffer));
    4150          80 :     if (BufferIsLocal(buffer))
    4151             :     {
    4152          32 :         buf = GetLocalBufferDescriptor(-buffer - 1);
    4153          32 :         loccount = LocalRefCount[-buffer - 1];
    4154          32 :         backend = MyProcNumber;
    4155             :     }
    4156             :     else
    4157             :     {
    4158          48 :         buf = GetBufferDescriptor(buffer - 1);
    4159          48 :         loccount = GetPrivateRefCount(buffer);
    4160          48 :         backend = INVALID_PROC_NUMBER;
    4161             :     }
    4162             : 
    4163             :     /* theoretically we should lock the bufhdr here */
    4164          80 :     buf_state = pg_atomic_read_u32(&buf->state);
    4165             : 
    4166          80 :     result = psprintf("[%03d] (rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",
    4167             :                       buffer,
    4168          80 :                       relpathbackend(BufTagGetRelFileLocator(&buf->tag), backend,
    4169             :                                      BufTagGetForkNum(&buf->tag)).str,
    4170             :                       buf->tag.blockNum, buf_state & BUF_FLAG_MASK,
    4171             :                       BUF_STATE_GET_REFCOUNT(buf_state), loccount);
    4172          80 :     return result;
    4173             : }
    4174             : 
    4175             : /*
    4176             :  * CheckPointBuffers
    4177             :  *
    4178             :  * Flush all dirty blocks in buffer pool to disk at checkpoint time.
    4179             :  *
    4180             :  * Note: temporary relations do not participate in checkpoints, so they don't
    4181             :  * need to be flushed.
    4182             :  */
    4183             : void
    4184        3414 : CheckPointBuffers(int flags)
    4185             : {
    4186        3414 :     BufferSync(flags);
    4187        3414 : }
    4188             : 
    4189             : /*
    4190             :  * BufferGetBlockNumber
    4191             :  *      Returns the block number associated with a buffer.
    4192             :  *
    4193             :  * Note:
    4194             :  *      Assumes that the buffer is valid and pinned, else the
    4195             :  *      value may be obsolete immediately...
    4196             :  */
    4197             : BlockNumber
    4198   100812846 : BufferGetBlockNumber(Buffer buffer)
    4199             : {
    4200             :     BufferDesc *bufHdr;
    4201             : 
    4202             :     Assert(BufferIsPinned(buffer));
    4203             : 
    4204   100812846 :     if (BufferIsLocal(buffer))
    4205     3807692 :         bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    4206             :     else
    4207    97005154 :         bufHdr = GetBufferDescriptor(buffer - 1);
    4208             : 
    4209             :     /* pinned, so OK to read tag without spinlock */
    4210   100812846 :     return bufHdr->tag.blockNum;
    4211             : }
    4212             : 
    4213             : /*
    4214             :  * BufferGetTag
    4215             :  *      Returns the relfilelocator, fork number and block number associated with
    4216             :  *      a buffer.
    4217             :  */
    4218             : void
    4219    29998000 : BufferGetTag(Buffer buffer, RelFileLocator *rlocator, ForkNumber *forknum,
    4220             :              BlockNumber *blknum)
    4221             : {
    4222             :     BufferDesc *bufHdr;
    4223             : 
    4224             :     /* Do the same checks as BufferGetBlockNumber. */
    4225             :     Assert(BufferIsPinned(buffer));
    4226             : 
    4227    29998000 :     if (BufferIsLocal(buffer))
    4228           0 :         bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    4229             :     else
    4230    29998000 :         bufHdr = GetBufferDescriptor(buffer - 1);
    4231             : 
    4232             :     /* pinned, so OK to read tag without spinlock */
    4233    29998000 :     *rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
    4234    29998000 :     *forknum = BufTagGetForkNum(&bufHdr->tag);
    4235    29998000 :     *blknum = bufHdr->tag.blockNum;
    4236    29998000 : }
    4237             : 
    4238             : /*
    4239             :  * FlushBuffer
    4240             :  *      Physically write out a shared buffer.
    4241             :  *
    4242             :  * NOTE: this actually just passes the buffer contents to the kernel; the
    4243             :  * real write to disk won't happen until the kernel feels like it.  This
    4244             :  * is okay from our point of view since we can redo the changes from WAL.
    4245             :  * However, we will need to force the changes to disk via fsync before
    4246             :  * we can checkpoint WAL.
    4247             :  *
    4248             :  * The caller must hold a pin on the buffer and have share-locked the
    4249             :  * buffer contents.  (Note: a share-lock does not prevent updates of
    4250             :  * hint bits in the buffer, so the page could change while the write
    4251             :  * is in progress, but we assume that that will not invalidate the data
    4252             :  * written.)
    4253             :  *
    4254             :  * If the caller has an smgr reference for the buffer's relation, pass it
    4255             :  * as the second parameter.  If not, pass NULL.
    4256             :  */
    4257             : static void
    4258     1116136 : FlushBuffer(BufferDesc *buf, SMgrRelation reln, IOObject io_object,
    4259             :             IOContext io_context)
    4260             : {
    4261             :     XLogRecPtr  recptr;
    4262             :     ErrorContextCallback errcallback;
    4263             :     instr_time  io_start;
    4264             :     Block       bufBlock;
    4265             :     char       *bufToWrite;
    4266             :     uint32      buf_state;
    4267             : 
    4268             :     /*
    4269             :      * Try to start an I/O operation.  If StartBufferIO returns false, then
    4270             :      * someone else flushed the buffer before we could, so we need not do
    4271             :      * anything.
    4272             :      */
    4273     1116136 :     if (!StartBufferIO(buf, false, false))
    4274          18 :         return;
    4275             : 
    4276             :     /* Setup error traceback support for ereport() */
    4277     1116118 :     errcallback.callback = shared_buffer_write_error_callback;
    4278     1116118 :     errcallback.arg = buf;
    4279     1116118 :     errcallback.previous = error_context_stack;
    4280     1116118 :     error_context_stack = &errcallback;
    4281             : 
    4282             :     /* Find smgr relation for buffer */
    4283     1116118 :     if (reln == NULL)
    4284     1107844 :         reln = smgropen(BufTagGetRelFileLocator(&buf->tag), INVALID_PROC_NUMBER);
    4285             : 
    4286             :     TRACE_POSTGRESQL_BUFFER_FLUSH_START(BufTagGetForkNum(&buf->tag),
    4287             :                                         buf->tag.blockNum,
    4288             :                                         reln->smgr_rlocator.locator.spcOid,
    4289             :                                         reln->smgr_rlocator.locator.dbOid,
    4290             :                                         reln->smgr_rlocator.locator.relNumber);
    4291             : 
    4292     1116118 :     buf_state = LockBufHdr(buf);
    4293             : 
    4294             :     /*
    4295             :      * Run PageGetLSN while holding header lock, since we don't have the
    4296             :      * buffer locked exclusively in all cases.
    4297             :      */
    4298     1116118 :     recptr = BufferGetLSN(buf);
    4299             : 
    4300             :     /* To check if block content changes while flushing. - vadim 01/17/97 */
    4301     1116118 :     buf_state &= ~BM_JUST_DIRTIED;
    4302     1116118 :     UnlockBufHdr(buf, buf_state);
    4303             : 
    4304             :     /*
    4305             :      * Force XLOG flush up to buffer's LSN.  This implements the basic WAL
    4306             :      * rule that log updates must hit disk before any of the data-file changes
    4307             :      * they describe do.
    4308             :      *
    4309             :      * However, this rule does not apply to unlogged relations, which will be
    4310             :      * lost after a crash anyway.  Most unlogged relation pages do not bear
    4311             :      * LSNs since we never emit WAL records for them, and therefore flushing
    4312             :      * up through the buffer LSN would be useless, but harmless.  However,
    4313             :      * GiST indexes use LSNs internally to track page-splits, and therefore
    4314             :      * unlogged GiST pages bear "fake" LSNs generated by
    4315             :      * GetFakeLSNForUnloggedRel.  It is unlikely but possible that the fake
    4316             :      * LSN counter could advance past the WAL insertion point; and if it did
    4317             :      * happen, attempting to flush WAL through that location would fail, with
    4318             :      * disastrous system-wide consequences.  To make sure that can't happen,
    4319             :      * skip the flush if the buffer isn't permanent.
    4320             :      */
    4321     1116118 :     if (buf_state & BM_PERMANENT)
    4322     1112566 :         XLogFlush(recptr);
    4323             : 
    4324             :     /*
    4325             :      * Now it's safe to write the buffer to disk. Note that no one else should
    4326             :      * have been able to write it, while we were busy with log flushing,
    4327             :      * because we got the exclusive right to perform I/O by setting the
    4328             :      * BM_IO_IN_PROGRESS bit.
    4329             :      */
    4330     1116118 :     bufBlock = BufHdrGetBlock(buf);
    4331             : 
    4332             :     /*
    4333             :      * Update page checksum if desired.  Since we have only shared lock on the
    4334             :      * buffer, other processes might be updating hint bits in it, so we must
    4335             :      * copy the page to private storage if we do checksumming.
    4336             :      */
    4337     1116118 :     bufToWrite = PageSetChecksumCopy((Page) bufBlock, buf->tag.blockNum);
    4338             : 
    4339     1116118 :     io_start = pgstat_prepare_io_time(track_io_timing);
    4340             : 
    4341             :     /*
    4342             :      * bufToWrite is either the shared buffer or a copy, as appropriate.
    4343             :      */
    4344     1116118 :     smgrwrite(reln,
    4345     1116118 :               BufTagGetForkNum(&buf->tag),
    4346             :               buf->tag.blockNum,
    4347             :               bufToWrite,
    4348             :               false);
    4349             : 
    4350             :     /*
    4351             :      * When a strategy is in use, only flushes of dirty buffers already in the
    4352             :      * strategy ring are counted as strategy writes (IOCONTEXT
    4353             :      * [BULKREAD|BULKWRITE|VACUUM] IOOP_WRITE) for the purpose of IO
    4354             :      * statistics tracking.
    4355             :      *
    4356             :      * If a shared buffer initially added to the ring must be flushed before
    4357             :      * being used, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE.
    4358             :      *
    4359             :      * If a shared buffer which was added to the ring later because the
    4360             :      * current strategy buffer is pinned or in use or because all strategy
    4361             :      * buffers were dirty and rejected (for BAS_BULKREAD operations only)
    4362             :      * requires flushing, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE
    4363             :      * (from_ring will be false).
    4364             :      *
    4365             :      * When a strategy is not in use, the write can only be a "regular" write
    4366             :      * of a dirty shared buffer (IOCONTEXT_NORMAL IOOP_WRITE).
    4367             :      */
    4368     1116118 :     pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
    4369             :                             IOOP_WRITE, io_start, 1, BLCKSZ);
    4370             : 
    4371     1116118 :     pgBufferUsage.shared_blks_written++;
    4372             : 
    4373             :     /*
    4374             :      * Mark the buffer as clean (unless BM_JUST_DIRTIED has become set) and
    4375             :      * end the BM_IO_IN_PROGRESS state.
    4376             :      */
    4377     1116118 :     TerminateBufferIO(buf, true, 0, true, false);
    4378             : 
    4379             :     TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(BufTagGetForkNum(&buf->tag),
    4380             :                                        buf->tag.blockNum,
    4381             :                                        reln->smgr_rlocator.locator.spcOid,
    4382             :                                        reln->smgr_rlocator.locator.dbOid,
    4383             :                                        reln->smgr_rlocator.locator.relNumber);
    4384             : 
    4385             :     /* Pop the error context stack */
    4386     1116118 :     error_context_stack = errcallback.previous;
    4387             : }
    4388             : 
    4389             : /*
    4390             :  * RelationGetNumberOfBlocksInFork
    4391             :  *      Determines the current number of pages in the specified relation fork.
    4392             :  *
    4393             :  * Note that the accuracy of the result will depend on the details of the
    4394             :  * relation's storage. For builtin AMs it'll be accurate, but for external AMs
    4395             :  * it might not be.
    4396             :  */
    4397             : BlockNumber
    4398     3696602 : RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
    4399             : {
    4400     3696602 :     if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind))
    4401             :     {
    4402             :         /*
    4403             :          * Not every table AM uses BLCKSZ wide fixed size blocks. Therefore
    4404             :          * tableam returns the size in bytes - but for the purpose of this
    4405             :          * routine, we want the number of blocks. Therefore divide, rounding
    4406             :          * up.
    4407             :          */
    4408             :         uint64      szbytes;
    4409             : 
    4410     2822178 :         szbytes = table_relation_size(relation, forkNum);
    4411             : 
    4412     2822140 :         return (szbytes + (BLCKSZ - 1)) / BLCKSZ;
    4413             :     }
    4414      874424 :     else if (RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
    4415             :     {
    4416      874424 :         return smgrnblocks(RelationGetSmgr(relation), forkNum);
    4417             :     }
    4418             :     else
    4419             :         Assert(false);
    4420             : 
    4421           0 :     return 0;                   /* keep compiler quiet */
    4422             : }
    4423             : 
    4424             : /*
    4425             :  * BufferIsPermanent
    4426             :  *      Determines whether a buffer will potentially still be around after
    4427             :  *      a crash.  Caller must hold a buffer pin.
    4428             :  */
    4429             : bool
    4430    18809034 : BufferIsPermanent(Buffer buffer)
    4431             : {
    4432             :     BufferDesc *bufHdr;
    4433             : 
    4434             :     /* Local buffers are used only for temp relations. */
    4435    18809034 :     if (BufferIsLocal(buffer))
    4436     1253868 :         return false;
    4437             : 
    4438             :     /* Make sure we've got a real buffer, and that we hold a pin on it. */
    4439             :     Assert(BufferIsValid(buffer));
    4440             :     Assert(BufferIsPinned(buffer));
    4441             : 
    4442             :     /*
    4443             :      * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
    4444             :      * need not bother with the buffer header spinlock.  Even if someone else
    4445             :      * changes the buffer header state while we're doing this, the state is
    4446             :      * changed atomically, so we'll read the old value or the new value, but
    4447             :      * not random garbage.
    4448             :      */
    4449    17555166 :     bufHdr = GetBufferDescriptor(buffer - 1);
    4450    17555166 :     return (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT) != 0;
    4451             : }
    4452             : 
    4453             : /*
    4454             :  * BufferGetLSNAtomic
    4455             :  *      Retrieves the LSN of the buffer atomically using a buffer header lock.
    4456             :  *      This is necessary for some callers who may not have an exclusive lock
    4457             :  *      on the buffer.
    4458             :  */
    4459             : XLogRecPtr
    4460    14178354 : BufferGetLSNAtomic(Buffer buffer)
    4461             : {
    4462    14178354 :     char       *page = BufferGetPage(buffer);
    4463             :     BufferDesc *bufHdr;
    4464             :     XLogRecPtr  lsn;
    4465             :     uint32      buf_state;
    4466             : 
    4467             :     /*
    4468             :      * If we don't need locking for correctness, fastpath out.
    4469             :      */
    4470    14178354 :     if (!XLogHintBitIsNeeded() || BufferIsLocal(buffer))
    4471      477480 :         return PageGetLSN(page);
    4472             : 
    4473             :     /* Make sure we've got a real buffer, and that we hold a pin on it. */
    4474             :     Assert(BufferIsValid(buffer));
    4475             :     Assert(BufferIsPinned(buffer));
    4476             : 
    4477    13700874 :     bufHdr = GetBufferDescriptor(buffer - 1);
    4478    13700874 :     buf_state = LockBufHdr(bufHdr);
    4479    13700874 :     lsn = PageGetLSN(page);
    4480    13700874 :     UnlockBufHdr(bufHdr, buf_state);
    4481             : 
    4482    13700874 :     return lsn;
    4483             : }
    4484             : 
    4485             : /* ---------------------------------------------------------------------
    4486             :  *      DropRelationBuffers
    4487             :  *
    4488             :  *      This function removes from the buffer pool all the pages of the
    4489             :  *      specified relation forks that have block numbers >= firstDelBlock.
    4490             :  *      (In particular, with firstDelBlock = 0, all pages are removed.)
    4491             :  *      Dirty pages are simply dropped, without bothering to write them
    4492             :  *      out first.  Therefore, this is NOT rollback-able, and so should be
    4493             :  *      used only with extreme caution!
    4494             :  *
    4495             :  *      Currently, this is called only from smgr.c when the underlying file
    4496             :  *      is about to be deleted or truncated (firstDelBlock is needed for
    4497             :  *      the truncation case).  The data in the affected pages would therefore
    4498             :  *      be deleted momentarily anyway, and there is no point in writing it.
    4499             :  *      It is the responsibility of higher-level code to ensure that the
    4500             :  *      deletion or truncation does not lose any data that could be needed
    4501             :  *      later.  It is also the responsibility of higher-level code to ensure
    4502             :  *      that no other process could be trying to load more pages of the
    4503             :  *      relation into buffers.
    4504             :  * --------------------------------------------------------------------
    4505             :  */
    4506             : void
    4507        1266 : DropRelationBuffers(SMgrRelation smgr_reln, ForkNumber *forkNum,
    4508             :                     int nforks, BlockNumber *firstDelBlock)
    4509             : {
    4510             :     int         i;
    4511             :     int         j;
    4512             :     RelFileLocatorBackend rlocator;
    4513             :     BlockNumber nForkBlock[MAX_FORKNUM];
    4514        1266 :     uint64      nBlocksToInvalidate = 0;
    4515             : 
    4516        1266 :     rlocator = smgr_reln->smgr_rlocator;
    4517             : 
    4518             :     /* If it's a local relation, it's localbuf.c's problem. */
    4519        1266 :     if (RelFileLocatorBackendIsTemp(rlocator))
    4520             :     {
    4521         748 :         if (rlocator.backend == MyProcNumber)
    4522         748 :             DropRelationLocalBuffers(rlocator.locator, forkNum, nforks,
    4523             :                                      firstDelBlock);
    4524             : 
    4525         830 :         return;
    4526             :     }
    4527             : 
    4528             :     /*
    4529             :      * To remove all the pages of the specified relation forks from the buffer
    4530             :      * pool, we need to scan the entire buffer pool but we can optimize it by
    4531             :      * finding the buffers from BufMapping table provided we know the exact
    4532             :      * size of each fork of the relation. The exact size is required to ensure
    4533             :      * that we don't leave any buffer for the relation being dropped as
    4534             :      * otherwise the background writer or checkpointer can lead to a PANIC
    4535             :      * error while flushing buffers corresponding to files that don't exist.
    4536             :      *
    4537             :      * To know the exact size, we rely on the size cached for each fork by us
    4538             :      * during recovery which limits the optimization to recovery and on
    4539             :      * standbys but we can easily extend it once we have shared cache for
    4540             :      * relation size.
