LCOV - code coverage report
Current view: top level - src/backend/storage/buffer - bufmgr.c (source / functions) Hit Total Coverage
Test: PostgreSQL 17devel Lines: 1375 1518 90.6 %
Date: 2024-05-19 07:11:14 Functions: 87 94 92.6 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * bufmgr.c
       4             :  *    buffer manager interface routines
       5             :  *
       6             :  * Portions Copyright (c) 1996-2024, 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             : #include "catalog/storage.h"
      44             : #include "catalog/storage_xlog.h"
      45             : #include "executor/instrument.h"
      46             : #include "lib/binaryheap.h"
      47             : #include "miscadmin.h"
      48             : #include "pg_trace.h"
      49             : #include "pgstat.h"
      50             : #include "postmaster/bgwriter.h"
      51             : #include "storage/buf_internals.h"
      52             : #include "storage/bufmgr.h"
      53             : #include "storage/fd.h"
      54             : #include "storage/ipc.h"
      55             : #include "storage/lmgr.h"
      56             : #include "storage/proc.h"
      57             : #include "storage/smgr.h"
      58             : #include "storage/standby.h"
      59             : #include "utils/memdebug.h"
      60             : #include "utils/ps_status.h"
      61             : #include "utils/rel.h"
      62             : #include "utils/resowner.h"
      63             : #include "utils/timestamp.h"
      64             : 
      65             : 
      66             : /* Note: these two macros only work on shared buffers, not local ones! */
      67             : #define BufHdrGetBlock(bufHdr)  ((Block) (BufferBlocks + ((Size) (bufHdr)->buf_id) * BLCKSZ))
      68             : #define BufferGetLSN(bufHdr)    (PageGetLSN(BufHdrGetBlock(bufHdr)))
      69             : 
      70             : /* Note: this macro only works on local buffers, not shared ones! */
      71             : #define LocalBufHdrGetBlock(bufHdr) \
      72             :     LocalBufferBlockPointers[-((bufHdr)->buf_id + 2)]
      73             : 
      74             : /* Bits in SyncOneBuffer's return value */
      75             : #define BUF_WRITTEN             0x01
      76             : #define BUF_REUSABLE            0x02
      77             : 
      78             : #define RELS_BSEARCH_THRESHOLD      20
      79             : 
      80             : /*
      81             :  * This is the size (in the number of blocks) above which we scan the
      82             :  * entire buffer pool to remove the buffers for all the pages of relation
      83             :  * being dropped. For the relations with size below this threshold, we find
      84             :  * the buffers by doing lookups in BufMapping table.
      85             :  */
      86             : #define BUF_DROP_FULL_SCAN_THRESHOLD        (uint64) (NBuffers / 32)
      87             : 
      88             : typedef struct PrivateRefCountEntry
      89             : {
      90             :     Buffer      buffer;
      91             :     int32       refcount;
      92             : } PrivateRefCountEntry;
      93             : 
      94             : /* 64 bytes, about the size of a cache line on common systems */
      95             : #define REFCOUNT_ARRAY_ENTRIES 8
      96             : 
      97             : /*
      98             :  * Status of buffers to checkpoint for a particular tablespace, used
      99             :  * internally in BufferSync.
     100             :  */
     101             : typedef struct CkptTsStatus
     102             : {
     103             :     /* oid of the tablespace */
     104             :     Oid         tsId;
     105             : 
     106             :     /*
     107             :      * Checkpoint progress for this tablespace. To make progress comparable
     108             :      * between tablespaces the progress is, for each tablespace, measured as a
     109             :      * number between 0 and the total number of to-be-checkpointed pages. Each
     110             :      * page checkpointed in this tablespace increments this space's progress
     111             :      * by progress_slice.
     112             :      */
     113             :     float8      progress;
     114             :     float8      progress_slice;
     115             : 
     116             :     /* number of to-be checkpointed pages in this tablespace */
     117             :     int         num_to_scan;
     118             :     /* already processed pages in this tablespace */
     119             :     int         num_scanned;
     120             : 
     121             :     /* current offset in CkptBufferIds for this tablespace */
     122             :     int         index;
     123             : } CkptTsStatus;
     124             : 
     125             : /*
     126             :  * Type for array used to sort SMgrRelations
     127             :  *
     128             :  * FlushRelationsAllBuffers shares the same comparator function with
     129             :  * DropRelationsAllBuffers. Pointer to this struct and RelFileLocator must be
     130             :  * compatible.
     131             :  */
     132             : typedef struct SMgrSortArray
     133             : {
     134             :     RelFileLocator rlocator;    /* This must be the first member */
     135             :     SMgrRelation srel;
     136             : } SMgrSortArray;
     137             : 
     138             : /* GUC variables */
     139             : bool        zero_damaged_pages = false;
     140             : int         bgwriter_lru_maxpages = 100;
     141             : double      bgwriter_lru_multiplier = 2.0;
     142             : bool        track_io_timing = false;
     143             : 
     144             : /*
     145             :  * How many buffers PrefetchBuffer callers should try to stay ahead of their
     146             :  * ReadBuffer calls by.  Zero means "never prefetch".  This value is only used
     147             :  * for buffers not belonging to tablespaces that have their
     148             :  * effective_io_concurrency parameter set.
     149             :  */
     150             : int         effective_io_concurrency = DEFAULT_EFFECTIVE_IO_CONCURRENCY;
     151             : 
     152             : /*
     153             :  * Like effective_io_concurrency, but used by maintenance code paths that might
     154             :  * benefit from a higher setting because they work on behalf of many sessions.
     155             :  * Overridden by the tablespace setting of the same name.
     156             :  */
     157             : int         maintenance_io_concurrency = DEFAULT_MAINTENANCE_IO_CONCURRENCY;
     158             : 
     159             : /*
     160             :  * Limit on how many blocks should be handled in single I/O operations.
     161             :  * StartReadBuffers() callers should respect it, as should other operations
     162             :  * that call smgr APIs directly.
     163             :  */
     164             : int         io_combine_limit = DEFAULT_IO_COMBINE_LIMIT;
     165             : 
     166             : /*
     167             :  * GUC variables about triggering kernel writeback for buffers written; OS
     168             :  * dependent defaults are set via the GUC mechanism.
     169             :  */
     170             : int         checkpoint_flush_after = DEFAULT_CHECKPOINT_FLUSH_AFTER;
     171             : int         bgwriter_flush_after = DEFAULT_BGWRITER_FLUSH_AFTER;
     172             : int         backend_flush_after = DEFAULT_BACKEND_FLUSH_AFTER;
     173             : 
     174             : /* local state for LockBufferForCleanup */
     175             : static BufferDesc *PinCountWaitBuf = NULL;
     176             : 
     177             : /*
     178             :  * Backend-Private refcount management:
     179             :  *
     180             :  * Each buffer also has a private refcount that keeps track of the number of
     181             :  * times the buffer is pinned in the current process.  This is so that the
     182             :  * shared refcount needs to be modified only once if a buffer is pinned more
     183             :  * than once by an individual backend.  It's also used to check that no buffers
     184             :  * are still pinned at the end of transactions and when exiting.
     185             :  *
     186             :  *
     187             :  * To avoid - as we used to - requiring an array with NBuffers entries to keep
     188             :  * track of local buffers, we use a small sequentially searched array
     189             :  * (PrivateRefCountArray) and an overflow hash table (PrivateRefCountHash) to
     190             :  * keep track of backend local pins.
     191             :  *
     192             :  * Until no more than REFCOUNT_ARRAY_ENTRIES buffers are pinned at once, all
     193             :  * refcounts are kept track of in the array; after that, new array entries
     194             :  * displace old ones into the hash table. That way a frequently used entry
     195             :  * can't get "stuck" in the hashtable while infrequent ones clog the array.
     196             :  *
     197             :  * Note that in most scenarios the number of pinned buffers will not exceed
     198             :  * REFCOUNT_ARRAY_ENTRIES.
     199             :  *
     200             :  *
     201             :  * To enter a buffer into the refcount tracking mechanism first reserve a free
     202             :  * entry using ReservePrivateRefCountEntry() and then later, if necessary,
     203             :  * fill it with NewPrivateRefCountEntry(). That split lets us avoid doing
     204             :  * memory allocations in NewPrivateRefCountEntry() which can be important
     205             :  * because in some scenarios it's called with a spinlock held...
     206             :  */
     207             : static struct PrivateRefCountEntry PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES];
     208             : static HTAB *PrivateRefCountHash = NULL;
     209             : static int32 PrivateRefCountOverflowed = 0;
     210             : static uint32 PrivateRefCountClock = 0;
     211             : static PrivateRefCountEntry *ReservedRefCountEntry = NULL;
     212             : 
     213             : static void ReservePrivateRefCountEntry(void);
     214             : static PrivateRefCountEntry *NewPrivateRefCountEntry(Buffer buffer);
     215             : static PrivateRefCountEntry *GetPrivateRefCountEntry(Buffer buffer, bool do_move);
     216             : static inline int32 GetPrivateRefCount(Buffer buffer);
     217             : static void ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref);
     218             : 
     219             : /* ResourceOwner callbacks to hold in-progress I/Os and buffer pins */
     220             : static void ResOwnerReleaseBufferIO(Datum res);
     221             : static char *ResOwnerPrintBufferIO(Datum res);
     222             : static void ResOwnerReleaseBufferPin(Datum res);
     223             : static char *ResOwnerPrintBufferPin(Datum res);
     224             : 
     225             : const ResourceOwnerDesc buffer_io_resowner_desc =
     226             : {
     227             :     .name = "buffer io",
     228             :     .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
     229             :     .release_priority = RELEASE_PRIO_BUFFER_IOS,
     230             :     .ReleaseResource = ResOwnerReleaseBufferIO,
     231             :     .DebugPrint = ResOwnerPrintBufferIO
     232             : };
     233             : 
     234             : const ResourceOwnerDesc buffer_pin_resowner_desc =
     235             : {
     236             :     .name = "buffer pin",
     237             :     .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
     238             :     .release_priority = RELEASE_PRIO_BUFFER_PINS,
     239             :     .ReleaseResource = ResOwnerReleaseBufferPin,
     240             :     .DebugPrint = ResOwnerPrintBufferPin
     241             : };
     242             : 
     243             : /*
     244             :  * Ensure that the PrivateRefCountArray has sufficient space to store one more
     245             :  * entry. This has to be called before using NewPrivateRefCountEntry() to fill
     246             :  * a new entry - but it's perfectly fine to not use a reserved entry.
     247             :  */
     248             : static void
     249    99026088 : ReservePrivateRefCountEntry(void)
     250             : {
     251             :     /* Already reserved (or freed), nothing to do */
     252    99026088 :     if (ReservedRefCountEntry != NULL)
     253    92363726 :         return;
     254             : 
     255             :     /*
     256             :      * First search for a free entry the array, that'll be sufficient in the
     257             :      * majority of cases.
     258             :      */
     259             :     {
     260             :         int         i;
     261             : 
     262    16169892 :         for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
     263             :         {
     264             :             PrivateRefCountEntry *res;
     265             : 
     266    16005066 :             res = &PrivateRefCountArray[i];
     267             : 
     268    16005066 :             if (res->buffer == InvalidBuffer)
     269             :             {
     270     6497536 :                 ReservedRefCountEntry = res;
     271     6497536 :                 return;
     272             :             }
     273             :         }
     274             :     }
     275             : 
     276             :     /*
     277             :      * No luck. All array entries are full. Move one array entry into the hash
     278             :      * table.
     279             :      */
     280             :     {
     281             :         /*
     282             :          * Move entry from the current clock position in the array into the
     283             :          * hashtable. Use that slot.
     284             :          */
     285             :         PrivateRefCountEntry *hashent;
     286             :         bool        found;
     287             : 
     288             :         /* select victim slot */
     289      164826 :         ReservedRefCountEntry =
     290      164826 :             &PrivateRefCountArray[PrivateRefCountClock++ % REFCOUNT_ARRAY_ENTRIES];
     291             : 
     292             :         /* Better be used, otherwise we shouldn't get here. */
     293             :         Assert(ReservedRefCountEntry->buffer != InvalidBuffer);
     294             : 
     295             :         /* enter victim array entry into hashtable */
     296      164826 :         hashent = hash_search(PrivateRefCountHash,
     297      164826 :                               &(ReservedRefCountEntry->buffer),
     298             :                               HASH_ENTER,
     299             :                               &found);
     300             :         Assert(!found);
     301      164826 :         hashent->refcount = ReservedRefCountEntry->refcount;
     302             : 
     303             :         /* clear the now free array slot */
     304      164826 :         ReservedRefCountEntry->buffer = InvalidBuffer;
     305      164826 :         ReservedRefCountEntry->refcount = 0;
     306             : 
     307      164826 :         PrivateRefCountOverflowed++;
     308             :     }
     309             : }
     310             : 
     311             : /*
     312             :  * Fill a previously reserved refcount entry.
     313             :  */
     314             : static PrivateRefCountEntry *
     315    89765352 : NewPrivateRefCountEntry(Buffer buffer)
     316             : {
     317             :     PrivateRefCountEntry *res;
     318             : 
     319             :     /* only allowed to be called when a reservation has been made */
     320             :     Assert(ReservedRefCountEntry != NULL);
     321             : 
     322             :     /* use up the reserved entry */
     323    89765352 :     res = ReservedRefCountEntry;
     324    89765352 :     ReservedRefCountEntry = NULL;
     325             : 
     326             :     /* and fill it */
     327    89765352 :     res->buffer = buffer;
     328    89765352 :     res->refcount = 0;
     329             : 
     330    89765352 :     return res;
     331             : }
     332             : 
     333             : /*
     334             :  * Return the PrivateRefCount entry for the passed buffer.
     335             :  *
     336             :  * Returns NULL if a buffer doesn't have a refcount entry. Otherwise, if
     337             :  * do_move is true, and the entry resides in the hashtable the entry is
     338             :  * optimized for frequent access by moving it to the array.
     339             :  */
     340             : static PrivateRefCountEntry *
     341   219969082 : GetPrivateRefCountEntry(Buffer buffer, bool do_move)
     342             : {
     343             :     PrivateRefCountEntry *res;
     344             :     int         i;
     345             : 
     346             :     Assert(BufferIsValid(buffer));
     347             :     Assert(!BufferIsLocal(buffer));
     348             : 
     349             :     /*
     350             :      * First search for references in the array, that'll be sufficient in the
     351             :      * majority of cases.
     352             :      */
     353  1045269234 :     for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
     354             :     {
     355   958784080 :         res = &PrivateRefCountArray[i];
     356             : 
     357   958784080 :         if (res->buffer == buffer)
     358   133483928 :             return res;
     359             :     }
     360             : 
     361             :     /*
     362             :      * By here we know that the buffer, if already pinned, isn't residing in
     363             :      * the array.
     364             :      *
     365             :      * Only look up the buffer in the hashtable if we've previously overflowed
     366             :      * into it.
     367             :      */
     368    86485154 :     if (PrivateRefCountOverflowed == 0)
     369    85905556 :         return NULL;
     370             : 
     371      579598 :     res = hash_search(PrivateRefCountHash, &buffer, HASH_FIND, NULL);
     372             : 
     373      579598 :     if (res == NULL)
     374      414114 :         return NULL;
     375      165484 :     else if (!do_move)
     376             :     {
     377             :         /* caller doesn't want us to move the hash entry into the array */
     378      150876 :         return res;
     379             :     }
     380             :     else
     381             :     {
     382             :         /* move buffer from hashtable into the free array slot */
     383             :         bool        found;
     384             :         PrivateRefCountEntry *free;
     385             : 
     386             :         /* Ensure there's a free array slot */
     387       14608 :         ReservePrivateRefCountEntry();
     388             : 
     389             :         /* Use up the reserved slot */
     390             :         Assert(ReservedRefCountEntry != NULL);
     391       14608 :         free = ReservedRefCountEntry;
     392       14608 :         ReservedRefCountEntry = NULL;
     393             :         Assert(free->buffer == InvalidBuffer);
     394             : 
     395             :         /* and fill it */
     396       14608 :         free->buffer = buffer;
     397       14608 :         free->refcount = res->refcount;
     398             : 
     399             :         /* delete from hashtable */
     400       14608 :         hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
     401             :         Assert(found);
     402             :         Assert(PrivateRefCountOverflowed > 0);
     403       14608 :         PrivateRefCountOverflowed--;
     404             : 
     405       14608 :         return free;
     406             :     }
     407             : }
     408             : 
     409             : /*
     410             :  * Returns how many times the passed buffer is pinned by this backend.
     411             :  *
     412             :  * Only works for shared memory buffers!
     413             :  */
     414             : static inline int32
     415     4090640 : GetPrivateRefCount(Buffer buffer)
     416             : {
     417             :     PrivateRefCountEntry *ref;
     418             : 
     419             :     Assert(BufferIsValid(buffer));
     420             :     Assert(!BufferIsLocal(buffer));
     421             : 
     422             :     /*
     423             :      * Not moving the entry - that's ok for the current users, but we might
     424             :      * want to change this one day.
     425             :      */
     426     4090640 :     ref = GetPrivateRefCountEntry(buffer, false);
     427             : 
     428     4090640 :     if (ref == NULL)
     429      895752 :         return 0;
     430     3194888 :     return ref->refcount;
     431             : }
     432             : 
     433             : /*
     434             :  * Release resources used to track the reference count of a buffer which we no
     435             :  * longer have pinned and don't want to pin again immediately.
     436             :  */
     437             : static void
     438    89765352 : ForgetPrivateRefCountEntry(PrivateRefCountEntry *ref)
     439             : {
     440             :     Assert(ref->refcount == 0);
     441             : 
     442    89765352 :     if (ref >= &PrivateRefCountArray[0] &&
     443             :         ref < &PrivateRefCountArray[REFCOUNT_ARRAY_ENTRIES])
     444             :     {
     445    89615134 :         ref->buffer = InvalidBuffer;
     446             : 
     447             :         /*
     448             :          * Mark the just used entry as reserved - in many scenarios that
     449             :          * allows us to avoid ever having to search the array/hash for free
     450             :          * entries.
     451             :          */
     452    89615134 :         ReservedRefCountEntry = ref;
     453             :     }
     454             :     else
     455             :     {
     456             :         bool        found;
     457      150218 :         Buffer      buffer = ref->buffer;
     458             : 
     459      150218 :         hash_search(PrivateRefCountHash, &buffer, HASH_REMOVE, &found);
     460             :         Assert(found);
     461             :         Assert(PrivateRefCountOverflowed > 0);
     462      150218 :         PrivateRefCountOverflowed--;
     463             :     }
     464    89765352 : }
     465             : 
     466             : /*
     467             :  * BufferIsPinned
     468             :  *      True iff the buffer is pinned (also checks for valid buffer number).
     469             :  *
     470             :  *      NOTE: what we check here is that *this* backend holds a pin on
     471             :  *      the buffer.  We do not care whether some other backend does.
     472             :  */
     473             : #define BufferIsPinned(bufnum) \
     474             : ( \
     475             :     !BufferIsValid(bufnum) ? \
     476             :         false \
     477             :     : \
     478             :         BufferIsLocal(bufnum) ? \
     479             :             (LocalRefCount[-(bufnum) - 1] > 0) \
     480             :         : \
     481             :     (GetPrivateRefCount(bufnum) > 0) \
     482             : )
     483             : 
     484             : 
     485             : static Buffer ReadBuffer_common(Relation rel,
     486             :                                 SMgrRelation smgr, char smgr_persistence,
     487             :                                 ForkNumber forkNum, BlockNumber blockNum,
     488             :                                 ReadBufferMode mode, BufferAccessStrategy strategy);
     489             : static BlockNumber ExtendBufferedRelCommon(BufferManagerRelation bmr,
     490             :                                            ForkNumber fork,
     491             :                                            BufferAccessStrategy strategy,
     492             :                                            uint32 flags,
     493             :                                            uint32 extend_by,
     494             :                                            BlockNumber extend_upto,
     495             :                                            Buffer *buffers,
     496             :                                            uint32 *extended_by);
     497             : static BlockNumber ExtendBufferedRelShared(BufferManagerRelation bmr,
     498             :                                            ForkNumber fork,
     499             :                                            BufferAccessStrategy strategy,
     500             :                                            uint32 flags,
     501             :                                            uint32 extend_by,
     502             :                                            BlockNumber extend_upto,
     503             :                                            Buffer *buffers,
     504             :                                            uint32 *extended_by);
     505             : static bool PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy);
     506             : static void PinBuffer_Locked(BufferDesc *buf);
     507             : static void UnpinBuffer(BufferDesc *buf);
     508             : static void UnpinBufferNoOwner(BufferDesc *buf);
     509             : static void BufferSync(int flags);
     510             : static uint32 WaitBufHdrUnlocked(BufferDesc *buf);
     511             : static int  SyncOneBuffer(int buf_id, bool skip_recently_used,
     512             :                           WritebackContext *wb_context);
     513             : static void WaitIO(BufferDesc *buf);
     514             : static bool StartBufferIO(BufferDesc *buf, bool forInput, bool nowait);
     515             : static void TerminateBufferIO(BufferDesc *buf, bool clear_dirty,
     516             :                               uint32 set_flag_bits, bool forget_owner);
     517             : static void AbortBufferIO(Buffer buffer);
     518             : static void shared_buffer_write_error_callback(void *arg);
     519             : static void local_buffer_write_error_callback(void *arg);
     520             : static inline BufferDesc *BufferAlloc(SMgrRelation smgr,
     521             :                                       char relpersistence,
     522             :                                       ForkNumber forkNum,
     523             :                                       BlockNumber blockNum,
     524             :                                       BufferAccessStrategy strategy,
     525             :                                       bool *foundPtr, IOContext io_context);
     526             : static Buffer GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context);
     527             : static void FlushBuffer(BufferDesc *buf, SMgrRelation reln,
     528             :                         IOObject io_object, IOContext io_context);
     529             : static void FindAndDropRelationBuffers(RelFileLocator rlocator,
     530             :                                        ForkNumber forkNum,
     531             :                                        BlockNumber nForkBlock,
     532             :                                        BlockNumber firstDelBlock);
     533             : static void RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
     534             :                                            RelFileLocator dstlocator,
     535             :                                            ForkNumber forkNum, bool permanent);
     536             : static void AtProcExit_Buffers(int code, Datum arg);
     537             : static void CheckForBufferLeaks(void);
     538             : static int  rlocator_comparator(const void *p1, const void *p2);
     539             : static inline int buffertag_comparator(const BufferTag *ba, const BufferTag *bb);
     540             : static inline int ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b);
     541             : static int  ts_ckpt_progress_comparator(Datum a, Datum b, void *arg);
     542             : 
     543             : 
     544             : /*
     545             :  * Implementation of PrefetchBuffer() for shared buffers.
     546             :  */
     547             : PrefetchBufferResult
     548     1355082 : PrefetchSharedBuffer(SMgrRelation smgr_reln,
     549             :                      ForkNumber forkNum,
     550             :                      BlockNumber blockNum)
     551             : {
     552     1355082 :     PrefetchBufferResult result = {InvalidBuffer, false};
     553             :     BufferTag   newTag;         /* identity of requested block */
     554             :     uint32      newHash;        /* hash value for newTag */
     555             :     LWLock     *newPartitionLock;   /* buffer partition lock for it */
     556             :     int         buf_id;
     557             : 
     558             :     Assert(BlockNumberIsValid(blockNum));
     559             : 
     560             :     /* create a tag so we can lookup the buffer */
     561     1355082 :     InitBufferTag(&newTag, &smgr_reln->smgr_rlocator.locator,
     562             :                   forkNum, blockNum);
     563             : 
     564             :     /* determine its hash code and partition lock ID */
     565     1355082 :     newHash = BufTableHashCode(&newTag);
     566     1355082 :     newPartitionLock = BufMappingPartitionLock(newHash);
     567             : 
     568             :     /* see if the block is in the buffer pool already */
     569     1355082 :     LWLockAcquire(newPartitionLock, LW_SHARED);
     570     1355082 :     buf_id = BufTableLookup(&newTag, newHash);
     571     1355082 :     LWLockRelease(newPartitionLock);
     572             : 
     573             :     /* If not in buffers, initiate prefetch */
     574     1355082 :     if (buf_id < 0)
     575             :     {
     576             : #ifdef USE_PREFETCH
     577             :         /*
     578             :          * Try to initiate an asynchronous read.  This returns false in
     579             :          * recovery if the relation file doesn't exist.
     580             :          */
     581      482918 :         if ((io_direct_flags & IO_DIRECT_DATA) == 0 &&
     582      241238 :             smgrprefetch(smgr_reln, forkNum, blockNum, 1))
     583             :         {
     584      241238 :             result.initiated_io = true;
     585             :         }
     586             : #endif                          /* USE_PREFETCH */
     587             :     }
     588             :     else
     589             :     {
     590             :         /*
     591             :          * Report the buffer it was in at that time.  The caller may be able
     592             :          * to avoid a buffer table lookup, but it's not pinned and it must be
     593             :          * rechecked!
     594             :          */
     595     1113402 :         result.recent_buffer = buf_id + 1;
     596             :     }
     597             : 
     598             :     /*
     599             :      * If the block *is* in buffers, we do nothing.  This is not really ideal:
     600             :      * the block might be just about to be evicted, which would be stupid
     601             :      * since we know we are going to need it soon.  But the only easy answer
     602             :      * is to bump the usage_count, which does not seem like a great solution:
     603             :      * when the caller does ultimately touch the block, usage_count would get
     604             :      * bumped again, resulting in too much favoritism for blocks that are
     605             :      * involved in a prefetch sequence. A real fix would involve some
     606             :      * additional per-buffer state, and it's not clear that there's enough of
     607             :      * a problem to justify that.
     608             :      */
     609             : 
     610     1355082 :     return result;
     611             : }
     612             : 
     613             : /*
     614             :  * PrefetchBuffer -- initiate asynchronous read of a block of a relation
     615             :  *
     616             :  * This is named by analogy to ReadBuffer but doesn't actually allocate a
     617             :  * buffer.  Instead it tries to ensure that a future ReadBuffer for the given
     618             :  * block will not be delayed by the I/O.  Prefetching is optional.
     619             :  *
     620             :  * There are three possible outcomes:
     621             :  *
     622             :  * 1.  If the block is already cached, the result includes a valid buffer that
     623             :  * could be used by the caller to avoid the need for a later buffer lookup, but
     624             :  * it's not pinned, so the caller must recheck it.
     625             :  *
     626             :  * 2.  If the kernel has been asked to initiate I/O, the initiated_io member is
     627             :  * true.  Currently there is no way to know if the data was already cached by
     628             :  * the kernel and therefore didn't really initiate I/O, and no way to know when
     629             :  * the I/O completes other than using synchronous ReadBuffer().
     630             :  *
     631             :  * 3.  Otherwise, the buffer wasn't already cached by PostgreSQL, and
     632             :  * USE_PREFETCH is not defined (this build doesn't support prefetching due to
     633             :  * lack of a kernel facility), direct I/O is enabled, or the underlying
     634             :  * relation file wasn't found and we are in recovery.  (If the relation file
     635             :  * wasn't found and we are not in recovery, an error is raised).
     636             :  */
     637             : PrefetchBufferResult
     638      388010 : PrefetchBuffer(Relation reln, ForkNumber forkNum, BlockNumber blockNum)
     639             : {
     640             :     Assert(RelationIsValid(reln));
     641             :     Assert(BlockNumberIsValid(blockNum));
     642             : 
     643      388010 :     if (RelationUsesLocalBuffers(reln))
     644             :     {
     645             :         /* see comments in ReadBufferExtended */
     646        6200 :         if (RELATION_IS_OTHER_TEMP(reln))
     647           0 :             ereport(ERROR,
     648             :                     (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     649             :                      errmsg("cannot access temporary tables of other sessions")));
     650             : 
     651             :         /* pass it off to localbuf.c */
     652        6200 :         return PrefetchLocalBuffer(RelationGetSmgr(reln), forkNum, blockNum);
     653             :     }
     654             :     else
     655             :     {
     656             :         /* pass it to the shared buffer version */
     657      381810 :         return PrefetchSharedBuffer(RelationGetSmgr(reln), forkNum, blockNum);
     658             :     }
     659             : }
     660             : 
     661             : /*
     662             :  * ReadRecentBuffer -- try to pin a block in a recently observed buffer
     663             :  *
     664             :  * Compared to ReadBuffer(), this avoids a buffer mapping lookup when it's
     665             :  * successful.  Return true if the buffer is valid and still has the expected
     666             :  * tag.  In that case, the buffer is pinned and the usage count is bumped.
     667             :  */
     668             : bool
     669      895760 : ReadRecentBuffer(RelFileLocator rlocator, ForkNumber forkNum, BlockNumber blockNum,
     670             :                  Buffer recent_buffer)
     671             : {
     672             :     BufferDesc *bufHdr;
     673             :     BufferTag   tag;
     674             :     uint32      buf_state;
     675             :     bool        have_private_ref;
     676             : 
     677             :     Assert(BufferIsValid(recent_buffer));
     678             : 
     679      895760 :     ResourceOwnerEnlarge(CurrentResourceOwner);
     680      895760 :     ReservePrivateRefCountEntry();
     681      895760 :     InitBufferTag(&tag, &rlocator, forkNum, blockNum);
     682             : 
     683      895760 :     if (BufferIsLocal(recent_buffer))
     684             :     {
     685           0 :         int         b = -recent_buffer - 1;
     686             : 
     687           0 :         bufHdr = GetLocalBufferDescriptor(b);
     688           0 :         buf_state = pg_atomic_read_u32(&bufHdr->state);
     689             : 
     690             :         /* Is it still valid and holding the right tag? */
     691           0 :         if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
     692             :         {
     693           0 :             PinLocalBuffer(bufHdr, true);
     694             : 
     695           0 :             pgBufferUsage.local_blks_hit++;
     696             : 
     697           0 :             return true;
     698             :         }
     699             :     }
     700             :     else
     701             :     {
     702      895760 :         bufHdr = GetBufferDescriptor(recent_buffer - 1);
     703      895760 :         have_private_ref = GetPrivateRefCount(recent_buffer) > 0;
     704             : 
     705             :         /*
     706             :          * Do we already have this buffer pinned with a private reference?  If
     707             :          * so, it must be valid and it is safe to check the tag without
     708             :          * locking.  If not, we have to lock the header first and then check.
     709             :          */
     710      895760 :         if (have_private_ref)
     711          12 :             buf_state = pg_atomic_read_u32(&bufHdr->state);
     712             :         else
     713      895748 :             buf_state = LockBufHdr(bufHdr);
     714             : 
     715      895760 :         if ((buf_state & BM_VALID) && BufferTagsEqual(&tag, &bufHdr->tag))
     716             :         {
     717             :             /*
     718             :              * It's now safe to pin the buffer.  We can't pin first and ask
     719             :              * questions later, because it might confuse code paths like
     720             :              * InvalidateBuffer() if we pinned a random non-matching buffer.
     721             :              */
     722      892958 :             if (have_private_ref)
     723           0 :                 PinBuffer(bufHdr, NULL);    /* bump pin count */
     724             :             else
     725      892958 :                 PinBuffer_Locked(bufHdr);   /* pin for first time */
     726             : 
     727      892958 :             pgBufferUsage.shared_blks_hit++;
     728             : 
     729      892958 :             return true;
     730             :         }
     731             : 
     732             :         /* If we locked the header above, now unlock. */
     733        2802 :         if (!have_private_ref)
     734        2790 :             UnlockBufHdr(bufHdr, buf_state);
     735             :     }
     736             : 
     737        2802 :     return false;
     738             : }
     739             : 
     740             : /*
     741             :  * ReadBuffer -- a shorthand for ReadBufferExtended, for reading from main
     742             :  *      fork with RBM_NORMAL mode and default strategy.
     743             :  */
     744             : Buffer
     745    69040296 : ReadBuffer(Relation reln, BlockNumber blockNum)
     746             : {
     747    69040296 :     return ReadBufferExtended(reln, MAIN_FORKNUM, blockNum, RBM_NORMAL, NULL);
     748             : }
     749             : 
     750             : /*
     751             :  * ReadBufferExtended -- returns a buffer containing the requested
     752             :  *      block of the requested relation.  If the blknum
     753             :  *      requested is P_NEW, extend the relation file and
     754             :  *      allocate a new block.  (Caller is responsible for
     755             :  *      ensuring that only one backend tries to extend a
     756             :  *      relation at the same time!)
     757             :  *
     758             :  * Returns: the buffer number for the buffer containing
     759             :  *      the block read.  The returned buffer has been pinned.
     760             :  *      Does not return on error --- elog's instead.
     761             :  *
     762             :  * Assume when this function is called, that reln has been opened already.
     763             :  *
     764             :  * In RBM_NORMAL mode, the page is read from disk, and the page header is
     765             :  * validated.  An error is thrown if the page header is not valid.  (But
     766             :  * note that an all-zero page is considered "valid"; see
     767             :  * PageIsVerifiedExtended().)
     768             :  *
     769             :  * RBM_ZERO_ON_ERROR is like the normal mode, but if the page header is not
     770             :  * valid, the page is zeroed instead of throwing an error. This is intended
     771             :  * for non-critical data, where the caller is prepared to repair errors.
     772             :  *
     773             :  * In RBM_ZERO_AND_LOCK mode, if the page isn't in buffer cache already, it's
     774             :  * filled with zeros instead of reading it from disk.  Useful when the caller
     775             :  * is going to fill the page from scratch, since this saves I/O and avoids
     776             :  * unnecessary failure if the page-on-disk has corrupt page headers.
     777             :  * The page is returned locked to ensure that the caller has a chance to
     778             :  * initialize the page before it's made visible to others.
     779             :  * Caution: do not use this mode to read a page that is beyond the relation's
     780             :  * current physical EOF; that is likely to cause problems in md.c when
     781             :  * the page is modified and written out. P_NEW is OK, though.
     782             :  *
     783             :  * RBM_ZERO_AND_CLEANUP_LOCK is the same as RBM_ZERO_AND_LOCK, but acquires
     784             :  * a cleanup-strength lock on the page.
     785             :  *
     786             :  * RBM_NORMAL_NO_LOG mode is treated the same as RBM_NORMAL here.
     787             :  *
     788             :  * If strategy is not NULL, a nondefault buffer access strategy is used.
     789             :  * See buffer/README for details.
     790             :  */
     791             : inline Buffer
     792    83815326 : ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
     793             :                    ReadBufferMode mode, BufferAccessStrategy strategy)
     794             : {
     795             :     Buffer      buf;
     796             : 
     797             :     /*
     798             :      * Reject attempts to read non-local temporary relations; we would be
     799             :      * likely to get wrong data since we have no visibility into the owning
     800             :      * session's local buffers.
