LCOV - code coverage report
Current view: top level - src/backend/storage/smgr - md.c (source / functions) Hit Total Coverage
Test: PostgreSQL 17devel Lines: 284 382 74.3 %
Date: 2023-12-07 05:10:43 Functions: 31 32 96.9 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * md.c
       4             :  *    This code manages relations that reside on magnetic disk.
       5             :  *
       6             :  * Or at least, that was what the Berkeley folk had in mind when they named
       7             :  * this file.  In reality, what this code provides is an interface from
       8             :  * the smgr API to Unix-like filesystem APIs, so it will work with any type
       9             :  * of device for which the operating system provides filesystem support.
      10             :  * It doesn't matter whether the bits are on spinning rust or some other
      11             :  * storage technology.
      12             :  *
      13             :  * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
      14             :  * Portions Copyright (c) 1994, Regents of the University of California
      15             :  *
      16             :  *
      17             :  * IDENTIFICATION
      18             :  *    src/backend/storage/smgr/md.c
      19             :  *
      20             :  *-------------------------------------------------------------------------
      21             :  */
      22             : #include "postgres.h"
      23             : 
      24             : #include <unistd.h>
      25             : #include <fcntl.h>
      26             : #include <sys/file.h>
      27             : 
      28             : #include "access/xlog.h"
      29             : #include "access/xlogutils.h"
      30             : #include "commands/tablespace.h"
      31             : #include "miscadmin.h"
      32             : #include "pg_trace.h"
      33             : #include "pgstat.h"
      34             : #include "postmaster/bgwriter.h"
      35             : #include "storage/bufmgr.h"
      36             : #include "storage/fd.h"
      37             : #include "storage/md.h"
      38             : #include "storage/relfilelocator.h"
      39             : #include "storage/smgr.h"
      40             : #include "storage/sync.h"
      41             : #include "utils/hsearch.h"
      42             : #include "utils/memutils.h"
      43             : 
      44             : /*
      45             :  * The magnetic disk storage manager keeps track of open file
      46             :  * descriptors in its own descriptor pool.  This is done to make it
      47             :  * easier to support relations that are larger than the operating
      48             :  * system's file size limit (often 2GBytes).  In order to do that,
      49             :  * we break relations up into "segment" files that are each shorter than
      50             :  * the OS file size limit.  The segment size is set by the RELSEG_SIZE
      51             :  * configuration constant in pg_config.h.
      52             :  *
      53             :  * On disk, a relation must consist of consecutively numbered segment
      54             :  * files in the pattern
      55             :  *  -- Zero or more full segments of exactly RELSEG_SIZE blocks each
      56             :  *  -- Exactly one partial segment of size 0 <= size < RELSEG_SIZE blocks
      57             :  *  -- Optionally, any number of inactive segments of size 0 blocks.
      58             :  * The full and partial segments are collectively the "active" segments.
      59             :  * Inactive segments are those that once contained data but are currently
      60             :  * not needed because of an mdtruncate() operation.  The reason for leaving
      61             :  * them present at size zero, rather than unlinking them, is that other
      62             :  * backends and/or the checkpointer might be holding open file references to
      63             :  * such segments.  If the relation expands again after mdtruncate(), such
      64             :  * that a deactivated segment becomes active again, it is important that
      65             :  * such file references still be valid --- else data might get written
      66             :  * out to an unlinked old copy of a segment file that will eventually
      67             :  * disappear.
      68             :  *
      69             :  * File descriptors are stored in the per-fork md_seg_fds arrays inside
      70             :  * SMgrRelation. The length of these arrays is stored in md_num_open_segs.
      71             :  * Note that a fork's md_num_open_segs having a specific value does not
      72             :  * necessarily mean the relation doesn't have additional segments; we may
      73             :  * just not have opened the next segment yet.  (We could not have "all
      74             :  * segments are in the array" as an invariant anyway, since another backend
      75             :  * could extend the relation while we aren't looking.)  We do not have
      76             :  * entries for inactive segments, however; as soon as we find a partial
      77             :  * segment, we assume that any subsequent segments are inactive.