    4541             :      *
    4542             :      * In recovery, we cache the value returned by the first lseek(SEEK_END)
    4543             :      * and the future writes keeps the cached value up-to-date. See
    4544             :      * smgrextend. It is possible that the value of the first lseek is smaller
    4545             :      * than the actual number of existing blocks in the file due to buggy
    4546             :      * Linux kernels that might not have accounted for the recent write. But
    4547             :      * that should be fine because there must not be any buffers after that
    4548             :      * file size.
    4549             :      */
    4550         718 :     for (i = 0; i < nforks; i++)
    4551             :     {
    4552             :         /* Get the number of blocks for a relation's fork */
    4553         610 :         nForkBlock[i] = smgrnblocks_cached(smgr_reln, forkNum[i]);
    4554             : 
    4555         610 :         if (nForkBlock[i] == InvalidBlockNumber)
    4556             :         {
    4557         410 :             nBlocksToInvalidate = InvalidBlockNumber;
    4558         410 :             break;
    4559             :         }
    4560             : 
    4561             :         /* calculate the number of blocks to be invalidated */
    4562         200 :         nBlocksToInvalidate += (nForkBlock[i] - firstDelBlock[i]);
    4563             :     }
    4564             : 
    4565             :     /*
    4566             :      * We apply the optimization iff the total number of blocks to invalidate
    4567             :      * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
    4568             :      */
    4569         518 :     if (BlockNumberIsValid(nBlocksToInvalidate) &&
    4570         108 :         nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
    4571             :     {
    4572         222 :         for (j = 0; j < nforks; j++)
    4573         140 :             FindAndDropRelationBuffers(rlocator.locator, forkNum[j],
    4574         140 :                                        nForkBlock[j], firstDelBlock[j]);
    4575          82 :         return;
    4576             :     }
    4577             : 
    4578     5550772 :     for (i = 0; i < NBuffers; i++)
    4579             :     {
    4580     5550336 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    4581             :         uint32      buf_state;
    4582             : 
    4583             :         /*
    4584             :          * We can make this a tad faster by prechecking the buffer tag before
    4585             :          * we attempt to lock the buffer; this saves a lot of lock
    4586             :          * acquisitions in typical cases.  It should be safe because the
    4587             :          * caller must have AccessExclusiveLock on the relation, or some other
    4588             :          * reason to be certain that no one is loading new pages of the rel
    4589             :          * into the buffer pool.  (Otherwise we might well miss such pages
    4590             :          * entirely.)  Therefore, while the tag might be changing while we
    4591             :          * look at it, it can't be changing *to* a value we care about, only
    4592             :          * *away* from such a value.  So false negatives are impossible, and
    4593             :          * false positives are safe because we'll recheck after getting the
    4594             :          * buffer lock.
    4595             :          *
    4596             :          * We could check forkNum and blockNum as well as the rlocator, but
    4597             :          * the incremental win from doing so seems small.
    4598             :          */
    4599     5550336 :         if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator))
    4600     5536494 :             continue;
    4601             : 
    4602       13842 :         buf_state = LockBufHdr(bufHdr);
    4603             : 
    4604       35780 :         for (j = 0; j < nforks; j++)
    4605             :         {
    4606       25064 :             if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator) &&
    4607       25064 :                 BufTagGetForkNum(&bufHdr->tag) == forkNum[j] &&
    4608       13648 :                 bufHdr->tag.blockNum >= firstDelBlock[j])
    4609             :             {
    4610        3126 :                 InvalidateBuffer(bufHdr);   /* releases spinlock */
    4611        3126 :                 break;
    4612             :             }
    4613             :         }
    4614       13842 :         if (j >= nforks)
    4615       10716 :             UnlockBufHdr(bufHdr, buf_state);
    4616             :     }
    4617             : }
    4618             : 
    4619             : /* ---------------------------------------------------------------------
    4620             :  *      DropRelationsAllBuffers
    4621             :  *
    4622             :  *      This function removes from the buffer pool all the pages of all
    4623             :  *      forks of the specified relations.  It's equivalent to calling
    4624             :  *      DropRelationBuffers once per fork per relation with firstDelBlock = 0.
    4625             :  *      --------------------------------------------------------------------
    4626             :  */
    4627             : void
    4628       26974 : DropRelationsAllBuffers(SMgrRelation *smgr_reln, int nlocators)
    4629             : {
    4630             :     int         i;
    4631       26974 :     int         n = 0;
    4632             :     SMgrRelation *rels;
    4633             :     BlockNumber (*block)[MAX_FORKNUM + 1];
    4634       26974 :     uint64      nBlocksToInvalidate = 0;
    4635             :     RelFileLocator *locators;
    4636       26974 :     bool        cached = true;
    4637             :     bool        use_bsearch;
    4638             : 
    4639       26974 :     if (nlocators == 0)
    4640           0 :         return;
    4641             : 
    4642       26974 :     rels = palloc(sizeof(SMgrRelation) * nlocators);    /* non-local relations */
    4643             : 
    4644             :     /* If it's a local relation, it's localbuf.c's problem. */
    4645      117928 :     for (i = 0; i < nlocators; i++)
    4646             :     {
    4647       90954 :         if (RelFileLocatorBackendIsTemp(smgr_reln[i]->smgr_rlocator))
    4648             :         {
    4649        6300 :             if (smgr_reln[i]->smgr_rlocator.backend == MyProcNumber)
    4650        6300 :                 DropRelationAllLocalBuffers(smgr_reln[i]->smgr_rlocator.locator);
    4651             :         }
    4652             :         else
    4653       84654 :             rels[n++] = smgr_reln[i];
    4654             :     }
    4655             : 
    4656             :     /*
    4657             :      * If there are no non-local relations, then we're done. Release the
    4658             :      * memory and return.
    4659             :      */
    4660       26974 :     if (n == 0)
    4661             :     {
    4662        1630 :         pfree(rels);
    4663        1630 :         return;
    4664             :     }
    4665             : 
    4666             :     /*
    4667             :      * This is used to remember the number of blocks for all the relations
    4668             :      * forks.
    4669             :      */
    4670             :     block = (BlockNumber (*)[MAX_FORKNUM + 1])
    4671       25344 :         palloc(sizeof(BlockNumber) * n * (MAX_FORKNUM + 1));
    4672             : 
    4673             :     /*
    4674             :      * We can avoid scanning the entire buffer pool if we know the exact size
    4675             :      * of each of the given relation forks. See DropRelationBuffers.
    4676             :      */
    4677       53022 :     for (i = 0; i < n && cached; i++)
    4678             :     {
    4679       43070 :         for (int j = 0; j <= MAX_FORKNUM; j++)
    4680             :         {
    4681             :             /* Get the number of blocks for a relation's fork. */
    4682       39252 :             block[i][j] = smgrnblocks_cached(rels[i], j);
    4683             : 
    4684             :             /* We need to only consider the relation forks that exists. */
    4685       39252 :             if (block[i][j] == InvalidBlockNumber)
    4686             :             {
    4687       35084 :                 if (!smgrexists(rels[i], j))
    4688       11224 :                     continue;
    4689       23860 :                 cached = false;
    4690       23860 :                 break;
    4691             :             }
    4692             : 
    4693             :             /* calculate the total number of blocks to be invalidated */
    4694        4168 :             nBlocksToInvalidate += block[i][j];
    4695             :         }
    4696             :     }
    4697             : 
    4698             :     /*
    4699             :      * We apply the optimization iff the total number of blocks to invalidate
    4700             :      * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
    4701             :      */
    4702       25344 :     if (cached && nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
    4703             :     {
    4704        2454 :         for (i = 0; i < n; i++)
    4705             :         {
    4706        6750 :             for (int j = 0; j <= MAX_FORKNUM; j++)
    4707             :             {
    4708             :                 /* ignore relation forks that doesn't exist */
    4709        5400 :                 if (!BlockNumberIsValid(block[i][j]))
    4710        4032 :                     continue;
    4711             : 
    4712             :                 /* drop all the buffers for a particular relation fork */
    4713        1368 :                 FindAndDropRelationBuffers(rels[i]->smgr_rlocator.locator,
    4714        1368 :                                            j, block[i][j], 0);
    4715             :             }
    4716             :         }
    4717             : 
    4718        1104 :         pfree(block);
    4719        1104 :         pfree(rels);
    4720        1104 :         return;
    4721             :     }
    4722             : 
    4723       24240 :     pfree(block);
    4724       24240 :     locators = palloc(sizeof(RelFileLocator) * n);  /* non-local relations */
    4725      107544 :     for (i = 0; i < n; i++)
    4726       83304 :         locators[i] = rels[i]->smgr_rlocator.locator;
    4727             : 
    4728             :     /*
    4729             :      * For low number of relations to drop just use a simple walk through, to
    4730             :      * save the bsearch overhead. The threshold to use is rather a guess than
    4731             :      * an exactly determined value, as it depends on many factors (CPU and RAM
    4732             :      * speeds, amount of shared buffers etc.).
    4733             :      */
    4734       24240 :     use_bsearch = n > RELS_BSEARCH_THRESHOLD;
    4735             : 
    4736             :     /* sort the list of rlocators if necessary */
    4737       24240 :     if (use_bsearch)
    4738         334 :         qsort(locators, n, sizeof(RelFileLocator), rlocator_comparator);
    4739             : 
    4740   262085040 :     for (i = 0; i < NBuffers; i++)
    4741             :     {
    4742   262060800 :         RelFileLocator *rlocator = NULL;
    4743   262060800 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    4744             :         uint32      buf_state;
    4745             : 
    4746             :         /*
    4747             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4748             :          * saves some cycles.
    4749             :          */
    4750             : 
    4751   262060800 :         if (!use_bsearch)
    4752             :         {
    4753             :             int         j;
    4754             : 
    4755  1043973036 :             for (j = 0; j < n; j++)
    4756             :             {
    4757   785610496 :                 if (BufTagMatchesRelFileLocator(&bufHdr->tag, &locators[j]))
    4758             :                 {
    4759      176724 :                     rlocator = &locators[j];
    4760      176724 :                     break;
    4761             :                 }
    4762             :             }
    4763             :         }
    4764             :         else
    4765             :         {
    4766             :             RelFileLocator locator;
    4767             : 
    4768     3521536 :             locator = BufTagGetRelFileLocator(&bufHdr->tag);
    4769     3521536 :             rlocator = bsearch(&locator,
    4770             :                                locators, n, sizeof(RelFileLocator),
    4771             :                                rlocator_comparator);
    4772             :         }
    4773             : 
    4774             :         /* buffer doesn't belong to any of the given relfilelocators; skip it */
    4775   262060800 :         if (rlocator == NULL)
    4776   261880608 :             continue;
    4777             : 
    4778      180192 :         buf_state = LockBufHdr(bufHdr);
    4779      180192 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, rlocator))
    4780      180192 :             InvalidateBuffer(bufHdr);   /* releases spinlock */
    4781             :         else
    4782           0 :             UnlockBufHdr(bufHdr, buf_state);
    4783             :     }
    4784             : 
    4785       24240 :     pfree(locators);
    4786       24240 :     pfree(rels);
    4787             : }
    4788             : 
    4789             : /* ---------------------------------------------------------------------
    4790             :  *      FindAndDropRelationBuffers
    4791             :  *
    4792             :  *      This function performs look up in BufMapping table and removes from the
    4793             :  *      buffer pool all the pages of the specified relation fork that has block
    4794             :  *      number >= firstDelBlock. (In particular, with firstDelBlock = 0, all
    4795             :  *      pages are removed.)
    4796             :  * --------------------------------------------------------------------
    4797             :  */
    4798             : static void
    4799        1508 : FindAndDropRelationBuffers(RelFileLocator rlocator, ForkNumber forkNum,
    4800             :                            BlockNumber nForkBlock,
    4801             :                            BlockNumber firstDelBlock)
    4802             : {
    4803             :     BlockNumber curBlock;
    4804             : 
    4805        3674 :     for (curBlock = firstDelBlock; curBlock < nForkBlock; curBlock++)
    4806             :     {
    4807             :         uint32      bufHash;    /* hash value for tag */
    4808             :         BufferTag   bufTag;     /* identity of requested block */
    4809             :         LWLock     *bufPartitionLock;   /* buffer partition lock for it */
    4810             :         int         buf_id;
    4811             :         BufferDesc *bufHdr;
    4812             :         uint32      buf_state;
    4813             : 
    4814             :         /* create a tag so we can lookup the buffer */
    4815        2166 :         InitBufferTag(&bufTag, &rlocator, forkNum, curBlock);
    4816             : 
    4817             :         /* determine its hash code and partition lock ID */
    4818        2166 :         bufHash = BufTableHashCode(&bufTag);
    4819        2166 :         bufPartitionLock = BufMappingPartitionLock(bufHash);
    4820             : 
    4821             :         /* Check that it is in the buffer pool. If not, do nothing. */
    4822        2166 :         LWLockAcquire(bufPartitionLock, LW_SHARED);
    4823        2166 :         buf_id = BufTableLookup(&bufTag, bufHash);
    4824        2166 :         LWLockRelease(bufPartitionLock);
    4825             : 
    4826        2166 :         if (buf_id < 0)
    4827         176 :             continue;
    4828             : 
    4829        1990 :         bufHdr = GetBufferDescriptor(buf_id);
    4830             : 
    4831             :         /*
    4832             :          * We need to lock the buffer header and recheck if the buffer is
    4833             :          * still associated with the same block because the buffer could be
    4834             :          * evicted by some other backend loading blocks for a different
    4835             :          * relation after we release lock on the BufMapping table.
    4836             :          */
    4837        1990 :         buf_state = LockBufHdr(bufHdr);
    4838             : 
    4839        3980 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator) &&
    4840        1990 :             BufTagGetForkNum(&bufHdr->tag) == forkNum &&
    4841        1990 :             bufHdr->tag.blockNum >= firstDelBlock)
    4842        1990 :             InvalidateBuffer(bufHdr);   /* releases spinlock */
    4843             :         else
    4844           0 :             UnlockBufHdr(bufHdr, buf_state);
    4845             :     }
    4846        1508 : }
    4847             : 
    4848             : /* ---------------------------------------------------------------------
    4849             :  *      DropDatabaseBuffers
    4850             :  *
    4851             :  *      This function removes all the buffers in the buffer cache for a
    4852             :  *      particular database.  Dirty pages are simply dropped, without
    4853             :  *      bothering to write them out first.  This is used when we destroy a
    4854             :  *      database, to avoid trying to flush data to disk when the directory
    4855             :  *      tree no longer exists.  Implementation is pretty similar to
    4856             :  *      DropRelationBuffers() which is for destroying just one relation.
    4857             :  * --------------------------------------------------------------------
    4858             :  */
    4859             : void
    4860         136 : DropDatabaseBuffers(Oid dbid)
    4861             : {
    4862             :     int         i;
    4863             : 
    4864             :     /*
    4865             :      * We needn't consider local buffers, since by assumption the target
    4866             :      * database isn't our own.
    4867             :      */
    4868             : 
    4869      895368 :     for (i = 0; i < NBuffers; i++)
    4870             :     {
    4871      895232 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    4872             :         uint32      buf_state;
    4873             : 
    4874             :         /*
    4875             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4876             :          * saves some cycles.
    4877             :          */
    4878      895232 :         if (bufHdr->tag.dbOid != dbid)
    4879      870148 :             continue;
    4880             : 
    4881       25084 :         buf_state = LockBufHdr(bufHdr);
    4882       25084 :         if (bufHdr->tag.dbOid == dbid)
    4883       25084 :             InvalidateBuffer(bufHdr);   /* releases spinlock */
    4884             :         else
    4885           0 :             UnlockBufHdr(bufHdr, buf_state);
    4886             :     }
    4887         136 : }
    4888             : 
    4889             : /* ---------------------------------------------------------------------
    4890             :  *      FlushRelationBuffers
    4891             :  *
    4892             :  *      This function writes all dirty pages of a relation out to disk
    4893             :  *      (or more accurately, out to kernel disk buffers), ensuring that the
    4894             :  *      kernel has an up-to-date view of the relation.
    4895             :  *
    4896             :  *      Generally, the caller should be holding AccessExclusiveLock on the
    4897             :  *      target relation to ensure that no other backend is busy dirtying
    4898             :  *      more blocks of the relation; the effects can't be expected to last
    4899             :  *      after the lock is released.
    4900             :  *
    4901             :  *      XXX currently it sequentially searches the buffer pool, should be
    4902             :  *      changed to more clever ways of searching.  This routine is not
    4903             :  *      used in any performance-critical code paths, so it's not worth
    4904             :  *      adding additional overhead to normal paths to make it go faster.
    4905             :  * --------------------------------------------------------------------
    4906             :  */
    4907             : void
    4908         276 : FlushRelationBuffers(Relation rel)
    4909             : {
    4910             :     int         i;
    4911             :     BufferDesc *bufHdr;
    4912         276 :     SMgrRelation srel = RelationGetSmgr(rel);
    4913             : 
    4914         276 :     if (RelationUsesLocalBuffers(rel))
    4915             :     {
    4916        1818 :         for (i = 0; i < NLocBuffer; i++)
    4917             :         {
    4918             :             uint32      buf_state;
    4919             : 
    4920        1800 :             bufHdr = GetLocalBufferDescriptor(i);
    4921        1800 :             if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
    4922         600 :                 ((buf_state = pg_atomic_read_u32(&bufHdr->state)) &
    4923             :                  (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    4924             :             {
    4925             :                 ErrorContextCallback errcallback;
    4926             : 
    4927             :                 /* Setup error traceback support for ereport() */
    4928         600 :                 errcallback.callback = local_buffer_write_error_callback;
    4929         600 :                 errcallback.arg = bufHdr;
    4930         600 :                 errcallback.previous = error_context_stack;
    4931         600 :                 error_context_stack = &errcallback;
    4932             : 
    4933             :                 /* Make sure we can handle the pin */
    4934         600 :                 ReservePrivateRefCountEntry();
    4935         600 :                 ResourceOwnerEnlarge(CurrentResourceOwner);
    4936             : 
    4937             :                 /*
    4938             :                  * Pin/unpin mostly to make valgrind work, but it also seems
    4939             :                  * like the right thing to do.
    4940             :                  */
    4941         600 :                 PinLocalBuffer(bufHdr, false);
    4942             : 
    4943             : 
    4944         600 :                 FlushLocalBuffer(bufHdr, srel);
    4945             : 
    4946         600 :                 UnpinLocalBuffer(BufferDescriptorGetBuffer(bufHdr));
    4947             : 
    4948             :                 /* Pop the error context stack */
    4949         600 :                 error_context_stack = errcallback.previous;
    4950             :             }
    4951             :         }
    4952             : 
    4953          18 :         return;
    4954             :     }
    4955             : 
    4956     3024386 :     for (i = 0; i < NBuffers; i++)
    4957             :     {
    4958             :         uint32      buf_state;
    4959             : 
    4960     3024128 :         bufHdr = GetBufferDescriptor(i);
    4961             : 
    4962             :         /*
    4963             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4964             :          * saves some cycles.