     801             :      */
     802    83815326 :     if (RELATION_IS_OTHER_TEMP(reln))
     803           0 :         ereport(ERROR,
     804             :                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
     805             :                  errmsg("cannot access temporary tables of other sessions")));
     806             : 
     807             :     /*
     808             :      * Read the buffer, and update pgstat counters to reflect a cache hit or
     809             :      * miss.
     810             :      */
     811    83815326 :     buf = ReadBuffer_common(reln, RelationGetSmgr(reln), 0,
     812             :                             forkNum, blockNum, mode, strategy);
     813             : 
     814    83815296 :     return buf;
     815             : }
     816             : 
     817             : 
     818             : /*
     819             :  * ReadBufferWithoutRelcache -- like ReadBufferExtended, but doesn't require
     820             :  *      a relcache entry for the relation.
     821             :  *
     822             :  * Pass permanent = true for a RELPERSISTENCE_PERMANENT relation, and
     823             :  * permanent = false for a RELPERSISTENCE_UNLOGGED relation. This function
     824             :  * cannot be used for temporary relations (and making that work might be
     825             :  * difficult, unless we only want to read temporary relations for our own
     826             :  * ProcNumber).
     827             :  */
     828             : Buffer
     829     5917596 : ReadBufferWithoutRelcache(RelFileLocator rlocator, ForkNumber forkNum,
     830             :                           BlockNumber blockNum, ReadBufferMode mode,
     831             :                           BufferAccessStrategy strategy, bool permanent)
     832             : {
     833     5917596 :     SMgrRelation smgr = smgropen(rlocator, INVALID_PROC_NUMBER);
     834             : 
     835     5917596 :     return ReadBuffer_common(NULL, smgr,
     836             :                              permanent ? RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED,
     837             :                              forkNum, blockNum,
     838             :                              mode, strategy);
     839             : }
     840             : 
     841             : /*
     842             :  * Convenience wrapper around ExtendBufferedRelBy() extending by one block.
     843             :  */
     844             : Buffer
     845       84654 : ExtendBufferedRel(BufferManagerRelation bmr,
     846             :                   ForkNumber forkNum,
     847             :                   BufferAccessStrategy strategy,
     848             :                   uint32 flags)
     849             : {
     850             :     Buffer      buf;
     851       84654 :     uint32      extend_by = 1;
     852             : 
     853       84654 :     ExtendBufferedRelBy(bmr, forkNum, strategy, flags, extend_by,
     854             :                         &buf, &extend_by);
     855             : 
     856       84654 :     return buf;
     857             : }
     858             : 
     859             : /*
     860             :  * Extend relation by multiple blocks.
     861             :  *
     862             :  * Tries to extend the relation by extend_by blocks. Depending on the
     863             :  * availability of resources the relation may end up being extended by a
     864             :  * smaller number of pages (unless an error is thrown, always by at least one
     865             :  * page). *extended_by is updated to the number of pages the relation has been
     866             :  * extended to.
     867             :  *
     868             :  * buffers needs to be an array that is at least extend_by long. Upon
     869             :  * completion, the first extend_by array elements will point to a pinned
     870             :  * buffer.
     871             :  *
     872             :  * If EB_LOCK_FIRST is part of flags, the first returned buffer is
     873             :  * locked. This is useful for callers that want a buffer that is guaranteed to
     874             :  * be empty.
     875             :  */
     876             : BlockNumber
     877      275362 : ExtendBufferedRelBy(BufferManagerRelation bmr,
     878             :                     ForkNumber fork,
     879             :                     BufferAccessStrategy strategy,
     880             :                     uint32 flags,
     881             :                     uint32 extend_by,
     882             :                     Buffer *buffers,
     883             :                     uint32 *extended_by)
     884             : {
     885             :     Assert((bmr.rel != NULL) != (bmr.smgr != NULL));
     886             :     Assert(bmr.smgr == NULL || bmr.relpersistence != 0);
     887             :     Assert(extend_by > 0);
     888             : 
     889      275362 :     if (bmr.smgr == NULL)
     890             :     {
     891      275362 :         bmr.smgr = RelationGetSmgr(bmr.rel);
     892      275362 :         bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
     893             :     }
     894             : 
     895      275362 :     return ExtendBufferedRelCommon(bmr, fork, strategy, flags,
     896             :                                    extend_by, InvalidBlockNumber,
     897             :                                    buffers, extended_by);
     898             : }
     899             : 
     900             : /*
     901             :  * Extend the relation so it is at least extend_to blocks large, return buffer
     902             :  * (extend_to - 1).
     903             :  *
     904             :  * This is useful for callers that want to write a specific page, regardless
     905             :  * of the current size of the relation (e.g. useful for visibilitymap and for
     906             :  * crash recovery).
     907             :  */
     908             : Buffer
     909       90822 : ExtendBufferedRelTo(BufferManagerRelation bmr,
     910             :                     ForkNumber fork,
     911             :                     BufferAccessStrategy strategy,
     912             :                     uint32 flags,
     913             :                     BlockNumber extend_to,
     914             :                     ReadBufferMode mode)
     915             : {
     916             :     BlockNumber current_size;
     917       90822 :     uint32      extended_by = 0;
     918       90822 :     Buffer      buffer = InvalidBuffer;
     919             :     Buffer      buffers[64];
     920             : 
     921             :     Assert((bmr.rel != NULL) != (bmr.smgr != NULL));
     922             :     Assert(bmr.smgr == NULL || bmr.relpersistence != 0);
     923             :     Assert(extend_to != InvalidBlockNumber && extend_to > 0);
     924             : 
     925       90822 :     if (bmr.smgr == NULL)
     926             :     {
     927       11444 :         bmr.smgr = RelationGetSmgr(bmr.rel);
     928       11444 :         bmr.relpersistence = bmr.rel->rd_rel->relpersistence;
     929             :     }
     930             : 
     931             :     /*
     932             :      * If desired, create the file if it doesn't exist.  If
     933             :      * smgr_cached_nblocks[fork] is positive then it must exist, no need for
     934             :      * an smgrexists call.
     935             :      */
     936       90822 :     if ((flags & EB_CREATE_FORK_IF_NEEDED) &&
     937       11444 :         (bmr.smgr->smgr_cached_nblocks[fork] == 0 ||
     938          22 :          bmr.smgr->smgr_cached_nblocks[fork] == InvalidBlockNumber) &&
     939       11422 :         !smgrexists(bmr.smgr, fork))
     940             :     {
     941       11408 :         LockRelationForExtension(bmr.rel, ExclusiveLock);
     942             : 
     943             :         /* recheck, fork might have been created concurrently */
     944       11408 :         if (!smgrexists(bmr.smgr, fork))
     945       11406 :             smgrcreate(bmr.smgr, fork, flags & EB_PERFORMING_RECOVERY);
     946             : 
     947       11408 :         UnlockRelationForExtension(bmr.rel, ExclusiveLock);
     948             :     }
     949             : 
     950             :     /*
     951             :      * If requested, invalidate size cache, so that smgrnblocks asks the
     952             :      * kernel.
     953             :      */
     954       90822 :     if (flags & EB_CLEAR_SIZE_CACHE)
     955       11444 :         bmr.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
     956             : 
     957             :     /*
     958             :      * Estimate how many pages we'll need to extend by. This avoids acquiring
     959             :      * unnecessarily many victim buffers.
     960             :      */
     961       90822 :     current_size = smgrnblocks(bmr.smgr, fork);
     962             : 
     963             :     /*
     964             :      * Since no-one else can be looking at the page contents yet, there is no
     965             :      * difference between an exclusive lock and a cleanup-strength lock. Note
     966             :      * that we pass the original mode to ReadBuffer_common() below, when
     967             :      * falling back to reading the buffer to a concurrent relation extension.
     968             :      */
     969       90822 :     if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
     970       78694 :         flags |= EB_LOCK_TARGET;
     971             : 
     972      185508 :     while (current_size < extend_to)
     973             :     {
     974       94686 :         uint32      num_pages = lengthof(buffers);
     975             :         BlockNumber first_block;
     976             : 
     977       94686 :         if ((uint64) current_size + num_pages > extend_to)
     978       94554 :             num_pages = extend_to - current_size;
     979             : 
     980       94686 :         first_block = ExtendBufferedRelCommon(bmr, fork, strategy, flags,
     981             :                                               num_pages, extend_to,
     982             :                                               buffers, &extended_by);
     983             : 
     984       94686 :         current_size = first_block + extended_by;
     985             :         Assert(num_pages != 0 || current_size >= extend_to);
     986             : 
     987      201414 :         for (uint32 i = 0; i < extended_by; i++)
     988             :         {
     989      106728 :             if (first_block + i != extend_to - 1)
     990       15920 :                 ReleaseBuffer(buffers[i]);
     991             :             else
     992       90808 :                 buffer = buffers[i];
     993             :         }
     994             :     }
     995             : 
     996             :     /*
     997             :      * It's possible that another backend concurrently extended the relation.
     998             :      * In that case read the buffer.
     999             :      *
    1000             :      * XXX: Should we control this via a flag?
    1001             :      */
    1002       90822 :     if (buffer == InvalidBuffer)
    1003             :     {
    1004             :         Assert(extended_by == 0);
    1005          14 :         buffer = ReadBuffer_common(bmr.rel, bmr.smgr, 0,
    1006             :                                    fork, extend_to - 1, mode, strategy);
    1007             :     }
    1008             : 
    1009       90822 :     return buffer;
    1010             : }
    1011             : 
    1012             : /*
    1013             :  * Zero a buffer and lock it, as part of the implementation of
    1014             :  * RBM_ZERO_AND_LOCK or RBM_ZERO_AND_CLEANUP_LOCK.  The buffer must be already
    1015             :  * pinned.  It does not have to be valid, but it is valid and locked on
    1016             :  * return.
    1017             :  */
    1018             : static void
    1019      500784 : ZeroBuffer(Buffer buffer, ReadBufferMode mode)
    1020             : {
    1021             :     BufferDesc *bufHdr;
    1022             :     uint32      buf_state;
    1023             : 
    1024             :     Assert(mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK);
    1025             : 
    1026      500784 :     if (BufferIsLocal(buffer))
    1027           0 :         bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    1028             :     else
    1029             :     {
    1030      500784 :         bufHdr = GetBufferDescriptor(buffer - 1);
    1031      500784 :         if (mode == RBM_ZERO_AND_LOCK)
    1032      498644 :             LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
    1033             :         else
    1034        2140 :             LockBufferForCleanup(buffer);
    1035             :     }
    1036             : 
    1037      500784 :     memset(BufferGetPage(buffer), 0, BLCKSZ);
    1038             : 
    1039      500784 :     if (BufferIsLocal(buffer))
    1040             :     {
    1041           0 :         buf_state = pg_atomic_read_u32(&bufHdr->state);
    1042           0 :         buf_state |= BM_VALID;
    1043           0 :         pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
    1044             :     }
    1045             :     else
    1046             :     {
    1047      500784 :         buf_state = LockBufHdr(bufHdr);
    1048      500784 :         buf_state |= BM_VALID;
    1049      500784 :         UnlockBufHdr(bufHdr, buf_state);
    1050             :     }
    1051      500784 : }
    1052             : 
    1053             : /*
    1054             :  * Pin a buffer for a given block.  *foundPtr is set to true if the block was
    1055             :  * already present, or false if more work is required to either read it in or
    1056             :  * zero it.
    1057             :  */
    1058             : static pg_attribute_always_inline Buffer
    1059    93938986 : PinBufferForBlock(Relation rel,
    1060             :                   SMgrRelation smgr,
    1061             :                   char smgr_persistence,
    1062             :                   ForkNumber forkNum,
    1063             :                   BlockNumber blockNum,
    1064             :                   BufferAccessStrategy strategy,
    1065             :                   bool *foundPtr)
    1066             : {
    1067             :     BufferDesc *bufHdr;
    1068             :     IOContext   io_context;
    1069             :     IOObject    io_object;
    1070             :     char        persistence;
    1071             : 
    1072             :     Assert(blockNum != P_NEW);
    1073             : 
    1074             :     /*
    1075             :      * If there is no Relation it usually implies recovery and thus permanent,
    1076             :      * but we take an argument because CreateAndCopyRelationData can reach us
    1077             :      * with only an SMgrRelation for an unlogged relation that we don't want
    1078             :      * to flag with BM_PERMANENT.
    1079             :      */
    1080    93938986 :     if (rel)
    1081    88021390 :         persistence = rel->rd_rel->relpersistence;
    1082     5917596 :     else if (smgr_persistence == 0)
    1083           0 :         persistence = RELPERSISTENCE_PERMANENT;
    1084             :     else
    1085     5917596 :         persistence = smgr_persistence;
    1086             : 
    1087    93938986 :     if (persistence == RELPERSISTENCE_TEMP)
    1088             :     {
    1089     2105366 :         io_context = IOCONTEXT_NORMAL;
    1090     2105366 :         io_object = IOOBJECT_TEMP_RELATION;
    1091             :     }
    1092             :     else
    1093             :     {
    1094    91833620 :         io_context = IOContextForStrategy(strategy);
    1095    91833620 :         io_object = IOOBJECT_RELATION;
    1096             :     }
    1097             : 
    1098             :     TRACE_POSTGRESQL_BUFFER_READ_START(forkNum, blockNum,
    1099             :                                        smgr->smgr_rlocator.locator.spcOid,
    1100             :                                        smgr->smgr_rlocator.locator.dbOid,
    1101             :                                        smgr->smgr_rlocator.locator.relNumber,
    1102             :                                        smgr->smgr_rlocator.backend);
    1103             : 
    1104    93938986 :     if (persistence == RELPERSISTENCE_TEMP)
    1105             :     {
    1106     2105366 :         bufHdr = LocalBufferAlloc(smgr, forkNum, blockNum, foundPtr);
    1107     2105366 :         if (*foundPtr)
    1108     2097758 :             pgBufferUsage.local_blks_hit++;
    1109             :     }
    1110             :     else
    1111             :     {
    1112    91833620 :         bufHdr = BufferAlloc(smgr, persistence, forkNum, blockNum,
    1113             :                              strategy, foundPtr, io_context);
    1114    91833620 :         if (*foundPtr)
    1115    89236058 :             pgBufferUsage.shared_blks_hit++;
    1116             :     }
    1117    93938986 :     if (rel)
    1118             :     {
    1119             :         /*
    1120             :          * While pgBufferUsage's "read" counter isn't bumped unless we reach
    1121             :          * WaitReadBuffers() (so, not for hits, and not for buffers that are
    1122             :          * zeroed instead), the per-relation stats always count them.
    1123             :          */
    1124    88021390 :         pgstat_count_buffer_read(rel);
    1125    88021390 :         if (*foundPtr)
    1126    86196328 :             pgstat_count_buffer_hit(rel);
    1127             :     }
    1128    93938986 :     if (*foundPtr)
    1129             :     {
    1130    91333816 :         VacuumPageHit++;
    1131    91333816 :         pgstat_count_io_op(io_object, io_context, IOOP_HIT);
    1132    91333816 :         if (VacuumCostActive)
    1133       31538 :             VacuumCostBalance += VacuumCostPageHit;
    1134             : 
    1135             :         TRACE_POSTGRESQL_BUFFER_READ_DONE(forkNum, blockNum,
    1136             :                                           smgr->smgr_rlocator.locator.spcOid,
    1137             :                                           smgr->smgr_rlocator.locator.dbOid,
    1138             :                                           smgr->smgr_rlocator.locator.relNumber,
    1139             :                                           smgr->smgr_rlocator.backend,
    1140             :                                           true);
    1141             :     }
    1142             : 
    1143    93938986 :     return BufferDescriptorGetBuffer(bufHdr);
    1144             : }
    1145             : 
    1146             : /*
    1147             :  * ReadBuffer_common -- common logic for all ReadBuffer variants
    1148             :  *
    1149             :  * smgr is required, rel is optional unless using P_NEW.
    1150             :  */
    1151             : static pg_attribute_always_inline Buffer
    1152    89732936 : ReadBuffer_common(Relation rel, SMgrRelation smgr, char smgr_persistence,
    1153             :                   ForkNumber forkNum,
    1154             :                   BlockNumber blockNum, ReadBufferMode mode,
    1155             :                   BufferAccessStrategy strategy)
    1156             : {
    1157             :     ReadBuffersOperation operation;
    1158             :     Buffer      buffer;
    1159             :     int         flags;
    1160             : 
    1161             :     /*
    1162             :      * Backward compatibility path, most code should use ExtendBufferedRel()
    1163             :      * instead, as acquiring the extension lock inside ExtendBufferedRel()
    1164             :      * scales a lot better.
    1165             :      */
    1166    89732936 :     if (unlikely(blockNum == P_NEW))
    1167             :     {
    1168         486 :         uint32      flags = EB_SKIP_EXTENSION_LOCK;
    1169             : 
    1170             :         /*
    1171             :          * Since no-one else can be looking at the page contents yet, there is
    1172             :          * no difference between an exclusive lock and a cleanup-strength
    1173             :          * lock.
    1174             :          */
    1175         486 :         if (mode == RBM_ZERO_AND_LOCK || mode == RBM_ZERO_AND_CLEANUP_LOCK)
    1176           0 :             flags |= EB_LOCK_FIRST;
    1177             : 
    1178         486 :         return ExtendBufferedRel(BMR_REL(rel), forkNum, strategy, flags);
    1179             :     }
    1180             : 
    1181    89732450 :     if (unlikely(mode == RBM_ZERO_AND_CLEANUP_LOCK ||
    1182             :                  mode == RBM_ZERO_AND_LOCK))
    1183             :     {
    1184             :         bool        found;
    1185             : 
    1186      500784 :         buffer = PinBufferForBlock(rel, smgr, smgr_persistence,
    1187             :                                    forkNum, blockNum, strategy, &found);
    1188      500784 :         ZeroBuffer(buffer, mode);
    1189      500784 :         return buffer;
    1190             :     }
    1191             : 
    1192    89231666 :     if (mode == RBM_ZERO_ON_ERROR)
    1193     1290460 :         flags = READ_BUFFERS_ZERO_ON_ERROR;
    1194             :     else
    1195    87941206 :         flags = 0;
    1196    89231666 :     operation.smgr = smgr;
    1197    89231666 :     operation.rel = rel;
    1198    89231666 :     operation.smgr_persistence = smgr_persistence;
    1199    89231666 :     operation.forknum = forkNum;
    1200    89231666 :     operation.strategy = strategy;
    1201    89231666 :     if (StartReadBuffer(&operation,
    1202             :                         &buffer,
    1203             :                         blockNum,
    1204             :                         flags))
    1205     1561300 :         WaitReadBuffers(&operation);
    1206             : 
    1207    89231636 :     return buffer;
    1208             : }
    1209             : 
    1210             : static pg_attribute_always_inline bool
    1211    93362778 : StartReadBuffersImpl(ReadBuffersOperation *operation,
    1212             :                      Buffer *buffers,
    1213             :                      BlockNumber blockNum,
    1214             :                      int *nblocks,
    1215             :                      int flags)
    1216             : {
    1217    93362778 :     int         actual_nblocks = *nblocks;
    1218    93362778 :     int         io_buffers_len = 0;
    1219             : 
    1220             :     Assert(*nblocks > 0);
    1221             :     Assert(*nblocks <= MAX_IO_COMBINE_LIMIT);
    1222             : 
    1223    95527014 :     for (int i = 0; i < actual_nblocks; ++i)
    1224             :     {
    1225             :         bool        found;
    1226             : 
    1227   186876404 :         buffers[i] = PinBufferForBlock(operation->rel,
    1228    93438202 :                                        operation->smgr,
    1229    93438202 :                                        operation->smgr_persistence,
    1230             :                                        operation->forknum,
    1231             :                                        blockNum + i,
    1232             :                                        operation->strategy,
    1233             :                                        &found);
    1234             : 
    1235    93438202 :         if (found)
    1236             :         {
    1237             :             /*
    1238             :              * Terminate the read as soon as we get a hit.  It could be a
    1239             :              * single buffer hit, or it could be a hit that follows a readable
    1240             :              * range.  We don't want to create more than one readable range,
    1241             :              * so we stop here.
    1242             :              */
    1243    91273966 :             actual_nblocks = i + 1;
    1244    91273966 :             break;
    1245             :         }
    1246             :         else
    1247             :         {
    1248             :             /* Extend the readable range to cover this block. */
    1249     2164236 :             io_buffers_len++;
    1250             :         }
    1251             :     }
    1252    93362778 :     *nblocks = actual_nblocks;
    1253             : 
    1254    93362778 :     if (likely(io_buffers_len == 0))
    1255    91272414 :         return false;
    1256             : 
    1257             :     /* Populate information needed for I/O. */
    1258     2090364 :     operation->buffers = buffers;
    1259     2090364 :     operation->blocknum = blockNum;
    1260     2090364 :     operation->flags = flags;
    1261     2090364 :     operation->nblocks = actual_nblocks;
    1262     2090364 :     operation->io_buffers_len = io_buffers_len;
    1263             : 
    1264     2090364 :     if (flags & READ_BUFFERS_ISSUE_ADVICE)
    1265             :     {
    1266             :         /*
    1267             :          * In theory we should only do this if PinBufferForBlock() had to
    1268             :          * allocate new buffers above.  That way, if two calls to
    1269             :          * StartReadBuffers() were made for the same blocks before
    1270             :          * WaitReadBuffers(), only the first would issue the advice. That'd be
    1271             :          * a better simulation of true asynchronous I/O, which would only
    1272             :          * start the I/O once, but isn't done here for simplicity.  Note also
    1273             :          * that the following call might actually issue two advice calls if we
    1274             :          * cross a segment boundary; in a true asynchronous version we might
    1275             :          * choose to process only one real I/O at a time in that case.
    1276             :          */
    1277         124 :         smgrprefetch(operation->smgr,
    1278             :                      operation->forknum,
    1279             :                      blockNum,
    1280         124 :                      operation->io_buffers_len);
    1281             :     }
    1282             : 
    1283             :     /* Indicate that WaitReadBuffers() should be called. */
    1284     2090364 :     return true;
    1285             : }
    1286             : 
    1287             : /*
    1288             :  * Begin reading a range of blocks beginning at blockNum and extending for
    1289             :  * *nblocks.  On return, up to *nblocks pinned buffers holding those blocks
    1290             :  * are written into the buffers array, and *nblocks is updated to contain the
    1291             :  * actual number, which may be fewer than requested.  Caller sets some of the
    1292             :  * members of operation; see struct definition.
    1293             :  *
    1294             :  * If false is returned, no I/O is necessary.  If true is returned, one I/O
    1295             :  * has been started, and WaitReadBuffers() must be called with the same
    1296             :  * operation object before the buffers are accessed.  Along with the operation
    1297             :  * object, the caller-supplied array of buffers must remain valid until
    1298             :  * WaitReadBuffers() is called.
    1299             :  *
    1300             :  * Currently the I/O is only started with optional operating system advice if
    1301             :  * requested by the caller with READ_BUFFERS_ISSUE_ADVICE, and the real I/O
    1302             :  * happens synchronously in WaitReadBuffers().  In future work, true I/O could
    1303             :  * be initiated here.
    1304             :  */
    1305             : bool
    1306     1552566 : StartReadBuffers(ReadBuffersOperation *operation,
    1307             :                  Buffer *buffers,
    1308             :                  BlockNumber blockNum,
    1309             :                  int *nblocks,
    1310             :                  int flags)
    1311             : {
    1312     1552566 :     return StartReadBuffersImpl(operation, buffers, blockNum, nblocks, flags);
    1313             : }
    1314             : 
    1315             : /*
    1316             :  * Single block version of the StartReadBuffers().  This might save a few
    1317             :  * instructions when called from another translation unit, because it is
    1318             :  * specialized for nblocks == 1.
    1319             :  */
    1320             : bool
    1321    91810212 : StartReadBuffer(ReadBuffersOperation *operation,
    1322             :                 Buffer *buffer,
    1323             :                 BlockNumber blocknum,
    1324             :                 int flags)
    1325             : {
    1326    91810212 :     int         nblocks = 1;
    1327             :     bool        result;
    1328             : 
    1329    91810212 :     result = StartReadBuffersImpl(operation, buffer, blocknum, &nblocks, flags);
    1330             :     Assert(nblocks == 1);       /* single block can't be short */
    1331             : 
    1332    91810212 :     return result;
    1333             : }
    1334             : 
    1335             : static inline bool
    1336     2164234 : WaitReadBuffersCanStartIO(Buffer buffer, bool nowait)
    1337             : {
    1338     2164234 :     if (BufferIsLocal(buffer))
    1339             :     {
    1340        7608 :         BufferDesc *bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    1341             : 
    1342        7608 :         return (pg_atomic_read_u32(&bufHdr->state) & BM_VALID) == 0;
    1343             :     }
    1344             :     else
    1345     2156626 :         return StartBufferIO(GetBufferDescriptor(buffer - 1), true, nowait);
    1346             : }
    1347             : 
    1348             : void
    1349     2090362 : WaitReadBuffers(ReadBuffersOperation *operation)
    1350             : {
    1351             :     Buffer     *buffers;
    1352             :     int         nblocks;
    1353             :     BlockNumber blocknum;
    1354             :     ForkNumber  forknum;
    1355             :     IOContext   io_context;
    1356             :     IOObject    io_object;
    1357             :     char        persistence;
    1358             : 
    1359             :     /*
    1360             :      * Currently operations are only allowed to include a read of some range,
    1361             :      * with an optional extra buffer that is already pinned at the end.  So
    1362             :      * nblocks can be at most one more than io_buffers_len.
    1363             :      */
    1364             :     Assert((operation->nblocks == operation->io_buffers_len) ||
    1365             :            (operation->nblocks == operation->io_buffers_len + 1));
    1366             : 
    1367             :     /* Find the range of the physical read we need to perform. */
    1368     2090362 :     nblocks = operation->io_buffers_len;
    1369     2090362 :     if (nblocks == 0)
    1370           0 :         return;                 /* nothing to do */
    1371             : 
    1372     2090362 :     buffers = &operation->buffers[0];
    1373     2090362 :     blocknum = operation->blocknum;
    1374     2090362 :     forknum = operation->forknum;
    1375             : 
    1376     2090362 :     persistence = operation->rel
    1377     1749830 :         ? operation->rel->rd_rel->relpersistence
    1378             :         : RELPERSISTENCE_PERMANENT;
    1379     2090362 :     if (persistence == RELPERSISTENCE_TEMP)
    1380             :     {
    1381        1584 :         io_context = IOCONTEXT_NORMAL;
    1382        1584 :         io_object = IOOBJECT_TEMP_RELATION;
    1383             :     }
    1384             :     else
    1385             :     {
    1386     2088778 :         io_context = IOContextForStrategy(operation->strategy);
    1387     2088778 :         io_object = IOOBJECT_RELATION;
    1388             :     }
    1389             : 
    1390             :     /*
    1391             :      * We count all these blocks as read by this backend.  This is traditional
    1392             :      * behavior, but might turn out to be not true if we find that someone
    1393             :      * else has beaten us and completed the read of some of these blocks.  In
    1394             :      * that case the system globally double-counts, but we traditionally don't
    1395             :      * count this as a "hit", and we don't have a separate counter for "miss,
    1396             :      * but another backend completed the read".
    1397             :      */
    1398     2090362 :     if (persistence == RELPERSISTENCE_TEMP)
    1399        1584 :         pgBufferUsage.local_blks_read += nblocks;
    1400             :     else
    1401     2088778 :         pgBufferUsage.shared_blks_read += nblocks;
    1402             : 
    1403     4180696 :     for (int i = 0; i < nblocks; ++i)
    1404             :     {
    1405             :         int         io_buffers_len;
    1406             :         Buffer      io_buffers[MAX_IO_COMBINE_LIMIT];
    1407             :         void       *io_pages[MAX_IO_COMBINE_LIMIT];
    1408             :         instr_time  io_start;
    1409             :         BlockNumber io_first_block;
    1410             : 
    1411             :         /*
    1412             :          * Skip this block if someone else has already completed it.  If an
    1413             :          * I/O is already in progress in another backend, this will wait for
    1414             :          * the outcome: either done, or something went wrong and we will
    1415             :          * retry.
    1416             :          */
    1417     2090364 :         if (!WaitReadBuffersCanStartIO(buffers[i], false))
    1418             :         {
    1419             :             /*
    1420             :              * Report this as a 'hit' for this backend, even though it must
    1421             :              * have started out as a miss in PinBufferForBlock().
    1422             :              */
    1423             :             TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, blocknum + i,
    1424             :                                               operation->smgr->smgr_rlocator.locator.spcOid,
    1425             :                                               operation->smgr->smgr_rlocator.locator.dbOid,
    1426             :                                               operation->smgr->smgr_rlocator.locator.relNumber,
    1427             :                                               operation->smgr->smgr_rlocator.backend,
    1428             :                                               true);
    1429        1480 :             continue;
    1430             :         }
    1431             : 
    1432             :         /* We found a buffer that we need to read in. */
    1433     2088884 :         io_buffers[0] = buffers[i];
    1434     2088884 :         io_pages[0] = BufferGetBlock(buffers[i]);
    1435     2088884 :         io_first_block = blocknum + i;
    1436     2088884 :         io_buffers_len = 1;
    1437             : 
    1438             :         /*
    1439             :          * How many neighboring-on-disk blocks can we can scatter-read into
    1440             :          * other buffers at the same time?  In this case we don't wait if we
    1441             :          * see an I/O already in progress.  We already hold BM_IO_IN_PROGRESS
    1442             :          * for the head block, so we should get on with that I/O as soon as
    1443             :          * possible.  We'll come back to this block again, above.
    1444             :          */
    1445     2236624 :         while ((i + 1) < nblocks &&
    1446       73870 :                WaitReadBuffersCanStartIO(buffers[i + 1], true))
    1447             :         {
    1448             :             /* Must be consecutive block numbers. */
    1449             :             Assert(BufferGetBlockNumber(buffers[i + 1]) ==
    1450             :                    BufferGetBlockNumber(buffers[i]) + 1);
    1451             : 
    1452       73870 :             io_buffers[io_buffers_len] = buffers[++i];
    1453       73870 :             io_pages[io_buffers_len++] = BufferGetBlock(buffers[i]);
    1454             :         }
    1455             : 
    1456     2088884 :         io_start = pgstat_prepare_io_time(track_io_timing);
    1457     2088884 :         smgrreadv(operation->smgr, forknum, io_first_block, io_pages, io_buffers_len);
    1458     2088854 :         pgstat_count_io_op_time(io_object, io_context, IOOP_READ, io_start,
    1459             :                                 io_buffers_len);
    1460             : 
    1461             :         /* Verify each block we read, and terminate the I/O. */
    1462     4251578 :         for (int j = 0; j < io_buffers_len; ++j)
    1463             :         {
    1464             :             BufferDesc *bufHdr;
    1465             :             Block       bufBlock;
    1466             : 
    1467     2162724 :             if (persistence == RELPERSISTENCE_TEMP)
    1468             :             {
    1469        7608 :                 bufHdr = GetLocalBufferDescriptor(-io_buffers[j] - 1);
    1470        7608 :                 bufBlock = LocalBufHdrGetBlock(bufHdr);
    1471             :             }
    1472             :             else
    1473             :             {
    1474     2155116 :                 bufHdr = GetBufferDescriptor(io_buffers[j] - 1);
    1475     2155116 :                 bufBlock = BufHdrGetBlock(bufHdr);
    1476             :             }
    1477             : 
    1478             :             /* check for garbage data */
    1479     2162724 :             if (!PageIsVerifiedExtended((Page) bufBlock, io_first_block + j,
    1480             :                                         PIV_LOG_WARNING | PIV_REPORT_STAT))
    1481             :             {
    1482           0 :                 if ((operation->flags & READ_BUFFERS_ZERO_ON_ERROR) || zero_damaged_pages)
    1483             :                 {
    1484           0 :                     ereport(WARNING,
    1485             :                             (errcode(ERRCODE_DATA_CORRUPTED),
    1486             :                              errmsg("invalid page in block %u of relation %s; zeroing out page",
    1487             :                                     io_first_block + j,
    1488             :                                     relpath(operation->smgr->smgr_rlocator, forknum))));
    1489           0 :                     memset(bufBlock, 0, BLCKSZ);
    1490             :                 }
    1491             :                 else
    1492           0 :                     ereport(ERROR,
    1493             :                             (errcode(ERRCODE_DATA_CORRUPTED),
    1494             :                              errmsg("invalid page in block %u of relation %s",
    1495             :                                     io_first_block + j,
    1496             :                                     relpath(operation->smgr->smgr_rlocator, forknum))));
    1497             :             }
    1498             : 
    1499             :             /* Terminate I/O and set BM_VALID. */
    1500     2162724 :             if (persistence == RELPERSISTENCE_TEMP)
    1501             :             {
    1502        7608 :                 uint32      buf_state = pg_atomic_read_u32(&bufHdr->state);
    1503             : 
    1504        7608 :                 buf_state |= BM_VALID;
    1505        7608 :                 pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
    1506             :             }
    1507             :             else
    1508             :             {
    1509             :                 /* Set BM_VALID, terminate IO, and wake up any waiters */
    1510     2155116 :                 TerminateBufferIO(bufHdr, false, BM_VALID, true);
    1511             :             }
    1512             : 
    1513             :             /* Report I/Os as completing individually. */
    1514             :             TRACE_POSTGRESQL_BUFFER_READ_DONE(forknum, io_first_block + j,
    1515             :                                               operation->smgr->smgr_rlocator.locator.spcOid,
    1516             :                                               operation->smgr->smgr_rlocator.locator.dbOid,
    1517             :                                               operation->smgr->smgr_rlocator.locator.relNumber,
    1518             :                                               operation->smgr->smgr_rlocator.backend,
    1519             :                                               false);
    1520             :         }
    1521             : 
    1522     2088854 :         VacuumPageMiss += io_buffers_len;
    1523     2088854 :         if (VacuumCostActive)
    1524         594 :             VacuumCostBalance += VacuumCostPageMiss * io_buffers_len;
    1525             :     }
    1526             : }
    1527             : 
    1528             : /*
    1529             :  * BufferAlloc -- subroutine for PinBufferForBlock.  Handles lookup of a shared
    1530             :  *      buffer.  If no buffer exists already, selects a replacement victim and
    1531             :  *      evicts the old page, but does NOT read in new page.
    1532             :  *
    1533             :  * "strategy" can be a buffer replacement strategy object, or NULL for
    1534             :  * the default strategy.  The selected buffer's usage_count is advanced when
    1535             :  * using the default strategy, but otherwise possibly not (see PinBuffer).
    1536             :  *
    1537             :  * The returned buffer is pinned and is already marked as holding the
    1538             :  * desired page.  If it already did have the desired page, *foundPtr is
    1539             :  * set true.  Otherwise, *foundPtr is set false.
    1540             :  *
    1541             :  * io_context is passed as an output parameter to avoid calling
    1542             :  * IOContextForStrategy() when there is a shared buffers hit and no IO
    1543             :  * statistics need be captured.