      78             :  *
      79             :  * The entire MdfdVec array is palloc'd in the MdCxt memory context.
      80             :  */
      81             : 
      82             : typedef struct _MdfdVec
      83             : {
      84             :     File        mdfd_vfd;       /* fd number in fd.c's pool */
      85             :     BlockNumber mdfd_segno;     /* segment number, from 0 */
      86             : } MdfdVec;
      87             : 
      88             : static MemoryContext MdCxt;     /* context for all MdfdVec objects */
      89             : 
      90             : 
      91             : /* Populate a file tag describing an md.c segment file. */
      92             : #define INIT_MD_FILETAG(a,xx_rlocator,xx_forknum,xx_segno) \
      93             : ( \
      94             :     memset(&(a), 0, sizeof(FileTag)), \
      95             :     (a).handler = SYNC_HANDLER_MD, \
      96             :     (a).rlocator = (xx_rlocator), \
      97             :     (a).forknum = (xx_forknum), \
      98             :     (a).segno = (xx_segno) \
      99             : )
     100             : 
     101             : 
     102             : /*** behavior for mdopen & _mdfd_getseg ***/
     103             : /* ereport if segment not present */
     104             : #define EXTENSION_FAIL              (1 << 0)
     105             : /* return NULL if segment not present */
     106             : #define EXTENSION_RETURN_NULL       (1 << 1)
     107             : /* create new segments as needed */
     108             : #define EXTENSION_CREATE            (1 << 2)
     109             : /* create new segments if needed during recovery */
     110             : #define EXTENSION_CREATE_RECOVERY   (1 << 3)
     111             : /*
     112             :  * Allow opening segments which are preceded by segments smaller than
     113             :  * RELSEG_SIZE, e.g. inactive segments (see above). Note that this breaks
     114             :  * mdnblocks() and related functionality henceforth - which currently is ok,
     115             :  * because this is only required in the checkpointer which never uses
     116             :  * mdnblocks().
     117             :  */
     118             : #define EXTENSION_DONT_CHECK_SIZE   (1 << 4)
     119             : /* don't try to open a segment, if not already open */
     120             : #define EXTENSION_DONT_OPEN         (1 << 5)
     121             : 
     122             : 
     123             : /* local routines */
     124             : static void mdunlinkfork(RelFileLocatorBackend rlocator, ForkNumber forknum,
     125             :                          bool isRedo);
     126             : static MdfdVec *mdopenfork(SMgrRelation reln, ForkNumber forknum, int behavior);
     127             : static void register_dirty_segment(SMgrRelation reln, ForkNumber forknum,
     128             :                                    MdfdVec *seg);
     129             : static void register_unlink_segment(RelFileLocatorBackend rlocator, ForkNumber forknum,
     130             :                                     BlockNumber segno);
     131             : static void register_forget_request(RelFileLocatorBackend rlocator, ForkNumber forknum,
     132             :                                     BlockNumber segno);
     133             : static void _fdvec_resize(SMgrRelation reln,
     134             :                           ForkNumber forknum,
     135             :                           int nseg);
     136             : static char *_mdfd_segpath(SMgrRelation reln, ForkNumber forknum,
     137             :                            BlockNumber segno);
     138             : static MdfdVec *_mdfd_openseg(SMgrRelation reln, ForkNumber forknum,
     139             :                               BlockNumber segno, int oflags);
     140             : static MdfdVec *_mdfd_getseg(SMgrRelation reln, ForkNumber forknum,
     141             :                              BlockNumber blkno, bool skipFsync, int behavior);
     142             : static BlockNumber _mdnblocks(SMgrRelation reln, ForkNumber forknum,
     143             :                               MdfdVec *seg);
     144             : 
     145             : static inline int
     146     1878010 : _mdfd_open_flags(void)
     147             : {
     148     1878010 :     int         flags = O_RDWR | PG_BINARY;
     149             : 
     150     1878010 :     if (io_direct_flags & IO_DIRECT_DATA)
     151         604 :         flags |= PG_O_DIRECT;
     152             : 
     153     1878010 :     return flags;
     154             : }
     155             : 
     156             : /*
     157             :  * mdinit() -- Initialize private state for magnetic disk storage manager.