    4965             :          */
    4966     3024128 :         if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator))
    4967     3023682 :             continue;
    4968             : 
    4969             :         /* Make sure we can handle the pin */
    4970         446 :         ReservePrivateRefCountEntry();
    4971         446 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    4972             : 
    4973         446 :         buf_state = LockBufHdr(bufHdr);
    4974         446 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
    4975         446 :             (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    4976             :         {
    4977         360 :             PinBuffer_Locked(bufHdr);
    4978         360 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    4979         360 :             FlushBuffer(bufHdr, srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    4980         360 :             LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    4981         360 :             UnpinBuffer(bufHdr);
    4982             :         }
    4983             :         else
    4984          86 :             UnlockBufHdr(bufHdr, buf_state);
    4985             :     }
    4986             : }
    4987             : 
    4988             : /* ---------------------------------------------------------------------
    4989             :  *      FlushRelationsAllBuffers
    4990             :  *
    4991             :  *      This function flushes out of the buffer pool all the pages of all
    4992             :  *      forks of the specified smgr relations.  It's equivalent to calling
    4993             :  *      FlushRelationBuffers once per relation.  The relations are assumed not
    4994             :  *      to use local buffers.
    4995             :  * --------------------------------------------------------------------
    4996             :  */
    4997             : void
    4998          24 : FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
    4999             : {
    5000             :     int         i;
    5001             :     SMgrSortArray *srels;
    5002             :     bool        use_bsearch;
    5003             : 
    5004          24 :     if (nrels == 0)
    5005           0 :         return;
    5006             : 
    5007             :     /* fill-in array for qsort */
    5008          24 :     srels = palloc(sizeof(SMgrSortArray) * nrels);
    5009             : 
    5010          48 :     for (i = 0; i < nrels; i++)
    5011             :     {
    5012             :         Assert(!RelFileLocatorBackendIsTemp(smgrs[i]->smgr_rlocator));
    5013             : 
    5014          24 :         srels[i].rlocator = smgrs[i]->smgr_rlocator.locator;
    5015          24 :         srels[i].srel = smgrs[i];
    5016             :     }
    5017             : 
    5018             :     /*
    5019             :      * Save the bsearch overhead for low number of relations to sync. See
    5020             :      * DropRelationsAllBuffers for details.
    5021             :      */
    5022          24 :     use_bsearch = nrels > RELS_BSEARCH_THRESHOLD;
    5023             : 
    5024             :     /* sort the list of SMgrRelations if necessary */
    5025          24 :     if (use_bsearch)
    5026           0 :         qsort(srels, nrels, sizeof(SMgrSortArray), rlocator_comparator);
    5027             : 
    5028      393240 :     for (i = 0; i < NBuffers; i++)
    5029             :     {
    5030      393216 :         SMgrSortArray *srelent = NULL;
    5031      393216 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    5032             :         uint32      buf_state;
    5033             : 
    5034             :         /*
    5035             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    5036             :          * saves some cycles.
    5037             :          */
    5038             : 
    5039      393216 :         if (!use_bsearch)
    5040             :         {
    5041             :             int         j;
    5042             : 
    5043      777604 :             for (j = 0; j < nrels; j++)
    5044             :             {
    5045      393216 :                 if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srels[j].rlocator))
    5046             :                 {
    5047        8828 :                     srelent = &srels[j];
    5048        8828 :                     break;
    5049             :                 }
    5050             :             }
    5051             :         }
    5052             :         else
    5053             :         {
    5054             :             RelFileLocator rlocator;
    5055             : 
    5056           0 :             rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
    5057           0 :             srelent = bsearch(&rlocator,
    5058             :                               srels, nrels, sizeof(SMgrSortArray),
    5059             :                               rlocator_comparator);
    5060             :         }
    5061             : 
    5062             :         /* buffer doesn't belong to any of the given relfilelocators; skip it */
    5063      393216 :         if (srelent == NULL)
    5064      384388 :             continue;
    5065             : 
    5066             :         /* Make sure we can handle the pin */
    5067        8828 :         ReservePrivateRefCountEntry();
    5068        8828 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    5069             : 
    5070        8828 :         buf_state = LockBufHdr(bufHdr);
    5071        8828 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srelent->rlocator) &&
    5072        8828 :             (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    5073             :         {
    5074        7914 :             PinBuffer_Locked(bufHdr);
    5075        7914 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    5076        7914 :             FlushBuffer(bufHdr, srelent->srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    5077        7914 :             LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    5078        7914 :             UnpinBuffer(bufHdr);
    5079             :         }
    5080             :         else
    5081         914 :             UnlockBufHdr(bufHdr, buf_state);
    5082             :     }
    5083             : 
    5084          24 :     pfree(srels);
    5085             : }
    5086             : 
    5087             : /* ---------------------------------------------------------------------
    5088             :  *      RelationCopyStorageUsingBuffer
    5089             :  *
    5090             :  *      Copy fork's data using bufmgr.  Same as RelationCopyStorage but instead
    5091             :  *      of using smgrread and smgrextend this will copy using bufmgr APIs.
    5092             :  *
    5093             :  *      Refer comments atop CreateAndCopyRelationData() for details about
    5094             :  *      'permanent' parameter.
    5095             :  * --------------------------------------------------------------------
    5096             :  */
    5097             : static void
    5098      146664 : RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
    5099             :                                RelFileLocator dstlocator,
    5100             :                                ForkNumber forkNum, bool permanent)
    5101             : {
    5102             :     Buffer      srcBuf;
    5103             :     Buffer      dstBuf;
    5104             :     Page        srcPage;
    5105             :     Page        dstPage;
    5106             :     bool        use_wal;
    5107             :     BlockNumber nblocks;
    5108             :     BlockNumber blkno;
    5109             :     PGIOAlignedBlock buf;
    5110             :     BufferAccessStrategy bstrategy_src;
    5111             :     BufferAccessStrategy bstrategy_dst;
    5112             :     BlockRangeReadStreamPrivate p;
    5113             :     ReadStream *src_stream;
    5114             :     SMgrRelation src_smgr;
    5115             : 
    5116             :     /*
    5117             :      * In general, we want to write WAL whenever wal_level > 'minimal', but we
    5118             :      * can skip it when copying any fork of an unlogged relation other than
    5119             :      * the init fork.
    5120             :      */
    5121      146664 :     use_wal = XLogIsNeeded() && (permanent || forkNum == INIT_FORKNUM);
    5122             : 
    5123             :     /* Get number of blocks in the source relation. */
    5124      146664 :     nblocks = smgrnblocks(smgropen(srclocator, INVALID_PROC_NUMBER),
    5125             :                           forkNum);
    5126             : 
    5127             :     /* Nothing to copy; just return. */
    5128      146664 :     if (nblocks == 0)
    5129       25582 :         return;
    5130             : 
    5131             :     /*
    5132             :      * Bulk extend the destination relation of the same size as the source
    5133             :      * relation before starting to copy block by block.
    5134             :      */
    5135      121082 :     memset(buf.data, 0, BLCKSZ);
    5136      121082 :     smgrextend(smgropen(dstlocator, INVALID_PROC_NUMBER), forkNum, nblocks - 1,
    5137             :                buf.data, true);
    5138             : 
    5139             :     /* This is a bulk operation, so use buffer access strategies. */
    5140      121082 :     bstrategy_src = GetAccessStrategy(BAS_BULKREAD);
    5141      121082 :     bstrategy_dst = GetAccessStrategy(BAS_BULKWRITE);
    5142             : 
    5143             :     /* Initialize streaming read */
    5144      121082 :     p.current_blocknum = 0;
    5145      121082 :     p.last_exclusive = nblocks;
    5146      121082 :     src_smgr = smgropen(srclocator, INVALID_PROC_NUMBER);
    5147             : 
    5148             :     /*
    5149             :      * It is safe to use batchmode as block_range_read_stream_cb takes no
    5150             :      * locks.
    5151             :      */
    5152      121082 :     src_stream = read_stream_begin_smgr_relation(READ_STREAM_FULL |
    5153             :                                                  READ_STREAM_USE_BATCHING,
    5154             :                                                  bstrategy_src,
    5155             :                                                  src_smgr,
    5156             :                                                  permanent ? RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED,
    5157             :                                                  forkNum,
    5158             :                                                  block_range_read_stream_cb,
    5159             :                                                  &p,
    5160             :                                                  0);
    5161             : 
    5162             :     /* Iterate over each block of the source relation file. */
    5163      583790 :     for (blkno = 0; blkno < nblocks; blkno++)
    5164             :     {
    5165      462712 :         CHECK_FOR_INTERRUPTS();
    5166             : 
    5167             :         /* Read block from source relation. */
    5168      462712 :         srcBuf = read_stream_next_buffer(src_stream, NULL);
    5169      462708 :         LockBuffer(srcBuf, BUFFER_LOCK_SHARE);
    5170      462708 :         srcPage = BufferGetPage(srcBuf);
    5171             : 
    5172      462708 :         dstBuf = ReadBufferWithoutRelcache(dstlocator, forkNum,
    5173             :                                            BufferGetBlockNumber(srcBuf),
    5174             :                                            RBM_ZERO_AND_LOCK, bstrategy_dst,
    5175             :                                            permanent);
    5176      462708 :         dstPage = BufferGetPage(dstBuf);
    5177             : 
    5178      462708 :         START_CRIT_SECTION();
    5179             : 
    5180             :         /* Copy page data from the source to the destination. */
    5181      462708 :         memcpy(dstPage, srcPage, BLCKSZ);
    5182      462708 :         MarkBufferDirty(dstBuf);
    5183             : 
    5184             :         /* WAL-log the copied page. */
    5185      462708 :         if (use_wal)
    5186      253980 :             log_newpage_buffer(dstBuf, true);
    5187             : 
    5188      462708 :         END_CRIT_SECTION();
    5189             : 
    5190      462708 :         UnlockReleaseBuffer(dstBuf);
    5191      462708 :         UnlockReleaseBuffer(srcBuf);
    5192             :     }
    5193             :     Assert(read_stream_next_buffer(src_stream, NULL) == InvalidBuffer);
    5194      121078 :     read_stream_end(src_stream);
    5195             : 
    5196      121078 :     FreeAccessStrategy(bstrategy_src);
    5197      121078 :     FreeAccessStrategy(bstrategy_dst);
    5198             : }
    5199             : 
    5200             : /* ---------------------------------------------------------------------
    5201             :  *      CreateAndCopyRelationData
    5202             :  *
    5203             :  *      Create destination relation storage and copy all forks from the
    5204             :  *      source relation to the destination.
    5205             :  *
    5206             :  *      Pass permanent as true for permanent relations and false for
    5207             :  *      unlogged relations.  Currently this API is not supported for
    5208             :  *      temporary relations.
    5209             :  * --------------------------------------------------------------------
    5210             :  */
    5211             : void
    5212      110248 : CreateAndCopyRelationData(RelFileLocator src_rlocator,
    5213             :                           RelFileLocator dst_rlocator, bool permanent)
    5214             : {
    5215             :     char        relpersistence;
    5216             :     SMgrRelation src_rel;
    5217             :     SMgrRelation dst_rel;
    5218             : 
    5219             :     /* Set the relpersistence. */
    5220      110248 :     relpersistence = permanent ?
    5221             :         RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED;
    5222             : 
    5223      110248 :     src_rel = smgropen(src_rlocator, INVALID_PROC_NUMBER);
    5224      110248 :     dst_rel = smgropen(dst_rlocator, INVALID_PROC_NUMBER);
    5225             : 
    5226             :     /*
    5227             :      * Create and copy all forks of the relation.  During create database we
    5228             :      * have a separate cleanup mechanism which deletes complete database
    5229             :      * directory.  Therefore, each individual relation doesn't need to be
    5230             :      * registered for cleanup.
    5231             :      */
    5232      110248 :     RelationCreateStorage(dst_rlocator, relpersistence, false);
    5233             : 
    5234             :     /* copy main fork. */
    5235      110248 :     RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, MAIN_FORKNUM,
    5236             :                                    permanent);
    5237             : 
    5238             :     /* copy those extra forks that exist */
    5239      110244 :     for (ForkNumber forkNum = MAIN_FORKNUM + 1;
    5240      440976 :          forkNum <= MAX_FORKNUM; forkNum++)
    5241             :     {
    5242      330732 :         if (smgrexists(src_rel, forkNum))
    5243             :         {
    5244       36416 :             smgrcreate(dst_rel, forkNum, false);
    5245             : 
    5246             :             /*
    5247             :              * WAL log creation if the relation is persistent, or this is the
    5248             :              * init fork of an unlogged relation.
    5249             :              */
    5250       36416 :             if (permanent || forkNum == INIT_FORKNUM)
    5251       36416 :                 log_smgrcreate(&dst_rlocator, forkNum);
    5252             : 
    5253             :             /* Copy a fork's data, block by block. */
    5254       36416 :             RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, forkNum,
    5255             :                                            permanent);
    5256             :         }
    5257             :     }
    5258      110244 : }
    5259             : 
    5260             : /* ---------------------------------------------------------------------
    5261             :  *      FlushDatabaseBuffers
    5262             :  *
    5263             :  *      This function writes all dirty pages of a database out to disk
    5264             :  *      (or more accurately, out to kernel disk buffers), ensuring that the
    5265             :  *      kernel has an up-to-date view of the database.
    5266             :  *
    5267             :  *      Generally, the caller should be holding an appropriate lock to ensure
    5268             :  *      no other backend is active in the target database; otherwise more
    5269             :  *      pages could get dirtied.
    5270             :  *
    5271             :  *      Note we don't worry about flushing any pages of temporary relations.
    5272             :  *      It's assumed these wouldn't be interesting.
    5273             :  * --------------------------------------------------------------------
    5274             :  */
    5275             : void
    5276           8 : FlushDatabaseBuffers(Oid dbid)
    5277             : {
    5278             :     int         i;
    5279             :     BufferDesc *bufHdr;
    5280             : 
    5281        1032 :     for (i = 0; i < NBuffers; i++)
    5282             :     {
    5283             :         uint32      buf_state;
    5284             : 
    5285        1024 :         bufHdr = GetBufferDescriptor(i);
    5286             : 
    5287             :         /*
    5288             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    5289             :          * saves some cycles.
    5290             :          */
    5291        1024 :         if (bufHdr->tag.dbOid != dbid)
    5292         722 :             continue;
    5293             : 
    5294             :         /* Make sure we can handle the pin */
    5295         302 :         ReservePrivateRefCountEntry();
    5296         302 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    5297             : 
    5298         302 :         buf_state = LockBufHdr(bufHdr);
    5299         302 :         if (bufHdr->tag.dbOid == dbid &&
    5300         302 :             (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    5301             :         {
    5302          68 :             PinBuffer_Locked(bufHdr);
    5303          68 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    5304          68 :             FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    5305          68 :             LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    5306          68 :             UnpinBuffer(bufHdr);
    5307             :         }
    5308             :         else
    5309         234 :             UnlockBufHdr(bufHdr, buf_state);
    5310             :     }
    5311           8 : }
    5312             : 
    5313             : /*
    5314             :  * Flush a previously, shared or exclusively, locked and pinned buffer to the
    5315             :  * OS.
    5316             :  */
    5317             : void
    5318         158 : FlushOneBuffer(Buffer buffer)
    5319             : {
    5320             :     BufferDesc *bufHdr;
    5321             : 
    5322             :     /* currently not needed, but no fundamental reason not to support */
    5323             :     Assert(!BufferIsLocal(buffer));
    5324             : 
    5325             :     Assert(BufferIsPinned(buffer));
    5326             : 
    5327         158 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5328             : 
    5329             :     Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
    5330             : 
    5331         158 :     FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    5332         158 : }
    5333             : 
    5334             : /*
    5335             :  * ReleaseBuffer -- release the pin on a buffer
    5336             :  */
    5337             : void
    5338   125020932 : ReleaseBuffer(Buffer buffer)
    5339             : {
    5340   125020932 :     if (!BufferIsValid(buffer))
    5341           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    5342             : 
    5343   125020932 :     if (BufferIsLocal(buffer))
    5344     3220056 :         UnpinLocalBuffer(buffer);
    5345             :     else
    5346   121800876 :         UnpinBuffer(GetBufferDescriptor(buffer - 1));
    5347   125020932 : }
    5348             : 
    5349             : /*
    5350             :  * UnlockReleaseBuffer -- release the content lock and pin on a buffer
    5351             :  *
    5352             :  * This is just a shorthand for a common combination.
    5353             :  */
    5354             : void
    5355    37996930 : UnlockReleaseBuffer(Buffer buffer)
    5356             : {
    5357    37996930 :     LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5358    37996930 :     ReleaseBuffer(buffer);
    5359    37996930 : }
    5360             : 
    5361             : /*
    5362             :  * IncrBufferRefCount
    5363             :  *      Increment the pin count on a buffer that we have *already* pinned
    5364             :  *      at least once.
    5365             :  *
    5366             :  *      This function cannot be used on a buffer we do not have pinned,
    5367             :  *      because it doesn't change the shared buffer state.
    5368             :  */
    5369             : void
    5370    23273244 : IncrBufferRefCount(Buffer buffer)
    5371             : {
    5372             :     Assert(BufferIsPinned(buffer));
    5373    23273244 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    5374    23273244 :     if (BufferIsLocal(buffer))
    5375      709186 :         LocalRefCount[-buffer - 1]++;
    5376             :     else
    5377             :     {
    5378             :         PrivateRefCountEntry *ref;
    5379             : 
    5380    22564058 :         ref = GetPrivateRefCountEntry(buffer, true);
    5381             :         Assert(ref != NULL);
    5382    22564058 :         ref->refcount++;
    5383             :     }
    5384    23273244 :     ResourceOwnerRememberBuffer(CurrentResourceOwner, buffer);
    5385    23273244 : }
    5386             : 
    5387             : /*
    5388             :  * MarkBufferDirtyHint
    5389             :  *
    5390             :  *  Mark a buffer dirty for non-critical changes.
    5391             :  *
    5392             :  * This is essentially the same as MarkBufferDirty, except:
    5393             :  *
    5394             :  * 1. The caller does not write WAL; so if checksums are enabled, we may need
    5395             :  *    to write an XLOG_FPI_FOR_HINT WAL record to protect against torn pages.
    5396             :  * 2. The caller might have only share-lock instead of exclusive-lock on the
    5397             :  *    buffer's content lock.