    1544             :  *
    1545             :  * No locks are held either at entry or exit.
    1546             :  */
    1547             : static pg_attribute_always_inline BufferDesc *
    1548    91833620 : BufferAlloc(SMgrRelation smgr, char relpersistence, ForkNumber forkNum,
    1549             :             BlockNumber blockNum,
    1550             :             BufferAccessStrategy strategy,
    1551             :             bool *foundPtr, IOContext io_context)
    1552             : {
    1553             :     BufferTag   newTag;         /* identity of requested block */
    1554             :     uint32      newHash;        /* hash value for newTag */
    1555             :     LWLock     *newPartitionLock;   /* buffer partition lock for it */
    1556             :     int         existing_buf_id;
    1557             :     Buffer      victim_buffer;
    1558             :     BufferDesc *victim_buf_hdr;
    1559             :     uint32      victim_buf_state;
    1560             : 
    1561             :     /* Make sure we will have room to remember the buffer pin */
    1562    91833620 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    1563    91833620 :     ReservePrivateRefCountEntry();
    1564             : 
    1565             :     /* create a tag so we can lookup the buffer */
    1566    91833620 :     InitBufferTag(&newTag, &smgr->smgr_rlocator.locator, forkNum, blockNum);
    1567             : 
    1568             :     /* determine its hash code and partition lock ID */
    1569    91833620 :     newHash = BufTableHashCode(&newTag);
    1570    91833620 :     newPartitionLock = BufMappingPartitionLock(newHash);
    1571             : 
    1572             :     /* see if the block is in the buffer pool already */
    1573    91833620 :     LWLockAcquire(newPartitionLock, LW_SHARED);
    1574    91833620 :     existing_buf_id = BufTableLookup(&newTag, newHash);
    1575    91833620 :     if (existing_buf_id >= 0)
    1576             :     {
    1577             :         BufferDesc *buf;
    1578             :         bool        valid;
    1579             : 
    1580             :         /*
    1581             :          * Found it.  Now, pin the buffer so no one can steal it from the
    1582             :          * buffer pool, and check to see if the correct data has been loaded
    1583             :          * into the buffer.
    1584             :          */
    1585    89237012 :         buf = GetBufferDescriptor(existing_buf_id);
    1586             : 
    1587    89237012 :         valid = PinBuffer(buf, strategy);
    1588             : 
    1589             :         /* Can release the mapping lock as soon as we've pinned it */
    1590    89237012 :         LWLockRelease(newPartitionLock);
    1591             : 
    1592    89237012 :         *foundPtr = true;
    1593             : 
    1594    89237012 :         if (!valid)
    1595             :         {
    1596             :             /*
    1597             :              * We can only get here if (a) someone else is still reading in
    1598             :              * the page, (b) a previous read attempt failed, or (c) someone
    1599             :              * called StartReadBuffers() but not yet WaitReadBuffers().
    1600             :              */
    1601        1160 :             *foundPtr = false;
    1602             :         }
    1603             : 
    1604    89237012 :         return buf;
    1605             :     }
    1606             : 
    1607             :     /*
    1608             :      * Didn't find it in the buffer pool.  We'll have to initialize a new
    1609             :      * buffer.  Remember to unlock the mapping lock while doing the work.
    1610             :      */
    1611     2596608 :     LWLockRelease(newPartitionLock);
    1612             : 
    1613             :     /*
    1614             :      * Acquire a victim buffer. Somebody else might try to do the same, we
    1615             :      * don't hold any conflicting locks. If so we'll have to undo our work
    1616             :      * later.
    1617             :      */
    1618     2596608 :     victim_buffer = GetVictimBuffer(strategy, io_context);
    1619     2596608 :     victim_buf_hdr = GetBufferDescriptor(victim_buffer - 1);
    1620             : 
    1621             :     /*
    1622             :      * Try to make a hashtable entry for the buffer under its new tag. If
    1623             :      * somebody else inserted another buffer for the tag, we'll release the
    1624             :      * victim buffer we acquired and use the already inserted one.
    1625             :      */
    1626     2596608 :     LWLockAcquire(newPartitionLock, LW_EXCLUSIVE);
    1627     2596608 :     existing_buf_id = BufTableInsert(&newTag, newHash, victim_buf_hdr->buf_id);
    1628     2596608 :     if (existing_buf_id >= 0)
    1629             :     {
    1630             :         BufferDesc *existing_buf_hdr;
    1631             :         bool        valid;
    1632             : 
    1633             :         /*
    1634             :          * Got a collision. Someone has already done what we were about to do.
    1635             :          * We'll just handle this as if it were found in the buffer pool in
    1636             :          * the first place.  First, give up the buffer we were planning to
    1637             :          * use.
    1638             :          *
    1639             :          * We could do this after releasing the partition lock, but then we'd
    1640             :          * have to call ResourceOwnerEnlarge() & ReservePrivateRefCountEntry()
    1641             :          * before acquiring the lock, for the rare case of such a collision.
    1642             :          */
    1643         550 :         UnpinBuffer(victim_buf_hdr);
    1644             : 
    1645             :         /*
    1646             :          * The victim buffer we acquired previously is clean and unused, let
    1647             :          * it be found again quickly
    1648             :          */
    1649         550 :         StrategyFreeBuffer(victim_buf_hdr);
    1650             : 
    1651             :         /* remaining code should match code at top of routine */
    1652             : 
    1653         550 :         existing_buf_hdr = GetBufferDescriptor(existing_buf_id);
    1654             : 
    1655         550 :         valid = PinBuffer(existing_buf_hdr, strategy);
    1656             : 
    1657             :         /* Can release the mapping lock as soon as we've pinned it */
    1658         550 :         LWLockRelease(newPartitionLock);
    1659             : 
    1660         550 :         *foundPtr = true;
    1661             : 
    1662         550 :         if (!valid)
    1663             :         {
    1664             :             /*
    1665             :              * We can only get here if (a) someone else is still reading in
    1666             :              * the page, (b) a previous read attempt failed, or (c) someone
    1667             :              * called StartReadBuffers() but not yet WaitReadBuffers().
    1668             :              */
    1669         344 :             *foundPtr = false;
    1670             :         }
    1671             : 
    1672         550 :         return existing_buf_hdr;
    1673             :     }
    1674             : 
    1675             :     /*
    1676             :      * Need to lock the buffer header too in order to change its tag.
    1677             :      */
    1678     2596058 :     victim_buf_state = LockBufHdr(victim_buf_hdr);
    1679             : 
    1680             :     /* some sanity checks while we hold the buffer header lock */
    1681             :     Assert(BUF_STATE_GET_REFCOUNT(victim_buf_state) == 1);
    1682             :     Assert(!(victim_buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY | BM_IO_IN_PROGRESS)));
    1683             : 
    1684     2596058 :     victim_buf_hdr->tag = newTag;
    1685             : 
    1686             :     /*
    1687             :      * Make sure BM_PERMANENT is set for buffers that must be written at every
    1688             :      * checkpoint.  Unlogged buffers only need to be written at shutdown
    1689             :      * checkpoints, except for their "init" forks, which need to be treated
    1690             :      * just like permanent relations.
    1691             :      */
    1692     2596058 :     victim_buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
    1693     2596058 :     if (relpersistence == RELPERSISTENCE_PERMANENT || forkNum == INIT_FORKNUM)
    1694     2595968 :         victim_buf_state |= BM_PERMANENT;
    1695             : 
    1696     2596058 :     UnlockBufHdr(victim_buf_hdr, victim_buf_state);
    1697             : 
    1698     2596058 :     LWLockRelease(newPartitionLock);
    1699             : 
    1700             :     /*
    1701             :      * Buffer contents are currently invalid.
    1702             :      */
    1703     2596058 :     *foundPtr = false;
    1704             : 
    1705     2596058 :     return victim_buf_hdr;
    1706             : }
    1707             : 
    1708             : /*
    1709             :  * InvalidateBuffer -- mark a shared buffer invalid and return it to the
    1710             :  * freelist.
    1711             :  *
    1712             :  * The buffer header spinlock must be held at entry.  We drop it before
    1713             :  * returning.  (This is sane because the caller must have locked the
    1714             :  * buffer in order to be sure it should be dropped.)
    1715             :  *
    1716             :  * This is used only in contexts such as dropping a relation.  We assume
    1717             :  * that no other backend could possibly be interested in using the page,
    1718             :  * so the only reason the buffer might be pinned is if someone else is
    1719             :  * trying to write it out.  We have to let them finish before we can
    1720             :  * reclaim the buffer.
    1721             :  *
    1722             :  * The buffer could get reclaimed by someone else while we are waiting
    1723             :  * to acquire the necessary locks; if so, don't mess it up.
    1724             :  */
    1725             : static void
    1726      188044 : InvalidateBuffer(BufferDesc *buf)
    1727             : {
    1728             :     BufferTag   oldTag;
    1729             :     uint32      oldHash;        /* hash value for oldTag */
    1730             :     LWLock     *oldPartitionLock;   /* buffer partition lock for it */
    1731             :     uint32      oldFlags;
    1732             :     uint32      buf_state;
    1733             : 
    1734             :     /* Save the original buffer tag before dropping the spinlock */
    1735      188044 :     oldTag = buf->tag;
    1736             : 
    1737      188044 :     buf_state = pg_atomic_read_u32(&buf->state);
    1738             :     Assert(buf_state & BM_LOCKED);
    1739      188044 :     UnlockBufHdr(buf, buf_state);
    1740             : 
    1741             :     /*
    1742             :      * Need to compute the old tag's hashcode and partition lock ID. XXX is it
    1743             :      * worth storing the hashcode in BufferDesc so we need not recompute it
    1744             :      * here?  Probably not.
    1745             :      */
    1746      188044 :     oldHash = BufTableHashCode(&oldTag);
    1747      188044 :     oldPartitionLock = BufMappingPartitionLock(oldHash);
    1748             : 
    1749      188048 : retry:
    1750             : 
    1751             :     /*
    1752             :      * Acquire exclusive mapping lock in preparation for changing the buffer's
    1753             :      * association.
    1754             :      */
    1755      188048 :     LWLockAcquire(oldPartitionLock, LW_EXCLUSIVE);
    1756             : 
    1757             :     /* Re-lock the buffer header */
    1758      188048 :     buf_state = LockBufHdr(buf);
    1759             : 
    1760             :     /* If it's changed while we were waiting for lock, do nothing */
    1761      188048 :     if (!BufferTagsEqual(&buf->tag, &oldTag))
    1762             :     {
    1763           4 :         UnlockBufHdr(buf, buf_state);
    1764           4 :         LWLockRelease(oldPartitionLock);
    1765           4 :         return;
    1766             :     }
    1767             : 
    1768             :     /*
    1769             :      * We assume the only reason for it to be pinned is that someone else is
    1770             :      * flushing the page out.  Wait for them to finish.  (This could be an
    1771             :      * infinite loop if the refcount is messed up... it would be nice to time
    1772             :      * out after awhile, but there seems no way to be sure how many loops may
    1773             :      * be needed.  Note that if the other guy has pinned the buffer but not
    1774             :      * yet done StartBufferIO, WaitIO will fall through and we'll effectively
    1775             :      * be busy-looping here.)
    1776             :      */
    1777      188044 :     if (BUF_STATE_GET_REFCOUNT(buf_state) != 0)
    1778             :     {
    1779           4 :         UnlockBufHdr(buf, buf_state);
    1780           4 :         LWLockRelease(oldPartitionLock);
    1781             :         /* safety check: should definitely not be our *own* pin */
    1782           4 :         if (GetPrivateRefCount(BufferDescriptorGetBuffer(buf)) > 0)
    1783           0 :             elog(ERROR, "buffer is pinned in InvalidateBuffer");
    1784           4 :         WaitIO(buf);
    1785           4 :         goto retry;
    1786             :     }
    1787             : 
    1788             :     /*
    1789             :      * Clear out the buffer's tag and flags.  We must do this to ensure that
    1790             :      * linear scans of the buffer array don't think the buffer is valid.
    1791             :      */
    1792      188040 :     oldFlags = buf_state & BUF_FLAG_MASK;
    1793      188040 :     ClearBufferTag(&buf->tag);
    1794      188040 :     buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
    1795      188040 :     UnlockBufHdr(buf, buf_state);
    1796             : 
    1797             :     /*
    1798             :      * Remove the buffer from the lookup hashtable, if it was in there.
    1799             :      */
    1800      188040 :     if (oldFlags & BM_TAG_VALID)
    1801      188040 :         BufTableDelete(&oldTag, oldHash);
    1802             : 
    1803             :     /*
    1804             :      * Done with mapping lock.
    1805             :      */
    1806      188040 :     LWLockRelease(oldPartitionLock);
    1807             : 
    1808             :     /*
    1809             :      * Insert the buffer at the head of the list of free buffers.
    1810             :      */
    1811      188040 :     StrategyFreeBuffer(buf);
    1812             : }
    1813             : 
    1814             : /*
    1815             :  * Helper routine for GetVictimBuffer()
    1816             :  *
    1817             :  * Needs to be called on a buffer with a valid tag, pinned, but without the
    1818             :  * buffer header spinlock held.
    1819             :  *
    1820             :  * Returns true if the buffer can be reused, in which case the buffer is only
    1821             :  * pinned by this backend and marked as invalid, false otherwise.
    1822             :  */
    1823             : static bool
    1824     1872944 : InvalidateVictimBuffer(BufferDesc *buf_hdr)
    1825             : {
    1826             :     uint32      buf_state;
    1827             :     uint32      hash;
    1828             :     LWLock     *partition_lock;
    1829             :     BufferTag   tag;
    1830             : 
    1831             :     Assert(GetPrivateRefCount(BufferDescriptorGetBuffer(buf_hdr)) == 1);
    1832             : 
    1833             :     /* have buffer pinned, so it's safe to read tag without lock */
    1834     1872944 :     tag = buf_hdr->tag;
    1835             : 
    1836     1872944 :     hash = BufTableHashCode(&tag);
    1837     1872944 :     partition_lock = BufMappingPartitionLock(hash);
    1838             : 
    1839     1872944 :     LWLockAcquire(partition_lock, LW_EXCLUSIVE);
    1840             : 
    1841             :     /* lock the buffer header */
    1842     1872944 :     buf_state = LockBufHdr(buf_hdr);
    1843             : 
    1844             :     /*
    1845             :      * We have the buffer pinned nobody else should have been able to unset
    1846             :      * this concurrently.
    1847             :      */
    1848             :     Assert(buf_state & BM_TAG_VALID);
    1849             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    1850             :     Assert(BufferTagsEqual(&buf_hdr->tag, &tag));
    1851             : 
    1852             :     /*
    1853             :      * If somebody else pinned the buffer since, or even worse, dirtied it,
    1854             :      * give up on this buffer: It's clearly in use.
    1855             :      */
    1856     1872944 :     if (BUF_STATE_GET_REFCOUNT(buf_state) != 1 || (buf_state & BM_DIRTY))
    1857             :     {
    1858             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    1859             : 
    1860         396 :         UnlockBufHdr(buf_hdr, buf_state);
    1861         396 :         LWLockRelease(partition_lock);
    1862             : 
    1863         396 :         return false;
    1864             :     }
    1865             : 
    1866             :     /*
    1867             :      * Clear out the buffer's tag and flags and usagecount.  This is not
    1868             :      * strictly required, as BM_TAG_VALID/BM_VALID needs to be checked before
    1869             :      * doing anything with the buffer. But currently it's beneficial, as the
    1870             :      * cheaper pre-check for several linear scans of shared buffers use the
    1871             :      * tag (see e.g. FlushDatabaseBuffers()).
    1872             :      */
    1873     1872548 :     ClearBufferTag(&buf_hdr->tag);
    1874     1872548 :     buf_state &= ~(BUF_FLAG_MASK | BUF_USAGECOUNT_MASK);
    1875     1872548 :     UnlockBufHdr(buf_hdr, buf_state);
    1876             : 
    1877             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    1878             : 
    1879             :     /* finally delete buffer from the buffer mapping table */
    1880     1872548 :     BufTableDelete(&tag, hash);
    1881             : 
    1882     1872548 :     LWLockRelease(partition_lock);
    1883             : 
    1884             :     Assert(!(buf_state & (BM_DIRTY | BM_VALID | BM_TAG_VALID)));
    1885             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    1886             :     Assert(BUF_STATE_GET_REFCOUNT(pg_atomic_read_u32(&buf_hdr->state)) > 0);
    1887             : 
    1888     1872548 :     return true;
    1889             : }
    1890             : 
    1891             : static Buffer
    1892     2988306 : GetVictimBuffer(BufferAccessStrategy strategy, IOContext io_context)
    1893             : {
    1894             :     BufferDesc *buf_hdr;
    1895             :     Buffer      buf;
    1896             :     uint32      buf_state;
    1897             :     bool        from_ring;
    1898             : 
    1899             :     /*
    1900             :      * Ensure, while the spinlock's not yet held, that there's a free refcount
    1901             :      * entry, and a resource owner slot for the pin.
    1902             :      */
    1903     2988306 :     ReservePrivateRefCountEntry();
    1904     2988306 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    1905             : 
    1906             :     /* we return here if a prospective victim buffer gets used concurrently */
    1907     2997742 : again:
    1908             : 
    1909             :     /*
    1910             :      * Select a victim buffer.  The buffer is returned with its header
    1911             :      * spinlock still held!
    1912             :      */
    1913     2997742 :     buf_hdr = StrategyGetBuffer(strategy, &buf_state, &from_ring);
    1914     2997742 :     buf = BufferDescriptorGetBuffer(buf_hdr);
    1915             : 
    1916             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 0);
    1917             : 
    1918             :     /* Pin the buffer and then release the buffer spinlock */
    1919     2997742 :     PinBuffer_Locked(buf_hdr);
    1920             : 
    1921             :     /*
    1922             :      * We shouldn't have any other pins for this buffer.
    1923             :      */
    1924     2997742 :     CheckBufferIsPinnedOnce(buf);
    1925             : 
    1926             :     /*
    1927             :      * If the buffer was dirty, try to write it out.  There is a race
    1928             :      * condition here, in that someone might dirty it after we released the
    1929             :      * buffer header lock above, or even while we are writing it out (since
    1930             :      * our share-lock won't prevent hint-bit updates).  We will recheck the
    1931             :      * dirty bit after re-locking the buffer header.
    1932             :      */
    1933     2997742 :     if (buf_state & BM_DIRTY)
    1934             :     {
    1935             :         LWLock     *content_lock;
    1936             : 
    1937             :         Assert(buf_state & BM_TAG_VALID);
    1938             :         Assert(buf_state & BM_VALID);
    1939             : 
    1940             :         /*
    1941             :          * We need a share-lock on the buffer contents to write it out (else
    1942             :          * we might write invalid data, eg because someone else is compacting
    1943             :          * the page contents while we write).  We must use a conditional lock
    1944             :          * acquisition here to avoid deadlock.  Even though the buffer was not
    1945             :          * pinned (and therefore surely not locked) when StrategyGetBuffer
    1946             :          * returned it, someone else could have pinned and exclusive-locked it
    1947             :          * by the time we get here. If we try to get the lock unconditionally,
    1948             :          * we'd block waiting for them; if they later block waiting for us,
    1949             :          * deadlock ensues. (This has been observed to happen when two
    1950             :          * backends are both trying to split btree index pages, and the second
    1951             :          * one just happens to be trying to split the page the first one got
    1952             :          * from StrategyGetBuffer.)
    1953             :          */
    1954      445706 :         content_lock = BufferDescriptorGetContentLock(buf_hdr);
    1955      445706 :         if (!LWLockConditionalAcquire(content_lock, LW_SHARED))
    1956             :         {
    1957             :             /*
    1958             :              * Someone else has locked the buffer, so give it up and loop back
    1959             :              * to get another one.
    1960             :              */
    1961           0 :             UnpinBuffer(buf_hdr);
    1962           0 :             goto again;
    1963             :         }
    1964             : 
    1965             :         /*
    1966             :          * If using a nondefault strategy, and writing the buffer would
    1967             :          * require a WAL flush, let the strategy decide whether to go ahead
    1968             :          * and write/reuse the buffer or to choose another victim.  We need a
    1969             :          * lock to inspect the page LSN, so this can't be done inside
    1970             :          * StrategyGetBuffer.
    1971             :          */
    1972      445706 :         if (strategy != NULL)
    1973             :         {
    1974             :             XLogRecPtr  lsn;
    1975             : 
    1976             :             /* Read the LSN while holding buffer header lock */
    1977      122978 :             buf_state = LockBufHdr(buf_hdr);
    1978      122978 :             lsn = BufferGetLSN(buf_hdr);
    1979      122978 :             UnlockBufHdr(buf_hdr, buf_state);
    1980             : 
    1981      122978 :             if (XLogNeedsFlush(lsn)
    1982       12962 :                 && StrategyRejectBuffer(strategy, buf_hdr, from_ring))
    1983             :             {
    1984        9040 :                 LWLockRelease(content_lock);
    1985        9040 :                 UnpinBuffer(buf_hdr);
    1986        9040 :                 goto again;
    1987             :             }
    1988             :         }
    1989             : 
    1990             :         /* OK, do the I/O */
    1991      436666 :         FlushBuffer(buf_hdr, NULL, IOOBJECT_RELATION, io_context);
    1992      436666 :         LWLockRelease(content_lock);
    1993             : 
    1994      436666 :         ScheduleBufferTagForWriteback(&BackendWritebackContext, io_context,
    1995             :                                       &buf_hdr->tag);
    1996             :     }
    1997             : 
    1998             : 
    1999     2988702 :     if (buf_state & BM_VALID)
    2000             :     {
    2001             :         /*
    2002             :          * When a BufferAccessStrategy is in use, blocks evicted from shared
    2003             :          * buffers are counted as IOOP_EVICT in the corresponding context
    2004             :          * (e.g. IOCONTEXT_BULKWRITE). Shared buffers are evicted by a
    2005             :          * strategy in two cases: 1) while initially claiming buffers for the
    2006             :          * strategy ring 2) to replace an existing strategy ring buffer
    2007             :          * because it is pinned or in use and cannot be reused.
    2008             :          *
    2009             :          * Blocks evicted from buffers already in the strategy ring are
    2010             :          * counted as IOOP_REUSE in the corresponding strategy context.
    2011             :          *
    2012             :          * At this point, we can accurately count evictions and reuses,
    2013             :          * because we have successfully claimed the valid buffer. Previously,
    2014             :          * we may have been forced to release the buffer due to concurrent
    2015             :          * pinners or erroring out.
    2016             :          */
    2017     1872942 :         pgstat_count_io_op(IOOBJECT_RELATION, io_context,
    2018     1872942 :                            from_ring ? IOOP_REUSE : IOOP_EVICT);
    2019             :     }
    2020             : 
    2021             :     /*
    2022             :      * If the buffer has an entry in the buffer mapping table, delete it. This
    2023             :      * can fail because another backend could have pinned or dirtied the
    2024             :      * buffer.
    2025             :      */
    2026     2988702 :     if ((buf_state & BM_TAG_VALID) && !InvalidateVictimBuffer(buf_hdr))
    2027             :     {
    2028         396 :         UnpinBuffer(buf_hdr);
    2029         396 :         goto again;
    2030             :     }
    2031             : 
    2032             :     /* a final set of sanity checks */
    2033             : #ifdef USE_ASSERT_CHECKING
    2034             :     buf_state = pg_atomic_read_u32(&buf_hdr->state);
    2035             : 
    2036             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
    2037             :     Assert(!(buf_state & (BM_TAG_VALID | BM_VALID | BM_DIRTY)));
    2038             : 
    2039             :     CheckBufferIsPinnedOnce(buf);
    2040             : #endif
    2041             : 
    2042     2988306 :     return buf;
    2043             : }
    2044             : 
    2045             : /*
    2046             :  * Limit the number of pins a batch operation may additionally acquire, to
    2047             :  * avoid running out of pinnable buffers.
    2048             :  *
    2049             :  * One additional pin is always allowed, as otherwise the operation likely
    2050             :  * cannot be performed at all.
    2051             :  *
    2052             :  * The number of allowed pins for a backend is computed based on
    2053             :  * shared_buffers and the maximum number of connections possible. That's very
    2054             :  * pessimistic, but outside of toy-sized shared_buffers it should allow
    2055             :  * sufficient pins.
    2056             :  */
    2057             : void
    2058      926720 : LimitAdditionalPins(uint32 *additional_pins)
    2059             : {
    2060             :     uint32      max_backends;
    2061             :     int         max_proportional_pins;
    2062             : 
    2063      926720 :     if (*additional_pins <= 1)
    2064      334542 :         return;
    2065             : 
    2066      592178 :     max_backends = MaxBackends + NUM_AUXILIARY_PROCS;
    2067      592178 :     max_proportional_pins = NBuffers / max_backends;
    2068             : 
    2069             :     /*
    2070             :      * Subtract the approximate number of buffers already pinned by this
    2071             :      * backend. We get the number of "overflowed" pins for free, but don't
    2072             :      * know the number of pins in PrivateRefCountArray. The cost of
    2073             :      * calculating that exactly doesn't seem worth it, so just assume the max.
    2074             :      */
    2075      592178 :     max_proportional_pins -= PrivateRefCountOverflowed + REFCOUNT_ARRAY_ENTRIES;
    2076             : 
    2077      592178 :     if (max_proportional_pins <= 0)
    2078      136862 :         max_proportional_pins = 1;
    2079             : 
    2080      592178 :     if (*additional_pins > max_proportional_pins)
    2081      138282 :         *additional_pins = max_proportional_pins;
    2082             : }
    2083             : 
    2084             : /*
    2085             :  * Logic shared between ExtendBufferedRelBy(), ExtendBufferedRelTo(). Just to
    2086             :  * avoid duplicating the tracing and relpersistence related logic.
    2087             :  */
    2088             : static BlockNumber
    2089      370048 : ExtendBufferedRelCommon(BufferManagerRelation bmr,
    2090             :                         ForkNumber fork,
    2091             :                         BufferAccessStrategy strategy,
    2092             :                         uint32 flags,
    2093             :                         uint32 extend_by,
    2094             :                         BlockNumber extend_upto,
    2095             :                         Buffer *buffers,
    2096             :                         uint32 *extended_by)
    2097             : {
    2098             :     BlockNumber first_block;
    2099             : 
    2100             :     TRACE_POSTGRESQL_BUFFER_EXTEND_START(fork,
    2101             :                                          bmr.smgr->smgr_rlocator.locator.spcOid,
    2102             :                                          bmr.smgr->smgr_rlocator.locator.dbOid,
    2103             :                                          bmr.smgr->smgr_rlocator.locator.relNumber,
    2104             :                                          bmr.smgr->smgr_rlocator.backend,
    2105             :                                          extend_by);
    2106             : 
    2107      370048 :     if (bmr.relpersistence == RELPERSISTENCE_TEMP)
    2108       17536 :         first_block = ExtendBufferedRelLocal(bmr, fork, flags,
    2109             :                                              extend_by, extend_upto,
    2110             :                                              buffers, &extend_by);
    2111             :     else
    2112      352512 :         first_block = ExtendBufferedRelShared(bmr, fork, strategy, flags,
    2113             :                                               extend_by, extend_upto,
    2114             :                                               buffers, &extend_by);
    2115      370048 :     *extended_by = extend_by;
    2116             : 
    2117             :     TRACE_POSTGRESQL_BUFFER_EXTEND_DONE(fork,
    2118             :                                         bmr.smgr->smgr_rlocator.locator.spcOid,
    2119             :                                         bmr.smgr->smgr_rlocator.locator.dbOid,
    2120             :                                         bmr.smgr->smgr_rlocator.locator.relNumber,
    2121             :                                         bmr.smgr->smgr_rlocator.backend,
    2122             :                                         *extended_by,
    2123             :                                         first_block);
    2124             : 
    2125      370048 :     return first_block;
    2126             : }
    2127             : 
    2128             : /*
    2129             :  * Implementation of ExtendBufferedRelBy() and ExtendBufferedRelTo() for
    2130             :  * shared buffers.
    2131             :  */
    2132             : static BlockNumber
    2133      352512 : ExtendBufferedRelShared(BufferManagerRelation bmr,
    2134             :                         ForkNumber fork,
    2135             :                         BufferAccessStrategy strategy,
    2136             :                         uint32 flags,
    2137             :                         uint32 extend_by,
    2138             :                         BlockNumber extend_upto,
    2139             :                         Buffer *buffers,
    2140             :                         uint32 *extended_by)
    2141             : {
    2142             :     BlockNumber first_block;
    2143      352512 :     IOContext   io_context = IOContextForStrategy(strategy);
    2144             :     instr_time  io_start;
    2145             : 
    2146      352512 :     LimitAdditionalPins(&extend_by);
    2147             : 
    2148             :     /*
    2149             :      * Acquire victim buffers for extension without holding extension lock.
    2150             :      * Writing out victim buffers is the most expensive part of extending the
    2151             :      * relation, particularly when doing so requires WAL flushes. Zeroing out
    2152             :      * the buffers is also quite expensive, so do that before holding the
    2153             :      * extension lock as well.
    2154             :      *
    2155             :      * These pages are pinned by us and not valid. While we hold the pin they
    2156             :      * can't be acquired as victim buffers by another backend.
    2157             :      */
    2158      744210 :     for (uint32 i = 0; i < extend_by; i++)
    2159             :     {
    2160             :         Block       buf_block;
    2161             : 
    2162      391698 :         buffers[i] = GetVictimBuffer(strategy, io_context);
    2163      391698 :         buf_block = BufHdrGetBlock(GetBufferDescriptor(buffers[i] - 1));
    2164             : 
    2165             :         /* new buffers are zero-filled */
    2166      391698 :         MemSet((char *) buf_block, 0, BLCKSZ);
    2167             :     }
    2168             : 
    2169             :     /*
    2170             :      * Lock relation against concurrent extensions, unless requested not to.
    2171             :      *
    2172             :      * We use the same extension lock for all forks. That's unnecessarily
    2173             :      * restrictive, but currently extensions for forks don't happen often
    2174             :      * enough to make it worth locking more granularly.
    2175             :      *
    2176             :      * Note that another backend might have extended the relation by the time
    2177             :      * we get the lock.
    2178             :      */
    2179      352512 :     if (!(flags & EB_SKIP_EXTENSION_LOCK))
    2180      259234 :         LockRelationForExtension(bmr.rel, ExclusiveLock);
    2181             : 
    2182             :     /*
    2183             :      * If requested, invalidate size cache, so that smgrnblocks asks the
    2184             :      * kernel.
    2185             :      */
    2186      352512 :     if (flags & EB_CLEAR_SIZE_CACHE)
    2187       12656 :         bmr.smgr->smgr_cached_nblocks[fork] = InvalidBlockNumber;
    2188             : 
    2189      352512 :     first_block = smgrnblocks(bmr.smgr, fork);
    2190             : 
    2191             :     /*
    2192             :      * Now that we have the accurate relation size, check if the caller wants
    2193             :      * us to extend to only up to a specific size. If there were concurrent
    2194             :      * extensions, we might have acquired too many buffers and need to release
    2195             :      * them.
    2196             :      */
    2197      352512 :     if (extend_upto != InvalidBlockNumber)
    2198             :     {
    2199       94410 :         uint32      orig_extend_by = extend_by;
    2200             : 
    2201       94410 :         if (first_block > extend_upto)
    2202           0 :             extend_by = 0;
    2203       94410 :         else if ((uint64) first_block + extend_by > extend_upto)
    2204          14 :             extend_by = extend_upto - first_block;
    2205             : 
    2206       94440 :         for (uint32 i = extend_by; i < orig_extend_by; i++)
    2207             :         {
    2208          30 :             BufferDesc *buf_hdr = GetBufferDescriptor(buffers[i] - 1);
    2209             : 
    2210             :             /*
    2211             :              * The victim buffer we acquired previously is clean and unused,
    2212             :              * let it be found again quickly
    2213             :              */
    2214          30 :             StrategyFreeBuffer(buf_hdr);
    2215          30 :             UnpinBuffer(buf_hdr);
    2216             :         }
    2217             : 
    2218       94410 :         if (extend_by == 0)
    2219             :         {
    2220          14 :             if (!(flags & EB_SKIP_EXTENSION_LOCK))
    2221          14 :                 UnlockRelationForExtension(bmr.rel, ExclusiveLock);
    2222          14 :             *extended_by = extend_by;
    2223          14 :             return first_block;
    2224             :         }
    2225             :     }
    2226             : 
    2227             :     /* Fail if relation is already at maximum possible length */
    2228      352498 :     if ((uint64) first_block + extend_by >= MaxBlockNumber)
    2229           0 :         ereport(ERROR,
    2230             :                 (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
    2231             :                  errmsg("cannot extend relation %s beyond %u blocks",
    2232             :                         relpath(bmr.smgr->smgr_rlocator, fork),
    2233             :                         MaxBlockNumber)));
    2234             : 
    2235             :     /*
    2236             :      * Insert buffers into buffer table, mark as IO_IN_PROGRESS.
    2237             :      *
    2238             :      * This needs to happen before we extend the relation, because as soon as
    2239             :      * we do, other backends can start to read in those pages.
    2240             :      */
    2241      744166 :     for (uint32 i = 0; i < extend_by; i++)
    2242             :     {
    2243      391668 :         Buffer      victim_buf = buffers[i];
    2244      391668 :         BufferDesc *victim_buf_hdr = GetBufferDescriptor(victim_buf - 1);
    2245             :         BufferTag   tag;
    2246             :         uint32      hash;
    2247             :         LWLock     *partition_lock;
    2248             :         int         existing_id;
    2249             : 
    2250             :         /* in case we need to pin an existing buffer below */
    2251      391668 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    2252      391668 :         ReservePrivateRefCountEntry();
    2253             : 
    2254      391668 :         InitBufferTag(&tag, &bmr.smgr->smgr_rlocator.locator, fork, first_block + i);
    2255      391668 :         hash = BufTableHashCode(&tag);
    2256      391668 :         partition_lock = BufMappingPartitionLock(hash);
    2257             : 
    2258      391668 :         LWLockAcquire(partition_lock, LW_EXCLUSIVE);
    2259             : 
    2260      391668 :         existing_id = BufTableInsert(&tag, hash, victim_buf_hdr->buf_id);
    2261             : 
    2262             :         /*
    2263             :          * We get here only in the corner case where we are trying to extend
    2264             :          * the relation but we found a pre-existing buffer. This can happen
    2265             :          * because a prior attempt at extending the relation failed, and
    2266             :          * because mdread doesn't complain about reads beyond EOF (when
    2267             :          * zero_damaged_pages is ON) and so a previous attempt to read a block
    2268             :          * beyond EOF could have left a "valid" zero-filled buffer.
    2269             :          * Unfortunately, we have also seen this case occurring because of
    2270             :          * buggy Linux kernels that sometimes return an lseek(SEEK_END) result
    2271             :          * that doesn't account for a recent write. In that situation, the
    2272             :          * pre-existing buffer would contain valid data that we don't want to
    2273             :          * overwrite.  Since the legitimate cases should always have left a
    2274             :          * zero-filled buffer, complain if not PageIsNew.
    2275             :          */
    2276      391668 :         if (existing_id >= 0)
    2277             :         {
    2278           0 :             BufferDesc *existing_hdr = GetBufferDescriptor(existing_id);
    2279             :             Block       buf_block;
    2280             :             bool        valid;
    2281             : 
    2282             :             /*
    2283             :              * Pin the existing buffer before releasing the partition lock,
    2284             :              * preventing it from being evicted.
    2285             :              */
    2286           0 :             valid = PinBuffer(existing_hdr, strategy);
    2287             : 
    2288           0 :             LWLockRelease(partition_lock);
    2289             : 
    2290             :             /*
    2291             :              * The victim buffer we acquired previously is clean and unused,
    2292             :              * let it be found again quickly
    2293             :              */
    2294           0 :             StrategyFreeBuffer(victim_buf_hdr);
    2295           0 :             UnpinBuffer(victim_buf_hdr);
    2296             : 
    2297           0 :             buffers[i] = BufferDescriptorGetBuffer(existing_hdr);
    2298           0 :             buf_block = BufHdrGetBlock(existing_hdr);
    2299             : 
    2300           0 :             if (valid && !PageIsNew((Page) buf_block))
    2301           0 :                 ereport(ERROR,
    2302             :                         (errmsg("unexpected data beyond EOF in block %u of relation %s",
    2303             :                                 existing_hdr->tag.blockNum, relpath(bmr.smgr->smgr_rlocator, fork)),
    2304             :                          errhint("This has been seen to occur with buggy kernels; consider updating your system.")));
    2305             : 
    2306             :             /*
    2307             :              * We *must* do smgr[zero]extend before succeeding, else the page
    2308             :              * will not be reserved by the kernel, and the next P_NEW call
    2309             :              * will decide to return the same page.  Clear the BM_VALID bit,
    2310             :              * do StartBufferIO() and proceed.
    2311             :              *
    2312             :              * Loop to handle the very small possibility that someone re-sets
    2313             :              * BM_VALID between our clearing it and StartBufferIO inspecting
    2314             :              * it.
    2315             :              */
    2316             :             do
    2317             :             {
    2318           0 :                 uint32      buf_state = LockBufHdr(existing_hdr);
    2319             : 
    2320           0 :                 buf_state &= ~BM_VALID;
    2321           0 :                 UnlockBufHdr(existing_hdr, buf_state);
    2322           0 :             } while (!StartBufferIO(existing_hdr, true, false));
    2323             :         }
    2324             :         else
    2325             :         {
    2326             :             uint32      buf_state;
    2327             : 
    2328      391668 :             buf_state = LockBufHdr(victim_buf_hdr);
    2329             : 
    2330             :             /* some sanity checks while we hold the buffer header lock */
    2331             :             Assert(!(buf_state & (BM_VALID | BM_TAG_VALID | BM_DIRTY | BM_JUST_DIRTIED)));
    2332             :             Assert(BUF_STATE_GET_REFCOUNT(buf_state) == 1);
    2333             : 
    2334      391668 :             victim_buf_hdr->tag = tag;
    2335             : 
    2336      391668 :             buf_state |= BM_TAG_VALID | BUF_USAGECOUNT_ONE;
    2337      391668 :             if (bmr.relpersistence == RELPERSISTENCE_PERMANENT || fork == INIT_FORKNUM)
    2338      383480 :                 buf_state |= BM_PERMANENT;
    2339             : 
    2340      391668 :             UnlockBufHdr(victim_buf_hdr, buf_state);
    2341             : 
    2342      391668 :             LWLockRelease(partition_lock);
    2343             : 
    2344             :             /* XXX: could combine the locked operations in it with the above */
    2345      391668 :             StartBufferIO(victim_buf_hdr, true, false);
    2346             :         }
    2347             :     }
    2348             : 
    2349      352498 :     io_start = pgstat_prepare_io_time(track_io_timing);
    2350             : 
    2351             :     /*
    2352             :      * Note: if smgrzeroextend fails, we will end up with buffers that are
    2353             :      * allocated but not marked BM_VALID.  The next relation extension will
    2354             :      * still select the same block number (because the relation didn't get any
    2355             :      * longer on disk) and so future attempts to extend the relation will find
    2356             :      * the same buffers (if they have not been recycled) but come right back
    2357             :      * here to try smgrzeroextend again.
    2358             :      *
    2359             :      * We don't need to set checksum for all-zero pages.
    2360             :      */
    2361      352498 :     smgrzeroextend(bmr.smgr, fork, first_block, extend_by, false);
    2362             : 
    2363             :     /*
    2364             :      * Release the file-extension lock; it's now OK for someone else to extend
    2365             :      * the relation some more.
    2366             :      *
    2367             :      * We remove IO_IN_PROGRESS after this, as waking up waiting backends can
    2368             :      * take noticeable time.
    2369             :      */
    2370      352498 :     if (!(flags & EB_SKIP_EXTENSION_LOCK))
    2371      259220 :         UnlockRelationForExtension(bmr.rel, ExclusiveLock);
    2372             : 
    2373      352498 :     pgstat_count_io_op_time(IOOBJECT_RELATION, io_context, IOOP_EXTEND,
    2374             :                             io_start, extend_by);
    2375             : 
    2376             :     /* Set BM_VALID, terminate IO, and wake up any waiters */
    2377      744166 :     for (uint32 i = 0; i < extend_by; i++)
    2378             :     {
    2379      391668 :         Buffer      buf = buffers[i];
    2380      391668 :         BufferDesc *buf_hdr = GetBufferDescriptor(buf - 1);
    2381      391668 :         bool        lock = false;
    2382             : 
    2383      391668 :         if (flags & EB_LOCK_FIRST && i == 0)
    2384      257616 :             lock = true;
    2385      134052 :         else if (flags & EB_LOCK_TARGET)
    2386             :         {
    2387             :             Assert(extend_upto != InvalidBlockNumber);
    2388       79758 :             if (first_block + i + 1 == extend_upto)
    2389       78694 :                 lock = true;
    2390             :         }
    2391             : 
    2392      391668 :         if (lock)
    2393      336310 :             LWLockAcquire(BufferDescriptorGetContentLock(buf_hdr), LW_EXCLUSIVE);
    2394             : 
    2395      391668 :         TerminateBufferIO(buf_hdr, false, BM_VALID, true);
    2396             :     }
    2397             : 
    2398      352498 :     pgBufferUsage.shared_blks_written += extend_by;
    2399             : 
    2400      352498 :     *extended_by = extend_by;
    2401             : 
    2402      352498 :     return first_block;
    2403             : }
    2404             : 
    2405             : /*
    2406             :  * BufferIsExclusiveLocked
    2407             :  *
    2408             :  *      Checks if buffer is exclusive-locked.
    2409             :  *
    2410             :  * Buffer must be pinned.
    2411             :  */
    2412             : bool
    2413           0 : BufferIsExclusiveLocked(Buffer buffer)
    2414             : {
    2415             :     BufferDesc *bufHdr;
    2416             : 
    2417           0 :     if (BufferIsLocal(buffer))
    2418             :     {
    2419           0 :         int         bufid = -buffer - 1;
    2420             : 
    2421           0 :         bufHdr = GetLocalBufferDescriptor(bufid);
    2422             :     }
    2423             :     else
    2424             :     {
    2425           0 :         bufHdr = GetBufferDescriptor(buffer - 1);
    2426             :     }
    2427             : 
    2428             :     Assert(BufferIsPinned(buffer));
    2429           0 :     return LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    2430             :                                 LW_EXCLUSIVE);
    2431             : }
    2432             : 
    2433             : /*
    2434             :  * BufferIsDirty
    2435             :  *
    2436             :  *      Checks if buffer is already dirty.
    2437             :  *
    2438             :  * Buffer must be pinned and exclusive-locked.  (Without an exclusive lock,
    2439             :  * the result may be stale before it's returned.)
    2440             :  */
    2441             : bool
    2442           0 : BufferIsDirty(Buffer buffer)
    2443             : {
    2444             :     BufferDesc *bufHdr;
    2445             : 
    2446           0 :     if (BufferIsLocal(buffer))
    2447             :     {
    2448           0 :         int         bufid = -buffer - 1;
    2449             : 
    2450           0 :         bufHdr = GetLocalBufferDescriptor(bufid);
    2451             :     }
    2452             :     else
    2453             :     {
    2454           0 :         bufHdr = GetBufferDescriptor(buffer - 1);
    2455             :     }
    2456             : 
    2457             :     Assert(BufferIsPinned(buffer));
    2458             :     Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    2459             :                                 LW_EXCLUSIVE));
    2460             : 
    2461           0 :     return pg_atomic_read_u32(&bufHdr->state) & BM_DIRTY;
    2462             : }
    2463             : 
    2464             : /*
    2465             :  * MarkBufferDirty
    2466             :  *
    2467             :  *      Marks buffer contents as dirty (actual write happens later).
    2468             :  *
    2469             :  * Buffer must be pinned and exclusive-locked.  (If caller does not hold
    2470             :  * exclusive lock, then somebody could be in process of writing the buffer,
    2471             :  * leading to risk of bad data written to disk.)
    2472             :  */
    2473             : void
    2474    38726248 : MarkBufferDirty(Buffer buffer)
    2475             : {
    2476             :     BufferDesc *bufHdr;
    2477             :     uint32      buf_state;
    2478             :     uint32      old_buf_state;
    2479             : 
    2480    38726248 :     if (!BufferIsValid(buffer))
    2481           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    2482             : 
    2483    38726248 :     if (BufferIsLocal(buffer))
    2484             :     {
    2485     2078558 :         MarkLocalBufferDirty(buffer);
    2486     2078558 :         return;
    2487             :     }
    2488             : 
    2489    36647690 :     bufHdr = GetBufferDescriptor(buffer - 1);
    2490             : 
    2491             :     Assert(BufferIsPinned(buffer));
    2492             :     Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    2493             :                                 LW_EXCLUSIVE));
    2494             : 
    2495    36647690 :     old_buf_state = pg_atomic_read_u32(&bufHdr->state);
    2496             :     for (;;)
    2497             :     {
    2498    36647938 :         if (old_buf_state & BM_LOCKED)
    2499          56 :             old_buf_state = WaitBufHdrUnlocked(bufHdr);
    2500             : 
    2501    36647938 :         buf_state = old_buf_state;
    2502             : 
    2503             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    2504    36647938 :         buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
    2505             : 
    2506    36647938 :         if (pg_atomic_compare_exchange_u32(&bufHdr->state, &old_buf_state,
    2507             :                                            buf_state))
    2508    36647690 :             break;
    2509             :     }
    2510             : 
    2511             :     /*
    2512             :      * If the buffer was not dirty already, do vacuum accounting.
    2513             :      */
    2514    36647690 :     if (!(old_buf_state & BM_DIRTY))
    2515             :     {
    2516     1062996 :         VacuumPageDirty++;
    2517     1062996 :         pgBufferUsage.shared_blks_dirtied++;
    2518     1062996 :         if (VacuumCostActive)
    2519        1948 :             VacuumCostBalance += VacuumCostPageDirty;
    2520             :     }
    2521             : }
    2522             : 
    2523             : /*
    2524             :  * ReleaseAndReadBuffer -- combine ReleaseBuffer() and ReadBuffer()
    2525             :  *
    2526             :  * Formerly, this saved one cycle of acquiring/releasing the BufMgrLock
    2527             :  * compared to calling the two routines separately.  Now it's mainly just
    2528             :  * a convenience function.  However, if the passed buffer is valid and
    2529             :  * already contains the desired block, we just return it as-is; and that
    2530             :  * does save considerable work compared to a full release and reacquire.
    2531             :  *
    2532             :  * Note: it is OK to pass buffer == InvalidBuffer, indicating that no old
    2533             :  * buffer actually needs to be released.  This case is the same as ReadBuffer,
    2534             :  * but can save some tests in the caller.
    2535             :  */
    2536             : Buffer
    2537    45246036 : ReleaseAndReadBuffer(Buffer buffer,
    2538             :                      Relation relation,
    2539             :                      BlockNumber blockNum)
    2540             : {
    2541    45246036 :     ForkNumber  forkNum = MAIN_FORKNUM;
    2542             :     BufferDesc *bufHdr;
    2543             : 
    2544    45246036 :     if (BufferIsValid(buffer))
    2545             :     {
    2546             :         Assert(BufferIsPinned(buffer));
    2547    26393450 :         if (BufferIsLocal(buffer))
    2548             :         {
    2549       11262 :             bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    2550       15282 :             if (bufHdr->tag.blockNum == blockNum &&
    2551        8040 :                 BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
    2552        4020 :                 BufTagGetForkNum(&bufHdr->tag) == forkNum)
    2553        4020 :                 return buffer;
    2554        7242 :             UnpinLocalBuffer(buffer);
    2555             :         }
    2556             :         else
    2557             :         {
    2558    26382188 :             bufHdr = GetBufferDescriptor(buffer - 1);
    2559             :             /* we have pin, so it's ok to examine tag without spinlock */
    2560    35339530 :             if (bufHdr->tag.blockNum == blockNum &&
    2561    17914684 :                 BufTagMatchesRelFileLocator(&bufHdr->tag, &relation->rd_locator) &&
    2562     8957342 :                 BufTagGetForkNum(&bufHdr->tag) == forkNum)
    2563     8957342 :                 return buffer;
    2564    17424846 :             UnpinBuffer(bufHdr);
    2565             :         }
    2566             :     }
    2567             : 
    2568    36284674 :     return ReadBuffer(relation, blockNum);
    2569             : }
    2570             : 
    2571             : /*
    2572             :  * PinBuffer -- make buffer unavailable for replacement.
    2573             :  *
    2574             :  * For the default access strategy, the buffer's usage_count is incremented
    2575             :  * when we first pin it; for other strategies we just make sure the usage_count
    2576             :  * isn't zero.  (The idea of the latter is that we don't want synchronized
    2577             :  * heap scans to inflate the count, but we need it to not be zero to discourage
    2578             :  * other backends from stealing buffers from our ring.  As long as we cycle
    2579             :  * through the ring faster than the global clock-sweep cycles, buffers in
    2580             :  * our ring won't be chosen as victims for replacement by other backends.)
    2581             :  *
    2582             :  * This should be applied only to shared buffers, never local ones.
    2583             :  *
    2584             :  * Since buffers are pinned/unpinned very frequently, pin buffers without
    2585             :  * taking the buffer header lock; instead update the state variable in loop of
    2586             :  * CAS operations. Hopefully it's just a single CAS.
    2587             :  *
    2588             :  * Note that ResourceOwnerEnlarge() and ReservePrivateRefCountEntry()
    2589             :  * must have been done already.
    2590             :  *
    2591             :  * Returns true if buffer is BM_VALID, else false.  This provision allows
    2592             :  * some callers to avoid an extra spinlock cycle.
    2593             :  */
    2594             : static bool
    2595    89237562 : PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
    2596             : {
    2597    89237562 :     Buffer      b = BufferDescriptorGetBuffer(buf);
    2598             :     bool        result;
    2599             :     PrivateRefCountEntry *ref;
    2600             : 
    2601             :     Assert(!BufferIsLocal(b));
    2602             :     Assert(ReservedRefCountEntry != NULL);
    2603             : 
    2604    89237562 :     ref = GetPrivateRefCountEntry(b, true);
    2605             : 
    2606    89237562 :     if (ref == NULL)
    2607             :     {
    2608             :         uint32      buf_state;
    2609             :         uint32      old_buf_state;
    2610             : 
    2611    85423918 :         ref = NewPrivateRefCountEntry(b);
    2612             : 
    2613    85423918 :         old_buf_state = pg_atomic_read_u32(&buf->state);
    2614             :         for (;;)
    2615             :         {
    2616    85461016 :             if (old_buf_state & BM_LOCKED)
    2617         328 :                 old_buf_state = WaitBufHdrUnlocked(buf);
    2618             : 
    2619    85461016 :             buf_state = old_buf_state;
    2620             : 
    2621             :             /* increase refcount */
    2622    85461016 :             buf_state += BUF_REFCOUNT_ONE;
    2623             : 
    2624    85461016 :             if (strategy == NULL)
    2625             :             {
    2626             :                 /* Default case: increase usagecount unless already max. */
    2627    84723730 :                 if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
    2628     4914902 :                     buf_state += BUF_USAGECOUNT_ONE;
    2629             :             }
    2630             :             else
    2631             :             {
    2632             :                 /*
    2633             :                  * Ring buffers shouldn't evict others from pool.  Thus we
    2634             :                  * don't make usagecount more than 1.
    2635             :                  */
    2636      737286 :                 if (BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
    2637       56004 :                     buf_state += BUF_USAGECOUNT_ONE;
    2638             :             }
    2639             : 
    2640    85461016 :             if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
    2641             :                                                buf_state))
    2642             :             {
    2643    85423918 :                 result = (buf_state & BM_VALID) != 0;
    2644             : 
    2645             :                 /*
    2646             :                  * Assume that we acquired a buffer pin for the purposes of
    2647             :                  * Valgrind buffer client checks (even in !result case) to
    2648             :                  * keep things simple.  Buffers that are unsafe to access are
    2649             :                  * not generally guaranteed to be marked undefined or
    2650             :                  * non-accessible in any case.
    2651             :                  */
    2652             :                 VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
    2653    85423918 :                 break;
    2654             :             }
    2655             :         }
    2656             :     }
    2657             :     else
    2658             :     {
    2659             :         /*
    2660             :          * If we previously pinned the buffer, it is likely to be valid, but
    2661             :          * it may not be if StartReadBuffers() was called and
    2662             :          * WaitReadBuffers() hasn't been called yet.  We'll check by loading
    2663             :          * the flags without locking.  This is racy, but it's OK to return
    2664             :          * false spuriously: when WaitReadBuffers() calls StartBufferIO(),
    2665             :          * it'll see that it's now valid.
    2666             :          *
    2667             :          * Note: We deliberately avoid a Valgrind client request here.
    2668             :          * Individual access methods can optionally superimpose buffer page
    2669             :          * client requests on top of our client requests to enforce that
    2670             :          * buffers are only accessed while locked (and pinned).  It's possible
    2671             :          * that the buffer page is legitimately non-accessible here.  We
    2672             :          * cannot meddle with that.
    2673             :          */
    2674     3813644 :         result = (pg_atomic_read_u32(&buf->state) & BM_VALID) != 0;
    2675             :     }
    2676             : 
    2677    89237562 :     ref->refcount++;
    2678             :     Assert(ref->refcount > 0);
    2679    89237562 :     ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
    2680    89237562 :     return result;
    2681             : }
    2682             : 
    2683             : /*
    2684             :  * PinBuffer_Locked -- as above, but caller already locked the buffer header.
    2685             :  * The spinlock is released before return.
    2686             :  *
    2687             :  * As this function is called with the spinlock held, the caller has to
    2688             :  * previously call ReservePrivateRefCountEntry() and
    2689             :  * ResourceOwnerEnlarge(CurrentResourceOwner);
    2690             :  *
    2691             :  * Currently, no callers of this function want to modify the buffer's
    2692             :  * usage_count at all, so there's no need for a strategy parameter.
    2693             :  * Also we don't bother with a BM_VALID test (the caller could check that for
    2694             :  * itself).
    2695             :  *
    2696             :  * Also all callers only ever use this function when it's known that the
    2697             :  * buffer can't have a preexisting pin by this backend. That allows us to skip
    2698             :  * searching the private refcount array & hash, which is a boon, because the
    2699             :  * spinlock is still held.
    2700             :  *
    2701             :  * Note: use of this routine is frequently mandatory, not just an optimization
    2702             :  * to save a spin lock/unlock cycle, because we need to pin a buffer before
    2703             :  * its state can change under us.
    2704             :  */
    2705             : static void
    2706     4341434 : PinBuffer_Locked(BufferDesc *buf)
    2707             : {
    2708             :     Buffer      b;
    2709             :     PrivateRefCountEntry *ref;
    2710             :     uint32      buf_state;
    2711             : 
    2712             :     /*
    2713             :      * As explained, We don't expect any preexisting pins. That allows us to
    2714             :      * manipulate the PrivateRefCount after releasing the spinlock
    2715             :      */
    2716             :     Assert(GetPrivateRefCountEntry(BufferDescriptorGetBuffer(buf), false) == NULL);
    2717             : 
    2718             :     /*
    2719             :      * Buffer can't have a preexisting pin, so mark its page as defined to
    2720             :      * Valgrind (this is similar to the PinBuffer() case where the backend
    2721             :      * doesn't already have a buffer pin)
    2722             :      */
    2723             :     VALGRIND_MAKE_MEM_DEFINED(BufHdrGetBlock(buf), BLCKSZ);
    2724             : 
    2725             :     /*
    2726             :      * Since we hold the buffer spinlock, we can update the buffer state and
    2727             :      * release the lock in one operation.
    2728             :      */
    2729     4341434 :     buf_state = pg_atomic_read_u32(&buf->state);
    2730             :     Assert(buf_state & BM_LOCKED);
    2731     4341434 :     buf_state += BUF_REFCOUNT_ONE;
    2732     4341434 :     UnlockBufHdr(buf, buf_state);
    2733             : 
    2734     4341434 :     b = BufferDescriptorGetBuffer(buf);
    2735             : 
    2736     4341434 :     ref = NewPrivateRefCountEntry(b);
    2737     4341434 :     ref->refcount++;
    2738             : 
    2739     4341434 :     ResourceOwnerRememberBuffer(CurrentResourceOwner, b);
    2740     4341434 : }
    2741             : 
    2742             : /*
    2743             :  * UnpinBuffer -- make buffer available for replacement.
    2744             :  *
    2745             :  * This should be applied only to shared buffers, never local ones.  This
    2746             :  * always adjusts CurrentResourceOwner.
    2747             :  */
    2748             : static void
    2749   110102978 : UnpinBuffer(BufferDesc *buf)
    2750             : {
    2751   110102978 :     Buffer      b = BufferDescriptorGetBuffer(buf);
    2752             : 
    2753   110102978 :     ResourceOwnerForgetBuffer(CurrentResourceOwner, b);
    2754   110102978 :     UnpinBufferNoOwner(buf);
    2755   110102978 : }
    2756             : 
    2757             : static void
    2758   110109938 : UnpinBufferNoOwner(BufferDesc *buf)
    2759             : {
    2760             :     PrivateRefCountEntry *ref;
    2761   110109938 :     Buffer      b = BufferDescriptorGetBuffer(buf);
    2762             : 
    2763             :     Assert(!BufferIsLocal(b));
    2764             : 
    2765             :     /* not moving as we're likely deleting it soon anyway */
    2766   110109938 :     ref = GetPrivateRefCountEntry(b, false);
    2767             :     Assert(ref != NULL);
    2768             :     Assert(ref->refcount > 0);
    2769   110109938 :     ref->refcount--;
    2770   110109938 :     if (ref->refcount == 0)
    2771             :     {
    2772             :         uint32      buf_state;
    2773             :         uint32      old_buf_state;
    2774             : 
    2775             :         /*
    2776             :          * Mark buffer non-accessible to Valgrind.
    2777             :          *
    2778             :          * Note that the buffer may have already been marked non-accessible
    2779             :          * within access method code that enforces that buffers are only
    2780             :          * accessed while a buffer lock is held.
    2781             :          */
    2782             :         VALGRIND_MAKE_MEM_NOACCESS(BufHdrGetBlock(buf), BLCKSZ);
    2783             : 
    2784             :         /* I'd better not still hold the buffer content lock */
    2785             :         Assert(!LWLockHeldByMe(BufferDescriptorGetContentLock(buf)));
    2786             : 
    2787             :         /*
    2788             :          * Decrement the shared reference count.
    2789             :          *
    2790             :          * Since buffer spinlock holder can update status using just write,
    2791             :          * it's not safe to use atomic decrement here; thus use a CAS loop.
    2792             :          */
    2793    89765352 :         old_buf_state = pg_atomic_read_u32(&buf->state);
    2794             :         for (;;)
    2795             :         {
    2796    89801294 :             if (old_buf_state & BM_LOCKED)
    2797         274 :                 old_buf_state = WaitBufHdrUnlocked(buf);
    2798             : 
    2799    89801294 :             buf_state = old_buf_state;
    2800             : 
    2801    89801294 :             buf_state -= BUF_REFCOUNT_ONE;
    2802             : 
    2803    89801294 :             if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
    2804             :                                                buf_state))
    2805    89765352 :                 break;
    2806             :         }
    2807             : 
    2808             :         /* Support LockBufferForCleanup() */
    2809    89765352 :         if (buf_state & BM_PIN_COUNT_WAITER)
    2810             :         {
    2811             :             /*
    2812             :              * Acquire the buffer header lock, re-check that there's a waiter.
    2813             :              * Another backend could have unpinned this buffer, and already
    2814             :              * woken up the waiter.  There's no danger of the buffer being
    2815             :              * replaced after we unpinned it above, as it's pinned by the
    2816             :              * waiter.
    2817             :              */
    2818           4 :             buf_state = LockBufHdr(buf);
    2819             : 
    2820           4 :             if ((buf_state & BM_PIN_COUNT_WAITER) &&
    2821           4 :                 BUF_STATE_GET_REFCOUNT(buf_state) == 1)
    2822           4 :             {
    2823             :                 /* we just released the last pin other than the waiter's */
    2824           4 :                 int         wait_backend_pgprocno = buf->wait_backend_pgprocno;
    2825             : 
    2826           4 :                 buf_state &= ~BM_PIN_COUNT_WAITER;
    2827           4 :                 UnlockBufHdr(buf, buf_state);
    2828           4 :                 ProcSendSignal(wait_backend_pgprocno);
    2829             :             }
    2830             :             else
    2831           0 :                 UnlockBufHdr(buf, buf_state);
    2832             :         }
    2833    89765352 :         ForgetPrivateRefCountEntry(ref);
    2834             :     }
    2835   110109938 : }
    2836             : 
    2837             : #define ST_SORT sort_checkpoint_bufferids
    2838             : #define ST_ELEMENT_TYPE CkptSortItem
    2839             : #define ST_COMPARE(a, b) ckpt_buforder_comparator(a, b)
    2840             : #define ST_SCOPE static
    2841             : #define ST_DEFINE
    2842             : #include <lib/sort_template.h>
    2843             : 
    2844             : /*
    2845             :  * BufferSync -- Write out all dirty buffers in the pool.
    2846             :  *
    2847             :  * This is called at checkpoint time to write out all dirty shared buffers.
    2848             :  * The checkpoint request flags should be passed in.  If CHECKPOINT_IMMEDIATE
    2849             :  * is set, we disable delays between writes; if CHECKPOINT_IS_SHUTDOWN,
    2850             :  * CHECKPOINT_END_OF_RECOVERY or CHECKPOINT_FLUSH_ALL is set, we write even
    2851             :  * unlogged buffers, which are otherwise skipped.  The remaining flags
    2852             :  * currently have no effect here.
    2853             :  */
    2854             : static void
    2855        1704 : BufferSync(int flags)
    2856             : {
    2857             :     uint32      buf_state;
    2858             :     int         buf_id;
    2859             :     int         num_to_scan;
    2860             :     int         num_spaces;
    2861             :     int         num_processed;
    2862             :     int         num_written;
    2863        1704 :     CkptTsStatus *per_ts_stat = NULL;
    2864             :     Oid         last_tsid;
    2865             :     binaryheap *ts_heap;
    2866             :     int         i;
    2867        1704 :     int         mask = BM_DIRTY;
    2868             :     WritebackContext wb_context;
    2869             : 
    2870             :     /*
    2871             :      * Unless this is a shutdown checkpoint or we have been explicitly told,
    2872             :      * we write only permanent, dirty buffers.  But at shutdown or end of
    2873             :      * recovery, we write all dirty buffers.
    2874             :      */
    2875        1704 :     if (!((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY |
    2876             :                     CHECKPOINT_FLUSH_ALL))))
    2877         550 :         mask |= BM_PERMANENT;
    2878             : 
    2879             :     /*
    2880             :      * Loop over all buffers, and mark the ones that need to be written with
    2881             :      * BM_CHECKPOINT_NEEDED.  Count them as we go (num_to_scan), so that we
    2882             :      * can estimate how much work needs to be done.
    2883             :      *
    2884             :      * This allows us to write only those pages that were dirty when the
    2885             :      * checkpoint began, and not those that get dirtied while it proceeds.
    2886             :      * Whenever a page with BM_CHECKPOINT_NEEDED is written out, either by us
    2887             :      * later in this function, or by normal backends or the bgwriter cleaning
    2888             :      * scan, the flag is cleared.  Any buffer dirtied after this point won't
    2889             :      * have the flag set.
    2890             :      *
    2891             :      * Note that if we fail to write some buffer, we may leave buffers with
    2892             :      * BM_CHECKPOINT_NEEDED still set.  This is OK since any such buffer would
    2893             :      * certainly need to be written for the next checkpoint attempt, too.
    2894             :      */
    2895        1704 :     num_to_scan = 0;
    2896    18230856 :     for (buf_id = 0; buf_id < NBuffers; buf_id++)
    2897             :     {
    2898    18229152 :         BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
    2899             : 
    2900             :         /*
    2901             :          * Header spinlock is enough to examine BM_DIRTY, see comment in
    2902             :          * SyncOneBuffer.
    2903             :          */
    2904    18229152 :         buf_state = LockBufHdr(bufHdr);
    2905             : 
    2906    18229152 :         if ((buf_state & mask) == mask)
    2907             :         {
    2908             :             CkptSortItem *item;
    2909             : 
    2910      428800 :             buf_state |= BM_CHECKPOINT_NEEDED;
    2911             : 
    2912      428800 :             item = &CkptBufferIds[num_to_scan++];
    2913      428800 :             item->buf_id = buf_id;
    2914      428800 :             item->tsId = bufHdr->tag.spcOid;
    2915      428800 :             item->relNumber = BufTagGetRelNumber(&bufHdr->tag);
    2916      428800 :             item->forkNum = BufTagGetForkNum(&bufHdr->tag);
    2917      428800 :             item->blockNum = bufHdr->tag.blockNum;
    2918             :         }
    2919             : 
    2920    18229152 :         UnlockBufHdr(bufHdr, buf_state);
    2921             : 
    2922             :         /* Check for barrier events in case NBuffers is large. */
    2923    18229152 :         if (ProcSignalBarrierPending)
    2924           0 :             ProcessProcSignalBarrier();
    2925             :     }
    2926             : 
    2927        1704 :     if (num_to_scan == 0)
    2928         554 :         return;                 /* nothing to do */
    2929             : 
    2930        1150 :     WritebackContextInit(&wb_context, &checkpoint_flush_after);
    2931             : 
    2932             :     TRACE_POSTGRESQL_BUFFER_SYNC_START(NBuffers, num_to_scan);
    2933             : 
    2934             :     /*
    2935             :      * Sort buffers that need to be written to reduce the likelihood of random
    2936             :      * IO. The sorting is also important for the implementation of balancing
    2937             :      * writes between tablespaces. Without balancing writes we'd potentially
    2938             :      * end up writing to the tablespaces one-by-one; possibly overloading the
    2939             :      * underlying system.
    2940             :      */
    2941        1150 :     sort_checkpoint_bufferids(CkptBufferIds, num_to_scan);
    2942             : 
    2943        1150 :     num_spaces = 0;
    2944             : 
    2945             :     /*
    2946             :      * Allocate progress status for each tablespace with buffers that need to
    2947             :      * be flushed. This requires the to-be-flushed array to be sorted.
    2948             :      */
    2949        1150 :     last_tsid = InvalidOid;
    2950      429950 :     for (i = 0; i < num_to_scan; i++)
    2951             :     {
    2952             :         CkptTsStatus *s;
    2953             :         Oid         cur_tsid;
    2954             : 
    2955      428800 :         cur_tsid = CkptBufferIds[i].tsId;
    2956             : 
    2957             :         /*
    2958             :          * Grow array of per-tablespace status structs, every time a new
    2959             :          * tablespace is found.
    2960             :          */
    2961      428800 :         if (last_tsid == InvalidOid || last_tsid != cur_tsid)
    2962        1806 :         {
    2963             :             Size        sz;
    2964             : 
    2965        1806 :             num_spaces++;
    2966             : 
    2967             :             /*
    2968             :              * Not worth adding grow-by-power-of-2 logic here - even with a
    2969             :              * few hundred tablespaces this should be fine.
    2970             :              */
    2971        1806 :             sz = sizeof(CkptTsStatus) * num_spaces;
    2972             : 
    2973        1806 :             if (per_ts_stat == NULL)
    2974        1150 :                 per_ts_stat = (CkptTsStatus *) palloc(sz);
    2975             :             else
    2976         656 :                 per_ts_stat = (CkptTsStatus *) repalloc(per_ts_stat, sz);
    2977             : 
    2978        1806 :             s = &per_ts_stat[num_spaces - 1];
    2979        1806 :             memset(s, 0, sizeof(*s));
    2980        1806 :             s->tsId = cur_tsid;
    2981             : 
    2982             :             /*
    2983             :              * The first buffer in this tablespace. As CkptBufferIds is sorted
    2984             :              * by tablespace all (s->num_to_scan) buffers in this tablespace
    2985             :              * will follow afterwards.
    2986             :              */
    2987        1806 :             s->index = i;
    2988             : 
    2989             :             /*
    2990             :              * progress_slice will be determined once we know how many buffers
    2991             :              * are in each tablespace, i.e. after this loop.
    2992             :              */
    2993             : 
    2994        1806 :             last_tsid = cur_tsid;
    2995             :         }
    2996             :         else
    2997             :         {
    2998      426994 :             s = &per_ts_stat[num_spaces - 1];
    2999             :         }
    3000             : 
    3001      428800 :         s->num_to_scan++;
    3002             : 
    3003             :         /* Check for barrier events. */
    3004      428800 :         if (ProcSignalBarrierPending)
    3005           0 :             ProcessProcSignalBarrier();
    3006             :     }
    3007             : 
    3008             :     Assert(num_spaces > 0);
    3009             : 
    3010             :     /*
    3011             :      * Build a min-heap over the write-progress in the individual tablespaces,
    3012             :      * and compute how large a portion of the total progress a single
    3013             :      * processed buffer is.