    5398             :  * 3. This function does not guarantee that the buffer is always marked dirty
    5399             :  *    (due to a race condition), so it cannot be used for important changes.
    5400             :  */
    5401             : void
    5402    19751290 : MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
    5403             : {
    5404             :     BufferDesc *bufHdr;
    5405    19751290 :     Page        page = BufferGetPage(buffer);
    5406             : 
    5407    19751290 :     if (!BufferIsValid(buffer))
    5408           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    5409             : 
    5410    19751290 :     if (BufferIsLocal(buffer))
    5411             :     {
    5412     1270218 :         MarkLocalBufferDirty(buffer);
    5413     1270218 :         return;
    5414             :     }
    5415             : 
    5416    18481072 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5417             : 
    5418             :     Assert(GetPrivateRefCount(buffer) > 0);
    5419             :     /* here, either share or exclusive lock is OK */
    5420             :     Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
    5421             : 
    5422             :     /*
    5423             :      * This routine might get called many times on the same page, if we are
    5424             :      * making the first scan after commit of an xact that added/deleted many
    5425             :      * tuples. So, be as quick as we can if the buffer is already dirty.  We
    5426             :      * do this by not acquiring spinlock if it looks like the status bits are
    5427             :      * already set.  Since we make this test unlocked, there's a chance we
    5428             :      * might fail to notice that the flags have just been cleared, and failed
    5429             :      * to reset them, due to memory-ordering issues.  But since this function
    5430             :      * is only intended to be used in cases where failing to write out the
    5431             :      * data would be harmless anyway, it doesn't really matter.
    5432             :      */
    5433    18481072 :     if ((pg_atomic_read_u32(&bufHdr->state) & (BM_DIRTY | BM_JUST_DIRTIED)) !=
    5434             :         (BM_DIRTY | BM_JUST_DIRTIED))
    5435             :     {
    5436     1611388 :         XLogRecPtr  lsn = InvalidXLogRecPtr;
    5437     1611388 :         bool        dirtied = false;
    5438     1611388 :         bool        delayChkptFlags = false;
    5439             :         uint32      buf_state;
    5440             : 
    5441             :         /*
    5442             :          * If we need to protect hint bit updates from torn writes, WAL-log a
    5443             :          * full page image of the page. This full page image is only necessary
    5444             :          * if the hint bit update is the first change to the page since the
    5445             :          * last checkpoint.
    5446             :          *
    5447             :          * We don't check full_page_writes here because that logic is included
    5448             :          * when we call XLogInsert() since the value changes dynamically.
    5449             :          */
    5450     3220584 :         if (XLogHintBitIsNeeded() &&
    5451     1609196 :             (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT))
    5452             :         {
    5453             :             /*
    5454             :              * If we must not write WAL, due to a relfilelocator-specific
    5455             :              * condition or being in recovery, don't dirty the page.  We can
    5456             :              * set the hint, just not dirty the page as a result so the hint
    5457             :              * is lost when we evict the page or shutdown.
    5458             :              *
    5459             :              * See src/backend/storage/page/README for longer discussion.
    5460             :              */
    5461     1732586 :             if (RecoveryInProgress() ||
    5462      123454 :                 RelFileLocatorSkippingWAL(BufTagGetRelFileLocator(&bufHdr->tag)))
    5463     1491364 :                 return;
    5464             : 
    5465             :             /*
    5466             :              * If the block is already dirty because we either made a change
    5467             :              * or set a hint already, then we don't need to write a full page
    5468             :              * image.  Note that aggressive cleaning of blocks dirtied by hint
    5469             :              * bit setting would increase the call rate. Bulk setting of hint
    5470             :              * bits would reduce the call rate...
    5471             :              *
    5472             :              * We must issue the WAL record before we mark the buffer dirty.
    5473             :              * Otherwise we might write the page before we write the WAL. That
    5474             :              * causes a race condition, since a checkpoint might occur between
    5475             :              * writing the WAL record and marking the buffer dirty. We solve
    5476             :              * that with a kluge, but one that is already in use during
    5477             :              * transaction commit to prevent race conditions. Basically, we
    5478             :              * simply prevent the checkpoint WAL record from being written
    5479             :              * until we have marked the buffer dirty. We don't start the
    5480             :              * checkpoint flush until we have marked dirty, so our checkpoint
    5481             :              * must flush the change to disk successfully or the checkpoint
    5482             :              * never gets written, so crash recovery will fix.
    5483             :              *
    5484             :              * It's possible we may enter here without an xid, so it is
    5485             :              * essential that CreateCheckPoint waits for virtual transactions
    5486             :              * rather than full transactionids.
    5487             :              */
    5488             :             Assert((MyProc->delayChkptFlags & DELAY_CHKPT_START) == 0);
    5489      117768 :             MyProc->delayChkptFlags |= DELAY_CHKPT_START;
    5490      117768 :             delayChkptFlags = true;
    5491      117768 :             lsn = XLogSaveBufferForHint(buffer, buffer_std);
    5492             :         }
    5493             : 
    5494      120024 :         buf_state = LockBufHdr(bufHdr);
    5495             : 
    5496             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    5497             : 
    5498      120024 :         if (!(buf_state & BM_DIRTY))
    5499             :         {
    5500      119938 :             dirtied = true;     /* Means "will be dirtied by this action" */
    5501             : 
    5502             :             /*
    5503             :              * Set the page LSN if we wrote a backup block. We aren't supposed
    5504             :              * to set this when only holding a share lock but as long as we
    5505             :              * serialise it somehow we're OK. We choose to set LSN while
    5506             :              * holding the buffer header lock, which causes any reader of an
    5507             :              * LSN who holds only a share lock to also obtain a buffer header
    5508             :              * lock before using PageGetLSN(), which is enforced in
    5509             :              * BufferGetLSNAtomic().
    5510             :              *
    5511             :              * If checksums are enabled, you might think we should reset the
    5512             :              * checksum here. That will happen when the page is written
    5513             :              * sometime later in this checkpoint cycle.
    5514             :              */
    5515      119938 :             if (!XLogRecPtrIsInvalid(lsn))
    5516       62566 :                 PageSetLSN(page, lsn);
    5517             :         }
    5518             : 
    5519      120024 :         buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
    5520      120024 :         UnlockBufHdr(bufHdr, buf_state);
    5521             : 
    5522      120024 :         if (delayChkptFlags)
    5523      117768 :             MyProc->delayChkptFlags &= ~DELAY_CHKPT_START;
    5524             : 
    5525      120024 :         if (dirtied)
    5526             :         {
    5527      119938 :             pgBufferUsage.shared_blks_dirtied++;
    5528      119938 :             if (VacuumCostActive)
    5529        3030 :                 VacuumCostBalance += VacuumCostPageDirty;
    5530             :         }
    5531             :     }
    5532             : }
    5533             : 
    5534             : /*
    5535             :  * Release buffer content locks for shared buffers.
    5536             :  *
    5537             :  * Used to clean up after errors.
    5538             :  *
    5539             :  * Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
    5540             :  * of releasing buffer content locks per se; the only thing we need to deal
    5541             :  * with here is clearing any PIN_COUNT request that was in progress.
    5542             :  */
    5543             : void
    5544      103750 : UnlockBuffers(void)
    5545             : {
    5546      103750 :     BufferDesc *buf = PinCountWaitBuf;
    5547             : 
    5548      103750 :     if (buf)
    5549             :     {
    5550             :         uint32      buf_state;
    5551             : 
    5552           0 :         buf_state = LockBufHdr(buf);
    5553             : 
    5554             :         /*
    5555             :          * Don't complain if flag bit not set; it could have been reset but we
    5556             :          * got a cancel/die interrupt before getting the signal.
    5557             :          */
    5558           0 :         if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
    5559           0 :             buf->wait_backend_pgprocno == MyProcNumber)
    5560           0 :             buf_state &= ~BM_PIN_COUNT_WAITER;
    5561             : 
    5562           0 :         UnlockBufHdr(buf, buf_state);
    5563             : 
    5564           0 :         PinCountWaitBuf = NULL;
    5565             :     }
    5566      103750 : }
    5567             : 
    5568             : /*
    5569             :  * Acquire or release the content_lock for the buffer.
    5570             :  */
    5571             : void
    5572   344533154 : LockBuffer(Buffer buffer, int mode)
    5573             : {
    5574             :     BufferDesc *buf;
    5575             : 
    5576             :     Assert(BufferIsPinned(buffer));
    5577   344533154 :     if (BufferIsLocal(buffer))
    5578    19799688 :         return;                 /* local buffers need no lock */
    5579             : 
    5580   324733466 :     buf = GetBufferDescriptor(buffer - 1);
    5581             : 
    5582   324733466 :     if (mode == BUFFER_LOCK_UNLOCK)
    5583   164350716 :         LWLockRelease(BufferDescriptorGetContentLock(buf));
    5584   160382750 :     else if (mode == BUFFER_LOCK_SHARE)
    5585   114022384 :         LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_SHARED);
    5586    46360366 :     else if (mode == BUFFER_LOCK_EXCLUSIVE)
    5587    46360366 :         LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_EXCLUSIVE);
    5588             :     else
    5589           0 :         elog(ERROR, "unrecognized buffer lock mode: %d", mode);
    5590             : }
    5591             : 
    5592             : /*
    5593             :  * Acquire the content_lock for the buffer, but only if we don't have to wait.
    5594             :  *
    5595             :  * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode.
    5596             :  */
    5597             : bool
    5598     3168926 : ConditionalLockBuffer(Buffer buffer)
    5599             : {
    5600             :     BufferDesc *buf;
    5601             : 
    5602             :     Assert(BufferIsPinned(buffer));
    5603     3168926 :     if (BufferIsLocal(buffer))
    5604      129308 :         return true;            /* act as though we got it */
    5605             : 
    5606     3039618 :     buf = GetBufferDescriptor(buffer - 1);
    5607             : 
    5608     3039618 :     return LWLockConditionalAcquire(BufferDescriptorGetContentLock(buf),
    5609             :                                     LW_EXCLUSIVE);
    5610             : }
    5611             : 
    5612             : /*
    5613             :  * Verify that this backend is pinning the buffer exactly once.
    5614             :  *
    5615             :  * NOTE: Like in BufferIsPinned(), what we check here is that *this* backend
    5616             :  * holds a pin on the buffer.  We do not care whether some other backend does.
    5617             :  */
    5618             : void
    5619     5074718 : CheckBufferIsPinnedOnce(Buffer buffer)
    5620             : {
    5621     5074718 :     if (BufferIsLocal(buffer))
    5622             :     {
    5623        1578 :         if (LocalRefCount[-buffer - 1] != 1)
    5624           0 :             elog(ERROR, "incorrect local pin count: %d",
    5625             :                  LocalRefCount[-buffer - 1]);
    5626             :     }
    5627             :     else
    5628             :     {
    5629     5073140 :         if (GetPrivateRefCount(buffer) != 1)
    5630           0 :             elog(ERROR, "incorrect local pin count: %d",
    5631             :                  GetPrivateRefCount(buffer));
    5632             :     }
    5633     5074718 : }
    5634             : 
    5635             : /*
    5636             :  * LockBufferForCleanup - lock a buffer in preparation for deleting items
    5637             :  *
    5638             :  * Items may be deleted from a disk page only when the caller (a) holds an
    5639             :  * exclusive lock on the buffer and (b) has observed that no other backend
    5640             :  * holds a pin on the buffer.  If there is a pin, then the other backend
    5641             :  * might have a pointer into the buffer (for example, a heapscan reference
    5642             :  * to an item --- see README for more details).  It's OK if a pin is added
    5643             :  * after the cleanup starts, however; the newly-arrived backend will be
    5644             :  * unable to look at the page until we release the exclusive lock.
    5645             :  *
    5646             :  * To implement this protocol, a would-be deleter must pin the buffer and
    5647             :  * then call LockBufferForCleanup().  LockBufferForCleanup() is similar to
    5648             :  * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE), except that it loops until
    5649             :  * it has successfully observed pin count = 1.
    5650             :  */
    5651             : void
    5652       43920 : LockBufferForCleanup(Buffer buffer)
    5653             : {
    5654             :     BufferDesc *bufHdr;
    5655       43920 :     TimestampTz waitStart = 0;
    5656       43920 :     bool        waiting = false;
    5657       43920 :     bool        logged_recovery_conflict = false;
    5658             : 
    5659             :     Assert(BufferIsPinned(buffer));
    5660             :     Assert(PinCountWaitBuf == NULL);
    5661             : 
    5662       43920 :     CheckBufferIsPinnedOnce(buffer);
    5663             : 
    5664             :     /*
    5665             :      * We do not yet need to be worried about in-progress AIOs holding a pin,
    5666             :      * as we, so far, only support doing reads via AIO and this function can
    5667             :      * only be called once the buffer is valid (i.e. no read can be in
    5668             :      * flight).
    5669             :      */
    5670             : 
    5671             :     /* Nobody else to wait for */
    5672       43920 :     if (BufferIsLocal(buffer))
    5673          32 :         return;
    5674             : 
    5675       43888 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5676             : 
    5677             :     for (;;)
    5678         120 :     {
    5679             :         uint32      buf_state;
    5680             : 
    5681             :         /* Try to acquire lock */
    5682       44008 :         LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
    5683       44008 :         buf_state = LockBufHdr(bufHdr);
    5684             : 
    5685             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    5686       44008 :         if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
    5687             :         {
    5688             :             /* Successfully acquired exclusive lock with pincount 1 */
    5689       43888 :             UnlockBufHdr(bufHdr, buf_state);
    5690             : 
    5691             :             /*
    5692             :              * Emit the log message if recovery conflict on buffer pin was
    5693             :              * resolved but the startup process waited longer than
    5694             :              * deadlock_timeout for it.
    5695             :              */
    5696       43888 :             if (logged_recovery_conflict)
    5697           4 :                 LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
    5698             :                                     waitStart, GetCurrentTimestamp(),
    5699             :                                     NULL, false);
    5700             : 
    5701       43888 :             if (waiting)
    5702             :             {
    5703             :                 /* reset ps display to remove the suffix if we added one */
    5704           4 :                 set_ps_display_remove_suffix();
    5705           4 :                 waiting = false;
    5706             :             }
    5707       43888 :             return;
    5708             :         }
    5709             :         /* Failed, so mark myself as waiting for pincount 1 */
    5710         120 :         if (buf_state & BM_PIN_COUNT_WAITER)
    5711             :         {
    5712           0 :             UnlockBufHdr(bufHdr, buf_state);
    5713           0 :             LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5714           0 :             elog(ERROR, "multiple backends attempting to wait for pincount 1");
    5715             :         }
    5716         120 :         bufHdr->wait_backend_pgprocno = MyProcNumber;
    5717         120 :         PinCountWaitBuf = bufHdr;
    5718         120 :         buf_state |= BM_PIN_COUNT_WAITER;
    5719         120 :         UnlockBufHdr(bufHdr, buf_state);
    5720         120 :         LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5721             : 
    5722             :         /* Wait to be signaled by UnpinBuffer() */
    5723         120 :         if (InHotStandby)
    5724             :         {
    5725          18 :             if (!waiting)
    5726             :             {
    5727             :                 /* adjust the process title to indicate that it's waiting */
    5728           4 :                 set_ps_display_suffix("waiting");
    5729           4 :                 waiting = true;
    5730             :             }
    5731             : 
    5732             :             /*
    5733             :              * Emit the log message if the startup process is waiting longer
    5734             :              * than deadlock_timeout for recovery conflict on buffer pin.
    5735             :              *
    5736             :              * Skip this if first time through because the startup process has
    5737             :              * not started waiting yet in this case. So, the wait start
    5738             :              * timestamp is set after this logic.
    5739             :              */
    5740          18 :             if (waitStart != 0 && !logged_recovery_conflict)
    5741             :             {
    5742           6 :                 TimestampTz now = GetCurrentTimestamp();
    5743             : 
    5744           6 :                 if (TimestampDifferenceExceeds(waitStart, now,
    5745             :                                                DeadlockTimeout))
    5746             :                 {
    5747           4 :                     LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
    5748             :                                         waitStart, now, NULL, true);
    5749           4 :                     logged_recovery_conflict = true;
    5750             :                 }
    5751             :             }
    5752             : 
    5753             :             /*
    5754             :              * Set the wait start timestamp if logging is enabled and first
    5755             :              * time through.
    5756             :              */
    5757          18 :             if (log_recovery_conflict_waits && waitStart == 0)
    5758           4 :                 waitStart = GetCurrentTimestamp();
    5759             : 
    5760             :             /* Publish the bufid that Startup process waits on */
    5761          18 :             SetStartupBufferPinWaitBufId(buffer - 1);
    5762             :             /* Set alarm and then wait to be signaled by UnpinBuffer() */
    5763          18 :             ResolveRecoveryConflictWithBufferPin();
    5764             :             /* Reset the published bufid */
    5765          18 :             SetStartupBufferPinWaitBufId(-1);
    5766             :         }
    5767             :         else
    5768         102 :             ProcWaitForSignal(WAIT_EVENT_BUFFER_PIN);
    5769             : 
    5770             :         /*
    5771             :          * Remove flag marking us as waiter. Normally this will not be set
    5772             :          * anymore, but ProcWaitForSignal() can return for other signals as
    5773             :          * well.  We take care to only reset the flag if we're the waiter, as
    5774             :          * theoretically another backend could have started waiting. That's
    5775             :          * impossible with the current usages due to table level locking, but
    5776             :          * better be safe.
    5777             :          */
    5778         120 :         buf_state = LockBufHdr(bufHdr);
    5779         120 :         if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
    5780          14 :             bufHdr->wait_backend_pgprocno == MyProcNumber)
    5781          14 :             buf_state &= ~BM_PIN_COUNT_WAITER;
    5782         120 :         UnlockBufHdr(bufHdr, buf_state);
    5783             : 
    5784         120 :         PinCountWaitBuf = NULL;
    5785             :         /* Loop back and try again */
    5786             :     }
    5787             : }
    5788             : 
    5789             : /*
    5790             :  * Check called from ProcessRecoveryConflictInterrupts() when Startup process
    5791             :  * requests cancellation of all pin holders that are blocking it.
    5792             :  */
    5793             : bool
    5794           6 : HoldingBufferPinThatDelaysRecovery(void)
    5795             : {
    5796           6 :     int         bufid = GetStartupBufferPinWaitBufId();
    5797             : 
    5798             :     /*
    5799             :      * If we get woken slowly then it's possible that the Startup process was
    5800             :      * already woken by other backends before we got here. Also possible that
    5801             :      * we get here by multiple interrupts or interrupts at inappropriate
    5802             :      * times, so make sure we do nothing if the bufid is not set.