    3014             :      */
    3015        1150 :     ts_heap = binaryheap_allocate(num_spaces,
    3016             :                                   ts_ckpt_progress_comparator,
    3017             :                                   NULL);
    3018             : 
    3019        2956 :     for (i = 0; i < num_spaces; i++)
    3020             :     {
    3021        1806 :         CkptTsStatus *ts_stat = &per_ts_stat[i];
    3022             : 
    3023        1806 :         ts_stat->progress_slice = (float8) num_to_scan / ts_stat->num_to_scan;
    3024             : 
    3025        1806 :         binaryheap_add_unordered(ts_heap, PointerGetDatum(ts_stat));
    3026             :     }
    3027             : 
    3028        1150 :     binaryheap_build(ts_heap);
    3029             : 
    3030             :     /*
    3031             :      * Iterate through to-be-checkpointed buffers and write the ones (still)
    3032             :      * marked with BM_CHECKPOINT_NEEDED. The writes are balanced between
    3033             :      * tablespaces; otherwise the sorting would lead to only one tablespace
    3034             :      * receiving writes at a time, making inefficient use of the hardware.
    3035             :      */
    3036        1150 :     num_processed = 0;
    3037        1150 :     num_written = 0;
    3038      429950 :     while (!binaryheap_empty(ts_heap))
    3039             :     {
    3040      428800 :         BufferDesc *bufHdr = NULL;
    3041             :         CkptTsStatus *ts_stat = (CkptTsStatus *)
    3042      428800 :             DatumGetPointer(binaryheap_first(ts_heap));
    3043             : 
    3044      428800 :         buf_id = CkptBufferIds[ts_stat->index].buf_id;
    3045             :         Assert(buf_id != -1);
    3046             : 
    3047      428800 :         bufHdr = GetBufferDescriptor(buf_id);
    3048             : 
    3049      428800 :         num_processed++;
    3050             : 
    3051             :         /*
    3052             :          * We don't need to acquire the lock here, because we're only looking
    3053             :          * at a single bit. It's possible that someone else writes the buffer
    3054             :          * and clears the flag right after we check, but that doesn't matter
    3055             :          * since SyncOneBuffer will then do nothing.  However, there is a
    3056             :          * further race condition: it's conceivable that between the time we
    3057             :          * examine the bit here and the time SyncOneBuffer acquires the lock,
    3058             :          * someone else not only wrote the buffer but replaced it with another
    3059             :          * page and dirtied it.  In that improbable case, SyncOneBuffer will
    3060             :          * write the buffer though we didn't need to.  It doesn't seem worth
    3061             :          * guarding against this, though.
    3062             :          */
    3063      428800 :         if (pg_atomic_read_u32(&bufHdr->state) & BM_CHECKPOINT_NEEDED)
    3064             :         {
    3065      424884 :             if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
    3066             :             {
    3067             :                 TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
    3068      424884 :                 PendingCheckpointerStats.buffers_written++;
    3069      424884 :                 num_written++;
    3070             :             }
    3071             :         }
    3072             : 
    3073             :         /*
    3074             :          * Measure progress independent of actually having to flush the buffer
    3075             :          * - otherwise writing become unbalanced.
    3076             :          */
    3077      428800 :         ts_stat->progress += ts_stat->progress_slice;
    3078      428800 :         ts_stat->num_scanned++;
    3079      428800 :         ts_stat->index++;
    3080             : 
    3081             :         /* Have all the buffers from the tablespace been processed? */
    3082      428800 :         if (ts_stat->num_scanned == ts_stat->num_to_scan)
    3083             :         {
    3084        1806 :             binaryheap_remove_first(ts_heap);
    3085             :         }
    3086             :         else
    3087             :         {
    3088             :             /* update heap with the new progress */
    3089      426994 :             binaryheap_replace_first(ts_heap, PointerGetDatum(ts_stat));
    3090             :         }
    3091             : 
    3092             :         /*
    3093             :          * Sleep to throttle our I/O rate.
    3094             :          *
    3095             :          * (This will check for barrier events even if it doesn't sleep.)
    3096             :          */
    3097      428800 :         CheckpointWriteDelay(flags, (double) num_processed / num_to_scan);
    3098             :     }
    3099             : 
    3100             :     /*
    3101             :      * Issue all pending flushes. Only checkpointer calls BufferSync(), so
    3102             :      * IOContext will always be IOCONTEXT_NORMAL.
    3103             :      */
    3104        1150 :     IssuePendingWritebacks(&wb_context, IOCONTEXT_NORMAL);
    3105             : 
    3106        1150 :     pfree(per_ts_stat);
    3107        1150 :     per_ts_stat = NULL;
    3108        1150 :     binaryheap_free(ts_heap);
    3109             : 
    3110             :     /*
    3111             :      * Update checkpoint statistics. As noted above, this doesn't include
    3112             :      * buffers written by other backends or bgwriter scan.
    3113             :      */
    3114        1150 :     CheckpointStats.ckpt_bufs_written += num_written;
    3115             : 
    3116             :     TRACE_POSTGRESQL_BUFFER_SYNC_DONE(NBuffers, num_written, num_to_scan);
    3117             : }
    3118             : 
    3119             : /*
    3120             :  * BgBufferSync -- Write out some dirty buffers in the pool.
    3121             :  *
    3122             :  * This is called periodically by the background writer process.
    3123             :  *
    3124             :  * Returns true if it's appropriate for the bgwriter process to go into
    3125             :  * low-power hibernation mode.  (This happens if the strategy clock sweep
    3126             :  * has been "lapped" and no buffer allocations have occurred recently,
    3127             :  * or if the bgwriter has been effectively disabled by setting
    3128             :  * bgwriter_lru_maxpages to 0.)
    3129             :  */
    3130             : bool
    3131       11978 : BgBufferSync(WritebackContext *wb_context)
    3132             : {
    3133             :     /* info obtained from freelist.c */
    3134             :     int         strategy_buf_id;
    3135             :     uint32      strategy_passes;
    3136             :     uint32      recent_alloc;
    3137             : 
    3138             :     /*
    3139             :      * Information saved between calls so we can determine the strategy
    3140             :      * point's advance rate and avoid scanning already-cleaned buffers.
    3141             :      */
    3142             :     static bool saved_info_valid = false;
    3143             :     static int  prev_strategy_buf_id;
    3144             :     static uint32 prev_strategy_passes;
    3145             :     static int  next_to_clean;
    3146             :     static uint32 next_passes;
    3147             : 
    3148             :     /* Moving averages of allocation rate and clean-buffer density */
    3149             :     static float smoothed_alloc = 0;
    3150             :     static float smoothed_density = 10.0;
    3151             : 
    3152             :     /* Potentially these could be tunables, but for now, not */
    3153       11978 :     float       smoothing_samples = 16;
    3154       11978 :     float       scan_whole_pool_milliseconds = 120000.0;
    3155             : 
    3156             :     /* Used to compute how far we scan ahead */
    3157             :     long        strategy_delta;
    3158             :     int         bufs_to_lap;
    3159             :     int         bufs_ahead;
    3160             :     float       scans_per_alloc;
    3161             :     int         reusable_buffers_est;
    3162             :     int         upcoming_alloc_est;
    3163             :     int         min_scan_buffers;
    3164             : 
    3165             :     /* Variables for the scanning loop proper */
    3166             :     int         num_to_scan;
    3167             :     int         num_written;
    3168             :     int         reusable_buffers;
    3169             : 
    3170             :     /* Variables for final smoothed_density update */
    3171             :     long        new_strategy_delta;
    3172             :     uint32      new_recent_alloc;
    3173             : 
    3174             :     /*
    3175             :      * Find out where the freelist clock sweep currently is, and how many
    3176             :      * buffer allocations have happened since our last call.
    3177             :      */
    3178       11978 :     strategy_buf_id = StrategySyncStart(&strategy_passes, &recent_alloc);
    3179             : 
    3180             :     /* Report buffer alloc counts to pgstat */
    3181       11978 :     PendingBgWriterStats.buf_alloc += recent_alloc;
    3182             : 
    3183             :     /*
    3184             :      * If we're not running the LRU scan, just stop after doing the stats
    3185             :      * stuff.  We mark the saved state invalid so that we can recover sanely
    3186             :      * if LRU scan is turned back on later.
    3187             :      */
    3188       11978 :     if (bgwriter_lru_maxpages <= 0)
    3189             :     {
    3190          34 :         saved_info_valid = false;
    3191          34 :         return true;
    3192             :     }
    3193             : 
    3194             :     /*
    3195             :      * Compute strategy_delta = how many buffers have been scanned by the
    3196             :      * clock sweep since last time.  If first time through, assume none. Then
    3197             :      * see if we are still ahead of the clock sweep, and if so, how many
    3198             :      * buffers we could scan before we'd catch up with it and "lap" it. Note:
    3199             :      * weird-looking coding of xxx_passes comparisons are to avoid bogus
    3200             :      * behavior when the passes counts wrap around.
    3201             :      */
    3202       11944 :     if (saved_info_valid)
    3203             :     {
    3204       11128 :         int32       passes_delta = strategy_passes - prev_strategy_passes;
    3205             : 
    3206       11128 :         strategy_delta = strategy_buf_id - prev_strategy_buf_id;
    3207       11128 :         strategy_delta += (long) passes_delta * NBuffers;
    3208             : 
    3209             :         Assert(strategy_delta >= 0);
    3210             : 
    3211       11128 :         if ((int32) (next_passes - strategy_passes) > 0)
    3212             :         {
    3213             :             /* we're one pass ahead of the strategy point */
    3214        2302 :             bufs_to_lap = strategy_buf_id - next_to_clean;
    3215             : #ifdef BGW_DEBUG
    3216             :             elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
    3217             :                  next_passes, next_to_clean,
    3218             :                  strategy_passes, strategy_buf_id,
    3219             :                  strategy_delta, bufs_to_lap);
    3220             : #endif
    3221             :         }
    3222        8826 :         else if (next_passes == strategy_passes &&
    3223        6884 :                  next_to_clean >= strategy_buf_id)
    3224             :         {
    3225             :             /* on same pass, but ahead or at least not behind */
    3226        6778 :             bufs_to_lap = NBuffers - (next_to_clean - strategy_buf_id);
    3227             : #ifdef BGW_DEBUG
    3228             :             elog(DEBUG2, "bgwriter ahead: bgw %u-%u strategy %u-%u delta=%ld lap=%d",
    3229             :                  next_passes, next_to_clean,
    3230             :                  strategy_passes, strategy_buf_id,
    3231             :                  strategy_delta, bufs_to_lap);
    3232             : #endif
    3233             :         }
    3234             :         else
    3235             :         {
    3236             :             /*
    3237             :              * We're behind, so skip forward to the strategy point and start
    3238             :              * cleaning from there.
    3239             :              */
    3240             : #ifdef BGW_DEBUG
    3241             :             elog(DEBUG2, "bgwriter behind: bgw %u-%u strategy %u-%u delta=%ld",
    3242             :                  next_passes, next_to_clean,
    3243             :                  strategy_passes, strategy_buf_id,
    3244             :                  strategy_delta);
    3245             : #endif
    3246        2048 :             next_to_clean = strategy_buf_id;
    3247        2048 :             next_passes = strategy_passes;
    3248        2048 :             bufs_to_lap = NBuffers;
    3249             :         }
    3250             :     }
    3251             :     else
    3252             :     {
    3253             :         /*
    3254             :          * Initializing at startup or after LRU scanning had been off. Always
    3255             :          * start at the strategy point.
    3256             :          */
    3257             : #ifdef BGW_DEBUG
    3258             :         elog(DEBUG2, "bgwriter initializing: strategy %u-%u",
    3259             :              strategy_passes, strategy_buf_id);
    3260             : #endif
    3261         816 :         strategy_delta = 0;
    3262         816 :         next_to_clean = strategy_buf_id;
    3263         816 :         next_passes = strategy_passes;
    3264         816 :         bufs_to_lap = NBuffers;
    3265             :     }
    3266             : 
    3267             :     /* Update saved info for next time */
    3268       11944 :     prev_strategy_buf_id = strategy_buf_id;
    3269       11944 :     prev_strategy_passes = strategy_passes;
    3270       11944 :     saved_info_valid = true;
    3271             : 
    3272             :     /*
    3273             :      * Compute how many buffers had to be scanned for each new allocation, ie,
    3274             :      * 1/density of reusable buffers, and track a moving average of that.
    3275             :      *
    3276             :      * If the strategy point didn't move, we don't update the density estimate
    3277             :      */
    3278       11944 :     if (strategy_delta > 0 && recent_alloc > 0)
    3279             :     {
    3280        2446 :         scans_per_alloc = (float) strategy_delta / (float) recent_alloc;
    3281        2446 :         smoothed_density += (scans_per_alloc - smoothed_density) /
    3282             :             smoothing_samples;
    3283             :     }
    3284             : 
    3285             :     /*
    3286             :      * Estimate how many reusable buffers there are between the current
    3287             :      * strategy point and where we've scanned ahead to, based on the smoothed
    3288             :      * density estimate.
    3289             :      */
    3290       11944 :     bufs_ahead = NBuffers - bufs_to_lap;
    3291       11944 :     reusable_buffers_est = (float) bufs_ahead / smoothed_density;
    3292             : 
    3293             :     /*
    3294             :      * Track a moving average of recent buffer allocations.  Here, rather than
    3295             :      * a true average we want a fast-attack, slow-decline behavior: we
    3296             :      * immediately follow any increase.
    3297             :      */
    3298       11944 :     if (smoothed_alloc <= (float) recent_alloc)
    3299        2922 :         smoothed_alloc = recent_alloc;
    3300             :     else
    3301        9022 :         smoothed_alloc += ((float) recent_alloc - smoothed_alloc) /
    3302             :             smoothing_samples;
    3303             : 
    3304             :     /* Scale the estimate by a GUC to allow more aggressive tuning. */
    3305       11944 :     upcoming_alloc_est = (int) (smoothed_alloc * bgwriter_lru_multiplier);
    3306             : 
    3307             :     /*
    3308             :      * If recent_alloc remains at zero for many cycles, smoothed_alloc will
    3309             :      * eventually underflow to zero, and the underflows produce annoying
    3310             :      * kernel warnings on some platforms.  Once upcoming_alloc_est has gone to
    3311             :      * zero, there's no point in tracking smaller and smaller values of
    3312             :      * smoothed_alloc, so just reset it to exactly zero to avoid this
    3313             :      * syndrome.  It will pop back up as soon as recent_alloc increases.
    3314             :      */
    3315       11944 :     if (upcoming_alloc_est == 0)
    3316        1078 :         smoothed_alloc = 0;
    3317             : 
    3318             :     /*
    3319             :      * Even in cases where there's been little or no buffer allocation
    3320             :      * activity, we want to make a small amount of progress through the buffer
    3321             :      * cache so that as many reusable buffers as possible are clean after an
    3322             :      * idle period.
    3323             :      *
    3324             :      * (scan_whole_pool_milliseconds / BgWriterDelay) computes how many times
    3325             :      * the BGW will be called during the scan_whole_pool time; slice the
    3326             :      * buffer pool into that many sections.
    3327             :      */
    3328       11944 :     min_scan_buffers = (int) (NBuffers / (scan_whole_pool_milliseconds / BgWriterDelay));
    3329             : 
    3330       11944 :     if (upcoming_alloc_est < (min_scan_buffers + reusable_buffers_est))
    3331             :     {
    3332             : #ifdef BGW_DEBUG
    3333             :         elog(DEBUG2, "bgwriter: alloc_est=%d too small, using min=%d + reusable_est=%d",
    3334             :              upcoming_alloc_est, min_scan_buffers, reusable_buffers_est);
    3335             : #endif
    3336        6354 :         upcoming_alloc_est = min_scan_buffers + reusable_buffers_est;
    3337             :     }
    3338             : 
    3339             :     /*
    3340             :      * Now write out dirty reusable buffers, working forward from the
    3341             :      * next_to_clean point, until we have lapped the strategy scan, or cleaned
    3342             :      * enough buffers to match our estimate of the next cycle's allocation
    3343             :      * requirements, or hit the bgwriter_lru_maxpages limit.
    3344             :      */
    3345             : 
    3346       11944 :     num_to_scan = bufs_to_lap;
    3347       11944 :     num_written = 0;
    3348       11944 :     reusable_buffers = reusable_buffers_est;
    3349             : 
    3350             :     /* Execute the LRU scan */
    3351     2480908 :     while (num_to_scan > 0 && reusable_buffers < upcoming_alloc_est)
    3352             :     {
    3353     2468964 :         int         sync_state = SyncOneBuffer(next_to_clean, true,
    3354             :                                                wb_context);
    3355             : 
    3356     2468964 :         if (++next_to_clean >= NBuffers)
    3357             :         {
    3358        2300 :             next_to_clean = 0;
    3359        2300 :             next_passes++;
    3360             :         }
    3361     2468964 :         num_to_scan--;
    3362             : 
    3363     2468964 :         if (sync_state & BUF_WRITTEN)
    3364             :         {
    3365       18778 :             reusable_buffers++;
    3366       18778 :             if (++num_written >= bgwriter_lru_maxpages)
    3367             :             {
    3368           0 :                 PendingBgWriterStats.maxwritten_clean++;
    3369           0 :                 break;
    3370             :             }
    3371             :         }
    3372     2450186 :         else if (sync_state & BUF_REUSABLE)
    3373     1894484 :             reusable_buffers++;
    3374             :     }
    3375             : 
    3376       11944 :     PendingBgWriterStats.buf_written_clean += num_written;
    3377             : 
    3378             : #ifdef BGW_DEBUG
    3379             :     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",
    3380             :          recent_alloc, smoothed_alloc, strategy_delta, bufs_ahead,
    3381             :          smoothed_density, reusable_buffers_est, upcoming_alloc_est,
    3382             :          bufs_to_lap - num_to_scan,
    3383             :          num_written,
    3384             :          reusable_buffers - reusable_buffers_est);
    3385             : #endif
    3386             : 
    3387             :     /*
    3388             :      * Consider the above scan as being like a new allocation scan.
    3389             :      * Characterize its density and update the smoothed one based on it. This
    3390             :      * effectively halves the moving average period in cases where both the
    3391             :      * strategy and the background writer are doing some useful scanning,
    3392             :      * which is helpful because a long memory isn't as desirable on the
    3393             :      * density estimates.
    3394             :      */
    3395       11944 :     new_strategy_delta = bufs_to_lap - num_to_scan;
    3396       11944 :     new_recent_alloc = reusable_buffers - reusable_buffers_est;
    3397       11944 :     if (new_strategy_delta > 0 && new_recent_alloc > 0)
    3398             :     {
    3399        9432 :         scans_per_alloc = (float) new_strategy_delta / (float) new_recent_alloc;
    3400        9432 :         smoothed_density += (scans_per_alloc - smoothed_density) /
    3401             :             smoothing_samples;
    3402             : 
    3403             : #ifdef BGW_DEBUG
    3404             :         elog(DEBUG2, "bgwriter: cleaner density alloc=%u scan=%ld density=%.2f new smoothed=%.2f",
    3405             :              new_recent_alloc, new_strategy_delta,
    3406             :              scans_per_alloc, smoothed_density);
    3407             : #endif
    3408             :     }
    3409             : 
    3410             :     /* Return true if OK to hibernate */
    3411       11944 :     return (bufs_to_lap == 0 && recent_alloc == 0);
    3412             : }
    3413             : 
    3414             : /*
    3415             :  * SyncOneBuffer -- process a single buffer during syncing.
    3416             :  *
    3417             :  * If skip_recently_used is true, we don't write currently-pinned buffers, nor
    3418             :  * buffers marked recently used, as these are not replacement candidates.
    3419             :  *
    3420             :  * Returns a bitmask containing the following flag bits:
    3421             :  *  BUF_WRITTEN: we wrote the buffer.
    3422             :  *  BUF_REUSABLE: buffer is available for replacement, ie, it has
    3423             :  *      pin count 0 and usage count 0.
    3424             :  *
    3425             :  * (BUF_WRITTEN could be set in error if FlushBuffer finds the buffer clean
    3426             :  * after locking it, but we don't care all that much.)
    3427             :  */
    3428             : static int
    3429     2893848 : SyncOneBuffer(int buf_id, bool skip_recently_used, WritebackContext *wb_context)
    3430             : {
    3431     2893848 :     BufferDesc *bufHdr = GetBufferDescriptor(buf_id);
    3432     2893848 :     int         result = 0;
    3433             :     uint32      buf_state;
    3434             :     BufferTag   tag;
    3435             : 
    3436             :     /* Make sure we can handle the pin */
    3437     2893848 :     ReservePrivateRefCountEntry();
    3438     2893848 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    3439             : 
    3440             :     /*
    3441             :      * Check whether buffer needs writing.
    3442             :      *
    3443             :      * We can make this check without taking the buffer content lock so long
    3444             :      * as we mark pages dirty in access methods *before* logging changes with
    3445             :      * XLogInsert(): if someone marks the buffer dirty just after our check we
    3446             :      * don't worry because our checkpoint.redo points before log record for
    3447             :      * upcoming changes and so we are not required to write such dirty buffer.
    3448             :      */
    3449     2893848 :     buf_state = LockBufHdr(bufHdr);
    3450             : 
    3451     2893848 :     if (BUF_STATE_GET_REFCOUNT(buf_state) == 0 &&
    3452     2892492 :         BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
    3453             :     {
    3454     1913888 :         result |= BUF_REUSABLE;
    3455             :     }
    3456      979960 :     else if (skip_recently_used)
    3457             :     {
    3458             :         /* Caller told us not to write recently-used buffers */
    3459      555702 :         UnlockBufHdr(bufHdr, buf_state);
    3460      555702 :         return result;
    3461             :     }
    3462             : 
    3463     2338146 :     if (!(buf_state & BM_VALID) || !(buf_state & BM_DIRTY))
    3464             :     {
    3465             :         /* It's clean, so nothing to do */
    3466     1894484 :         UnlockBufHdr(bufHdr, buf_state);
    3467     1894484 :         return result;
    3468             :     }
    3469             : 
    3470             :     /*
    3471             :      * Pin it, share-lock it, write it.  (FlushBuffer will do nothing if the
    3472             :      * buffer is clean by the time we've locked it.)
    3473             :      */
    3474      443662 :     PinBuffer_Locked(bufHdr);
    3475      443662 :     LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    3476             : 
    3477      443662 :     FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    3478             : 
    3479      443662 :     LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    3480             : 
    3481      443662 :     tag = bufHdr->tag;
    3482             : 
    3483      443662 :     UnpinBuffer(bufHdr);
    3484             : 
    3485             :     /*
    3486             :      * SyncOneBuffer() is only called by checkpointer and bgwriter, so
    3487             :      * IOContext will always be IOCONTEXT_NORMAL.
    3488             :      */
    3489      443662 :     ScheduleBufferTagForWriteback(wb_context, IOCONTEXT_NORMAL, &tag);
    3490             : 
    3491      443662 :     return result | BUF_WRITTEN;
    3492             : }
    3493             : 
    3494             : /*
    3495             :  *      AtEOXact_Buffers - clean up at end of transaction.
    3496             :  *
    3497             :  *      As of PostgreSQL 8.0, buffer pins should get released by the
    3498             :  *      ResourceOwner mechanism.  This routine is just a debugging
    3499             :  *      cross-check that no pins remain.
    3500             :  */
    3501             : void
    3502      557564 : AtEOXact_Buffers(bool isCommit)
    3503             : {
    3504      557564 :     CheckForBufferLeaks();
    3505             : 
    3506      557564 :     AtEOXact_LocalBuffers(isCommit);
    3507             : 
    3508             :     Assert(PrivateRefCountOverflowed == 0);
    3509      557564 : }
    3510             : 
    3511             : /*
    3512             :  * Initialize access to shared buffer pool
    3513             :  *
    3514             :  * This is called during backend startup (whether standalone or under the
    3515             :  * postmaster).  It sets up for this backend's access to the already-existing
    3516             :  * buffer pool.
    3517             :  */
    3518             : void
    3519       29816 : InitBufferPoolAccess(void)
    3520             : {
    3521             :     HASHCTL     hash_ctl;
    3522             : 
    3523       29816 :     memset(&PrivateRefCountArray, 0, sizeof(PrivateRefCountArray));
    3524             : 
    3525       29816 :     hash_ctl.keysize = sizeof(int32);
    3526       29816 :     hash_ctl.entrysize = sizeof(PrivateRefCountEntry);
    3527             : 
    3528       29816 :     PrivateRefCountHash = hash_create("PrivateRefCount", 100, &hash_ctl,
    3529             :                                       HASH_ELEM | HASH_BLOBS);
    3530             : 
    3531             :     /*
    3532             :      * AtProcExit_Buffers needs LWLock access, and thereby has to be called at
    3533             :      * the corresponding phase of backend shutdown.
    3534             :      */
    3535             :     Assert(MyProc != NULL);
    3536       29816 :     on_shmem_exit(AtProcExit_Buffers, 0);
    3537       29816 : }
    3538             : 
    3539             : /*
    3540             :  * During backend exit, ensure that we released all shared-buffer locks and
    3541             :  * assert that we have no remaining pins.
    3542             :  */
    3543             : static void
    3544       29816 : AtProcExit_Buffers(int code, Datum arg)
    3545             : {
    3546       29816 :     UnlockBuffers();
    3547             : 
    3548       29816 :     CheckForBufferLeaks();
    3549             : 
    3550             :     /* localbuf.c needs a chance too */
    3551       29816 :     AtProcExit_LocalBuffers();
    3552       29816 : }
    3553             : 
    3554             : /*
    3555             :  *      CheckForBufferLeaks - ensure this backend holds no buffer pins
    3556             :  *
    3557             :  *      As of PostgreSQL 8.0, buffer pins should get released by the
    3558             :  *      ResourceOwner mechanism.  This routine is just a debugging
    3559             :  *      cross-check that no pins remain.
    3560             :  */
    3561             : static void
    3562      587380 : CheckForBufferLeaks(void)
    3563             : {
    3564             : #ifdef USE_ASSERT_CHECKING
    3565             :     int         RefCountErrors = 0;
    3566             :     PrivateRefCountEntry *res;
    3567             :     int         i;
    3568             :     char       *s;
    3569             : 
    3570             :     /* check the array */
    3571             :     for (i = 0; i < REFCOUNT_ARRAY_ENTRIES; i++)
    3572             :     {
    3573             :         res = &PrivateRefCountArray[i];
    3574             : 
    3575             :         if (res->buffer != InvalidBuffer)
    3576             :         {
    3577             :             s = DebugPrintBufferRefcount(res->buffer);
    3578             :             elog(WARNING, "buffer refcount leak: %s", s);
    3579             :             pfree(s);
    3580             : 
    3581             :             RefCountErrors++;
    3582             :         }
    3583             :     }
    3584             : 
    3585             :     /* if necessary search the hash */
    3586             :     if (PrivateRefCountOverflowed)
    3587             :     {
    3588             :         HASH_SEQ_STATUS hstat;
    3589             : 
    3590             :         hash_seq_init(&hstat, PrivateRefCountHash);
    3591             :         while ((res = (PrivateRefCountEntry *) hash_seq_search(&hstat)) != NULL)
    3592             :         {
    3593             :             s = DebugPrintBufferRefcount(res->buffer);
    3594             :             elog(WARNING, "buffer refcount leak: %s", s);
    3595             :             pfree(s);
    3596             :             RefCountErrors++;
    3597             :         }
    3598             :     }
    3599             : 
    3600             :     Assert(RefCountErrors == 0);
    3601             : #endif
    3602      587380 : }
    3603             : 
    3604             : /*
    3605             :  * Helper routine to issue warnings when a buffer is unexpectedly pinned
    3606             :  */
    3607             : char *
    3608           0 : DebugPrintBufferRefcount(Buffer buffer)
    3609             : {
    3610             :     BufferDesc *buf;
    3611             :     int32       loccount;
    3612             :     char       *path;
    3613             :     char       *result;
    3614             :     ProcNumber  backend;
    3615             :     uint32      buf_state;
    3616             : 
    3617             :     Assert(BufferIsValid(buffer));
    3618           0 :     if (BufferIsLocal(buffer))
    3619             :     {
    3620           0 :         buf = GetLocalBufferDescriptor(-buffer - 1);
    3621           0 :         loccount = LocalRefCount[-buffer - 1];
    3622           0 :         backend = MyProcNumber;
    3623             :     }
    3624             :     else
    3625             :     {
    3626           0 :         buf = GetBufferDescriptor(buffer - 1);
    3627           0 :         loccount = GetPrivateRefCount(buffer);
    3628           0 :         backend = INVALID_PROC_NUMBER;
    3629             :     }
    3630             : 
    3631             :     /* theoretically we should lock the bufhdr here */
    3632           0 :     path = relpathbackend(BufTagGetRelFileLocator(&buf->tag), backend,
    3633             :                           BufTagGetForkNum(&buf->tag));
    3634           0 :     buf_state = pg_atomic_read_u32(&buf->state);
    3635             : 
    3636           0 :     result = psprintf("[%03d] (rel=%s, blockNum=%u, flags=0x%x, refcount=%u %d)",
    3637             :                       buffer, path,
    3638             :                       buf->tag.blockNum, buf_state & BUF_FLAG_MASK,
    3639             :                       BUF_STATE_GET_REFCOUNT(buf_state), loccount);
    3640           0 :     pfree(path);
    3641           0 :     return result;
    3642             : }
    3643             : 
    3644             : /*
    3645             :  * CheckPointBuffers
    3646             :  *
    3647             :  * Flush all dirty blocks in buffer pool to disk at checkpoint time.
    3648             :  *
    3649             :  * Note: temporary relations do not participate in checkpoints, so they don't
    3650             :  * need to be flushed.
    3651             :  */
    3652             : void
    3653        1704 : CheckPointBuffers(int flags)
    3654             : {
    3655        1704 :     BufferSync(flags);
    3656        1704 : }
    3657             : 
    3658             : /*
    3659             :  * BufferGetBlockNumber
    3660             :  *      Returns the block number associated with a buffer.
    3661             :  *
    3662             :  * Note:
    3663             :  *      Assumes that the buffer is valid and pinned, else the
    3664             :  *      value may be obsolete immediately...
    3665             :  */
    3666             : BlockNumber
    3667    88646330 : BufferGetBlockNumber(Buffer buffer)
    3668             : {
    3669             :     BufferDesc *bufHdr;
    3670             : 
    3671             :     Assert(BufferIsPinned(buffer));
    3672             : 
    3673    88646330 :     if (BufferIsLocal(buffer))
    3674     3311940 :         bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    3675             :     else
    3676    85334390 :         bufHdr = GetBufferDescriptor(buffer - 1);
    3677             : 
    3678             :     /* pinned, so OK to read tag without spinlock */
    3679    88646330 :     return bufHdr->tag.blockNum;
    3680             : }
    3681             : 
    3682             : /*
    3683             :  * BufferGetTag
    3684             :  *      Returns the relfilelocator, fork number and block number associated with
    3685             :  *      a buffer.
    3686             :  */
    3687             : void
    3688    26830198 : BufferGetTag(Buffer buffer, RelFileLocator *rlocator, ForkNumber *forknum,
    3689             :              BlockNumber *blknum)
    3690             : {
    3691             :     BufferDesc *bufHdr;
    3692             : 
    3693             :     /* Do the same checks as BufferGetBlockNumber. */
    3694             :     Assert(BufferIsPinned(buffer));
    3695             : 
    3696    26830198 :     if (BufferIsLocal(buffer))
    3697           0 :         bufHdr = GetLocalBufferDescriptor(-buffer - 1);
    3698             :     else
    3699    26830198 :         bufHdr = GetBufferDescriptor(buffer - 1);
    3700             : 
    3701             :     /* pinned, so OK to read tag without spinlock */
    3702    26830198 :     *rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
    3703    26830198 :     *forknum = BufTagGetForkNum(&bufHdr->tag);
    3704    26830198 :     *blknum = bufHdr->tag.blockNum;
    3705    26830198 : }
    3706             : 
    3707             : /*
    3708             :  * FlushBuffer
    3709             :  *      Physically write out a shared buffer.
    3710             :  *
    3711             :  * NOTE: this actually just passes the buffer contents to the kernel; the
    3712             :  * real write to disk won't happen until the kernel feels like it.  This
    3713             :  * is okay from our point of view since we can redo the changes from WAL.
    3714             :  * However, we will need to force the changes to disk via fsync before
    3715             :  * we can checkpoint WAL.
    3716             :  *
    3717             :  * The caller must hold a pin on the buffer and have share-locked the
    3718             :  * buffer contents.  (Note: a share-lock does not prevent updates of
    3719             :  * hint bits in the buffer, so the page could change while the write
    3720             :  * is in progress, but we assume that that will not invalidate the data
    3721             :  * written.)
    3722             :  *
    3723             :  * If the caller has an smgr reference for the buffer's relation, pass it
    3724             :  * as the second parameter.  If not, pass NULL.
    3725             :  */
    3726             : static void
    3727      887458 : FlushBuffer(BufferDesc *buf, SMgrRelation reln, IOObject io_object,
    3728             :             IOContext io_context)
    3729             : {
    3730             :     XLogRecPtr  recptr;
    3731             :     ErrorContextCallback errcallback;
    3732             :     instr_time  io_start;
    3733             :     Block       bufBlock;
    3734             :     char       *bufToWrite;
    3735             :     uint32      buf_state;
    3736             : 
    3737             :     /*
    3738             :      * Try to start an I/O operation.  If StartBufferIO returns false, then
    3739             :      * someone else flushed the buffer before we could, so we need not do
    3740             :      * anything.
    3741             :      */
    3742      887458 :     if (!StartBufferIO(buf, false, false))
    3743           0 :         return;
    3744             : 
    3745             :     /* Setup error traceback support for ereport() */
    3746      887458 :     errcallback.callback = shared_buffer_write_error_callback;
    3747      887458 :     errcallback.arg = (void *) buf;
    3748      887458 :     errcallback.previous = error_context_stack;
    3749      887458 :     error_context_stack = &errcallback;
    3750             : 
    3751             :     /* Find smgr relation for buffer */
    3752      887458 :     if (reln == NULL)
    3753      880394 :         reln = smgropen(BufTagGetRelFileLocator(&buf->tag), INVALID_PROC_NUMBER);
    3754             : 
    3755             :     TRACE_POSTGRESQL_BUFFER_FLUSH_START(BufTagGetForkNum(&buf->tag),
    3756             :                                         buf->tag.blockNum,
    3757             :                                         reln->smgr_rlocator.locator.spcOid,
    3758             :                                         reln->smgr_rlocator.locator.dbOid,
    3759             :                                         reln->smgr_rlocator.locator.relNumber);
    3760             : 
    3761      887458 :     buf_state = LockBufHdr(buf);
    3762             : 
    3763             :     /*
    3764             :      * Run PageGetLSN while holding header lock, since we don't have the
    3765             :      * buffer locked exclusively in all cases.
    3766             :      */
    3767      887458 :     recptr = BufferGetLSN(buf);
    3768             : 
    3769             :     /* To check if block content changes while flushing. - vadim 01/17/97 */
    3770      887458 :     buf_state &= ~BM_JUST_DIRTIED;
    3771      887458 :     UnlockBufHdr(buf, buf_state);
    3772             : 
    3773             :     /*
    3774             :      * Force XLOG flush up to buffer's LSN.  This implements the basic WAL
    3775             :      * rule that log updates must hit disk before any of the data-file changes
    3776             :      * they describe do.