    5803             :      */
    5804           6 :     if (bufid < 0)
    5805           2 :         return false;
    5806             : 
    5807           4 :     if (GetPrivateRefCount(bufid + 1) > 0)
    5808           4 :         return true;
    5809             : 
    5810           0 :     return false;
    5811             : }
    5812             : 
    5813             : /*
    5814             :  * ConditionalLockBufferForCleanup - as above, but don't wait to get the lock
    5815             :  *
    5816             :  * We won't loop, but just check once to see if the pin count is OK.  If
    5817             :  * not, return false with no lock held.
    5818             :  */
    5819             : bool
    5820     1320676 : ConditionalLockBufferForCleanup(Buffer buffer)
    5821             : {
    5822             :     BufferDesc *bufHdr;
    5823             :     uint32      buf_state,
    5824             :                 refcount;
    5825             : 
    5826             :     Assert(BufferIsValid(buffer));
    5827             : 
    5828             :     /* see AIO related comment in LockBufferForCleanup() */
    5829             : 
    5830     1320676 :     if (BufferIsLocal(buffer))
    5831             :     {
    5832        1608 :         refcount = LocalRefCount[-buffer - 1];
    5833             :         /* There should be exactly one pin */
    5834             :         Assert(refcount > 0);
    5835        1608 :         if (refcount != 1)
    5836          42 :             return false;
    5837             :         /* Nobody else to wait for */
    5838        1566 :         return true;
    5839             :     }
    5840             : 
    5841             :     /* There should be exactly one local pin */
    5842     1319068 :     refcount = GetPrivateRefCount(buffer);
    5843             :     Assert(refcount);
    5844     1319068 :     if (refcount != 1)
    5845         424 :         return false;
    5846             : 
    5847             :     /* Try to acquire lock */
    5848     1318644 :     if (!ConditionalLockBuffer(buffer))
    5849          78 :         return false;
    5850             : 
    5851     1318566 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5852     1318566 :     buf_state = LockBufHdr(bufHdr);
    5853     1318566 :     refcount = BUF_STATE_GET_REFCOUNT(buf_state);
    5854             : 
    5855             :     Assert(refcount > 0);
    5856     1318566 :     if (refcount == 1)
    5857             :     {
    5858             :         /* Successfully acquired exclusive lock with pincount 1 */
    5859     1318042 :         UnlockBufHdr(bufHdr, buf_state);
    5860     1318042 :         return true;
    5861             :     }
    5862             : 
    5863             :     /* Failed, so release the lock */
    5864         524 :     UnlockBufHdr(bufHdr, buf_state);
    5865         524 :     LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5866         524 :     return false;
    5867             : }
    5868             : 
    5869             : /*
    5870             :  * IsBufferCleanupOK - as above, but we already have the lock
    5871             :  *
    5872             :  * Check whether it's OK to perform cleanup on a buffer we've already
    5873             :  * locked.  If we observe that the pin count is 1, our exclusive lock
    5874             :  * happens to be a cleanup lock, and we can proceed with anything that
    5875             :  * would have been allowable had we sought a cleanup lock originally.
    5876             :  */
    5877             : bool
    5878        3300 : IsBufferCleanupOK(Buffer buffer)
    5879             : {
    5880             :     BufferDesc *bufHdr;
    5881             :     uint32      buf_state;
    5882             : 
    5883             :     Assert(BufferIsValid(buffer));
    5884             : 
    5885             :     /* see AIO related comment in LockBufferForCleanup() */
    5886             : 
    5887        3300 :     if (BufferIsLocal(buffer))
    5888             :     {
    5889             :         /* There should be exactly one pin */
    5890           0 :         if (LocalRefCount[-buffer - 1] != 1)
    5891           0 :             return false;
    5892             :         /* Nobody else to wait for */
    5893           0 :         return true;
    5894             :     }
    5895             : 
    5896             :     /* There should be exactly one local pin */
    5897        3300 :     if (GetPrivateRefCount(buffer) != 1)
    5898           0 :         return false;
    5899             : 
    5900        3300 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5901             : 
    5902             :     /* caller must hold exclusive lock on buffer */
    5903             :     Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    5904             :                                 LW_EXCLUSIVE));
    5905             : 
    5906        3300 :     buf_state = LockBufHdr(bufHdr);
    5907             : 
    5908             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    5909        3300 :     if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
    5910             :     {
    5911             :         /* pincount is OK. */
    5912        3300 :         UnlockBufHdr(bufHdr, buf_state);
    5913        3300 :         return true;
    5914             :     }
    5915             : 
    5916           0 :     UnlockBufHdr(bufHdr, buf_state);
    5917           0 :     return false;
    5918             : }
    5919             : 
    5920             : 
    5921             : /*
    5922             :  *  Functions for buffer I/O handling
    5923             :  *
    5924             :  *  Also note that these are used only for shared buffers, not local ones.
    5925             :  */
    5926             : 
    5927             : /*
    5928             :  * WaitIO -- Block until the IO_IN_PROGRESS flag on 'buf' is cleared.
    5929             :  */
    5930             : static void
    5931       14920 : WaitIO(BufferDesc *buf)
    5932             : {
    5933       14920 :     ConditionVariable *cv = BufferDescriptorGetIOCV(buf);
    5934             : 
    5935       14920 :     ConditionVariablePrepareToSleep(cv);
    5936             :     for (;;)
    5937       14822 :     {
    5938             :         uint32      buf_state;
    5939             :         PgAioWaitRef iow;
    5940             : 
    5941             :         /*
    5942             :          * It may not be necessary to acquire the spinlock to check the flag
    5943             :          * here, but since this test is essential for correctness, we'd better
    5944             :          * play it safe.
    5945             :          */
    5946       29742 :         buf_state = LockBufHdr(buf);
    5947             : 
    5948             :         /*
    5949             :          * Copy the wait reference while holding the spinlock. This protects
    5950             :          * against a concurrent TerminateBufferIO() in another backend from
    5951             :          * clearing the wref while it's being read.
    5952             :          */
    5953       29742 :         iow = buf->io_wref;
    5954       29742 :         UnlockBufHdr(buf, buf_state);
    5955             : 
    5956             :         /* no IO in progress, we don't need to wait */
    5957       29742 :         if (!(buf_state & BM_IO_IN_PROGRESS))
    5958       14920 :             break;
    5959             : 
    5960             :         /*
    5961             :          * The buffer has asynchronous IO in progress, wait for it to
    5962             :          * complete.
    5963             :          */
    5964       14822 :         if (pgaio_wref_valid(&iow))
    5965             :         {
    5966       12332 :             pgaio_wref_wait(&iow);
    5967             : 
    5968             :             /*
    5969             :              * The AIO subsystem internally uses condition variables and thus
    5970             :              * might remove this backend from the BufferDesc's CV. While that
    5971             :              * wouldn't cause a correctness issue (the first CV sleep just
    5972             :              * immediately returns if not already registered), it seems worth
    5973             :              * avoiding unnecessary loop iterations, given that we take care
    5974             :              * to do so at the start of the function.
    5975             :              */
    5976       12332 :             ConditionVariablePrepareToSleep(cv);
    5977       12332 :             continue;
    5978             :         }
    5979             : 
    5980             :         /* wait on BufferDesc->cv, e.g. for concurrent synchronous IO */
    5981        2490 :         ConditionVariableSleep(cv, WAIT_EVENT_BUFFER_IO);
    5982             :     }
    5983       14920 :     ConditionVariableCancelSleep();
    5984       14920 : }
    5985             : 
    5986             : /*
    5987             :  * StartBufferIO: begin I/O on this buffer
    5988             :  *  (Assumptions)
    5989             :  *  My process is executing no IO on this buffer
    5990             :  *  The buffer is Pinned
    5991             :  *
    5992             :  * In some scenarios multiple backends could attempt the same I/O operation
    5993             :  * concurrently.  If someone else has already started I/O on this buffer then
    5994             :  * we will wait for completion of the IO using WaitIO().
    5995             :  *
    5996             :  * Input operations are only attempted on buffers that are not BM_VALID,
    5997             :  * and output operations only on buffers that are BM_VALID and BM_DIRTY,
    5998             :  * so we can always tell if the work is already done.
    5999             :  *
    6000             :  * Returns true if we successfully marked the buffer as I/O busy,
    6001             :  * false if someone else already did the work.
    6002             :  *
    6003             :  * If nowait is true, then we don't wait for an I/O to be finished by another
    6004             :  * backend.  In that case, false indicates either that the I/O was already
    6005             :  * finished, or is still in progress.  This is useful for callers that want to
    6006             :  * find out if they can perform the I/O as part of a larger operation, without
    6007             :  * waiting for the answer or distinguishing the reasons why not.
    6008             :  */
    6009             : bool
    6010     4911060 : StartBufferIO(BufferDesc *buf, bool forInput, bool nowait)
    6011             : {
    6012             :     uint32      buf_state;
    6013             : 
    6014     4911060 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    6015             : 
    6016             :     for (;;)
    6017             :     {
    6018     4925978 :         buf_state = LockBufHdr(buf);
    6019             : 
    6020     4925978 :         if (!(buf_state & BM_IO_IN_PROGRESS))
    6021     4911052 :             break;
    6022       14926 :         UnlockBufHdr(buf, buf_state);
    6023       14926 :         if (nowait)
    6024           8 :             return false;
    6025       14918 :         WaitIO(buf);
    6026             :     }
    6027             : 
    6028             :     /* Once we get here, there is definitely no I/O active on this buffer */
    6029             : 
    6030             :     /* Check if someone else already did the I/O */
    6031     4911052 :     if (forInput ? (buf_state & BM_VALID) : !(buf_state & BM_DIRTY))
    6032             :     {
    6033       16398 :         UnlockBufHdr(buf, buf_state);
    6034       16398 :         return false;
    6035             :     }
    6036             : 
    6037     4894654 :     buf_state |= BM_IO_IN_PROGRESS;
    6038     4894654 :     UnlockBufHdr(buf, buf_state);
    6039             : 
    6040     4894654 :     ResourceOwnerRememberBufferIO(CurrentResourceOwner,
    6041             :                                   BufferDescriptorGetBuffer(buf));
    6042             : 
    6043     4894654 :     return true;
    6044             : }
    6045             : 
    6046             : /*
    6047             :  * TerminateBufferIO: release a buffer we were doing I/O on
    6048             :  *  (Assumptions)
    6049             :  *  My process is executing IO for the buffer
    6050             :  *  BM_IO_IN_PROGRESS bit is set for the buffer
    6051             :  *  The buffer is Pinned
    6052             :  *
    6053             :  * If clear_dirty is true and BM_JUST_DIRTIED is not set, we clear the
    6054             :  * buffer's BM_DIRTY flag.  This is appropriate when terminating a
    6055             :  * successful write.  The check on BM_JUST_DIRTIED is necessary to avoid
    6056             :  * marking the buffer clean if it was re-dirtied while we were writing.
    6057             :  *
    6058             :  * set_flag_bits gets ORed into the buffer's flags.  It must include
    6059             :  * BM_IO_ERROR in a failure case.  For successful completion it could
    6060             :  * be 0, or BM_VALID if we just finished reading in the page.
    6061             :  *
    6062             :  * If forget_owner is true, we release the buffer I/O from the current
    6063             :  * resource owner. (forget_owner=false is used when the resource owner itself
    6064             :  * is being released)
    6065             :  */
    6066             : void
    6067     4619434 : TerminateBufferIO(BufferDesc *buf, bool clear_dirty, uint32 set_flag_bits,
    6068             :                   bool forget_owner, bool release_aio)
    6069             : {
    6070             :     uint32      buf_state;
    6071             : 
    6072     4619434 :     buf_state = LockBufHdr(buf);
    6073             : 
    6074             :     Assert(buf_state & BM_IO_IN_PROGRESS);
    6075     4619434 :     buf_state &= ~BM_IO_IN_PROGRESS;
    6076             : 
    6077             :     /* Clear earlier errors, if this IO failed, it'll be marked again */
    6078     4619434 :     buf_state &= ~BM_IO_ERROR;
    6079             : 
    6080     4619434 :     if (clear_dirty && !(buf_state & BM_JUST_DIRTIED))
    6081     1116044 :         buf_state &= ~(BM_DIRTY | BM_CHECKPOINT_NEEDED);
    6082             : 
    6083     4619434 :     if (release_aio)
    6084             :     {
    6085             :         /* release ownership by the AIO subsystem */
    6086             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    6087     2502086 :         buf_state -= BUF_REFCOUNT_ONE;
    6088     2502086 :         pgaio_wref_clear(&buf->io_wref);
    6089             :     }
    6090             : 
    6091     4619434 :     buf_state |= set_flag_bits;
    6092     4619434 :     UnlockBufHdr(buf, buf_state);
    6093             : 
    6094     4619434 :     if (forget_owner)
    6095     2117306 :         ResourceOwnerForgetBufferIO(CurrentResourceOwner,
    6096             :                                     BufferDescriptorGetBuffer(buf));
    6097             : 
    6098     4619434 :     ConditionVariableBroadcast(BufferDescriptorGetIOCV(buf));
    6099             : 
    6100             :     /*
    6101             :      * Support LockBufferForCleanup()
    6102             :      *
    6103             :      * We may have just released the last pin other than the waiter's. In most
    6104             :      * cases, this backend holds another pin on the buffer. But, if, for
    6105             :      * example, this backend is completing an IO issued by another backend, it
    6106             :      * may be time to wake the waiter.
    6107             :      */
    6108     4619434 :     if (release_aio && (buf_state & BM_PIN_COUNT_WAITER))
    6109           0 :         WakePinCountWaiter(buf);
    6110     4619434 : }
    6111             : 
    6112             : /*
    6113             :  * AbortBufferIO: Clean up active buffer I/O after an error.
    6114             :  *
    6115             :  *  All LWLocks we might have held have been released,
    6116             :  *  but we haven't yet released buffer pins, so the buffer is still pinned.
    6117             :  *
    6118             :  *  If I/O was in progress, we always set BM_IO_ERROR, even though it's
    6119             :  *  possible the error condition wasn't related to the I/O.
    6120             :  *
    6121             :  *  Note: this does not remove the buffer I/O from the resource owner.
    6122             :  *  That's correct when we're releasing the whole resource owner, but
    6123             :  *  beware if you use this in other contexts.
    6124             :  */
    6125             : static void
    6126          30 : AbortBufferIO(Buffer buffer)
    6127             : {
    6128          30 :     BufferDesc *buf_hdr = GetBufferDescriptor(buffer - 1);
    6129             :     uint32      buf_state;
    6130             : 
    6131          30 :     buf_state = LockBufHdr(buf_hdr);
    6132             :     Assert(buf_state & (BM_IO_IN_PROGRESS | BM_TAG_VALID));
    6133             : 
    6134          30 :     if (!(buf_state & BM_VALID))
    6135             :     {
    6136             :         Assert(!(buf_state & BM_DIRTY));
    6137          30 :         UnlockBufHdr(buf_hdr, buf_state);
    6138             :     }
    6139             :     else
    6140             :     {
    6141             :         Assert(buf_state & BM_DIRTY);
    6142           0 :         UnlockBufHdr(buf_hdr, buf_state);
    6143             : 
    6144             :         /* Issue notice if this is not the first failure... */
    6145           0 :         if (buf_state & BM_IO_ERROR)
    6146             :         {
    6147             :             /* Buffer is pinned, so we can read tag without spinlock */
    6148           0 :             ereport(WARNING,
    6149             :                     (errcode(ERRCODE_IO_ERROR),
    6150             :                      errmsg("could not write block %u of %s",
    6151             :                             buf_hdr->tag.blockNum,
    6152             :                             relpathperm(BufTagGetRelFileLocator(&buf_hdr->tag),
    6153             :                                         BufTagGetForkNum(&buf_hdr->tag)).str),
    6154             :                      errdetail("Multiple failures --- write error might be permanent.")));
    6155             :         }
    6156             :     }
    6157             : 
    6158          30 :     TerminateBufferIO(buf_hdr, false, BM_IO_ERROR, false, false);
    6159          30 : }
    6160             : 
    6161             : /*
    6162             :  * Error context callback for errors occurring during shared buffer writes.
    6163             :  */
    6164             : static void
    6165          94 : shared_buffer_write_error_callback(void *arg)
    6166             : {
    6167          94 :     BufferDesc *bufHdr = (BufferDesc *) arg;
    6168             : 
    6169             :     /* Buffer is pinned, so we can read the tag without locking the spinlock */
    6170          94 :     if (bufHdr != NULL)
    6171         188 :         errcontext("writing block %u of relation \"%s\"",
    6172             :                    bufHdr->tag.blockNum,
    6173          94 :                    relpathperm(BufTagGetRelFileLocator(&bufHdr->tag),
    6174             :                                BufTagGetForkNum(&bufHdr->tag)).str);
    6175          94 : }
    6176             : 
    6177             : /*
    6178             :  * Error context callback for errors occurring during local buffer writes.
    6179             :  */
    6180             : static void
    6181           0 : local_buffer_write_error_callback(void *arg)
    6182             : {
    6183           0 :     BufferDesc *bufHdr = (BufferDesc *) arg;
    6184             : 
    6185           0 :     if (bufHdr != NULL)
    6186           0 :         errcontext("writing block %u of relation \"%s\"",
    6187             :                    bufHdr->tag.blockNum,
    6188           0 :                    relpathbackend(BufTagGetRelFileLocator(&bufHdr->tag),
    6189             :                                   MyProcNumber,
    6190             :                                   BufTagGetForkNum(&bufHdr->tag)).str);
    6191           0 : }
    6192             : 
    6193             : /*
    6194             :  * RelFileLocator qsort/bsearch comparator; see RelFileLocatorEquals.
    6195             :  */
    6196             : static int
    6197    18430980 : rlocator_comparator(const void *p1, const void *p2)
    6198             : {
    6199    18430980 :     RelFileLocator n1 = *(const RelFileLocator *) p1;
    6200    18430980 :     RelFileLocator n2 = *(const RelFileLocator *) p2;
    6201             : 
    6202    18430980 :     if (n1.relNumber < n2.relNumber)
    6203    18358248 :         return -1;
    6204       72732 :     else if (n1.relNumber > n2.relNumber)
    6205       69264 :         return 1;
    6206             : 
    6207        3468 :     if (n1.dbOid < n2.dbOid)
    6208           0 :         return -1;
    6209        3468 :     else if (n1.dbOid > n2.dbOid)
    6210           0 :         return 1;
    6211             : 
    6212        3468 :     if (n1.spcOid < n2.spcOid)
    6213           0 :         return -1;
    6214        3468 :     else if (n1.spcOid > n2.spcOid)
    6215           0 :         return 1;
    6216             :     else
    6217        3468 :         return 0;
    6218             : }
    6219             : 
    6220             : /*
    6221             :  * Lock buffer header - set BM_LOCKED in buffer state.