    3777             :      *
    3778             :      * However, this rule does not apply to unlogged relations, which will be
    3779             :      * lost after a crash anyway.  Most unlogged relation pages do not bear
    3780             :      * LSNs since we never emit WAL records for them, and therefore flushing
    3781             :      * up through the buffer LSN would be useless, but harmless.  However,
    3782             :      * GiST indexes use LSNs internally to track page-splits, and therefore
    3783             :      * unlogged GiST pages bear "fake" LSNs generated by
    3784             :      * GetFakeLSNForUnloggedRel.  It is unlikely but possible that the fake
    3785             :      * LSN counter could advance past the WAL insertion point; and if it did
    3786             :      * happen, attempting to flush WAL through that location would fail, with
    3787             :      * disastrous system-wide consequences.  To make sure that can't happen,
    3788             :      * skip the flush if the buffer isn't permanent.
    3789             :      */
    3790      887458 :     if (buf_state & BM_PERMANENT)
    3791      883354 :         XLogFlush(recptr);
    3792             : 
    3793             :     /*
    3794             :      * Now it's safe to write buffer to disk. Note that no one else should
    3795             :      * have been able to write it while we were busy with log flushing because
    3796             :      * only one process at a time can set the BM_IO_IN_PROGRESS bit.
    3797             :      */
    3798      887458 :     bufBlock = BufHdrGetBlock(buf);
    3799             : 
    3800             :     /*
    3801             :      * Update page checksum if desired.  Since we have only shared lock on the
    3802             :      * buffer, other processes might be updating hint bits in it, so we must
    3803             :      * copy the page to private storage if we do checksumming.
    3804             :      */
    3805      887458 :     bufToWrite = PageSetChecksumCopy((Page) bufBlock, buf->tag.blockNum);
    3806             : 
    3807      887458 :     io_start = pgstat_prepare_io_time(track_io_timing);
    3808             : 
    3809             :     /*
    3810             :      * bufToWrite is either the shared buffer or a copy, as appropriate.
    3811             :      */
    3812      887458 :     smgrwrite(reln,
    3813      887458 :               BufTagGetForkNum(&buf->tag),
    3814             :               buf->tag.blockNum,
    3815             :               bufToWrite,
    3816             :               false);
    3817             : 
    3818             :     /*
    3819             :      * When a strategy is in use, only flushes of dirty buffers already in the
    3820             :      * strategy ring are counted as strategy writes (IOCONTEXT
    3821             :      * [BULKREAD|BULKWRITE|VACUUM] IOOP_WRITE) for the purpose of IO
    3822             :      * statistics tracking.
    3823             :      *
    3824             :      * If a shared buffer initially added to the ring must be flushed before
    3825             :      * being used, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE.
    3826             :      *
    3827             :      * If a shared buffer which was added to the ring later because the
    3828             :      * current strategy buffer is pinned or in use or because all strategy
    3829             :      * buffers were dirty and rejected (for BAS_BULKREAD operations only)
    3830             :      * requires flushing, this is counted as an IOCONTEXT_NORMAL IOOP_WRITE
    3831             :      * (from_ring will be false).
    3832             :      *
    3833             :      * When a strategy is not in use, the write can only be a "regular" write
    3834             :      * of a dirty shared buffer (IOCONTEXT_NORMAL IOOP_WRITE).
    3835             :      */
    3836      887458 :     pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
    3837             :                             IOOP_WRITE, io_start, 1);
    3838             : 
    3839      887458 :     pgBufferUsage.shared_blks_written++;
    3840             : 
    3841             :     /*
    3842             :      * Mark the buffer as clean (unless BM_JUST_DIRTIED has become set) and
    3843             :      * end the BM_IO_IN_PROGRESS state.
    3844             :      */
    3845      887458 :     TerminateBufferIO(buf, true, 0, true);
    3846             : 
    3847             :     TRACE_POSTGRESQL_BUFFER_FLUSH_DONE(BufTagGetForkNum(&buf->tag),
    3848             :                                        buf->tag.blockNum,
    3849             :                                        reln->smgr_rlocator.locator.spcOid,
    3850             :                                        reln->smgr_rlocator.locator.dbOid,
    3851             :                                        reln->smgr_rlocator.locator.relNumber);
    3852             : 
    3853             :     /* Pop the error context stack */
    3854      887458 :     error_context_stack = errcallback.previous;
    3855             : }
    3856             : 
    3857             : /*
    3858             :  * RelationGetNumberOfBlocksInFork
    3859             :  *      Determines the current number of pages in the specified relation fork.
    3860             :  *
    3861             :  * Note that the accuracy of the result will depend on the details of the
    3862             :  * relation's storage. For builtin AMs it'll be accurate, but for external AMs
    3863             :  * it might not be.
    3864             :  */
    3865             : BlockNumber
    3866     2816554 : RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum)
    3867             : {
    3868     2816554 :     if (RELKIND_HAS_TABLE_AM(relation->rd_rel->relkind))
    3869             :     {
    3870             :         /*
    3871             :          * Not every table AM uses BLCKSZ wide fixed size blocks. Therefore
    3872             :          * tableam returns the size in bytes - but for the purpose of this
    3873             :          * routine, we want the number of blocks. Therefore divide, rounding
    3874             :          * up.
    3875             :          */
    3876             :         uint64      szbytes;
    3877             : 
    3878     2104332 :         szbytes = table_relation_size(relation, forkNum);
    3879             : 
    3880     2104294 :         return (szbytes + (BLCKSZ - 1)) / BLCKSZ;
    3881             :     }
    3882      712222 :     else if (RELKIND_HAS_STORAGE(relation->rd_rel->relkind))
    3883             :     {
    3884      712222 :         return smgrnblocks(RelationGetSmgr(relation), forkNum);
    3885             :     }
    3886             :     else
    3887             :         Assert(false);
    3888             : 
    3889           0 :     return 0;                   /* keep compiler quiet */
    3890             : }
    3891             : 
    3892             : /*
    3893             :  * BufferIsPermanent
    3894             :  *      Determines whether a buffer will potentially still be around after
    3895             :  *      a crash.  Caller must hold a buffer pin.
    3896             :  */
    3897             : bool
    3898    17606078 : BufferIsPermanent(Buffer buffer)
    3899             : {
    3900             :     BufferDesc *bufHdr;
    3901             : 
    3902             :     /* Local buffers are used only for temp relations. */
    3903    17606078 :     if (BufferIsLocal(buffer))
    3904     1145278 :         return false;
    3905             : 
    3906             :     /* Make sure we've got a real buffer, and that we hold a pin on it. */
    3907             :     Assert(BufferIsValid(buffer));
    3908             :     Assert(BufferIsPinned(buffer));
    3909             : 
    3910             :     /*
    3911             :      * BM_PERMANENT can't be changed while we hold a pin on the buffer, so we
    3912             :      * need not bother with the buffer header spinlock.  Even if someone else
    3913             :      * changes the buffer header state while we're doing this, the state is
    3914             :      * changed atomically, so we'll read the old value or the new value, but
    3915             :      * not random garbage.
    3916             :      */
    3917    16460800 :     bufHdr = GetBufferDescriptor(buffer - 1);
    3918    16460800 :     return (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT) != 0;
    3919             : }
    3920             : 
    3921             : /*
    3922             :  * BufferGetLSNAtomic
    3923             :  *      Retrieves the LSN of the buffer atomically using a buffer header lock.
    3924             :  *      This is necessary for some callers who may not have an exclusive lock
    3925             :  *      on the buffer.
    3926             :  */
    3927             : XLogRecPtr
    3928    13421994 : BufferGetLSNAtomic(Buffer buffer)
    3929             : {
    3930    13421994 :     BufferDesc *bufHdr = GetBufferDescriptor(buffer - 1);
    3931    13421994 :     char       *page = BufferGetPage(buffer);
    3932             :     XLogRecPtr  lsn;
    3933             :     uint32      buf_state;
    3934             : 
    3935             :     /*
    3936             :      * If we don't need locking for correctness, fastpath out.
    3937             :      */
    3938    13421994 :     if (!XLogHintBitIsNeeded() || BufferIsLocal(buffer))
    3939    10188792 :         return PageGetLSN(page);
    3940             : 
    3941             :     /* Make sure we've got a real buffer, and that we hold a pin on it. */
    3942             :     Assert(BufferIsValid(buffer));
    3943             :     Assert(BufferIsPinned(buffer));
    3944             : 
    3945     3233202 :     buf_state = LockBufHdr(bufHdr);
    3946     3233202 :     lsn = PageGetLSN(page);
    3947     3233202 :     UnlockBufHdr(bufHdr, buf_state);
    3948             : 
    3949     3233202 :     return lsn;
    3950             : }
    3951             : 
    3952             : /* ---------------------------------------------------------------------
    3953             :  *      DropRelationBuffers
    3954             :  *
    3955             :  *      This function removes from the buffer pool all the pages of the
    3956             :  *      specified relation forks that have block numbers >= firstDelBlock.
    3957             :  *      (In particular, with firstDelBlock = 0, all pages are removed.)
    3958             :  *      Dirty pages are simply dropped, without bothering to write them
    3959             :  *      out first.  Therefore, this is NOT rollback-able, and so should be
    3960             :  *      used only with extreme caution!
    3961             :  *
    3962             :  *      Currently, this is called only from smgr.c when the underlying file
    3963             :  *      is about to be deleted or truncated (firstDelBlock is needed for
    3964             :  *      the truncation case).  The data in the affected pages would therefore
    3965             :  *      be deleted momentarily anyway, and there is no point in writing it.
    3966             :  *      It is the responsibility of higher-level code to ensure that the
    3967             :  *      deletion or truncation does not lose any data that could be needed
    3968             :  *      later.  It is also the responsibility of higher-level code to ensure
    3969             :  *      that no other process could be trying to load more pages of the
    3970             :  *      relation into buffers.
    3971             :  * --------------------------------------------------------------------
    3972             :  */
    3973             : void
    3974        1096 : DropRelationBuffers(SMgrRelation smgr_reln, ForkNumber *forkNum,
    3975             :                     int nforks, BlockNumber *firstDelBlock)
    3976             : {
    3977             :     int         i;
    3978             :     int         j;
    3979             :     RelFileLocatorBackend rlocator;
    3980             :     BlockNumber nForkBlock[MAX_FORKNUM];
    3981        1096 :     uint64      nBlocksToInvalidate = 0;
    3982             : 
    3983        1096 :     rlocator = smgr_reln->smgr_rlocator;
    3984             : 
    3985             :     /* If it's a local relation, it's localbuf.c's problem. */
    3986        1096 :     if (RelFileLocatorBackendIsTemp(rlocator))
    3987             :     {
    3988         658 :         if (rlocator.backend == MyProcNumber)
    3989             :         {
    3990        1350 :             for (j = 0; j < nforks; j++)
    3991         692 :                 DropRelationLocalBuffers(rlocator.locator, forkNum[j],
    3992         692 :                                          firstDelBlock[j]);
    3993             :         }
    3994         726 :         return;
    3995             :     }
    3996             : 
    3997             :     /*
    3998             :      * To remove all the pages of the specified relation forks from the buffer
    3999             :      * pool, we need to scan the entire buffer pool but we can optimize it by
    4000             :      * finding the buffers from BufMapping table provided we know the exact
    4001             :      * size of each fork of the relation. The exact size is required to ensure
    4002             :      * that we don't leave any buffer for the relation being dropped as
    4003             :      * otherwise the background writer or checkpointer can lead to a PANIC
    4004             :      * error while flushing buffers corresponding to files that don't exist.
    4005             :      *
    4006             :      * To know the exact size, we rely on the size cached for each fork by us
    4007             :      * during recovery which limits the optimization to recovery and on
    4008             :      * standbys but we can easily extend it once we have shared cache for
    4009             :      * relation size.
    4010             :      *
    4011             :      * In recovery, we cache the value returned by the first lseek(SEEK_END)
    4012             :      * and the future writes keeps the cached value up-to-date. See
    4013             :      * smgrextend. It is possible that the value of the first lseek is smaller
    4014             :      * than the actual number of existing blocks in the file due to buggy
    4015             :      * Linux kernels that might not have accounted for the recent write. But
    4016             :      * that should be fine because there must not be any buffers after that
    4017             :      * file size.
    4018             :      */
    4019         582 :     for (i = 0; i < nforks; i++)
    4020             :     {
    4021             :         /* Get the number of blocks for a relation's fork */
    4022         502 :         nForkBlock[i] = smgrnblocks_cached(smgr_reln, forkNum[i]);
    4023             : 
    4024         502 :         if (nForkBlock[i] == InvalidBlockNumber)
    4025             :         {
    4026         358 :             nBlocksToInvalidate = InvalidBlockNumber;
    4027         358 :             break;
    4028             :         }
    4029             : 
    4030             :         /* calculate the number of blocks to be invalidated */
    4031         144 :         nBlocksToInvalidate += (nForkBlock[i] - firstDelBlock[i]);
    4032             :     }
    4033             : 
    4034             :     /*
    4035             :      * We apply the optimization iff the total number of blocks to invalidate
    4036             :      * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
    4037             :      */
    4038         438 :     if (BlockNumberIsValid(nBlocksToInvalidate) &&
    4039          80 :         nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
    4040             :     {
    4041         186 :         for (j = 0; j < nforks; j++)
    4042         118 :             FindAndDropRelationBuffers(rlocator.locator, forkNum[j],
    4043         118 :                                        nForkBlock[j], firstDelBlock[j]);
    4044          68 :         return;
    4045             :     }
    4046             : 
    4047     5054578 :     for (i = 0; i < NBuffers; i++)
    4048             :     {
    4049     5054208 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    4050             :         uint32      buf_state;
    4051             : 
    4052             :         /*
    4053             :          * We can make this a tad faster by prechecking the buffer tag before
    4054             :          * we attempt to lock the buffer; this saves a lot of lock
    4055             :          * acquisitions in typical cases.  It should be safe because the
    4056             :          * caller must have AccessExclusiveLock on the relation, or some other
    4057             :          * reason to be certain that no one is loading new pages of the rel
    4058             :          * into the buffer pool.  (Otherwise we might well miss such pages
    4059             :          * entirely.)  Therefore, while the tag might be changing while we
    4060             :          * look at it, it can't be changing *to* a value we care about, only
    4061             :          * *away* from such a value.  So false negatives are impossible, and
    4062             :          * false positives are safe because we'll recheck after getting the
    4063             :          * buffer lock.
    4064             :          *
    4065             :          * We could check forkNum and blockNum as well as the rlocator, but
    4066             :          * the incremental win from doing so seems small.
    4067             :          */
    4068     5054208 :         if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator))
    4069     5041958 :             continue;
    4070             : 
    4071       12250 :         buf_state = LockBufHdr(bufHdr);
    4072             : 
    4073       31896 :         for (j = 0; j < nforks; j++)
    4074             :         {
    4075       22264 :             if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator.locator) &&
    4076       22264 :                 BufTagGetForkNum(&bufHdr->tag) == forkNum[j] &&
    4077       12100 :                 bufHdr->tag.blockNum >= firstDelBlock[j])
    4078             :             {
    4079        2618 :                 InvalidateBuffer(bufHdr);   /* releases spinlock */
    4080        2618 :                 break;
    4081             :             }
    4082             :         }
    4083       12250 :         if (j >= nforks)
    4084        9632 :             UnlockBufHdr(bufHdr, buf_state);
    4085             :     }
    4086             : }
    4087             : 
    4088             : /* ---------------------------------------------------------------------
    4089             :  *      DropRelationsAllBuffers
    4090             :  *
    4091             :  *      This function removes from the buffer pool all the pages of all
    4092             :  *      forks of the specified relations.  It's equivalent to calling
    4093             :  *      DropRelationBuffers once per fork per relation with firstDelBlock = 0.
    4094             :  *      --------------------------------------------------------------------
    4095             :  */
    4096             : void
    4097       23882 : DropRelationsAllBuffers(SMgrRelation *smgr_reln, int nlocators)
    4098             : {
    4099             :     int         i;
    4100       23882 :     int         n = 0;
    4101             :     SMgrRelation *rels;
    4102             :     BlockNumber (*block)[MAX_FORKNUM + 1];
    4103       23882 :     uint64      nBlocksToInvalidate = 0;
    4104             :     RelFileLocator *locators;
    4105       23882 :     bool        cached = true;
    4106             :     bool        use_bsearch;
    4107             : 
    4108       23882 :     if (nlocators == 0)
    4109           0 :         return;
    4110             : 
    4111       23882 :     rels = palloc(sizeof(SMgrRelation) * nlocators);    /* non-local relations */
    4112             : 
    4113             :     /* If it's a local relation, it's localbuf.c's problem. */
    4114      106358 :     for (i = 0; i < nlocators; i++)
    4115             :     {
    4116       82476 :         if (RelFileLocatorBackendIsTemp(smgr_reln[i]->smgr_rlocator))
    4117             :         {
    4118        5880 :             if (smgr_reln[i]->smgr_rlocator.backend == MyProcNumber)
    4119        5880 :                 DropRelationAllLocalBuffers(smgr_reln[i]->smgr_rlocator.locator);
    4120             :         }
    4121             :         else
    4122       76596 :             rels[n++] = smgr_reln[i];
    4123             :     }
    4124             : 
    4125             :     /*
    4126             :      * If there are no non-local relations, then we're done. Release the
    4127             :      * memory and return.
    4128             :      */
    4129       23882 :     if (n == 0)
    4130             :     {
    4131        1506 :         pfree(rels);
    4132        1506 :         return;
    4133             :     }
    4134             : 
    4135             :     /*
    4136             :      * This is used to remember the number of blocks for all the relations
    4137             :      * forks.
    4138             :      */
    4139             :     block = (BlockNumber (*)[MAX_FORKNUM + 1])
    4140       22376 :         palloc(sizeof(BlockNumber) * n * (MAX_FORKNUM + 1));
    4141             : 
    4142             :     /*
    4143             :      * We can avoid scanning the entire buffer pool if we know the exact size
    4144             :      * of each of the given relation forks. See DropRelationBuffers.
    4145             :      */
    4146       47324 :     for (i = 0; i < n && cached; i++)
    4147             :     {
    4148       41612 :         for (int j = 0; j <= MAX_FORKNUM; j++)
    4149             :         {
    4150             :             /* Get the number of blocks for a relation's fork. */
    4151       37468 :             block[i][j] = smgrnblocks_cached(rels[i], j);
    4152             : 
    4153             :             /* We need to only consider the relation forks that exists. */
    4154       37468 :             if (block[i][j] == InvalidBlockNumber)
    4155             :             {
    4156       32968 :                 if (!smgrexists(rels[i], j))
    4157       12164 :                     continue;
    4158       20804 :                 cached = false;
    4159       20804 :                 break;
    4160             :             }
    4161             : 
    4162             :             /* calculate the total number of blocks to be invalidated */
    4163        4500 :             nBlocksToInvalidate += block[i][j];
    4164             :         }
    4165             :     }
    4166             : 
    4167             :     /*
    4168             :      * We apply the optimization iff the total number of blocks to invalidate
    4169             :      * is below the BUF_DROP_FULL_SCAN_THRESHOLD.
    4170             :      */
    4171       22376 :     if (cached && nBlocksToInvalidate < BUF_DROP_FULL_SCAN_THRESHOLD)
    4172             :     {
    4173        2502 :         for (i = 0; i < n; i++)
    4174             :         {
    4175        6930 :             for (int j = 0; j <= MAX_FORKNUM; j++)
    4176             :             {
    4177             :                 /* ignore relation forks that doesn't exist */
    4178        5544 :                 if (!BlockNumberIsValid(block[i][j]))
    4179        4140 :                     continue;
    4180             : 
    4181             :                 /* drop all the buffers for a particular relation fork */
    4182        1404 :                 FindAndDropRelationBuffers(rels[i]->smgr_rlocator.locator,
    4183        1404 :                                            j, block[i][j], 0);
    4184             :             }
    4185             :         }
    4186             : 
    4187        1116 :         pfree(block);
    4188        1116 :         pfree(rels);
    4189        1116 :         return;
    4190             :     }
    4191             : 
    4192       21260 :     pfree(block);
    4193       21260 :     locators = palloc(sizeof(RelFileLocator) * n);  /* non-local relations */
    4194       96470 :     for (i = 0; i < n; i++)
    4195       75210 :         locators[i] = rels[i]->smgr_rlocator.locator;
    4196             : 
    4197             :     /*
    4198             :      * For low number of relations to drop just use a simple walk through, to
    4199             :      * save the bsearch overhead. The threshold to use is rather a guess than
    4200             :      * an exactly determined value, as it depends on many factors (CPU and RAM
    4201             :      * speeds, amount of shared buffers etc.).
    4202             :      */
    4203       21260 :     use_bsearch = n > RELS_BSEARCH_THRESHOLD;
    4204             : 
    4205             :     /* sort the list of rlocators if necessary */
    4206       21260 :     if (use_bsearch)
    4207         330 :         qsort(locators, n, sizeof(RelFileLocator), rlocator_comparator);
    4208             : 
    4209   234845708 :     for (i = 0; i < NBuffers; i++)
    4210             :     {
    4211   234824448 :         RelFileLocator *rlocator = NULL;
    4212   234824448 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    4213             :         uint32      buf_state;
    4214             : 
    4215             :         /*
    4216             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4217             :          * saves some cycles.
    4218             :          */
    4219             : 
    4220   234824448 :         if (!use_bsearch)
    4221             :         {
    4222             :             int         j;
    4223             : 
    4224   948912512 :             for (j = 0; j < n; j++)
    4225             :             {
    4226   717705916 :                 if (BufTagMatchesRelFileLocator(&bufHdr->tag, &locators[j]))
    4227             :                 {
    4228      161852 :                     rlocator = &locators[j];
    4229      161852 :                     break;
    4230             :                 }
    4231             :             }
    4232             :         }
    4233             :         else
    4234             :         {
    4235             :             RelFileLocator locator;
    4236             : 
    4237     3456000 :             locator = BufTagGetRelFileLocator(&bufHdr->tag);
    4238     3456000 :             rlocator = bsearch((const void *) &(locator),
    4239             :                                locators, n, sizeof(RelFileLocator),
    4240             :                                rlocator_comparator);
    4241             :         }
    4242             : 
    4243             :         /* buffer doesn't belong to any of the given relfilelocators; skip it */
    4244   234824448 :         if (rlocator == NULL)
    4245   234658868 :             continue;
    4246             : 
    4247      165580 :         buf_state = LockBufHdr(bufHdr);
    4248      165580 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, rlocator))
    4249      165580 :             InvalidateBuffer(bufHdr);   /* releases spinlock */
    4250             :         else
    4251           0 :             UnlockBufHdr(bufHdr, buf_state);
    4252             :     }
    4253             : 
    4254       21260 :     pfree(locators);
    4255       21260 :     pfree(rels);
    4256             : }
    4257             : 
    4258             : /* ---------------------------------------------------------------------
    4259             :  *      FindAndDropRelationBuffers
    4260             :  *
    4261             :  *      This function performs look up in BufMapping table and removes from the
    4262             :  *      buffer pool all the pages of the specified relation fork that has block
    4263             :  *      number >= firstDelBlock. (In particular, with firstDelBlock = 0, all
    4264             :  *      pages are removed.)
    4265             :  * --------------------------------------------------------------------
    4266             :  */
    4267             : static void
    4268        1522 : FindAndDropRelationBuffers(RelFileLocator rlocator, ForkNumber forkNum,
    4269             :                            BlockNumber nForkBlock,
    4270             :                            BlockNumber firstDelBlock)
    4271             : {
    4272             :     BlockNumber curBlock;
    4273             : 
    4274        3720 :     for (curBlock = firstDelBlock; curBlock < nForkBlock; curBlock++)
    4275             :     {
    4276             :         uint32      bufHash;    /* hash value for tag */
    4277             :         BufferTag   bufTag;     /* identity of requested block */
    4278             :         LWLock     *bufPartitionLock;   /* buffer partition lock for it */
    4279             :         int         buf_id;
    4280             :         BufferDesc *bufHdr;
    4281             :         uint32      buf_state;
    4282             : 
    4283             :         /* create a tag so we can lookup the buffer */
    4284        2198 :         InitBufferTag(&bufTag, &rlocator, forkNum, curBlock);
    4285             : 
    4286             :         /* determine its hash code and partition lock ID */
    4287        2198 :         bufHash = BufTableHashCode(&bufTag);
    4288        2198 :         bufPartitionLock = BufMappingPartitionLock(bufHash);
    4289             : 
    4290             :         /* Check that it is in the buffer pool. If not, do nothing. */
    4291        2198 :         LWLockAcquire(bufPartitionLock, LW_SHARED);
    4292        2198 :         buf_id = BufTableLookup(&bufTag, bufHash);
    4293        2198 :         LWLockRelease(bufPartitionLock);
    4294             : 
    4295        2198 :         if (buf_id < 0)
    4296         246 :             continue;
    4297             : 
    4298        1952 :         bufHdr = GetBufferDescriptor(buf_id);
    4299             : 
    4300             :         /*
    4301             :          * We need to lock the buffer header and recheck if the buffer is
    4302             :          * still associated with the same block because the buffer could be
    4303             :          * evicted by some other backend loading blocks for a different
    4304             :          * relation after we release lock on the BufMapping table.
    4305             :          */
    4306        1952 :         buf_state = LockBufHdr(bufHdr);
    4307             : 
    4308        3904 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rlocator) &&
    4309        1952 :             BufTagGetForkNum(&bufHdr->tag) == forkNum &&
    4310        1952 :             bufHdr->tag.blockNum >= firstDelBlock)
    4311        1952 :             InvalidateBuffer(bufHdr);   /* releases spinlock */
    4312             :         else
    4313           0 :             UnlockBufHdr(bufHdr, buf_state);
    4314             :     }
    4315        1522 : }
    4316             : 
    4317             : /* ---------------------------------------------------------------------
    4318             :  *      DropDatabaseBuffers
    4319             :  *
    4320             :  *      This function removes all the buffers in the buffer cache for a
    4321             :  *      particular database.  Dirty pages are simply dropped, without
    4322             :  *      bothering to write them out first.  This is used when we destroy a
    4323             :  *      database, to avoid trying to flush data to disk when the directory
    4324             :  *      tree no longer exists.  Implementation is pretty similar to
    4325             :  *      DropRelationBuffers() which is for destroying just one relation.
    4326             :  * --------------------------------------------------------------------
    4327             :  */
    4328             : void
    4329          94 : DropDatabaseBuffers(Oid dbid)
    4330             : {
    4331             :     int         i;
    4332             : 
    4333             :     /*
    4334             :      * We needn't consider local buffers, since by assumption the target
    4335             :      * database isn't our own.
    4336             :      */
    4337             : 
    4338      434782 :     for (i = 0; i < NBuffers; i++)
    4339             :     {
    4340      434688 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    4341             :         uint32      buf_state;
    4342             : 
    4343             :         /*
    4344             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4345             :          * saves some cycles.
    4346             :          */
    4347      434688 :         if (bufHdr->tag.dbOid != dbid)
    4348      416794 :             continue;
    4349             : 
    4350       17894 :         buf_state = LockBufHdr(bufHdr);
    4351       17894 :         if (bufHdr->tag.dbOid == dbid)
    4352       17894 :             InvalidateBuffer(bufHdr);   /* releases spinlock */
    4353             :         else
    4354           0 :             UnlockBufHdr(bufHdr, buf_state);
    4355             :     }
    4356          94 : }
    4357             : 
    4358             : /* -----------------------------------------------------------------
    4359             :  *      PrintBufferDescs
    4360             :  *
    4361             :  *      this function prints all the buffer descriptors, for debugging
    4362             :  *      use only.
    4363             :  * -----------------------------------------------------------------
    4364             :  */
    4365             : #ifdef NOT_USED
    4366             : void
    4367             : PrintBufferDescs(void)
    4368             : {
    4369             :     int         i;
    4370             : 
    4371             :     for (i = 0; i < NBuffers; ++i)
    4372             :     {
    4373             :         BufferDesc *buf = GetBufferDescriptor(i);
    4374             :         Buffer      b = BufferDescriptorGetBuffer(buf);
    4375             : 
    4376             :         /* theoretically we should lock the bufhdr here */
    4377             :         elog(LOG,
    4378             :              "[%02d] (freeNext=%d, rel=%s, "
    4379             :              "blockNum=%u, flags=0x%x, refcount=%u %d)",
    4380             :              i, buf->freeNext,
    4381             :              relpathbackend(BufTagGetRelFileLocator(&buf->tag),
    4382             :                             INVALID_PROC_NUMBER, BufTagGetForkNum(&buf->tag)),
    4383             :              buf->tag.blockNum, buf->flags,
    4384             :              buf->refcount, GetPrivateRefCount(b));
    4385             :     }
    4386             : }
    4387             : #endif
    4388             : 
    4389             : #ifdef NOT_USED
    4390             : void
    4391             : PrintPinnedBufs(void)
    4392             : {
    4393             :     int         i;
    4394             : 
    4395             :     for (i = 0; i < NBuffers; ++i)
    4396             :     {
    4397             :         BufferDesc *buf = GetBufferDescriptor(i);
    4398             :         Buffer      b = BufferDescriptorGetBuffer(buf);
    4399             : 
    4400             :         if (GetPrivateRefCount(b) > 0)
    4401             :         {
    4402             :             /* theoretically we should lock the bufhdr here */
    4403             :             elog(LOG,
    4404             :                  "[%02d] (freeNext=%d, rel=%s, "
    4405             :                  "blockNum=%u, flags=0x%x, refcount=%u %d)",
    4406             :                  i, buf->freeNext,
    4407             :                  relpathperm(BufTagGetRelFileLocator(&buf->tag),
    4408             :                              BufTagGetForkNum(&buf->tag)),
    4409             :                  buf->tag.blockNum, buf->flags,
    4410             :                  buf->refcount, GetPrivateRefCount(b));
    4411             :         }
    4412             :     }
    4413             : }
    4414             : #endif
    4415             : 
    4416             : /* ---------------------------------------------------------------------
    4417             :  *      FlushRelationBuffers
    4418             :  *
    4419             :  *      This function writes all dirty pages of a relation out to disk
    4420             :  *      (or more accurately, out to kernel disk buffers), ensuring that the
    4421             :  *      kernel has an up-to-date view of the relation.
    4422             :  *
    4423             :  *      Generally, the caller should be holding AccessExclusiveLock on the
    4424             :  *      target relation to ensure that no other backend is busy dirtying
    4425             :  *      more blocks of the relation; the effects can't be expected to last
    4426             :  *      after the lock is released.
    4427             :  *
    4428             :  *      XXX currently it sequentially searches the buffer pool, should be
    4429             :  *      changed to more clever ways of searching.  This routine is not
    4430             :  *      used in any performance-critical code paths, so it's not worth
    4431             :  *      adding additional overhead to normal paths to make it go faster.
    4432             :  * --------------------------------------------------------------------
    4433             :  */
    4434             : void
    4435         262 : FlushRelationBuffers(Relation rel)
    4436             : {
    4437             :     int         i;
    4438             :     BufferDesc *bufHdr;
    4439         262 :     SMgrRelation srel = RelationGetSmgr(rel);
    4440             : 
    4441         262 :     if (RelationUsesLocalBuffers(rel))
    4442             :     {
    4443        1818 :         for (i = 0; i < NLocBuffer; i++)
    4444             :         {
    4445             :             uint32      buf_state;
    4446             :             instr_time  io_start;
    4447             : 
    4448        1800 :             bufHdr = GetLocalBufferDescriptor(i);
    4449        1800 :             if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
    4450         600 :                 ((buf_state = pg_atomic_read_u32(&bufHdr->state)) &
    4451             :                  (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    4452             :             {
    4453             :                 ErrorContextCallback errcallback;
    4454             :                 Page        localpage;
    4455             : 
    4456         594 :                 localpage = (char *) LocalBufHdrGetBlock(bufHdr);
    4457             : 
    4458             :                 /* Setup error traceback support for ereport() */
    4459         594 :                 errcallback.callback = local_buffer_write_error_callback;
    4460         594 :                 errcallback.arg = (void *) bufHdr;
    4461         594 :                 errcallback.previous = error_context_stack;
    4462         594 :                 error_context_stack = &errcallback;
    4463             : 
    4464         594 :                 PageSetChecksumInplace(localpage, bufHdr->tag.blockNum);
    4465             : 
    4466         594 :                 io_start = pgstat_prepare_io_time(track_io_timing);
    4467             : 
    4468         594 :                 smgrwrite(srel,
    4469         594 :                           BufTagGetForkNum(&bufHdr->tag),
    4470             :                           bufHdr->tag.blockNum,
    4471             :                           localpage,
    4472             :                           false);
    4473             : 
    4474         594 :                 pgstat_count_io_op_time(IOOBJECT_TEMP_RELATION,
    4475             :                                         IOCONTEXT_NORMAL, IOOP_WRITE,
    4476             :                                         io_start, 1);
    4477             : 
    4478         594 :                 buf_state &= ~(BM_DIRTY | BM_JUST_DIRTIED);
    4479         594 :                 pg_atomic_unlocked_write_u32(&bufHdr->state, buf_state);
    4480             : 
    4481         594 :                 pgBufferUsage.local_blks_written++;
    4482             : 
    4483             :                 /* Pop the error context stack */
    4484         594 :                 error_context_stack = errcallback.previous;
    4485             :             }
    4486             :         }
    4487             : 
    4488          18 :         return;
    4489             :     }
    4490             : 
    4491     2860020 :     for (i = 0; i < NBuffers; i++)
    4492             :     {
    4493             :         uint32      buf_state;
    4494             : 
    4495     2859776 :         bufHdr = GetBufferDescriptor(i);
    4496             : 
    4497             :         /*
    4498             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4499             :          * saves some cycles.
    4500             :          */
    4501     2859776 :         if (!BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator))
    4502     2859362 :             continue;
    4503             : 
    4504             :         /* Make sure we can handle the pin */
    4505         414 :         ReservePrivateRefCountEntry();
    4506         414 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    4507             : 
    4508         414 :         buf_state = LockBufHdr(bufHdr);
    4509         414 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, &rel->rd_locator) &&
    4510         414 :             (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    4511             :         {
    4512         330 :             PinBuffer_Locked(bufHdr);
    4513         330 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    4514         330 :             FlushBuffer(bufHdr, srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    4515         330 :             LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    4516         330 :             UnpinBuffer(bufHdr);
    4517             :         }
    4518             :         else
    4519          84 :             UnlockBufHdr(bufHdr, buf_state);
    4520             :     }
    4521             : }
    4522             : 
    4523             : /* ---------------------------------------------------------------------
    4524             :  *      FlushRelationsAllBuffers
    4525             :  *
    4526             :  *      This function flushes out of the buffer pool all the pages of all
    4527             :  *      forks of the specified smgr relations.  It's equivalent to calling
    4528             :  *      FlushRelationBuffers once per relation.  The relations are assumed not
    4529             :  *      to use local buffers.
    4530             :  * --------------------------------------------------------------------
    4531             :  */
    4532             : void
    4533          18 : FlushRelationsAllBuffers(SMgrRelation *smgrs, int nrels)
    4534             : {
    4535             :     int         i;
    4536             :     SMgrSortArray *srels;
    4537             :     bool        use_bsearch;
    4538             : 
    4539          18 :     if (nrels == 0)
    4540           0 :         return;
    4541             : 
    4542             :     /* fill-in array for qsort */
    4543          18 :     srels = palloc(sizeof(SMgrSortArray) * nrels);
    4544             : 
    4545          36 :     for (i = 0; i < nrels; i++)
    4546             :     {
    4547             :         Assert(!RelFileLocatorBackendIsTemp(smgrs[i]->smgr_rlocator));
    4548             : 
    4549          18 :         srels[i].rlocator = smgrs[i]->smgr_rlocator.locator;
    4550          18 :         srels[i].srel = smgrs[i];
    4551             :     }
    4552             : 
    4553             :     /*
    4554             :      * Save the bsearch overhead for low number of relations to sync. See
    4555             :      * DropRelationsAllBuffers for details.
    4556             :      */
    4557          18 :     use_bsearch = nrels > RELS_BSEARCH_THRESHOLD;
    4558             : 
    4559             :     /* sort the list of SMgrRelations if necessary */
    4560          18 :     if (use_bsearch)
    4561           0 :         qsort(srels, nrels, sizeof(SMgrSortArray), rlocator_comparator);
    4562             : 
    4563      294930 :     for (i = 0; i < NBuffers; i++)
    4564             :     {
    4565      294912 :         SMgrSortArray *srelent = NULL;
    4566      294912 :         BufferDesc *bufHdr = GetBufferDescriptor(i);
    4567             :         uint32      buf_state;
    4568             : 
    4569             :         /*
    4570             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4571             :          * saves some cycles.
    4572             :          */
    4573             : 
    4574      294912 :         if (!use_bsearch)
    4575             :         {
    4576             :             int         j;
    4577             : 
    4578      582188 :             for (j = 0; j < nrels; j++)
    4579             :             {
    4580      294912 :                 if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srels[j].rlocator))
    4581             :                 {
    4582        7636 :                     srelent = &srels[j];
    4583        7636 :                     break;
    4584             :                 }
    4585             :             }
    4586             :         }
    4587             :         else
    4588             :         {
    4589             :             RelFileLocator rlocator;
    4590             : 
    4591           0 :             rlocator = BufTagGetRelFileLocator(&bufHdr->tag);
    4592           0 :             srelent = bsearch((const void *) &(rlocator),
    4593             :                               srels, nrels, sizeof(SMgrSortArray),
    4594             :                               rlocator_comparator);
    4595             :         }
    4596             : 
    4597             :         /* buffer doesn't belong to any of the given relfilelocators; skip it */
    4598      294912 :         if (srelent == NULL)
    4599      287276 :             continue;
    4600             : 
    4601             :         /* Make sure we can handle the pin */
    4602        7636 :         ReservePrivateRefCountEntry();
    4603        7636 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    4604             : 
    4605        7636 :         buf_state = LockBufHdr(bufHdr);
    4606        7636 :         if (BufTagMatchesRelFileLocator(&bufHdr->tag, &srelent->rlocator) &&
    4607        7636 :             (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    4608             :         {
    4609        6734 :             PinBuffer_Locked(bufHdr);
    4610        6734 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    4611        6734 :             FlushBuffer(bufHdr, srelent->srel, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    4612        6734 :             LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    4613        6734 :             UnpinBuffer(bufHdr);
    4614             :         }
    4615             :         else
    4616         902 :             UnlockBufHdr(bufHdr, buf_state);
    4617             :     }
    4618             : 
    4619          18 :     pfree(srels);
    4620             : }
    4621             : 
    4622             : /* ---------------------------------------------------------------------
    4623             :  *      RelationCopyStorageUsingBuffer
    4624             :  *
    4625             :  *      Copy fork's data using bufmgr.  Same as RelationCopyStorage but instead
    4626             :  *      of using smgrread and smgrextend this will copy using bufmgr APIs.
    4627             :  *
    4628             :  *      Refer comments atop CreateAndCopyRelationData() for details about
    4629             :  *      'permanent' parameter.
    4630             :  * --------------------------------------------------------------------
    4631             :  */
    4632             : static void
    4633      128500 : RelationCopyStorageUsingBuffer(RelFileLocator srclocator,
    4634             :                                RelFileLocator dstlocator,
    4635             :                                ForkNumber forkNum, bool permanent)
    4636             : {
    4637             :     Buffer      srcBuf;
    4638             :     Buffer      dstBuf;
    4639             :     Page        srcPage;
    4640             :     Page        dstPage;
    4641             :     bool        use_wal;
    4642             :     BlockNumber nblocks;
    4643             :     BlockNumber blkno;
    4644             :     PGIOAlignedBlock buf;
    4645             :     BufferAccessStrategy bstrategy_src;
    4646             :     BufferAccessStrategy bstrategy_dst;
    4647             : 
    4648             :     /*
    4649             :      * In general, we want to write WAL whenever wal_level > 'minimal', but we
    4650             :      * can skip it when copying any fork of an unlogged relation other than
    4651             :      * the init fork.
    4652             :      */
    4653      128500 :     use_wal = XLogIsNeeded() && (permanent || forkNum == INIT_FORKNUM);
    4654             : 
    4655             :     /* Get number of blocks in the source relation. */
    4656      128500 :     nblocks = smgrnblocks(smgropen(srclocator, INVALID_PROC_NUMBER),
    4657             :                           forkNum);
    4658             : 
    4659             :     /* Nothing to copy; just return. */
    4660      128500 :     if (nblocks == 0)
    4661       22132 :         return;
    4662             : 
    4663             :     /*
    4664             :      * Bulk extend the destination relation of the same size as the source
    4665             :      * relation before starting to copy block by block.
    4666             :      */
    4667      106368 :     memset(buf.data, 0, BLCKSZ);
    4668      106368 :     smgrextend(smgropen(dstlocator, INVALID_PROC_NUMBER), forkNum, nblocks - 1,
    4669             :                buf.data, true);
    4670             : 
    4671             :     /* This is a bulk operation, so use buffer access strategies. */
    4672      106368 :     bstrategy_src = GetAccessStrategy(BAS_BULKREAD);
    4673      106368 :     bstrategy_dst = GetAccessStrategy(BAS_BULKWRITE);
    4674             : 
    4675             :     /* Iterate over each block of the source relation file. */
    4676      503726 :     for (blkno = 0; blkno < nblocks; blkno++)
    4677             :     {
    4678      397358 :         CHECK_FOR_INTERRUPTS();
    4679             : 
    4680             :         /* Read block from source relation. */
    4681      397358 :         srcBuf = ReadBufferWithoutRelcache(srclocator, forkNum, blkno,
    4682             :                                            RBM_NORMAL, bstrategy_src,
    4683             :                                            permanent);
    4684      397358 :         LockBuffer(srcBuf, BUFFER_LOCK_SHARE);
    4685      397358 :         srcPage = BufferGetPage(srcBuf);
    4686             : 
    4687      397358 :         dstBuf = ReadBufferWithoutRelcache(dstlocator, forkNum, blkno,
    4688             :                                            RBM_ZERO_AND_LOCK, bstrategy_dst,
    4689             :                                            permanent);
    4690      397358 :         dstPage = BufferGetPage(dstBuf);
    4691             : 
    4692      397358 :         START_CRIT_SECTION();
    4693             : 
    4694             :         /* Copy page data from the source to the destination. */
    4695      397358 :         memcpy(dstPage, srcPage, BLCKSZ);
    4696      397358 :         MarkBufferDirty(dstBuf);
    4697             : 
    4698             :         /* WAL-log the copied page. */
    4699      397358 :         if (use_wal)
    4700      221626 :             log_newpage_buffer(dstBuf, true);
    4701             : 
    4702      397358 :         END_CRIT_SECTION();
    4703             : 
    4704      397358 :         UnlockReleaseBuffer(dstBuf);
    4705      397358 :         UnlockReleaseBuffer(srcBuf);
    4706             :     }
    4707             : 
    4708      106368 :     FreeAccessStrategy(bstrategy_src);
    4709      106368 :     FreeAccessStrategy(bstrategy_dst);
    4710             : }
    4711             : 
    4712             : /* ---------------------------------------------------------------------
    4713             :  *      CreateAndCopyRelationData
    4714             :  *
    4715             :  *      Create destination relation storage and copy all forks from the
    4716             :  *      source relation to the destination.
    4717             :  *
    4718             :  *      Pass permanent as true for permanent relations and false for
    4719             :  *      unlogged relations.  Currently this API is not supported for
    4720             :  *      temporary relations.
    4721             :  * --------------------------------------------------------------------
    4722             :  */
    4723             : void
    4724       96380 : CreateAndCopyRelationData(RelFileLocator src_rlocator,
    4725             :                           RelFileLocator dst_rlocator, bool permanent)
    4726             : {
    4727             :     char        relpersistence;
    4728             :     SMgrRelation src_rel;
    4729             :     SMgrRelation dst_rel;
    4730             : 
    4731             :     /* Set the relpersistence. */
    4732       96380 :     relpersistence = permanent ?
    4733             :         RELPERSISTENCE_PERMANENT : RELPERSISTENCE_UNLOGGED;
    4734             : 
    4735       96380 :     src_rel = smgropen(src_rlocator, INVALID_PROC_NUMBER);
    4736       96380 :     dst_rel = smgropen(dst_rlocator, INVALID_PROC_NUMBER);
    4737             : 
    4738             :     /*
    4739             :      * Create and copy all forks of the relation.  During create database we
    4740             :      * have a separate cleanup mechanism which deletes complete database
    4741             :      * directory.  Therefore, each individual relation doesn't need to be
    4742             :      * registered for cleanup.
    4743             :      */
    4744       96380 :     RelationCreateStorage(dst_rlocator, relpersistence, false);
    4745             : 
    4746             :     /* copy main fork. */
    4747       96380 :     RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, MAIN_FORKNUM,
    4748             :                                    permanent);
    4749             : 
    4750             :     /* copy those extra forks that exist */
    4751      385520 :     for (ForkNumber forkNum = MAIN_FORKNUM + 1;
    4752      289140 :          forkNum <= MAX_FORKNUM; forkNum++)
    4753             :     {
    4754      289140 :         if (smgrexists(src_rel, forkNum))
    4755             :         {
    4756       32120 :             smgrcreate(dst_rel, forkNum, false);
    4757             : 
    4758             :             /*
    4759             :              * WAL log creation if the relation is persistent, or this is the
    4760             :              * init fork of an unlogged relation.
    4761             :              */
    4762       32120 :             if (permanent || forkNum == INIT_FORKNUM)
    4763       32120 :                 log_smgrcreate(&dst_rlocator, forkNum);
    4764             : 
    4765             :             /* Copy a fork's data, block by block. */
    4766       32120 :             RelationCopyStorageUsingBuffer(src_rlocator, dst_rlocator, forkNum,
    4767             :                                            permanent);
    4768             :         }
    4769             :     }
    4770       96380 : }
    4771             : 
    4772             : /* ---------------------------------------------------------------------
    4773             :  *      FlushDatabaseBuffers
    4774             :  *
    4775             :  *      This function writes all dirty pages of a database out to disk
    4776             :  *      (or more accurately, out to kernel disk buffers), ensuring that the
    4777             :  *      kernel has an up-to-date view of the database.
    4778             :  *
    4779             :  *      Generally, the caller should be holding an appropriate lock to ensure
    4780             :  *      no other backend is active in the target database; otherwise more
    4781             :  *      pages could get dirtied.
    4782             :  *
    4783             :  *      Note we don't worry about flushing any pages of temporary relations.
    4784             :  *      It's assumed these wouldn't be interesting.
    4785             :  * --------------------------------------------------------------------
    4786             :  */
    4787             : void
    4788           6 : FlushDatabaseBuffers(Oid dbid)
    4789             : {
    4790             :     int         i;
    4791             :     BufferDesc *bufHdr;
    4792             : 
    4793         774 :     for (i = 0; i < NBuffers; i++)
    4794             :     {
    4795             :         uint32      buf_state;
    4796             : 
    4797         768 :         bufHdr = GetBufferDescriptor(i);
    4798             : 
    4799             :         /*
    4800             :          * As in DropRelationBuffers, an unlocked precheck should be safe and
    4801             :          * saves some cycles.
    4802             :          */
    4803         768 :         if (bufHdr->tag.dbOid != dbid)
    4804         540 :             continue;
    4805             : 
    4806             :         /* Make sure we can handle the pin */
    4807         228 :         ReservePrivateRefCountEntry();
    4808         228 :         ResourceOwnerEnlarge(CurrentResourceOwner);
    4809             : 
    4810         228 :         buf_state = LockBufHdr(bufHdr);
    4811         228 :         if (bufHdr->tag.dbOid == dbid &&
    4812         228 :             (buf_state & (BM_VALID | BM_DIRTY)) == (BM_VALID | BM_DIRTY))
    4813             :         {
    4814           8 :             PinBuffer_Locked(bufHdr);
    4815           8 :             LWLockAcquire(BufferDescriptorGetContentLock(bufHdr), LW_SHARED);
    4816           8 :             FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    4817           8 :             LWLockRelease(BufferDescriptorGetContentLock(bufHdr));
    4818           8 :             UnpinBuffer(bufHdr);
    4819             :         }
    4820             :         else
    4821         220 :             UnlockBufHdr(bufHdr, buf_state);
    4822             :     }
    4823           6 : }
    4824             : 
    4825             : /*
    4826             :  * Flush a previously, shared or exclusively, locked and pinned buffer to the
    4827             :  * OS.
    4828             :  */
    4829             : void
    4830          58 : FlushOneBuffer(Buffer buffer)
    4831             : {
    4832             :     BufferDesc *bufHdr;
    4833             : 
    4834             :     /* currently not needed, but no fundamental reason not to support */
    4835             :     Assert(!BufferIsLocal(buffer));
    4836             : 
    4837             :     Assert(BufferIsPinned(buffer));
    4838             : 
    4839          58 :     bufHdr = GetBufferDescriptor(buffer - 1);
    4840             : 
    4841             :     Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
    4842             : 
    4843          58 :     FlushBuffer(bufHdr, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    4844          58 : }
    4845             : 
    4846             : /*
    4847             :  * ReleaseBuffer -- release the pin on a buffer
    4848             :  */
    4849             : void
    4850    95030142 : ReleaseBuffer(Buffer buffer)
    4851             : {
    4852    95030142 :     if (!BufferIsValid(buffer))
    4853           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    4854             : 
    4855    95030142 :     if (BufferIsLocal(buffer))
    4856     2812760 :         UnpinLocalBuffer(buffer);
    4857             :     else
    4858    92217382 :         UnpinBuffer(GetBufferDescriptor(buffer - 1));
    4859    95030142 : }
    4860             : 
    4861             : /*
    4862             :  * UnlockReleaseBuffer -- release the content lock and pin on a buffer
    4863             :  *
    4864             :  * This is just a shorthand for a common combination.
    4865             :  */
    4866             : void
    4867    28900580 : UnlockReleaseBuffer(Buffer buffer)
    4868             : {
    4869    28900580 :     LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    4870    28900580 :     ReleaseBuffer(buffer);
    4871    28900580 : }
    4872             : 
    4873             : /*
    4874             :  * IncrBufferRefCount
    4875             :  *      Increment the pin count on a buffer that we have *already* pinned
    4876             :  *      at least once.
    4877             :  *
    4878             :  *      This function cannot be used on a buffer we do not have pinned,
    4879             :  *      because it doesn't change the shared buffer state.
    4880             :  */
    4881             : void
    4882    17222316 : IncrBufferRefCount(Buffer buffer)
    4883             : {
    4884             :     Assert(BufferIsPinned(buffer));
    4885    17222316 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    4886    17222316 :     if (BufferIsLocal(buffer))
    4887      691374 :         LocalRefCount[-buffer - 1]++;
    4888             :     else
    4889             :     {
    4890             :         PrivateRefCountEntry *ref;
    4891             : 
    4892    16530942 :         ref = GetPrivateRefCountEntry(buffer, true);
    4893             :         Assert(ref != NULL);
    4894    16530942 :         ref->refcount++;
    4895             :     }
    4896    17222316 :     ResourceOwnerRememberBuffer(CurrentResourceOwner, buffer);
    4897    17222316 : }
    4898             : 
    4899             : /*
    4900             :  * MarkBufferDirtyHint
    4901             :  *
    4902             :  *  Mark a buffer dirty for non-critical changes.
    4903             :  *
    4904             :  * This is essentially the same as MarkBufferDirty, except:
    4905             :  *
    4906             :  * 1. The caller does not write WAL; so if checksums are enabled, we may need
    4907             :  *    to write an XLOG_FPI_FOR_HINT WAL record to protect against torn pages.
    4908             :  * 2. The caller might have only share-lock instead of exclusive-lock on the
    4909             :  *    buffer's content lock.
    4910             :  * 3. This function does not guarantee that the buffer is always marked dirty
    4911             :  *    (due to a race condition), so it cannot be used for important changes.
    4912             :  */
    4913             : void
    4914    18442510 : MarkBufferDirtyHint(Buffer buffer, bool buffer_std)
    4915             : {
    4916             :     BufferDesc *bufHdr;
    4917    18442510 :     Page        page = BufferGetPage(buffer);
    4918             : 
    4919    18442510 :     if (!BufferIsValid(buffer))
    4920           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    4921             : 
    4922    18442510 :     if (BufferIsLocal(buffer))
    4923             :     {
    4924     1157368 :         MarkLocalBufferDirty(buffer);
    4925     1157368 :         return;
    4926             :     }
    4927             : 
    4928    17285142 :     bufHdr = GetBufferDescriptor(buffer - 1);
    4929             : 
    4930             :     Assert(GetPrivateRefCount(buffer) > 0);
    4931             :     /* here, either share or exclusive lock is OK */
    4932             :     Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
    4933             : 
    4934             :     /*
    4935             :      * This routine might get called many times on the same page, if we are
    4936             :      * making the first scan after commit of an xact that added/deleted many
    4937             :      * tuples. So, be as quick as we can if the buffer is already dirty.  We
    4938             :      * do this by not acquiring spinlock if it looks like the status bits are
    4939             :      * already set.  Since we make this test unlocked, there's a chance we
    4940             :      * might fail to notice that the flags have just been cleared, and failed
    4941             :      * to reset them, due to memory-ordering issues.  But since this function
    4942             :      * is only intended to be used in cases where failing to write out the
    4943             :      * data would be harmless anyway, it doesn't really matter.
    4944             :      */
    4945    17285142 :     if ((pg_atomic_read_u32(&bufHdr->state) & (BM_DIRTY | BM_JUST_DIRTIED)) !=
    4946             :         (BM_DIRTY | BM_JUST_DIRTIED))
    4947             :     {
    4948     2055030 :         XLogRecPtr  lsn = InvalidXLogRecPtr;
    4949     2055030 :         bool        dirtied = false;
    4950     2055030 :         bool        delayChkptFlags = false;
    4951             :         uint32      buf_state;
    4952             : 
    4953             :         /*
    4954             :          * If we need to protect hint bit updates from torn writes, WAL-log a
    4955             :          * full page image of the page. This full page image is only necessary
    4956             :          * if the hint bit update is the first change to the page since the
    4957             :          * last checkpoint.
    4958             :          *
    4959             :          * We don't check full_page_writes here because that logic is included
    4960             :          * when we call XLogInsert() since the value changes dynamically.
    4961             :          */
    4962     4083520 :         if (XLogHintBitIsNeeded() &&
    4963     2028490 :             (pg_atomic_read_u32(&bufHdr->state) & BM_PERMANENT))
    4964             :         {
    4965             :             /*
    4966             :              * If we must not write WAL, due to a relfilelocator-specific
    4967             :              * condition or being in recovery, don't dirty the page.  We can
    4968             :              * set the hint, just not dirty the page as a result so the hint
    4969             :              * is lost when we evict the page or shutdown.
    4970             :              *
    4971             :              * See src/backend/storage/page/README for longer discussion.
    4972             :              */
    4973     2100516 :             if (RecoveryInProgress() ||
    4974       72032 :                 RelFileLocatorSkippingWAL(BufTagGetRelFileLocator(&bufHdr->tag)))
    4975     1956452 :                 return;
    4976             : 
    4977             :             /*
    4978             :              * If the block is already dirty because we either made a change
    4979             :              * or set a hint already, then we don't need to write a full page
    4980             :              * image.  Note that aggressive cleaning of blocks dirtied by hint
    4981             :              * bit setting would increase the call rate. Bulk setting of hint
    4982             :              * bits would reduce the call rate...
    4983             :              *
    4984             :              * We must issue the WAL record before we mark the buffer dirty.
    4985             :              * Otherwise we might write the page before we write the WAL. That
    4986             :              * causes a race condition, since a checkpoint might occur between
    4987             :              * writing the WAL record and marking the buffer dirty. We solve
    4988             :              * that with a kluge, but one that is already in use during
    4989             :              * transaction commit to prevent race conditions. Basically, we
    4990             :              * simply prevent the checkpoint WAL record from being written
    4991             :              * until we have marked the buffer dirty. We don't start the
    4992             :              * checkpoint flush until we have marked dirty, so our checkpoint
    4993             :              * must flush the change to disk successfully or the checkpoint
    4994             :              * never gets written, so crash recovery will fix.
    4995             :              *
    4996             :              * It's possible we may enter here without an xid, so it is
    4997             :              * essential that CreateCheckPoint waits for virtual transactions
    4998             :              * rather than full transactionids.
    4999             :              */
    5000             :             Assert((MyProc->delayChkptFlags & DELAY_CHKPT_START) == 0);
    5001       72032 :             MyProc->delayChkptFlags |= DELAY_CHKPT_START;
    5002       72032 :             delayChkptFlags = true;
    5003       72032 :             lsn = XLogSaveBufferForHint(buffer, buffer_std);
    5004             :         }
    5005             : 
    5006       98578 :         buf_state = LockBufHdr(bufHdr);
    5007             : 
    5008             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    5009             : 
    5010       98578 :         if (!(buf_state & BM_DIRTY))
    5011             :         {
    5012       98548 :             dirtied = true;     /* Means "will be dirtied by this action" */
    5013             : 
    5014             :             /*
    5015             :              * Set the page LSN if we wrote a backup block. We aren't supposed
    5016             :              * to set this when only holding a share lock but as long as we
    5017             :              * serialise it somehow we're OK. We choose to set LSN while
    5018             :              * holding the buffer header lock, which causes any reader of an
    5019             :              * LSN who holds only a share lock to also obtain a buffer header
    5020             :              * lock before using PageGetLSN(), which is enforced in
    5021             :              * BufferGetLSNAtomic().
    5022             :              *
    5023             :              * If checksums are enabled, you might think we should reset the
    5024             :              * checksum here. That will happen when the page is written
    5025             :              * sometime later in this checkpoint cycle.
    5026             :              */
    5027       98548 :             if (!XLogRecPtrIsInvalid(lsn))
    5028       10960 :                 PageSetLSN(page, lsn);
    5029             :         }
    5030             : 
    5031       98578 :         buf_state |= BM_DIRTY | BM_JUST_DIRTIED;
    5032       98578 :         UnlockBufHdr(bufHdr, buf_state);
    5033             : 
    5034       98578 :         if (delayChkptFlags)
    5035       72032 :             MyProc->delayChkptFlags &= ~DELAY_CHKPT_START;
    5036             : 
    5037       98578 :         if (dirtied)
    5038             :         {
    5039       98548 :             VacuumPageDirty++;
    5040       98548 :             pgBufferUsage.shared_blks_dirtied++;
    5041       98548 :             if (VacuumCostActive)
    5042         150 :                 VacuumCostBalance += VacuumCostPageDirty;
    5043             :         }
    5044             :     }
    5045             : }
    5046             : 
    5047             : /*
    5048             :  * Release buffer content locks for shared buffers.
    5049             :  *
    5050             :  * Used to clean up after errors.
    5051             :  *
    5052             :  * Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
    5053             :  * of releasing buffer content locks per se; the only thing we need to deal
    5054             :  * with here is clearing any PIN_COUNT request that was in progress.
    5055             :  */
    5056             : void
    5057       83620 : UnlockBuffers(void)
    5058             : {
    5059       83620 :     BufferDesc *buf = PinCountWaitBuf;
    5060             : 
    5061       83620 :     if (buf)
    5062             :     {
    5063             :         uint32      buf_state;
    5064             : 
    5065           0 :         buf_state = LockBufHdr(buf);
    5066             : 
    5067             :         /*
    5068             :          * Don't complain if flag bit not set; it could have been reset but we
    5069             :          * got a cancel/die interrupt before getting the signal.
    5070             :          */
    5071           0 :         if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
    5072           0 :             buf->wait_backend_pgprocno == MyProcNumber)
    5073           0 :             buf_state &= ~BM_PIN_COUNT_WAITER;
    5074             : 
    5075           0 :         UnlockBufHdr(buf, buf_state);
    5076             : 
    5077           0 :         PinCountWaitBuf = NULL;
    5078             :     }
    5079       83620 : }
    5080             : 
    5081             : /*
    5082             :  * Acquire or release the content_lock for the buffer.
    5083             :  */
    5084             : void
    5085   280845540 : LockBuffer(Buffer buffer, int mode)
    5086             : {
    5087             :     BufferDesc *buf;
    5088             : 
    5089             :     Assert(BufferIsPinned(buffer));
    5090   280845540 :     if (BufferIsLocal(buffer))
    5091    18848014 :         return;                 /* local buffers need no lock */
    5092             : 
    5093   261997526 :     buf = GetBufferDescriptor(buffer - 1);
    5094             : 
    5095   261997526 :     if (mode == BUFFER_LOCK_UNLOCK)
    5096   132127974 :         LWLockRelease(BufferDescriptorGetContentLock(buf));
    5097   129869552 :     else if (mode == BUFFER_LOCK_SHARE)
    5098    92636210 :         LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_SHARED);
    5099    37233342 :     else if (mode == BUFFER_LOCK_EXCLUSIVE)
    5100    37233342 :         LWLockAcquire(BufferDescriptorGetContentLock(buf), LW_EXCLUSIVE);
    5101             :     else
    5102           0 :         elog(ERROR, "unrecognized buffer lock mode: %d", mode);
    5103             : }
    5104             : 
    5105             : /*
    5106             :  * Acquire the content_lock for the buffer, but only if we don't have to wait.
    5107             :  *
    5108             :  * This assumes the caller wants BUFFER_LOCK_EXCLUSIVE mode.
    5109             :  */
    5110             : bool
    5111     2052478 : ConditionalLockBuffer(Buffer buffer)
    5112             : {
    5113             :     BufferDesc *buf;
    5114             : 
    5115             :     Assert(BufferIsPinned(buffer));
    5116     2052478 :     if (BufferIsLocal(buffer))
    5117      129570 :         return true;            /* act as though we got it */
    5118             : 
    5119     1922908 :     buf = GetBufferDescriptor(buffer - 1);
    5120             : 
    5121     1922908 :     return LWLockConditionalAcquire(BufferDescriptorGetContentLock(buf),
    5122             :                                     LW_EXCLUSIVE);
    5123             : }
    5124             : 
    5125             : /*
    5126             :  * Verify that this backend is pinning the buffer exactly once.
    5127             :  *
    5128             :  * NOTE: Like in BufferIsPinned(), what we check here is that *this* backend
    5129             :  * holds a pin on the buffer.  We do not care whether some other backend does.
    5130             :  */
    5131             : void
    5132     3029960 : CheckBufferIsPinnedOnce(Buffer buffer)
    5133             : {
    5134     3029960 :     if (BufferIsLocal(buffer))
    5135             :     {
    5136          32 :         if (LocalRefCount[-buffer - 1] != 1)
    5137           0 :             elog(ERROR, "incorrect local pin count: %d",
    5138             :                  LocalRefCount[-buffer - 1]);
    5139             :     }
    5140             :     else
    5141             :     {
    5142     3029928 :         if (GetPrivateRefCount(buffer) != 1)
    5143           0 :             elog(ERROR, "incorrect local pin count: %d",
    5144             :                  GetPrivateRefCount(buffer));
    5145             :     }
    5146     3029960 : }
    5147             : 
    5148             : /*
    5149             :  * LockBufferForCleanup - lock a buffer in preparation for deleting items
    5150             :  *
    5151             :  * Items may be deleted from a disk page only when the caller (a) holds an
    5152             :  * exclusive lock on the buffer and (b) has observed that no other backend
    5153             :  * holds a pin on the buffer.  If there is a pin, then the other backend
    5154             :  * might have a pointer into the buffer (for example, a heapscan reference
    5155             :  * to an item --- see README for more details).  It's OK if a pin is added
    5156             :  * after the cleanup starts, however; the newly-arrived backend will be
    5157             :  * unable to look at the page until we release the exclusive lock.
    5158             :  *
    5159             :  * To implement this protocol, a would-be deleter must pin the buffer and
    5160             :  * then call LockBufferForCleanup().  LockBufferForCleanup() is similar to
    5161             :  * LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE), except that it loops until
    5162             :  * it has successfully observed pin count = 1.
    5163             :  */
    5164             : void
    5165       32218 : LockBufferForCleanup(Buffer buffer)
    5166             : {
    5167             :     BufferDesc *bufHdr;
    5168       32218 :     TimestampTz waitStart = 0;
    5169       32218 :     bool        waiting = false;
    5170       32218 :     bool        logged_recovery_conflict = false;
    5171             : 
    5172             :     Assert(BufferIsPinned(buffer));
    5173             :     Assert(PinCountWaitBuf == NULL);
    5174             : 
    5175       32218 :     CheckBufferIsPinnedOnce(buffer);
    5176             : 
    5177             :     /* Nobody else to wait for */
    5178       32218 :     if (BufferIsLocal(buffer))
    5179          32 :         return;
    5180             : 
    5181       32186 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5182             : 
    5183             :     for (;;)
    5184          20 :     {
    5185             :         uint32      buf_state;
    5186             : 
    5187             :         /* Try to acquire lock */
    5188       32206 :         LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
    5189       32206 :         buf_state = LockBufHdr(bufHdr);
    5190             : 
    5191             :         Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    5192       32206 :         if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
    5193             :         {
    5194             :             /* Successfully acquired exclusive lock with pincount 1 */
    5195       32186 :             UnlockBufHdr(bufHdr, buf_state);
    5196             : 
    5197             :             /*
    5198             :              * Emit the log message if recovery conflict on buffer pin was
    5199             :              * resolved but the startup process waited longer than
    5200             :              * deadlock_timeout for it.
    5201             :              */
    5202       32186 :             if (logged_recovery_conflict)
    5203           4 :                 LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
    5204             :                                     waitStart, GetCurrentTimestamp(),
    5205             :                                     NULL, false);
    5206             : 
    5207       32186 :             if (waiting)
    5208             :             {
    5209             :                 /* reset ps display to remove the suffix if we added one */
    5210           4 :                 set_ps_display_remove_suffix();
    5211           4 :                 waiting = false;
    5212             :             }
    5213       32186 :             return;
    5214             :         }
    5215             :         /* Failed, so mark myself as waiting for pincount 1 */
    5216          20 :         if (buf_state & BM_PIN_COUNT_WAITER)
    5217             :         {
    5218           0 :             UnlockBufHdr(bufHdr, buf_state);
    5219           0 :             LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5220           0 :             elog(ERROR, "multiple backends attempting to wait for pincount 1");
    5221             :         }
    5222          20 :         bufHdr->wait_backend_pgprocno = MyProcNumber;
    5223          20 :         PinCountWaitBuf = bufHdr;
    5224          20 :         buf_state |= BM_PIN_COUNT_WAITER;
    5225          20 :         UnlockBufHdr(bufHdr, buf_state);
    5226          20 :         LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5227             : 
    5228             :         /* Wait to be signaled by UnpinBuffer() */
    5229          20 :         if (InHotStandby)
    5230             :         {
    5231          20 :             if (!waiting)
    5232             :             {
    5233             :                 /* adjust the process title to indicate that it's waiting */
    5234           4 :                 set_ps_display_suffix("waiting");
    5235           4 :                 waiting = true;
    5236             :             }
    5237             : 
    5238             :             /*
    5239             :              * Emit the log message if the startup process is waiting longer
    5240             :              * than deadlock_timeout for recovery conflict on buffer pin.
    5241             :              *
    5242             :              * Skip this if first time through because the startup process has
    5243             :              * not started waiting yet in this case. So, the wait start
    5244             :              * timestamp is set after this logic.
    5245             :              */
    5246          20 :             if (waitStart != 0 && !logged_recovery_conflict)
    5247             :             {
    5248           6 :                 TimestampTz now = GetCurrentTimestamp();
    5249             : 
    5250           6 :                 if (TimestampDifferenceExceeds(waitStart, now,
    5251             :                                                DeadlockTimeout))
    5252             :                 {
    5253           4 :                     LogRecoveryConflict(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN,
    5254             :                                         waitStart, now, NULL, true);
    5255           4 :                     logged_recovery_conflict = true;
    5256             :                 }
    5257             :             }
    5258             : 
    5259             :             /*
    5260             :              * Set the wait start timestamp if logging is enabled and first
    5261             :              * time through.
    5262             :              */
    5263          20 :             if (log_recovery_conflict_waits && waitStart == 0)
    5264           4 :                 waitStart = GetCurrentTimestamp();
    5265             : 
    5266             :             /* Publish the bufid that Startup process waits on */
    5267          20 :             SetStartupBufferPinWaitBufId(buffer - 1);
    5268             :             /* Set alarm and then wait to be signaled by UnpinBuffer() */
    5269          20 :             ResolveRecoveryConflictWithBufferPin();
    5270             :             /* Reset the published bufid */
    5271          20 :             SetStartupBufferPinWaitBufId(-1);
    5272             :         }
    5273             :         else
    5274           0 :             ProcWaitForSignal(WAIT_EVENT_BUFFER_PIN);
    5275             : 
    5276             :         /*
    5277             :          * Remove flag marking us as waiter. Normally this will not be set
    5278             :          * anymore, but ProcWaitForSignal() can return for other signals as
    5279             :          * well.  We take care to only reset the flag if we're the waiter, as
    5280             :          * theoretically another backend could have started waiting. That's
    5281             :          * impossible with the current usages due to table level locking, but
    5282             :          * better be safe.