    6222             :  */
    6223             : uint32
    6224    73418542 : LockBufHdr(BufferDesc *desc)
    6225             : {
    6226             :     SpinDelayStatus delayStatus;
    6227             :     uint32      old_buf_state;
    6228             : 
    6229             :     Assert(!BufferIsLocal(BufferDescriptorGetBuffer(desc)));
    6230             : 
    6231    73418542 :     init_local_spin_delay(&delayStatus);
    6232             : 
    6233             :     while (true)
    6234             :     {
    6235             :         /* set BM_LOCKED flag */
    6236    73439558 :         old_buf_state = pg_atomic_fetch_or_u32(&desc->state, BM_LOCKED);
    6237             :         /* if it wasn't set before we're OK */
    6238    73439558 :         if (!(old_buf_state & BM_LOCKED))
    6239    73418542 :             break;
    6240       21016 :         perform_spin_delay(&delayStatus);
    6241             :     }
    6242    73418542 :     finish_spin_delay(&delayStatus);
    6243    73418542 :     return old_buf_state | BM_LOCKED;
    6244             : }
    6245             : 
    6246             : /*
    6247             :  * Wait until the BM_LOCKED flag isn't set anymore and return the buffer's
    6248             :  * state at that point.
    6249             :  *
    6250             :  * Obviously the buffer could be locked by the time the value is returned, so
    6251             :  * this is primarily useful in CAS style loops.
    6252             :  */
    6253             : static uint32
    6254        3388 : WaitBufHdrUnlocked(BufferDesc *buf)
    6255             : {
    6256             :     SpinDelayStatus delayStatus;
    6257             :     uint32      buf_state;
    6258             : 
    6259        3388 :     init_local_spin_delay(&delayStatus);
    6260             : 
    6261        3388 :     buf_state = pg_atomic_read_u32(&buf->state);
    6262             : 
    6263       23196 :     while (buf_state & BM_LOCKED)
    6264             :     {
    6265       19808 :         perform_spin_delay(&delayStatus);
    6266       19808 :         buf_state = pg_atomic_read_u32(&buf->state);
    6267             :     }
    6268             : 
    6269        3388 :     finish_spin_delay(&delayStatus);
    6270             : 
    6271        3388 :     return buf_state;
    6272             : }
    6273             : 
    6274             : /*
    6275             :  * BufferTag comparator.
    6276             :  */
    6277             : static inline int
    6278           0 : buffertag_comparator(const BufferTag *ba, const BufferTag *bb)
    6279             : {
    6280             :     int         ret;
    6281             :     RelFileLocator rlocatora;
    6282             :     RelFileLocator rlocatorb;
    6283             : 
    6284           0 :     rlocatora = BufTagGetRelFileLocator(ba);
    6285           0 :     rlocatorb = BufTagGetRelFileLocator(bb);
    6286             : 
    6287           0 :     ret = rlocator_comparator(&rlocatora, &rlocatorb);
    6288             : 
    6289           0 :     if (ret != 0)
    6290           0 :         return ret;
    6291             : 
    6292           0 :     if (BufTagGetForkNum(ba) < BufTagGetForkNum(bb))
    6293           0 :         return -1;
    6294           0 :     if (BufTagGetForkNum(ba) > BufTagGetForkNum(bb))
    6295           0 :         return 1;
    6296             : 
    6297           0 :     if (ba->blockNum < bb->blockNum)
    6298           0 :         return -1;
    6299           0 :     if (ba->blockNum > bb->blockNum)
    6300           0 :         return 1;
    6301             : 
    6302           0 :     return 0;
    6303             : }
    6304             : 
    6305             : /*
    6306             :  * Comparator determining the writeout order in a checkpoint.
    6307             :  *
    6308             :  * It is important that tablespaces are compared first, the logic balancing
    6309             :  * writes between tablespaces relies on it.
    6310             :  */
    6311             : static inline int
    6312     5918144 : ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b)
    6313             : {
    6314             :     /* compare tablespace */
    6315     5918144 :     if (a->tsId < b->tsId)
    6316       16704 :         return -1;
    6317     5901440 :     else if (a->tsId > b->tsId)
    6318       55210 :         return 1;
    6319             :     /* compare relation */
    6320     5846230 :     if (a->relNumber < b->relNumber)
    6321     1654884 :         return -1;
    6322     4191346 :     else if (a->relNumber > b->relNumber)
    6323     1573842 :         return 1;
    6324             :     /* compare fork */
    6325     2617504 :     else if (a->forkNum < b->forkNum)
    6326      109464 :         return -1;
    6327     2508040 :     else if (a->forkNum > b->forkNum)
    6328      115530 :         return 1;
    6329             :     /* compare block number */
    6330     2392510 :     else if (a->blockNum < b->blockNum)
    6331     1174116 :         return -1;
    6332     1218394 :     else if (a->blockNum > b->blockNum)
    6333     1145530 :         return 1;
    6334             :     /* equal page IDs are unlikely, but not impossible */
    6335       72864 :     return 0;
    6336             : }
    6337             : 
    6338             : /*
    6339             :  * Comparator for a Min-Heap over the per-tablespace checkpoint completion
    6340             :  * progress.
    6341             :  */
    6342             : static int
    6343      481652 : ts_ckpt_progress_comparator(Datum a, Datum b, void *arg)
    6344             : {
    6345      481652 :     CkptTsStatus *sa = (CkptTsStatus *) DatumGetPointer(a);
    6346      481652 :     CkptTsStatus *sb = (CkptTsStatus *) DatumGetPointer(b);
    6347             : 
    6348             :     /* we want a min-heap, so return 1 for the a < b */
    6349      481652 :     if (sa->progress < sb->progress)
    6350      431730 :         return 1;
    6351       49922 :     else if (sa->progress == sb->progress)
    6352        1612 :         return 0;
    6353             :     else
    6354       48310 :         return -1;
    6355             : }
    6356             : 
    6357             : /*
    6358             :  * Initialize a writeback context, discarding potential previous state.
    6359             :  *
    6360             :  * *max_pending is a pointer instead of an immediate value, so the coalesce
    6361             :  * limits can easily changed by the GUC mechanism, and so calling code does
    6362             :  * not have to check the current configuration. A value of 0 means that no
    6363             :  * writeback control will be performed.
    6364             :  */
    6365             : void
    6366        5324 : WritebackContextInit(WritebackContext *context, int *max_pending)
    6367             : {
    6368             :     Assert(*max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
    6369             : 
    6370        5324 :     context->max_pending = max_pending;
    6371        5324 :     context->nr_pending = 0;
    6372        5324 : }
    6373             : 
    6374             : /*
    6375             :  * Add buffer to list of pending writeback requests.
    6376             :  */
    6377             : void
    6378     1105698 : ScheduleBufferTagForWriteback(WritebackContext *wb_context, IOContext io_context,
    6379             :                               BufferTag *tag)
    6380             : {
    6381             :     PendingWriteback *pending;
    6382             : 
    6383             :     /*
    6384             :      * As pg_flush_data() doesn't do anything with fsync disabled, there's no
    6385             :      * point in tracking in that case.
    6386             :      */
    6387     1105698 :     if (io_direct_flags & IO_DIRECT_DATA ||
    6388     1104654 :         !enableFsync)
    6389     1105698 :         return;
    6390             : 
    6391             :     /*
    6392             :      * Add buffer to the pending writeback array, unless writeback control is
    6393             :      * disabled.
    6394             :      */
    6395           0 :     if (*wb_context->max_pending > 0)
    6396             :     {
    6397             :         Assert(*wb_context->max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
    6398             : 
    6399           0 :         pending = &wb_context->pending_writebacks[wb_context->nr_pending++];
    6400             : 
    6401           0 :         pending->tag = *tag;
    6402             :     }
    6403             : 
    6404             :     /*
    6405             :      * Perform pending flushes if the writeback limit is exceeded. This
    6406             :      * includes the case where previously an item has been added, but control
    6407             :      * is now disabled.
    6408             :      */
    6409           0 :     if (wb_context->nr_pending >= *wb_context->max_pending)
    6410           0 :         IssuePendingWritebacks(wb_context, io_context);
    6411             : }
    6412             : 
    6413             : #define ST_SORT sort_pending_writebacks
    6414             : #define ST_ELEMENT_TYPE PendingWriteback
    6415             : #define ST_COMPARE(a, b) buffertag_comparator(&a->tag, &b->tag)
    6416             : #define ST_SCOPE static
    6417             : #define ST_DEFINE
    6418             : #include "lib/sort_template.h"
    6419             : 
    6420             : /*
    6421             :  * Issue all pending writeback requests, previously scheduled with
    6422             :  * ScheduleBufferTagForWriteback, to the OS.
    6423             :  *
    6424             :  * Because this is only used to improve the OSs IO scheduling we try to never
    6425             :  * error out - it's just a hint.
    6426             :  */
    6427             : void
    6428        2086 : IssuePendingWritebacks(WritebackContext *wb_context, IOContext io_context)
    6429             : {
    6430             :     instr_time  io_start;
    6431             :     int         i;
    6432             : 
    6433        2086 :     if (wb_context->nr_pending == 0)
    6434        2086 :         return;
    6435             : 
    6436             :     /*
    6437             :      * Executing the writes in-order can make them a lot faster, and allows to
    6438             :      * merge writeback requests to consecutive blocks into larger writebacks.
    6439             :      */
    6440           0 :     sort_pending_writebacks(wb_context->pending_writebacks,
    6441           0 :                             wb_context->nr_pending);
    6442             : 
    6443           0 :     io_start = pgstat_prepare_io_time(track_io_timing);
    6444             : 
    6445             :     /*
    6446             :      * Coalesce neighbouring writes, but nothing else. For that we iterate
    6447             :      * through the, now sorted, array of pending flushes, and look forward to
    6448             :      * find all neighbouring (or identical) writes.
    6449             :      */
    6450           0 :     for (i = 0; i < wb_context->nr_pending; i++)
    6451             :     {
    6452             :         PendingWriteback *cur;
    6453             :         PendingWriteback *next;
    6454             :         SMgrRelation reln;
    6455             :         int         ahead;
    6456             :         BufferTag   tag;
    6457             :         RelFileLocator currlocator;
    6458           0 :         Size        nblocks = 1;
    6459             : 
    6460           0 :         cur = &wb_context->pending_writebacks[i];
    6461           0 :         tag = cur->tag;
    6462           0 :         currlocator = BufTagGetRelFileLocator(&tag);
    6463             : 
    6464             :         /*
    6465             :          * Peek ahead, into following writeback requests, to see if they can
    6466             :          * be combined with the current one.
    6467             :          */
    6468           0 :         for (ahead = 0; i + ahead + 1 < wb_context->nr_pending; ahead++)
    6469             :         {
    6470             : 
    6471           0 :             next = &wb_context->pending_writebacks[i + ahead + 1];
    6472             : 
    6473             :             /* different file, stop */
    6474           0 :             if (!RelFileLocatorEquals(currlocator,
    6475           0 :                                       BufTagGetRelFileLocator(&next->tag)) ||
    6476           0 :                 BufTagGetForkNum(&cur->tag) != BufTagGetForkNum(&next->tag))
    6477             :                 break;
    6478             : 
    6479             :             /* ok, block queued twice, skip */
    6480           0 :             if (cur->tag.blockNum == next->tag.blockNum)
    6481           0 :                 continue;
    6482             : 
    6483             :             /* only merge consecutive writes */
    6484           0 :             if (cur->tag.blockNum + 1 != next->tag.blockNum)
    6485           0 :                 break;
    6486             : 
    6487           0 :             nblocks++;
    6488           0 :             cur = next;
    6489             :         }
    6490             : 
    6491           0 :         i += ahead;
    6492             : 
    6493             :         /* and finally tell the kernel to write the data to storage */
    6494           0 :         reln = smgropen(currlocator, INVALID_PROC_NUMBER);
    6495           0 :         smgrwriteback(reln, BufTagGetForkNum(&tag), tag.blockNum, nblocks);
    6496             :     }
    6497             : 
    6498             :     /*
    6499             :      * Assume that writeback requests are only issued for buffers containing
    6500             :      * blocks of permanent relations.
    6501             :      */
    6502           0 :     pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
    6503           0 :                             IOOP_WRITEBACK, io_start, wb_context->nr_pending, 0);
    6504             : 
    6505           0 :     wb_context->nr_pending = 0;
    6506             : }
    6507             : 
    6508             : /* ResourceOwner callbacks */
    6509             : 
    6510             : static void
    6511          30 : ResOwnerReleaseBufferIO(Datum res)
    6512             : {
    6513          30 :     Buffer      buffer = DatumGetInt32(res);
    6514             : 
    6515          30 :     AbortBufferIO(buffer);
    6516          30 : }
    6517             : 
    6518             : static char *
    6519           0 : ResOwnerPrintBufferIO(Datum res)
    6520             : {
    6521           0 :     Buffer      buffer = DatumGetInt32(res);
    6522             : 
    6523           0 :     return psprintf("lost track of buffer IO on buffer %d", buffer);
    6524             : }
    6525             : 
    6526             : static void
    6527       14812 : ResOwnerReleaseBufferPin(Datum res)
    6528             : {
    6529       14812 :     Buffer      buffer = DatumGetInt32(res);
    6530             : 
    6531             :     /* Like ReleaseBuffer, but don't call ResourceOwnerForgetBuffer */
    6532       14812 :     if (!BufferIsValid(buffer))
    6533           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    6534             : 
    6535       14812 :     if (BufferIsLocal(buffer))
    6536        5970 :         UnpinLocalBufferNoOwner(buffer);
    6537             :     else
    6538        8842 :         UnpinBufferNoOwner(GetBufferDescriptor(buffer - 1));
    6539       14812 : }
    6540             : 
    6541             : static char *
    6542           0 : ResOwnerPrintBufferPin(Datum res)
    6543             : {
    6544           0 :     return DebugPrintBufferRefcount(DatumGetInt32(res));
    6545             : }
    6546             : 
    6547             : /*
    6548             :  * Helper function to evict unpinned buffer whose buffer header lock is
    6549             :  * already acquired.
    6550             :  */
    6551             : static bool
    6552        4276 : EvictUnpinnedBufferInternal(BufferDesc *desc, bool *buffer_flushed)
    6553             : {
    6554             :     uint32      buf_state;
    6555             :     bool        result;
    6556             : 
    6557        4276 :     *buffer_flushed = false;
    6558             : 
    6559        4276 :     buf_state = pg_atomic_read_u32(&(desc->state));
    6560             :     Assert(buf_state & BM_LOCKED);
    6561             : 
    6562        4276 :     if ((buf_state & BM_VALID) == 0)
    6563             :     {
    6564           0 :         UnlockBufHdr(desc, buf_state);
    6565           0 :         return false;
    6566             :     }
    6567             : 
    6568             :     /* Check that it's not pinned already. */
    6569        4276 :     if (BUF_STATE_GET_REFCOUNT(buf_state) > 0)
    6570             :     {
    6571           0 :         UnlockBufHdr(desc, buf_state);
    6572           0 :         return false;
    6573             :     }
    6574             : 
    6575        4276 :     PinBuffer_Locked(desc);     /* releases spinlock */
    6576             : 
    6577             :     /* If it was dirty, try to clean it once. */
    6578        4276 :     if (buf_state & BM_DIRTY)
    6579             :     {
    6580        1938 :         LWLockAcquire(BufferDescriptorGetContentLock(desc), LW_SHARED);
    6581        1938 :         FlushBuffer(desc, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    6582        1938 :         *buffer_flushed = true;
    6583        1938 :         LWLockRelease(BufferDescriptorGetContentLock(desc));
    6584             :     }
    6585             : 
    6586             :     /* This will return false if it becomes dirty or someone else pins it. */
    6587        4276 :     result = InvalidateVictimBuffer(desc);
    6588             : 
    6589        4276 :     UnpinBuffer(desc);
    6590             : 
    6591        4276 :     return result;
    6592             : }
    6593             : 
    6594             : /*
    6595             :  * Try to evict the current block in a shared buffer.
    6596             :  *
    6597             :  * This function is intended for testing/development use only!
    6598             :  *
    6599             :  * To succeed, the buffer must not be pinned on entry, so if the caller had a
    6600             :  * particular block in mind, it might already have been replaced by some other
    6601             :  * block by the time this function runs.  It's also unpinned on return, so the
    6602             :  * buffer might be occupied again by the time control is returned, potentially
    6603             :  * even by the same block.  This inherent raciness without other interlocking
    6604             :  * makes the function unsuitable for non-testing usage.
    6605             :  *
    6606             :  * *buffer_flushed is set to true if the buffer was dirty and has been
    6607             :  * flushed, false otherwise.  However, *buffer_flushed=true does not
    6608             :  * necessarily mean that we flushed the buffer, it could have been flushed by
    6609             :  * someone else.
    6610             :  *
    6611             :  * Returns true if the buffer was valid and it has now been made invalid.
    6612             :  * Returns false if it wasn't valid, if it couldn't be evicted due to a pin,
    6613             :  * or if the buffer becomes dirty again while we're trying to write it out.
    6614             :  */
    6615             : bool
    6616         280 : EvictUnpinnedBuffer(Buffer buf, bool *buffer_flushed)
    6617             : {
    6618             :     BufferDesc *desc;
    6619             : 
    6620             :     Assert(BufferIsValid(buf) && !BufferIsLocal(buf));
    6621             : 
    6622             :     /* Make sure we can pin the buffer. */
    6623         280 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    6624         280 :     ReservePrivateRefCountEntry();
    6625             : 
    6626         280 :     desc = GetBufferDescriptor(buf - 1);
    6627         280 :     LockBufHdr(desc);
    6628             : 
    6629         280 :     return EvictUnpinnedBufferInternal(desc, buffer_flushed);
    6630             : }
    6631             : 
    6632             : /*
    6633             :  * Try to evict all the shared buffers.
    6634             :  *
    6635             :  * This function is intended for testing/development use only! See
    6636             :  * EvictUnpinnedBuffer().