    5283             :          */
    5284          20 :         buf_state = LockBufHdr(bufHdr);
    5285          20 :         if ((buf_state & BM_PIN_COUNT_WAITER) != 0 &&
    5286          16 :             bufHdr->wait_backend_pgprocno == MyProcNumber)
    5287          16 :             buf_state &= ~BM_PIN_COUNT_WAITER;
    5288          20 :         UnlockBufHdr(bufHdr, buf_state);
    5289             : 
    5290          20 :         PinCountWaitBuf = NULL;
    5291             :         /* Loop back and try again */
    5292             :     }
    5293             : }
    5294             : 
    5295             : /*
    5296             :  * Check called from ProcessRecoveryConflictInterrupts() when Startup process
    5297             :  * requests cancellation of all pin holders that are blocking it.
    5298             :  */
    5299             : bool
    5300           8 : HoldingBufferPinThatDelaysRecovery(void)
    5301             : {
    5302           8 :     int         bufid = GetStartupBufferPinWaitBufId();
    5303             : 
    5304             :     /*
    5305             :      * If we get woken slowly then it's possible that the Startup process was
    5306             :      * already woken by other backends before we got here. Also possible that
    5307             :      * we get here by multiple interrupts or interrupts at inappropriate
    5308             :      * times, so make sure we do nothing if the bufid is not set.
    5309             :      */
    5310           8 :     if (bufid < 0)
    5311           4 :         return false;
    5312             : 
    5313           4 :     if (GetPrivateRefCount(bufid + 1) > 0)
    5314           4 :         return true;
    5315             : 
    5316           0 :     return false;
    5317             : }
    5318             : 
    5319             : /*
    5320             :  * ConditionalLockBufferForCleanup - as above, but don't wait to get the lock
    5321             :  *
    5322             :  * We won't loop, but just check once to see if the pin count is OK.  If
    5323             :  * not, return false with no lock held.
    5324             :  */
    5325             : bool
    5326      162522 : ConditionalLockBufferForCleanup(Buffer buffer)
    5327             : {
    5328             :     BufferDesc *bufHdr;
    5329             :     uint32      buf_state,
    5330             :                 refcount;
    5331             : 
    5332             :     Assert(BufferIsValid(buffer));
    5333             : 
    5334      162522 :     if (BufferIsLocal(buffer))
    5335             :     {
    5336        1582 :         refcount = LocalRefCount[-buffer - 1];
    5337             :         /* There should be exactly one pin */
    5338             :         Assert(refcount > 0);
    5339        1582 :         if (refcount != 1)
    5340          42 :             return false;
    5341             :         /* Nobody else to wait for */
    5342        1540 :         return true;
    5343             :     }
    5344             : 
    5345             :     /* There should be exactly one local pin */
    5346      160940 :     refcount = GetPrivateRefCount(buffer);
    5347             :     Assert(refcount);
    5348      160940 :     if (refcount != 1)
    5349         278 :         return false;
    5350             : 
    5351             :     /* Try to acquire lock */
    5352      160662 :     if (!ConditionalLockBuffer(buffer))
    5353          32 :         return false;
    5354             : 
    5355      160630 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5356      160630 :     buf_state = LockBufHdr(bufHdr);
    5357      160630 :     refcount = BUF_STATE_GET_REFCOUNT(buf_state);
    5358             : 
    5359             :     Assert(refcount > 0);
    5360      160630 :     if (refcount == 1)
    5361             :     {
    5362             :         /* Successfully acquired exclusive lock with pincount 1 */
    5363      160574 :         UnlockBufHdr(bufHdr, buf_state);
    5364      160574 :         return true;
    5365             :     }
    5366             : 
    5367             :     /* Failed, so release the lock */
    5368          56 :     UnlockBufHdr(bufHdr, buf_state);
    5369          56 :     LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    5370          56 :     return false;
    5371             : }
    5372             : 
    5373             : /*
    5374             :  * IsBufferCleanupOK - as above, but we already have the lock
    5375             :  *
    5376             :  * Check whether it's OK to perform cleanup on a buffer we've already
    5377             :  * locked.  If we observe that the pin count is 1, our exclusive lock
    5378             :  * happens to be a cleanup lock, and we can proceed with anything that
    5379             :  * would have been allowable had we sought a cleanup lock originally.
    5380             :  */
    5381             : bool
    5382        4004 : IsBufferCleanupOK(Buffer buffer)
    5383             : {
    5384             :     BufferDesc *bufHdr;
    5385             :     uint32      buf_state;
    5386             : 
    5387             :     Assert(BufferIsValid(buffer));
    5388             : 
    5389        4004 :     if (BufferIsLocal(buffer))
    5390             :     {
    5391             :         /* There should be exactly one pin */
    5392           0 :         if (LocalRefCount[-buffer - 1] != 1)
    5393           0 :             return false;
    5394             :         /* Nobody else to wait for */
    5395           0 :         return true;
    5396             :     }
    5397             : 
    5398             :     /* There should be exactly one local pin */
    5399        4004 :     if (GetPrivateRefCount(buffer) != 1)
    5400           0 :         return false;
    5401             : 
    5402        4004 :     bufHdr = GetBufferDescriptor(buffer - 1);
    5403             : 
    5404             :     /* caller must hold exclusive lock on buffer */
    5405             :     Assert(LWLockHeldByMeInMode(BufferDescriptorGetContentLock(bufHdr),
    5406             :                                 LW_EXCLUSIVE));
    5407             : 
    5408        4004 :     buf_state = LockBufHdr(bufHdr);
    5409             : 
    5410             :     Assert(BUF_STATE_GET_REFCOUNT(buf_state) > 0);
    5411        4004 :     if (BUF_STATE_GET_REFCOUNT(buf_state) == 1)
    5412             :     {
    5413             :         /* pincount is OK. */
    5414        4004 :         UnlockBufHdr(bufHdr, buf_state);
    5415        4004 :         return true;
    5416             :     }
    5417             : 
    5418           0 :     UnlockBufHdr(bufHdr, buf_state);
    5419           0 :     return false;
    5420             : }
    5421             : 
    5422             : 
    5423             : /*
    5424             :  *  Functions for buffer I/O handling
    5425             :  *
    5426             :  *  Note: We assume that nested buffer I/O never occurs.
    5427             :  *  i.e at most one BM_IO_IN_PROGRESS bit is set per proc.
    5428             :  *
    5429             :  *  Also note that these are used only for shared buffers, not local ones.
    5430             :  */
    5431             : 
    5432             : /*
    5433             :  * WaitIO -- Block until the IO_IN_PROGRESS flag on 'buf' is cleared.
    5434             :  */
    5435             : static void
    5436         792 : WaitIO(BufferDesc *buf)
    5437             : {
    5438         792 :     ConditionVariable *cv = BufferDescriptorGetIOCV(buf);
    5439             : 
    5440         792 :     ConditionVariablePrepareToSleep(cv);
    5441             :     for (;;)
    5442         724 :     {
    5443             :         uint32      buf_state;
    5444             : 
    5445             :         /*
    5446             :          * It may not be necessary to acquire the spinlock to check the flag
    5447             :          * here, but since this test is essential for correctness, we'd better
    5448             :          * play it safe.
    5449             :          */
    5450        1516 :         buf_state = LockBufHdr(buf);
    5451        1516 :         UnlockBufHdr(buf, buf_state);
    5452             : 
    5453        1516 :         if (!(buf_state & BM_IO_IN_PROGRESS))
    5454         792 :             break;
    5455         724 :         ConditionVariableSleep(cv, WAIT_EVENT_BUFFER_IO);
    5456             :     }
    5457         792 :     ConditionVariableCancelSleep();
    5458         792 : }
    5459             : 
    5460             : /*
    5461             :  * StartBufferIO: begin I/O on this buffer
    5462             :  *  (Assumptions)
    5463             :  *  My process is executing no IO
    5464             :  *  The buffer is Pinned
    5465             :  *
    5466             :  * In some scenarios there are race conditions in which multiple backends
    5467             :  * could attempt the same I/O operation concurrently.  If someone else
    5468             :  * has already started I/O on this buffer then we will block on the
    5469             :  * I/O condition variable until he's done.
    5470             :  *
    5471             :  * Input operations are only attempted on buffers that are not BM_VALID,
    5472             :  * and output operations only on buffers that are BM_VALID and BM_DIRTY,
    5473             :  * so we can always tell if the work is already done.
    5474             :  *
    5475             :  * Returns true if we successfully marked the buffer as I/O busy,
    5476             :  * false if someone else already did the work.
    5477             :  *
    5478             :  * If nowait is true, then we don't wait for an I/O to be finished by another
    5479             :  * backend.  In that case, false indicates either that the I/O was already
    5480             :  * finished, or is still in progress.  This is useful for callers that want to
    5481             :  * find out if they can perform the I/O as part of a larger operation, without
    5482             :  * waiting for the answer or distinguishing the reasons why not.
    5483             :  */
    5484             : static bool
    5485     3435752 : StartBufferIO(BufferDesc *buf, bool forInput, bool nowait)
    5486             : {
    5487             :     uint32      buf_state;
    5488             : 
    5489     3435752 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    5490             : 
    5491             :     for (;;)
    5492             :     {
    5493     3436540 :         buf_state = LockBufHdr(buf);
    5494             : 
    5495     3436540 :         if (!(buf_state & BM_IO_IN_PROGRESS))
    5496     3435752 :             break;
    5497         788 :         UnlockBufHdr(buf, buf_state);
    5498         788 :         if (nowait)
    5499           0 :             return false;
    5500         788 :         WaitIO(buf);
    5501             :     }
    5502             : 
    5503             :     /* Once we get here, there is definitely no I/O active on this buffer */
    5504             : 
    5505     3435752 :     if (forInput ? (buf_state & BM_VALID) : !(buf_state & BM_DIRTY))
    5506             :     {
    5507             :         /* someone else already did the I/O */
    5508        1480 :         UnlockBufHdr(buf, buf_state);
    5509        1480 :         return false;
    5510             :     }
    5511             : 
    5512     3434272 :     buf_state |= BM_IO_IN_PROGRESS;
    5513     3434272 :     UnlockBufHdr(buf, buf_state);
    5514             : 
    5515     3434272 :     ResourceOwnerRememberBufferIO(CurrentResourceOwner,
    5516             :                                   BufferDescriptorGetBuffer(buf));
    5517             : 
    5518     3434272 :     return true;
    5519             : }
    5520             : 
    5521             : /*
    5522             :  * TerminateBufferIO: release a buffer we were doing I/O on
    5523             :  *  (Assumptions)
    5524             :  *  My process is executing IO for the buffer
    5525             :  *  BM_IO_IN_PROGRESS bit is set for the buffer
    5526             :  *  The buffer is Pinned
    5527             :  *
    5528             :  * If clear_dirty is true and BM_JUST_DIRTIED is not set, we clear the
    5529             :  * buffer's BM_DIRTY flag.  This is appropriate when terminating a
    5530             :  * successful write.  The check on BM_JUST_DIRTIED is necessary to avoid
    5531             :  * marking the buffer clean if it was re-dirtied while we were writing.
    5532             :  *
    5533             :  * set_flag_bits gets ORed into the buffer's flags.  It must include
    5534             :  * BM_IO_ERROR in a failure case.  For successful completion it could
    5535             :  * be 0, or BM_VALID if we just finished reading in the page.
    5536             :  *
    5537             :  * If forget_owner is true, we release the buffer I/O from the current
    5538             :  * resource owner. (forget_owner=false is used when the resource owner itself
    5539             :  * is being released)
    5540             :  */
    5541             : static void
    5542     3434272 : TerminateBufferIO(BufferDesc *buf, bool clear_dirty, uint32 set_flag_bits,
    5543             :                   bool forget_owner)
    5544             : {
    5545             :     uint32      buf_state;
    5546             : 
    5547     3434272 :     buf_state = LockBufHdr(buf);
    5548             : 
    5549             :     Assert(buf_state & BM_IO_IN_PROGRESS);
    5550             : 
    5551     3434272 :     buf_state &= ~(BM_IO_IN_PROGRESS | BM_IO_ERROR);
    5552     3434272 :     if (clear_dirty && !(buf_state & BM_JUST_DIRTIED))
    5553      887428 :         buf_state &= ~(BM_DIRTY | BM_CHECKPOINT_NEEDED);
    5554             : 
    5555     3434272 :     buf_state |= set_flag_bits;
    5556     3434272 :     UnlockBufHdr(buf, buf_state);
    5557             : 
    5558     3434272 :     if (forget_owner)
    5559     3434242 :         ResourceOwnerForgetBufferIO(CurrentResourceOwner,
    5560             :                                     BufferDescriptorGetBuffer(buf));
    5561             : 
    5562     3434272 :     ConditionVariableBroadcast(BufferDescriptorGetIOCV(buf));
    5563     3434272 : }
    5564             : 
    5565             : /*
    5566             :  * AbortBufferIO: Clean up active buffer I/O after an error.
    5567             :  *
    5568             :  *  All LWLocks we might have held have been released,
    5569             :  *  but we haven't yet released buffer pins, so the buffer is still pinned.
    5570             :  *
    5571             :  *  If I/O was in progress, we always set BM_IO_ERROR, even though it's
    5572             :  *  possible the error condition wasn't related to the I/O.
    5573             :  *
    5574             :  *  Note: this does not remove the buffer I/O from the resource owner.
    5575             :  *  That's correct when we're releasing the whole resource owner, but
    5576             :  *  beware if you use this in other contexts.
    5577             :  */
    5578             : static void
    5579          30 : AbortBufferIO(Buffer buffer)
    5580             : {
    5581          30 :     BufferDesc *buf_hdr = GetBufferDescriptor(buffer - 1);
    5582             :     uint32      buf_state;
    5583             : 
    5584          30 :     buf_state = LockBufHdr(buf_hdr);
    5585             :     Assert(buf_state & (BM_IO_IN_PROGRESS | BM_TAG_VALID));
    5586             : 
    5587          30 :     if (!(buf_state & BM_VALID))
    5588             :     {
    5589             :         Assert(!(buf_state & BM_DIRTY));
    5590          30 :         UnlockBufHdr(buf_hdr, buf_state);
    5591             :     }
    5592             :     else
    5593             :     {
    5594             :         Assert(buf_state & BM_DIRTY);
    5595           0 :         UnlockBufHdr(buf_hdr, buf_state);
    5596             : 
    5597             :         /* Issue notice if this is not the first failure... */
    5598           0 :         if (buf_state & BM_IO_ERROR)
    5599             :         {
    5600             :             /* Buffer is pinned, so we can read tag without spinlock */
    5601             :             char       *path;
    5602             : 
    5603           0 :             path = relpathperm(BufTagGetRelFileLocator(&buf_hdr->tag),
    5604             :                                BufTagGetForkNum(&buf_hdr->tag));
    5605           0 :             ereport(WARNING,
    5606             :                     (errcode(ERRCODE_IO_ERROR),
    5607             :                      errmsg("could not write block %u of %s",
    5608             :                             buf_hdr->tag.blockNum, path),
    5609             :                      errdetail("Multiple failures --- write error might be permanent.")));
    5610           0 :             pfree(path);
    5611             :         }
    5612             :     }
    5613             : 
    5614          30 :     TerminateBufferIO(buf_hdr, false, BM_IO_ERROR, false);
    5615          30 : }
    5616             : 
    5617             : /*
    5618             :  * Error context callback for errors occurring during shared buffer writes.
    5619             :  */
    5620             : static void
    5621          80 : shared_buffer_write_error_callback(void *arg)
    5622             : {
    5623          80 :     BufferDesc *bufHdr = (BufferDesc *) arg;
    5624             : 
    5625             :     /* Buffer is pinned, so we can read the tag without locking the spinlock */
    5626          80 :     if (bufHdr != NULL)
    5627             :     {
    5628          80 :         char       *path = relpathperm(BufTagGetRelFileLocator(&bufHdr->tag),
    5629             :                                        BufTagGetForkNum(&bufHdr->tag));
    5630             : 
    5631          80 :         errcontext("writing block %u of relation %s",
    5632             :                    bufHdr->tag.blockNum, path);
    5633          80 :         pfree(path);
    5634             :     }
    5635          80 : }
    5636             : 
    5637             : /*
    5638             :  * Error context callback for errors occurring during local buffer writes.
    5639             :  */
    5640             : static void
    5641           0 : local_buffer_write_error_callback(void *arg)
    5642             : {
    5643           0 :     BufferDesc *bufHdr = (BufferDesc *) arg;
    5644             : 
    5645           0 :     if (bufHdr != NULL)
    5646             :     {
    5647           0 :         char       *path = relpathbackend(BufTagGetRelFileLocator(&bufHdr->tag),
    5648             :                                           MyProcNumber,
    5649             :                                           BufTagGetForkNum(&bufHdr->tag));
    5650             : 
    5651           0 :         errcontext("writing block %u of relation %s",
    5652             :                    bufHdr->tag.blockNum, path);
    5653           0 :         pfree(path);
    5654             :     }
    5655           0 : }
    5656             : 
    5657             : /*
    5658             :  * RelFileLocator qsort/bsearch comparator; see RelFileLocatorEquals.
    5659             :  */
    5660             : static int
    5661    19568672 : rlocator_comparator(const void *p1, const void *p2)
    5662             : {
    5663    19568672 :     RelFileLocator n1 = *(const RelFileLocator *) p1;
    5664    19568672 :     RelFileLocator n2 = *(const RelFileLocator *) p2;
    5665             : 
    5666    19568672 :     if (n1.relNumber < n2.relNumber)
    5667    18262118 :         return -1;
    5668     1306554 :     else if (n1.relNumber > n2.relNumber)
    5669      258360 :         return 1;
    5670             : 
    5671     1048194 :     if (n1.dbOid < n2.dbOid)
    5672       76360 :         return -1;
    5673      971834 :     else if (n1.dbOid > n2.dbOid)
    5674       98544 :         return 1;
    5675             : 
    5676      873290 :     if (n1.spcOid < n2.spcOid)
    5677           0 :         return -1;
    5678      873290 :     else if (n1.spcOid > n2.spcOid)
    5679           0 :         return 1;
    5680             :     else
    5681      873290 :         return 0;
    5682             : }
    5683             : 
    5684             : /*
    5685             :  * Lock buffer header - set BM_LOCKED in buffer state.
    5686             :  */
    5687             : uint32
    5688    46916596 : LockBufHdr(BufferDesc *desc)
    5689             : {
    5690             :     SpinDelayStatus delayStatus;
    5691             :     uint32      old_buf_state;
    5692             : 
    5693             :     Assert(!BufferIsLocal(BufferDescriptorGetBuffer(desc)));
    5694             : 
    5695    46916596 :     init_local_spin_delay(&delayStatus);
    5696             : 
    5697             :     while (true)
    5698             :     {
    5699             :         /* set BM_LOCKED flag */
    5700    46950942 :         old_buf_state = pg_atomic_fetch_or_u32(&desc->state, BM_LOCKED);
    5701             :         /* if it wasn't set before we're OK */
    5702    46950942 :         if (!(old_buf_state & BM_LOCKED))
    5703    46916596 :             break;
    5704       34346 :         perform_spin_delay(&delayStatus);
    5705             :     }
    5706    46916596 :     finish_spin_delay(&delayStatus);
    5707    46916596 :     return old_buf_state | BM_LOCKED;
    5708             : }
    5709             : 
    5710             : /*
    5711             :  * Wait until the BM_LOCKED flag isn't set anymore and return the buffer's
    5712             :  * state at that point.
    5713             :  *
    5714             :  * Obviously the buffer could be locked by the time the value is returned, so
    5715             :  * this is primarily useful in CAS style loops.
    5716             :  */
    5717             : static uint32
    5718         658 : WaitBufHdrUnlocked(BufferDesc *buf)
    5719             : {
    5720             :     SpinDelayStatus delayStatus;
    5721             :     uint32      buf_state;
    5722             : 
    5723         658 :     init_local_spin_delay(&delayStatus);
    5724             : 
    5725         658 :     buf_state = pg_atomic_read_u32(&buf->state);
    5726             : 
    5727        5088 :     while (buf_state & BM_LOCKED)
    5728             :     {
    5729        4430 :         perform_spin_delay(&delayStatus);
    5730        4430 :         buf_state = pg_atomic_read_u32(&buf->state);
    5731             :     }
    5732             : 
    5733         658 :     finish_spin_delay(&delayStatus);
    5734             : 
    5735         658 :     return buf_state;
    5736             : }
    5737             : 
    5738             : /*
    5739             :  * BufferTag comparator.
    5740             :  */
    5741             : static inline int
    5742     1466034 : buffertag_comparator(const BufferTag *ba, const BufferTag *bb)
    5743             : {
    5744             :     int         ret;
    5745             :     RelFileLocator rlocatora;
    5746             :     RelFileLocator rlocatorb;
    5747             : 
    5748     1466034 :     rlocatora = BufTagGetRelFileLocator(ba);
    5749     1466034 :     rlocatorb = BufTagGetRelFileLocator(bb);
    5750             : 
    5751     1466034 :     ret = rlocator_comparator(&rlocatora, &rlocatorb);
    5752             : 
    5753     1466034 :     if (ret != 0)
    5754      596472 :         return ret;
    5755             : 
    5756      869562 :     if (BufTagGetForkNum(ba) < BufTagGetForkNum(bb))
    5757       57834 :         return -1;
    5758      811728 :     if (BufTagGetForkNum(ba) > BufTagGetForkNum(bb))
    5759       36062 :         return 1;
    5760             : 
    5761      775666 :     if (ba->blockNum < bb->blockNum)
    5762      521436 :         return -1;
    5763      254230 :     if (ba->blockNum > bb->blockNum)
    5764      253384 :         return 1;
    5765             : 
    5766         846 :     return 0;
    5767             : }
    5768             : 
    5769             : /*
    5770             :  * Comparator determining the writeout order in a checkpoint.
    5771             :  *
    5772             :  * It is important that tablespaces are compared first, the logic balancing
    5773             :  * writes between tablespaces relies on it.
    5774             :  */
    5775             : static inline int
    5776     4551572 : ckpt_buforder_comparator(const CkptSortItem *a, const CkptSortItem *b)
    5777             : {
    5778             :     /* compare tablespace */
    5779     4551572 :     if (a->tsId < b->tsId)
    5780        9380 :         return -1;
    5781     4542192 :     else if (a->tsId > b->tsId)
    5782       30062 :         return 1;
    5783             :     /* compare relation */
    5784     4512130 :     if (a->relNumber < b->relNumber)
    5785     1284646 :         return -1;
    5786     3227484 :     else if (a->relNumber > b->relNumber)
    5787     1233142 :         return 1;
    5788             :     /* compare fork */
    5789     1994342 :     else if (a->forkNum < b->forkNum)
    5790       79496 :         return -1;
    5791     1914846 :     else if (a->forkNum > b->forkNum)
    5792       96620 :         return 1;
    5793             :     /* compare block number */
    5794     1818226 :     else if (a->blockNum < b->blockNum)
    5795      883104 :         return -1;
    5796      935122 :     else if (a->blockNum > b->blockNum)
    5797      868402 :         return 1;
    5798             :     /* equal page IDs are unlikely, but not impossible */
    5799       66720 :     return 0;
    5800             : }
    5801             : 
    5802             : /*
    5803             :  * Comparator for a Min-Heap over the per-tablespace checkpoint completion
    5804             :  * progress.
    5805             :  */
    5806             : static int
    5807      370840 : ts_ckpt_progress_comparator(Datum a, Datum b, void *arg)
    5808             : {
    5809      370840 :     CkptTsStatus *sa = (CkptTsStatus *) a;
    5810      370840 :     CkptTsStatus *sb = (CkptTsStatus *) b;
    5811             : 
    5812             :     /* we want a min-heap, so return 1 for the a < b */
    5813      370840 :     if (sa->progress < sb->progress)
    5814      357442 :         return 1;
    5815       13398 :     else if (sa->progress == sb->progress)
    5816         860 :         return 0;
    5817             :     else
    5818       12538 :         return -1;
    5819             : }
    5820             : 
    5821             : /*
    5822             :  * Initialize a writeback context, discarding potential previous state.
    5823             :  *
    5824             :  * *max_pending is a pointer instead of an immediate value, so the coalesce
    5825             :  * limits can easily changed by the GUC mechanism, and so calling code does
    5826             :  * not have to check the current configuration. A value of 0 means that no
    5827             :  * writeback control will be performed.
    5828             :  */
    5829             : void
    5830        3746 : WritebackContextInit(WritebackContext *context, int *max_pending)
    5831             : {
    5832             :     Assert(*max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
    5833             : 
    5834        3746 :     context->max_pending = max_pending;
    5835        3746 :     context->nr_pending = 0;
    5836        3746 : }
    5837             : 
    5838             : /*
    5839             :  * Add buffer to list of pending writeback requests.
    5840             :  */
    5841             : void
    5842      880328 : ScheduleBufferTagForWriteback(WritebackContext *wb_context, IOContext io_context,
    5843             :                               BufferTag *tag)
    5844             : {
    5845             :     PendingWriteback *pending;
    5846             : 
    5847      880328 :     if (io_direct_flags & IO_DIRECT_DATA)
    5848        1106 :         return;
    5849             : 
    5850             :     /*
    5851             :      * Add buffer to the pending writeback array, unless writeback control is
    5852             :      * disabled.
    5853             :      */
    5854      879222 :     if (*wb_context->max_pending > 0)
    5855             :     {
    5856             :         Assert(*wb_context->max_pending <= WRITEBACK_MAX_PENDING_FLUSHES);
    5857             : 
    5858      443586 :         pending = &wb_context->pending_writebacks[wb_context->nr_pending++];
    5859             : 
    5860      443586 :         pending->tag = *tag;
    5861             :     }
    5862             : 
    5863             :     /*
    5864             :      * Perform pending flushes if the writeback limit is exceeded. This
    5865             :      * includes the case where previously an item has been added, but control
    5866             :      * is now disabled.
    5867             :      */
    5868      879222 :     if (wb_context->nr_pending >= *wb_context->max_pending)
    5869      448804 :         IssuePendingWritebacks(wb_context, io_context);
    5870             : }
    5871             : 
    5872             : #define ST_SORT sort_pending_writebacks
    5873             : #define ST_ELEMENT_TYPE PendingWriteback
    5874             : #define ST_COMPARE(a, b) buffertag_comparator(&a->tag, &b->tag)
    5875             : #define ST_SCOPE static
    5876             : #define ST_DEFINE
    5877             : #include <lib/sort_template.h>
    5878             : 
    5879             : /*
    5880             :  * Issue all pending writeback requests, previously scheduled with
    5881             :  * ScheduleBufferTagForWriteback, to the OS.
    5882             :  *
    5883             :  * Because this is only used to improve the OSs IO scheduling we try to never
    5884             :  * error out - it's just a hint.
    5885             :  */
    5886             : void
    5887      449954 : IssuePendingWritebacks(WritebackContext *wb_context, IOContext io_context)
    5888             : {
    5889             :     instr_time  io_start;
    5890             :     int         i;
    5891             : 
    5892      449954 :     if (wb_context->nr_pending == 0)
    5893      435732 :         return;
    5894             : 
    5895             :     /*
    5896             :      * Executing the writes in-order can make them a lot faster, and allows to
    5897             :      * merge writeback requests to consecutive blocks into larger writebacks.
    5898             :      */
    5899       14222 :     sort_pending_writebacks(wb_context->pending_writebacks,
    5900       14222 :                             wb_context->nr_pending);
    5901             : 
    5902       14222 :     io_start = pgstat_prepare_io_time(track_io_timing);
    5903             : 
    5904             :     /*
    5905             :      * Coalesce neighbouring writes, but nothing else. For that we iterate
    5906             :      * through the, now sorted, array of pending flushes, and look forward to
    5907             :      * find all neighbouring (or identical) writes.
    5908             :      */
    5909      147392 :     for (i = 0; i < wb_context->nr_pending; i++)
    5910             :     {
    5911             :         PendingWriteback *cur;
    5912             :         PendingWriteback *next;
    5913             :         SMgrRelation reln;
    5914             :         int         ahead;
    5915             :         BufferTag   tag;
    5916             :         RelFileLocator currlocator;
    5917      133170 :         Size        nblocks = 1;
    5918             : 
    5919      133170 :         cur = &wb_context->pending_writebacks[i];
    5920      133170 :         tag = cur->tag;
    5921      133170 :         currlocator = BufTagGetRelFileLocator(&tag);
    5922             : 
    5923             :         /*
    5924             :          * Peek ahead, into following writeback requests, to see if they can
    5925             :          * be combined with the current one.
    5926             :          */
    5927      440684 :         for (ahead = 0; i + ahead + 1 < wb_context->nr_pending; ahead++)
    5928             :         {
    5929             : 
    5930      426462 :             next = &wb_context->pending_writebacks[i + ahead + 1];
    5931             : 
    5932             :             /* different file, stop */
    5933      426462 :             if (!RelFileLocatorEquals(currlocator,
    5934      342758 :                                       BufTagGetRelFileLocator(&next->tag)) ||
    5935      342758 :                 BufTagGetForkNum(&cur->tag) != BufTagGetForkNum(&next->tag))
    5936             :                 break;
    5937             : 
    5938             :             /* ok, block queued twice, skip */
    5939      314908 :             if (cur->tag.blockNum == next->tag.blockNum)
    5940         746 :                 continue;
    5941             : 
    5942             :             /* only merge consecutive writes */
    5943      314162 :             if (cur->tag.blockNum + 1 != next->tag.blockNum)
    5944        7394 :                 break;
    5945             : 
    5946      306768 :             nblocks++;
    5947      306768 :             cur = next;
    5948             :         }
    5949             : 
    5950      133170 :         i += ahead;
    5951             : 
    5952             :         /* and finally tell the kernel to write the data to storage */
    5953      133170 :         reln = smgropen(currlocator, INVALID_PROC_NUMBER);
    5954      133170 :         smgrwriteback(reln, BufTagGetForkNum(&tag), tag.blockNum, nblocks);
    5955             :     }
    5956             : 
    5957             :     /*
    5958             :      * Assume that writeback requests are only issued for buffers containing
    5959             :      * blocks of permanent relations.
    5960             :      */
    5961       14222 :     pgstat_count_io_op_time(IOOBJECT_RELATION, io_context,
    5962       14222 :                             IOOP_WRITEBACK, io_start, wb_context->nr_pending);
    5963             : 
    5964       14222 :     wb_context->nr_pending = 0;
    5965             : }
    5966             : 
    5967             : /* ResourceOwner callbacks */
    5968             : 
    5969             : static void
    5970          30 : ResOwnerReleaseBufferIO(Datum res)
    5971             : {
    5972          30 :     Buffer      buffer = DatumGetInt32(res);
    5973             : 
    5974          30 :     AbortBufferIO(buffer);
    5975          30 : }
    5976             : 
    5977             : static char *
    5978           0 : ResOwnerPrintBufferIO(Datum res)
    5979             : {
    5980           0 :     Buffer      buffer = DatumGetInt32(res);
    5981             : 
    5982           0 :     return psprintf("lost track of buffer IO on buffer %d", buffer);
    5983             : }
    5984             : 
    5985             : static void
    5986        7714 : ResOwnerReleaseBufferPin(Datum res)
    5987             : {
    5988        7714 :     Buffer      buffer = DatumGetInt32(res);
    5989             : 
    5990             :     /* Like ReleaseBuffer, but don't call ResourceOwnerForgetBuffer */
    5991        7714 :     if (!BufferIsValid(buffer))
    5992           0 :         elog(ERROR, "bad buffer ID: %d", buffer);
    5993             : 
    5994        7714 :     if (BufferIsLocal(buffer))
    5995         754 :         UnpinLocalBufferNoOwner(buffer);
    5996             :     else
    5997        6960 :         UnpinBufferNoOwner(GetBufferDescriptor(buffer - 1));
    5998        7714 : }
    5999             : 
    6000             : static char *
    6001           0 : ResOwnerPrintBufferPin(Datum res)
    6002             : {
    6003           0 :     return DebugPrintBufferRefcount(DatumGetInt32(res));
    6004             : }
    6005             : 
    6006             : /*
    6007             :  * Try to evict the current block in a shared buffer.
    6008             :  *
    6009             :  * This function is intended for testing/development use only!
    6010             :  *
    6011             :  * To succeed, the buffer must not be pinned on entry, so if the caller had a
    6012             :  * particular block in mind, it might already have been replaced by some other
    6013             :  * block by the time this function runs.  It's also unpinned on return, so the
    6014             :  * buffer might be occupied again by the time control is returned, potentially
    6015             :  * even by the same block.  This inherent raciness without other interlocking
    6016             :  * makes the function unsuitable for non-testing usage.
    6017             :  *
    6018             :  * Returns true if the buffer was valid and it has now been made invalid.
    6019             :  * Returns false if it wasn't valid, if it couldn't be evicted due to a pin,
    6020             :  * or if the buffer becomes dirty again while we're trying to write it out.
    6021             :  */
    6022             : bool
    6023           0 : EvictUnpinnedBuffer(Buffer buf)
    6024             : {
    6025             :     BufferDesc *desc;
    6026             :     uint32      buf_state;
    6027             :     bool        result;
    6028             : 
    6029             :     /* Make sure we can pin the buffer. */
    6030           0 :     ResourceOwnerEnlarge(CurrentResourceOwner);
    6031           0 :     ReservePrivateRefCountEntry();
    6032             : 
    6033             :     Assert(!BufferIsLocal(buf));
    6034           0 :     desc = GetBufferDescriptor(buf - 1);
    6035             : 
    6036             :     /* Lock the header and check if it's valid. */
    6037           0 :     buf_state = LockBufHdr(desc);
    6038           0 :     if ((buf_state & BM_VALID) == 0)
    6039             :     {
    6040           0 :         UnlockBufHdr(desc, buf_state);
    6041           0 :         return false;
    6042             :     }
    6043             : 
    6044             :     /* Check that it's not pinned already. */
    6045           0 :     if (BUF_STATE_GET_REFCOUNT(buf_state) > 0)
    6046             :     {
    6047           0 :         UnlockBufHdr(desc, buf_state);
    6048           0 :         return false;
    6049             :     }
    6050             : 
    6051           0 :     PinBuffer_Locked(desc);     /* releases spinlock */
    6052             : 
    6053             :     /* If it was dirty, try to clean it once. */
    6054           0 :     if (buf_state & BM_DIRTY)
    6055             :     {
    6056           0 :         LWLockAcquire(BufferDescriptorGetContentLock(desc), LW_SHARED);
    6057           0 :         FlushBuffer(desc, NULL, IOOBJECT_RELATION, IOCONTEXT_NORMAL);
    6058           0 :         LWLockRelease(BufferDescriptorGetContentLock(desc));
    6059             :     }
    6060             : 
    6061             :     /* This will return false if it becomes dirty or someone else pins it. */
    6062           0 :     result = InvalidateVictimBuffer(desc);
    6063             : 
    6064           0 :     UnpinBuffer(desc);
    6065             : 
    6066           0 :     return result;
    6067             : }

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