    6637             :  *
    6638             :  * The buffers_* parameters are mandatory and indicate the total count of
    6639             :  * buffers that:
    6640             :  * - buffers_evicted - were evicted
    6641             :  * - buffers_flushed - were flushed
    6642             :  * - buffers_skipped - could not be evicted
    6643             :  */
    6644             : void
    6645           2 : EvictAllUnpinnedBuffers(int32 *buffers_evicted, int32 *buffers_flushed,
    6646             :                         int32 *buffers_skipped)
    6647             : {
    6648           2 :     *buffers_evicted = 0;
    6649           2 :     *buffers_skipped = 0;
    6650           2 :     *buffers_flushed = 0;
    6651             : 
    6652       32770 :     for (int buf = 1; buf <= NBuffers; buf++)
    6653             :     {
    6654       32768 :         BufferDesc *desc = GetBufferDescriptor(buf - 1);
    6655             :         uint32      buf_state;
    6656             :         bool        buffer_flushed;
    6657             : 
    6658       32768 :         buf_state = pg_atomic_read_u32(&desc->state);
    6659       32768 :         if (!(buf_state & BM_VALID))
    6660       28772 :             continue;
    6661             : 
    6662        3996 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    6663        3996 :         ReservePrivateRefCountEntry();
    6664             : 
    6665        3996 :         LockBufHdr(desc);
    6666             : 
    6667        3996 :         if (EvictUnpinnedBufferInternal(desc, &buffer_flushed))
    6668        3996 :             (*buffers_evicted)++;
    6669             :         else
    6670           0 :             (*buffers_skipped)++;
    6671             : 
    6672        3996 :         if (buffer_flushed)
    6673        1900 :             (*buffers_flushed)++;
    6674             :     }
    6675           2 : }
    6676             : 
    6677             : /*
    6678             :  * Try to evict all the shared buffers containing provided relation's pages.
    6679             :  *
    6680             :  * This function is intended for testing/development use only! See
    6681             :  * EvictUnpinnedBuffer().
    6682             :  *
    6683             :  * The caller must hold at least AccessShareLock on the relation to prevent
    6684             :  * the relation from being dropped.
    6685             :  *
    6686             :  * The buffers_* parameters are mandatory and indicate the total count of
    6687             :  * buffers that:
    6688             :  * - buffers_evicted - were evicted
    6689             :  * - buffers_flushed - were flushed
    6690             :  * - buffers_skipped - could not be evicted
    6691             :  */
    6692             : void
    6693           2 : EvictRelUnpinnedBuffers(Relation rel, int32 *buffers_evicted,
    6694             :                         int32 *buffers_flushed, int32 *buffers_skipped)
    6695             : {
    6696             :     Assert(!RelationUsesLocalBuffers(rel));
    6697             : 
    6698           2 :     *buffers_skipped = 0;
    6699           2 :     *buffers_evicted = 0;
    6700           2 :     *buffers_flushed = 0;
    6701             : 
    6702       32770 :     for (int buf = 1; buf <= NBuffers; buf++)
    6703             :     {
    6704       32768 :         BufferDesc *desc = GetBufferDescriptor(buf - 1);
    6705       32768 :         uint32      buf_state = pg_atomic_read_u32(&(desc->state));
    6706             :         bool        buffer_flushed;
    6707             : 
    6708             :         /* An unlocked precheck should be safe and saves some cycles. */
    6709       32768 :         if ((buf_state & BM_VALID) == 0 ||
    6710          54 :             !BufTagMatchesRelFileLocator(&desc->tag, &rel->rd_locator))
    6711       32768 :             continue;
    6712             : 
    6713             :         /* Make sure we can pin the buffer. */
    6714           0 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    6715           0 :         ReservePrivateRefCountEntry();
    6716             : 
    6717           0 :         buf_state = LockBufHdr(desc);
    6718             : 
    6719             :         /* recheck, could have changed without the lock */
    6720           0 :         if ((buf_state & BM_VALID) == 0 ||
    6721           0 :             !BufTagMatchesRelFileLocator(&desc->tag, &rel->rd_locator))
    6722             :         {
    6723           0 :             UnlockBufHdr(desc, buf_state);
    6724           0 :             continue;
    6725             :         }
    6726             : 
    6727           0 :         if (EvictUnpinnedBufferInternal(desc, &buffer_flushed))
    6728           0 :             (*buffers_evicted)++;
    6729             :         else
    6730           0 :             (*buffers_skipped)++;
    6731             : 
    6732           0 :         if (buffer_flushed)
    6733           0 :             (*buffers_flushed)++;
    6734             :     }
    6735           2 : }
    6736             : 
    6737             : /*
    6738             :  * Generic implementation of the AIO handle staging callback for readv/writev
    6739             :  * on local/shared buffers.
    6740             :  *
    6741             :  * Each readv/writev can target multiple buffers. The buffers have already
    6742             :  * been registered with the IO handle.
    6743             :  *
    6744             :  * To make the IO ready for execution ("staging"), we need to ensure that the
    6745             :  * targeted buffers are in an appropriate state while the IO is ongoing. For
    6746             :  * that the AIO subsystem needs to have its own buffer pin, otherwise an error
    6747             :  * in this backend could lead to this backend's buffer pin being released as
    6748             :  * part of error handling, which in turn could lead to the buffer being
    6749             :  * replaced while IO is ongoing.
    6750             :  */
    6751             : static pg_attribute_always_inline void
    6752     2464496 : buffer_stage_common(PgAioHandle *ioh, bool is_write, bool is_temp)
    6753             : {
    6754             :     uint64     *io_data;
    6755             :     uint8       handle_data_len;
    6756             :     PgAioWaitRef io_ref;
    6757     2464496 :     BufferTag   first PG_USED_FOR_ASSERTS_ONLY = {0};
    6758             : 
    6759     2464496 :     io_data = pgaio_io_get_handle_data(ioh, &handle_data_len);
    6760             : 
    6761     2464496 :     pgaio_io_get_wref(ioh, &io_ref);
    6762             : 
    6763             :     /* iterate over all buffers affected by the vectored readv/writev */
    6764     5258614 :     for (int i = 0; i < handle_data_len; i++)
    6765             :     {
    6766     2794118 :         Buffer      buffer = (Buffer) io_data[i];
    6767     2794118 :         BufferDesc *buf_hdr = is_temp ?
    6768       16812 :             GetLocalBufferDescriptor(-buffer - 1)
    6769     2794118 :             : GetBufferDescriptor(buffer - 1);
    6770             :         uint32      buf_state;
    6771             : 
    6772             :         /*
    6773             :          * Check that all the buffers are actually ones that could conceivably
    6774             :          * be done in one IO, i.e. are sequential. This is the last
    6775             :          * buffer-aware code before IO is actually executed and confusion
    6776             :          * about which buffers are targeted by IO can be hard to debug, making
    6777             :          * it worth doing extra-paranoid checks.
    6778             :          */
    6779     2794118 :         if (i == 0)
    6780     2464496 :             first = buf_hdr->tag;
    6781             :         else
    6782             :         {
    6783             :             Assert(buf_hdr->tag.relNumber == first.relNumber);
    6784             :             Assert(buf_hdr->tag.blockNum == first.blockNum + i);
    6785             :         }
    6786             : 
    6787     2794118 :         if (is_temp)
    6788       16812 :             buf_state = pg_atomic_read_u32(&buf_hdr->state);
    6789             :         else
    6790     2777306 :             buf_state = LockBufHdr(buf_hdr);
    6791             : 
    6792             :         /* verify the buffer is in the expected state */
    6793             :         Assert(buf_state & BM_TAG_VALID);
    6794             :         if (is_write)
    6795             :         {
    6796             :             Assert(buf_state & BM_VALID);
    6797             :             Assert(buf_state & BM_DIRTY);
    6798             :         }
    6799             :         else
    6800             :         {
    6801             :             Assert(!(buf_state & BM_VALID));
    6802             :             Assert(!(buf_state & BM_DIRTY));
    6803             :         }
    6804             : 
    6805             :         /* temp buffers don't use BM_IO_IN_PROGRESS */
    6806     2794118 :         if (!is_temp)
    6807             :             Assert(buf_state & BM_IO_IN_PROGRESS);
    6808             : 
    6809             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) >= 1);
    6810             : 
    6811             :         /*
    6812             :          * Reflect that the buffer is now owned by the AIO subsystem.
    6813             :          *
    6814             :          * For local buffers: This can't be done just via LocalRefCount, as
    6815             :          * one might initially think, as this backend could error out while
    6816             :          * AIO is still in progress, releasing all the pins by the backend
    6817             :          * itself.
    6818             :          *
    6819             :          * This pin is released again in TerminateBufferIO().
    6820             :          */
    6821     2794118 :         buf_state += BUF_REFCOUNT_ONE;
    6822     2794118 :         buf_hdr->io_wref = io_ref;
    6823             : 
    6824     2794118 :         if (is_temp)
    6825       16812 :             pg_atomic_unlocked_write_u32(&buf_hdr->state, buf_state);
    6826             :         else
    6827     2777306 :             UnlockBufHdr(buf_hdr, buf_state);
    6828             : 
    6829             :         /*
    6830             :          * Ensure the content lock that prevents buffer modifications while
    6831             :          * the buffer is being written out is not released early due to an
    6832             :          * error.
    6833             :          */
    6834     2794118 :         if (is_write && !is_temp)
    6835             :         {
    6836             :             LWLock     *content_lock;
    6837             : 
    6838           0 :             content_lock = BufferDescriptorGetContentLock(buf_hdr);
    6839             : 
    6840             :             Assert(LWLockHeldByMe(content_lock));
    6841             : 
    6842             :             /*
    6843             :              * Lock is now owned by AIO subsystem.
    6844             :              */
    6845           0 :             LWLockDisown(content_lock);
    6846             :         }
    6847             : 
    6848             :         /*
    6849             :          * Stop tracking this buffer via the resowner - the AIO system now
    6850             :          * keeps track.
    6851             :          */
    6852     2794118 :         if (!is_temp)
    6853     2777306 :             ResourceOwnerForgetBufferIO(CurrentResourceOwner, buffer);
    6854             :     }
    6855     2464496 : }
    6856             : 
    6857             : /*
    6858             :  * Decode readv errors as encoded by buffer_readv_encode_error().
    6859             :  */
    6860             : static inline void
    6861         698 : buffer_readv_decode_error(PgAioResult result,
    6862             :                           bool *zeroed_any,
    6863             :                           bool *ignored_any,
    6864             :                           uint8 *zeroed_or_error_count,
    6865             :                           uint8 *checkfail_count,
    6866             :                           uint8 *first_off)
    6867             : {
    6868         698 :     uint32      rem_error = result.error_data;
    6869             : 
    6870             :     /* see static asserts in buffer_readv_encode_error */
    6871             : #define READV_COUNT_BITS    7
    6872             : #define READV_COUNT_MASK    ((1 << READV_COUNT_BITS) - 1)
    6873             : 
    6874         698 :     *zeroed_any = rem_error & 1;
    6875         698 :     rem_error >>= 1;
    6876             : 
    6877         698 :     *ignored_any = rem_error & 1;
    6878         698 :     rem_error >>= 1;
    6879             : 
    6880         698 :     *zeroed_or_error_count = rem_error & READV_COUNT_MASK;
    6881         698 :     rem_error >>= READV_COUNT_BITS;
    6882             : 
    6883         698 :     *checkfail_count = rem_error & READV_COUNT_MASK;
    6884         698 :     rem_error >>= READV_COUNT_BITS;
    6885             : 
    6886         698 :     *first_off = rem_error & READV_COUNT_MASK;
    6887         698 :     rem_error >>= READV_COUNT_BITS;
    6888         698 : }
    6889             : 
    6890             : /*
    6891             :  * Helper to encode errors for buffer_readv_complete()
    6892             :  *
    6893             :  * Errors are encoded as follows:
    6894             :  * - bit 0 indicates whether any page was zeroed (1) or not (0)
    6895             :  * - bit 1 indicates whether any checksum failure was ignored (1) or not (0)
    6896             :  * - next READV_COUNT_BITS bits indicate the number of errored or zeroed pages
    6897             :  * - next READV_COUNT_BITS bits indicate the number of checksum failures
    6898             :  * - next READV_COUNT_BITS bits indicate the first offset of the first page
    6899             :  *   that was errored or zeroed or, if no errors/zeroes, the first ignored
    6900             :  *   checksum
    6901             :  */
    6902             : static inline void
    6903         384 : buffer_readv_encode_error(PgAioResult *result,
    6904             :                           bool is_temp,
    6905             :                           bool zeroed_any,
    6906             :                           bool ignored_any,
    6907             :                           uint8 error_count,
    6908             :                           uint8 zeroed_count,
    6909             :                           uint8 checkfail_count,
    6910             :                           uint8 first_error_off,
    6911             :                           uint8 first_zeroed_off,
    6912             :                           uint8 first_ignored_off)
    6913             : {
    6914             : 
    6915         384 :     uint8       shift = 0;
    6916         384 :     uint8       zeroed_or_error_count =
    6917             :         error_count > 0 ? error_count : zeroed_count;
    6918             :     uint8       first_off;
    6919             : 
    6920             :     StaticAssertStmt(PG_IOV_MAX <= 1 << READV_COUNT_BITS,
    6921             :                      "PG_IOV_MAX is bigger than reserved space for error data");
    6922             :     StaticAssertStmt((1 + 1 + 3 * READV_COUNT_BITS) <= PGAIO_RESULT_ERROR_BITS,
    6923             :                      "PGAIO_RESULT_ERROR_BITS is insufficient for buffer_readv");
    6924             : 
    6925             :     /*
    6926             :      * We only have space to encode one offset - but luckily that's good
    6927             :      * enough. If there is an error, the error is the interesting offset, same
    6928             :      * with a zeroed buffer vs an ignored buffer.
    6929             :      */
    6930         384 :     if (error_count > 0)
    6931         188 :         first_off = first_error_off;
    6932         196 :     else if (zeroed_count > 0)
    6933         160 :         first_off = first_zeroed_off;
    6934             :     else
    6935          36 :         first_off = first_ignored_off;
    6936             : 
    6937             :     Assert(!zeroed_any || error_count == 0);
    6938             : 
    6939         384 :     result->error_data = 0;
    6940             : 
    6941         384 :     result->error_data |= zeroed_any << shift;
    6942         384 :     shift += 1;
    6943             : 
    6944         384 :     result->error_data |= ignored_any << shift;
    6945         384 :     shift += 1;
    6946             : 
    6947         384 :     result->error_data |= ((uint32) zeroed_or_error_count) << shift;
    6948         384 :     shift += READV_COUNT_BITS;
    6949             : 
    6950         384 :     result->error_data |= ((uint32) checkfail_count) << shift;
    6951         384 :     shift += READV_COUNT_BITS;
    6952             : 
    6953         384 :     result->error_data |= ((uint32) first_off) << shift;
    6954         384 :     shift += READV_COUNT_BITS;
    6955             : 
    6956         384 :     result->id = is_temp ? PGAIO_HCB_LOCAL_BUFFER_READV :
    6957             :         PGAIO_HCB_SHARED_BUFFER_READV;
    6958             : 
    6959         384 :     if (error_count > 0)
    6960         188 :         result->status = PGAIO_RS_ERROR;
    6961             :     else
    6962         196 :         result->status = PGAIO_RS_WARNING;
    6963             : 
    6964             :     /*
    6965             :      * The encoding is complicated enough to warrant cross-checking it against
    6966             :      * the decode function.
    6967             :      */
    6968             : #ifdef USE_ASSERT_CHECKING
    6969             :     {
    6970             :         bool        zeroed_any_2,
    6971             :                     ignored_any_2;
    6972             :         uint8       zeroed_or_error_count_2,
    6973             :                     checkfail_count_2,
    6974             :                     first_off_2;
    6975             : 
    6976             :         buffer_readv_decode_error(*result,
    6977             :                                   &zeroed_any_2, &ignored_any_2,
    6978             :                                   &zeroed_or_error_count_2,
    6979             :                                   &checkfail_count_2,
    6980             :                                   &first_off_2);
    6981             :         Assert(zeroed_any == zeroed_any_2);
    6982             :         Assert(ignored_any == ignored_any_2);
    6983             :         Assert(zeroed_or_error_count == zeroed_or_error_count_2);
    6984             :         Assert(checkfail_count == checkfail_count_2);
    6985             :         Assert(first_off == first_off_2);
    6986             :     }
    6987             : #endif
    6988             : 
    6989             : #undef READV_COUNT_BITS
    6990             : #undef READV_COUNT_MASK
    6991         384 : }
    6992             : 
    6993             : /*
    6994             :  * Helper for AIO readv completion callbacks, supporting both shared and temp
    6995             :  * buffers. Gets called once for each buffer in a multi-page read.
    6996             :  */
    6997             : static pg_attribute_always_inline void
    6998     2518898 : buffer_readv_complete_one(PgAioTargetData *td, uint8 buf_off, Buffer buffer,
    6999             :                           uint8 flags, bool failed, bool is_temp,
    7000             :                           bool *buffer_invalid,
    7001             :                           bool *failed_checksum,
    7002             :                           bool *ignored_checksum,
    7003             :                           bool *zeroed_buffer)
    7004             : {
    7005     2518898 :     BufferDesc *buf_hdr = is_temp ?
    7006       16812 :         GetLocalBufferDescriptor(-buffer - 1)
    7007     2518898 :         : GetBufferDescriptor(buffer - 1);
    7008     2518898 :     BufferTag   tag = buf_hdr->tag;
    7009     2518898 :     char       *bufdata = BufferGetBlock(buffer);
    7010             :     uint32      set_flag_bits;
    7011             :     int         piv_flags;
    7012             : 
    7013             :     /* check that the buffer is in the expected state for a read */
    7014             : #ifdef USE_ASSERT_CHECKING
    7015             :     {
    7016             :         uint32      buf_state = pg_atomic_read_u32(&buf_hdr->state);
    7017             : 
    7018             :         Assert(buf_state & BM_TAG_VALID);
    7019             :         Assert(!(buf_state & BM_VALID));
    7020             :         /* temp buffers don't use BM_IO_IN_PROGRESS */
    7021             :         if (!is_temp)
    7022             :             Assert(buf_state & BM_IO_IN_PROGRESS);
    7023             :         Assert(!(buf_state & BM_DIRTY));
    7024             :     }
    7025             : #endif
    7026             : 
    7027     2518898 :     *buffer_invalid = false;
    7028     2518898 :     *failed_checksum = false;
    7029     2518898 :     *ignored_checksum = false;
    7030     2518898 :     *zeroed_buffer = false;
    7031             : 
    7032             :     /*
    7033             :      * We ask PageIsVerified() to only log the message about checksum errors,
    7034             :      * as the completion might be run in any backend (or IO workers). We will
    7035             :      * report checksum errors in buffer_readv_report().
    7036             :      */
    7037     2518898 :     piv_flags = PIV_LOG_LOG;
    7038             : 
    7039             :     /* the local zero_damaged_pages may differ from the definer's */
    7040     2518898 :     if (flags & READ_BUFFERS_IGNORE_CHECKSUM_FAILURES)
    7041          76 :         piv_flags |= PIV_IGNORE_CHECKSUM_FAILURE;
    7042             : 
    7043             :     /* Check for garbage data. */
    7044     2518898 :     if (!failed)
    7045             :     {
    7046             :         /*
    7047             :          * If the buffer is not currently pinned by this backend, e.g. because
    7048             :          * we're completing this IO after an error, the buffer data will have
    7049             :          * been marked as inaccessible when the buffer was unpinned. The AIO
    7050             :          * subsystem holds a pin, but that doesn't prevent the buffer from
    7051             :          * having been marked as inaccessible. The completion might also be
    7052             :          * executed in a different process.
    7053             :          */
    7054             : #ifdef USE_VALGRIND
    7055             :         if (!BufferIsPinned(buffer))
    7056             :             VALGRIND_MAKE_MEM_DEFINED(bufdata, BLCKSZ);
    7057             : #endif
    7058             : 
    7059     2518840 :         if (!PageIsVerified((Page) bufdata, tag.blockNum, piv_flags,
    7060             :                             failed_checksum))
    7061             :         {
    7062         192 :             if (flags & READ_BUFFERS_ZERO_ON_ERROR)
    7063             :             {
    7064          92 :                 memset(bufdata, 0, BLCKSZ);
    7065          92 :                 *zeroed_buffer = true;
    7066             :             }
    7067             :             else
    7068             :             {
    7069         100 :                 *buffer_invalid = true;
    7070             :                 /* mark buffer as having failed */
    7071         100 :                 failed = true;
    7072             :             }
    7073             :         }
    7074     2518648 :         else if (*failed_checksum)
    7075          24 :             *ignored_checksum = true;
    7076             : 
    7077             :         /* undo what we did above */
    7078             : #ifdef USE_VALGRIND
    7079             :         if (!BufferIsPinned(buffer))
    7080             :             VALGRIND_MAKE_MEM_NOACCESS(bufdata, BLCKSZ);
    7081             : #endif
    7082             : 
    7083             :         /*
    7084             :          * Immediately log a message about the invalid page, but only to the
    7085             :          * server log. The reason to do so immediately is that this may be
    7086             :          * executed in a different backend than the one that originated the
    7087             :          * request. The reason to do so immediately is that the originator
    7088             :          * might not process the query result immediately (because it is busy
    7089             :          * doing another part of query processing) or at all (e.g. if it was
    7090             :          * cancelled or errored out due to another IO also failing). The
    7091             :          * definer of the IO will emit an ERROR or WARNING when processing the
    7092             :          * IO's results
    7093             :          *
    7094             :          * To avoid duplicating the code to emit these log messages, we reuse
    7095             :          * buffer_readv_report().
    7096             :          */
    7097     2518840 :         if (*buffer_invalid || *failed_checksum || *zeroed_buffer)
    7098             :         {
    7099         216 :             PgAioResult result_one = {0};
    7100             : 
    7101         216 :             buffer_readv_encode_error(&result_one, is_temp,
    7102         216 :                                       *zeroed_buffer,
    7103         216 :                                       *ignored_checksum,
    7104         216 :                                       *buffer_invalid,
    7105         216 :                                       *zeroed_buffer ? 1 : 0,
    7106         216 :                                       *failed_checksum ? 1 : 0,
    7107             :                                       buf_off, buf_off, buf_off);
    7108         216 :             pgaio_result_report(result_one, td, LOG_SERVER_ONLY);
    7109             :         }
    7110             :     }
    7111             : 
    7112             :     /* Terminate I/O and set BM_VALID. */
    7113     2518898 :     set_flag_bits = failed ? BM_IO_ERROR : BM_VALID;
    7114     2518898 :     if (is_temp)
    7115       16812 :         TerminateLocalBufferIO(buf_hdr, false, set_flag_bits, true);
    7116             :     else
    7117     2502086 :         TerminateBufferIO(buf_hdr, false, set_flag_bits, false, true);
    7118             : 
    7119             :     /*
    7120             :      * Call the BUFFER_READ_DONE tracepoint in the callback, even though the
    7121             :      * callback may not be executed in the same backend that called
    7122             :      * BUFFER_READ_START. The alternative would be to defer calling the
    7123             :      * tracepoint to a later point (e.g. the local completion callback for
    7124             :      * shared buffer reads), which seems even less helpful.
    7125             :      */
    7126             :     TRACE_POSTGRESQL_BUFFER_READ_DONE(tag.forkNum,
    7127             :                                       tag.blockNum,
    7128             :                                       tag.spcOid,
    7129             :                                       tag.dbOid,
    7130             :                                       tag.relNumber,
    7131             :                                       is_temp ? MyProcNumber : INVALID_PROC_NUMBER,
    7132             :                                       false);
    7133     2518898 : }
    7134             : 
    7135             : /*
    7136             :  * Perform completion handling of a single AIO read. This read may cover
    7137             :  * multiple blocks / buffers.
    7138             :  *
    7139             :  * Shared between shared and local buffers, to reduce code duplication.
    7140             :  */
    7141             : static pg_attribute_always_inline PgAioResult
    7142     2255356 : buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
    7143             :                       uint8 cb_data, bool is_temp)
    7144             : {
    7145     2255356 :     PgAioResult result = prior_result;
    7146     2255356 :     PgAioTargetData *td = pgaio_io_get_target_data(ioh);
    7147     2255356 :     uint8       first_error_off = 0;
    7148     2255356 :     uint8       first_zeroed_off = 0;
    7149     2255356 :     uint8       first_ignored_off = 0;
    7150     2255356 :     uint8       error_count = 0;
    7151     2255356 :     uint8       zeroed_count = 0;
    7152     2255356 :     uint8       ignored_count = 0;
    7153     2255356 :     uint8       checkfail_count = 0;
    7154             :     uint64     *io_data;
    7155             :     uint8       handle_data_len;
    7156             : 
    7157             :     if (is_temp)
    7158             :     {
    7159             :         Assert(td->smgr.is_temp);
    7160             :         Assert(pgaio_io_get_owner(ioh) == MyProcNumber);
    7161             :     }
    7162             :     else
    7163             :         Assert(!td->smgr.is_temp);
    7164             : 
    7165             :     /*
    7166             :      * Iterate over all the buffers affected by this IO and call the
    7167             :      * per-buffer completion function for each buffer.
    7168             :      */
    7169     2255356 :     io_data = pgaio_io_get_handle_data(ioh, &handle_data_len);
    7170     4774254 :     for (uint8 buf_off = 0; buf_off < handle_data_len; buf_off++)
    7171             :     {
    7172     2518898 :         Buffer      buf = io_data[buf_off];
    7173             :         bool        failed;
    7174     2518898 :         bool        failed_verification = false;
    7175     2518898 :         bool        failed_checksum = false;
    7176     2518898 :         bool        zeroed_buffer = false;
    7177     2518898 :         bool        ignored_checksum = false;
    7178             : 
    7179             :         Assert(BufferIsValid(buf));
    7180             : 
    7181             :         /*
    7182             :          * If the entire I/O failed on a lower-level, each buffer needs to be
    7183             :          * marked as failed. In case of a partial read, the first few buffers
    7184             :          * may be ok.
    7185             :          */
    7186     2518898 :         failed =
    7187     2518898 :             prior_result.status == PGAIO_RS_ERROR
    7188     2518898 :             || prior_result.result <= buf_off;
    7189             : 
    7190     2518898 :         buffer_readv_complete_one(td, buf_off, buf, cb_data, failed, is_temp,
    7191             :                                   &failed_verification,
    7192             :                                   &failed_checksum,
    7193             :                                   &ignored_checksum,
    7194             :                                   &zeroed_buffer);
    7195             : 
    7196             :         /*
    7197             :          * Track information about the number of different kinds of error
    7198             :          * conditions across all pages, as there can be multiple pages failing
    7199             :          * verification as part of one IO.
    7200             :          */
    7201     2518898 :         if (failed_verification && !zeroed_buffer && error_count++ == 0)
    7202          88 :             first_error_off = buf_off;
    7203     2518898 :         if (zeroed_buffer && zeroed_count++ == 0)
    7204          68 :             first_zeroed_off = buf_off;
    7205     2518898 :         if (ignored_checksum && ignored_count++ == 0)
    7206          20 :             first_ignored_off = buf_off;
    7207     2518898 :         if (failed_checksum)
    7208          64 :             checkfail_count++;
    7209             :     }
    7210             : 
    7211             :     /*
    7212             :      * If the smgr read succeeded [partially] and page verification failed for
    7213             :      * some of the pages, adjust the IO's result state appropriately.
    7214             :      */
    7215     2255356 :     if (prior_result.status != PGAIO_RS_ERROR &&
    7216     2255250 :         (error_count > 0 || ignored_count > 0 || zeroed_count > 0))
    7217             :     {
    7218         168 :         buffer_readv_encode_error(&result, is_temp,
    7219             :                                   zeroed_count > 0, ignored_count > 0,
    7220             :                                   error_count, zeroed_count, checkfail_count,
    7221             :                                   first_error_off, first_zeroed_off,
    7222             :                                   first_ignored_off);
    7223         168 :         pgaio_result_report(result, td, DEBUG1);
    7224             :     }
    7225             : 
    7226             :     /*
    7227             :      * For shared relations this reporting is done in
    7228             :      * shared_buffer_readv_complete_local().
    7229             :      */
    7230     2255356 :     if (is_temp && checkfail_count > 0)
    7231           4 :         pgstat_report_checksum_failures_in_db(td->smgr.rlocator.dbOid,
    7232             :                                               checkfail_count);
    7233             : 
    7234     2255356 :     return result;
    7235             : }
    7236             : 
    7237             : /*
    7238             :  * AIO error reporting callback for aio_shared_buffer_readv_cb and
    7239             :  * aio_local_buffer_readv_cb.
    7240             :  *
    7241             :  * The error is encoded / decoded in buffer_readv_encode_error() /
    7242             :  * buffer_readv_decode_error().
    7243             :  */
    7244             : static void
    7245         544 : buffer_readv_report(PgAioResult result, const PgAioTargetData *td,
    7246             :                     int elevel)
    7247             : {
    7248         544 :     int         nblocks = td->smgr.nblocks;
    7249         544 :     BlockNumber first = td->smgr.blockNum;
    7250         544 :     BlockNumber last = first + nblocks - 1;
    7251         544 :     ProcNumber  errProc =
    7252         544 :         td->smgr.is_temp ? MyProcNumber : INVALID_PROC_NUMBER;
    7253             :     RelPathStr  rpath =
    7254         544 :         relpathbackend(td->smgr.rlocator, errProc, td->smgr.forkNum);
    7255             :     bool        zeroed_any,
    7256             :                 ignored_any;
    7257             :     uint8       zeroed_or_error_count,
    7258             :                 checkfail_count,
    7259             :                 first_off;
    7260             :     uint8       affected_count;
    7261             :     const char *msg_one,
    7262             :                *msg_mult,
    7263             :                *det_mult,
    7264             :                *hint_mult;
    7265             : 
    7266         544 :     buffer_readv_decode_error(result, &zeroed_any, &ignored_any,
    7267             :                               &zeroed_or_error_count,
    7268             :                               &checkfail_count,
    7269             :                               &first_off);
    7270             : 
    7271             :     /*
    7272             :      * Treat a read that had both zeroed buffers *and* ignored checksums as a
    7273             :      * special case, it's too irregular to be emitted the same way as the
    7274             :      * other cases.
    7275             :      */
    7276         544 :     if (zeroed_any && ignored_any)
    7277             :     {
    7278             :         Assert(zeroed_any && ignored_any);
    7279             :         Assert(nblocks > 1); /* same block can't be both zeroed and ignored */
    7280             :         Assert(result.status != PGAIO_RS_ERROR);
    7281           8 :         affected_count = zeroed_or_error_count;
    7282             : 
    7283           8 :         ereport(elevel,
    7284             :                 errcode(ERRCODE_DATA_CORRUPTED),
    7285             :                 errmsg("zeroing %u page(s) and ignoring %u checksum failure(s) among blocks %u..%u of relation \"%s\"",
    7286             :                        affected_count, checkfail_count, first, last, rpath.str),
    7287             :                 affected_count > 1 ?
    7288             :                 errdetail("Block %u held the first zeroed page.",
    7289             :                           first + first_off) : 0,
    7290             :                 errhint_plural("See server log for details about the other %d invalid block.",
    7291             :                                "See server log for details about the other %d invalid blocks.",
    7292             :                                affected_count + checkfail_count - 1,
    7293             :                                affected_count + checkfail_count - 1));
    7294           8 :         return;
    7295             :     }
    7296             : 
    7297             :     /*
    7298             :      * The other messages are highly repetitive. To avoid duplicating a long
    7299             :      * and complicated ereport(), gather the translated format strings
    7300             :      * separately and then do one common ereport.
    7301             :      */
    7302         536 :     if (result.status == PGAIO_RS_ERROR)
    7303             :     {
    7304             :         Assert(!zeroed_any);    /* can't have invalid pages when zeroing them */
    7305         272 :         affected_count = zeroed_or_error_count;
    7306         272 :         msg_one = _("invalid page in block %u of relation \"%s\"");
    7307         272 :         msg_mult = _("%u invalid pages among blocks %u..%u of relation \"%s\"");
    7308         272 :         det_mult = _("Block %u held the first invalid page.");
    7309         272 :         hint_mult = _("See server log for the other %u invalid block(s).");
    7310             :     }
    7311         264 :     else if (zeroed_any && !ignored_any)
    7312             :     {
    7313         216 :         affected_count = zeroed_or_error_count;
    7314         216 :         msg_one = _("invalid page in block %u of relation \"%s\"; zeroing out page");
    7315         216 :         msg_mult = _("zeroing out %u invalid pages among blocks %u..%u of relation \"%s\"");
    7316         216 :         det_mult = _("Block %u held the first zeroed page.");
    7317         216 :         hint_mult = _("See server log for the other %u zeroed block(s).");
    7318             :     }
    7319          48 :     else if (!zeroed_any && ignored_any)
    7320             :     {
    7321          48 :         affected_count = checkfail_count;
    7322          48 :         msg_one = _("ignoring checksum failure in block %u of relation \"%s\"");
    7323          48 :         msg_mult = _("ignoring %u checksum failures among blocks %u..%u of relation \"%s\"");
    7324          48 :         det_mult = _("Block %u held the first ignored page.");
    7325          48 :         hint_mult = _("See server log for the other %u ignored block(s).");
    7326             :     }
    7327             :     else
    7328           0 :         pg_unreachable();
    7329             : 
    7330         536 :     ereport(elevel,
    7331             :             errcode(ERRCODE_DATA_CORRUPTED),
    7332             :             affected_count == 1 ?
    7333             :             errmsg_internal(msg_one, first + first_off, rpath.str) :
    7334             :             errmsg_internal(msg_mult, affected_count, first, last, rpath.str),
    7335             :             affected_count > 1 ? errdetail_internal(det_mult, first + first_off) : 0,
    7336             :             affected_count > 1 ? errhint_internal(hint_mult, affected_count - 1) : 0);
    7337             : }
    7338             : 
    7339             : static void
    7340     2460890 : shared_buffer_readv_stage(PgAioHandle *ioh, uint8 cb_data)
    7341             : {
    7342     2460890 :     buffer_stage_common(ioh, false, false);
    7343     2460890 : }
    7344             : 
    7345             : static PgAioResult
    7346     2251750 : shared_buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
    7347             :                              uint8 cb_data)
    7348             : {
    7349     2251750 :     return buffer_readv_complete(ioh, prior_result, cb_data, false);
    7350             : }
    7351             : 
    7352             : /*
    7353             :  * We need a backend-local completion callback for shared buffers, to be able
    7354             :  * to report checksum errors correctly. Unfortunately that can only safely
    7355             :  * happen if the reporting backend has previously called
    7356             :  * pgstat_prepare_report_checksum_failure(), which we can only guarantee in
    7357             :  * the backend that started the IO. Hence this callback.
    7358             :  */
    7359             : static PgAioResult
    7360     2460890 : shared_buffer_readv_complete_local(PgAioHandle *ioh, PgAioResult prior_result,
    7361             :                                    uint8 cb_data)
    7362             : {
    7363             :     bool        zeroed_any,
    7364             :                 ignored_any;
    7365             :     uint8       zeroed_or_error_count,
    7366             :                 checkfail_count,
    7367             :                 first_off;
    7368             : 
    7369     2460890 :     if (prior_result.status == PGAIO_RS_OK)
    7370     2460736 :         return prior_result;
    7371             : 
    7372         154 :     buffer_readv_decode_error(prior_result,
    7373             :                               &zeroed_any,
    7374             :                               &ignored_any,
    7375             :                               &zeroed_or_error_count,
    7376             :                               &checkfail_count,
    7377             :                               &first_off);
    7378             : 
    7379         154 :     if (checkfail_count)
    7380             :     {
    7381          48 :         PgAioTargetData *td = pgaio_io_get_target_data(ioh);
    7382             : 
    7383          48 :         pgstat_report_checksum_failures_in_db(td->smgr.rlocator.dbOid,
    7384             :                                               checkfail_count);
    7385             :     }
    7386             : 
    7387         154 :     return prior_result;
    7388             : }
    7389             : 
    7390             : static void
    7391        3606 : local_buffer_readv_stage(PgAioHandle *ioh, uint8 cb_data)
    7392             : {
    7393        3606 :     buffer_stage_common(ioh, false, true);
    7394        3606 : }
    7395             : 
    7396             : static PgAioResult
    7397        3606 : local_buffer_readv_complete(PgAioHandle *ioh, PgAioResult prior_result,
    7398             :                             uint8 cb_data)
    7399             : {
    7400        3606 :     return buffer_readv_complete(ioh, prior_result, cb_data, true);
    7401             : }
    7402             : 
    7403             : /* readv callback is passed READ_BUFFERS_* flags as callback data */
    7404             : const PgAioHandleCallbacks aio_shared_buffer_readv_cb = {
    7405             :     .stage = shared_buffer_readv_stage,
    7406             :     .complete_shared = shared_buffer_readv_complete,
    7407             :     /* need a local callback to report checksum failures */
    7408             :     .complete_local = shared_buffer_readv_complete_local,
    7409             :     .report = buffer_readv_report,
    7410             : };
    7411             : 
    7412             : /* readv callback is passed READ_BUFFERS_* flags as callback data */
    7413             : const PgAioHandleCallbacks aio_local_buffer_readv_cb = {
    7414             :     .stage = local_buffer_readv_stage,
    7415             : 
    7416             :     /*
    7417             :      * Note that this, in contrast to the shared_buffers case, uses
    7418             :      * complete_local, as only the issuing backend has access to the required
    7419             :      * datastructures. This is important in case the IO completion may be
    7420             :      * consumed incidentally by another backend.
    7421             :      */
    7422             :     .complete_local = local_buffer_readv_complete,
    7423             :     .report = buffer_readv_report,
    7424             : };

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