     158             :  */
     159             : void
     160       27816 : mdinit(void)
     161             : {
     162       27816 :     MdCxt = AllocSetContextCreate(TopMemoryContext,
     163             :                                   "MdSmgr",
     164             :                                   ALLOCSET_DEFAULT_SIZES);
     165       27816 : }
     166             : 
     167             : /*
     168             :  * mdexists() -- Does the physical file exist?
     169             :  *
     170             :  * Note: this will return true for lingering files, with pending deletions
     171             :  */
     172             : bool
     173     1731224 : mdexists(SMgrRelation reln, ForkNumber forknum)
     174             : {
     175             :     /*
     176             :      * Close it first, to ensure that we notice if the fork has been unlinked
     177             :      * since we opened it.  As an optimization, we can skip that in recovery,
     178             :      * which already closes relations when dropping them.
     179             :      */
     180     1731224 :     if (!InRecovery)
     181      772306 :         mdclose(reln, forknum);
     182             : 
     183     1731224 :     return (mdopenfork(reln, forknum, EXTENSION_RETURN_NULL) != NULL);
     184             : }
     185             : 
     186             : /*
     187             :  * mdcreate() -- Create a new relation on magnetic disk.
     188             :  *
     189             :  * If isRedo is true, it's okay for the relation to exist already.
     190             :  */
     191             : void
     192     5386914 : mdcreate(SMgrRelation reln, ForkNumber forknum, bool isRedo)
     193             : {
     194             :     MdfdVec    *mdfd;
     195             :     char       *path;
     196             :     File        fd;
     197             : 
     198     5386914 :     if (isRedo && reln->md_num_open_segs[forknum] > 0)
     199     5131684 :         return;                 /* created and opened already... */
     200             : 
     201             :     Assert(reln->md_num_open_segs[forknum] == 0);
     202             : 
     203             :     /*
     204             :      * We may be using the target table space for the first time in this
     205             :      * database, so create a per-database subdirectory if needed.
     206             :      *
     207             :      * XXX this is a fairly ugly violation of module layering, but this seems
     208             :      * to be the best place to put the check.  Maybe TablespaceCreateDbspace
     209             :      * should be here and not in commands/tablespace.c?  But that would imply
     210             :      * importing a lot of stuff that smgr.c oughtn't know, either.
     211             :      */
     212      255230 :     TablespaceCreateDbspace(reln->smgr_rlocator.locator.spcOid,
     213             :                             reln->smgr_rlocator.locator.dbOid,
     214             :                             isRedo);
     215             : 
     216      255230 :     path = relpath(reln->smgr_rlocator, forknum);
     217             : 
     218      255230 :     fd = PathNameOpenFile(path, _mdfd_open_flags() | O_CREAT | O_EXCL);
     219             : 
     220      255230 :     if (fd < 0)
     221             :     {
     222        7252 :         int         save_errno = errno;
     223             : 
     224        7252 :         if (isRedo)
     225        7252 :             fd = PathNameOpenFile(path, _mdfd_open_flags());
     226        7252 :         if (fd < 0)
     227             :         {
     228             :             /* be sure to report the error reported by create, not open */
     229           0 :             errno = save_errno;
     230           0 :             ereport(ERROR,
     231             :                     (errcode_for_file_access(),
     232             :                      errmsg("could not create file \"%s\": %m", path)));
     233             :         }
     234             :     }
     235             : 
     236      255230 :     pfree(path);
     237             : 
     238      255230 :     _fdvec_resize(reln, forknum, 1);
     239      255230 :     mdfd = &reln->md_seg_fds[forknum][0];
     240      255230 :     mdfd->mdfd_vfd = fd;
     241      255230 :     mdfd->mdfd_segno = 0;
     242             : 
     243      255230 :     if (!SmgrIsTemp(reln))
     244      249312 :         register_dirty_segment(reln, forknum, mdfd);
     245             : }
     246             : 
     247             : /*
     248             :  * mdunlink() -- Unlink a relation.
     249             :  *
     250             :  * Note that we're passed a RelFileLocatorBackend --- by the time this is called,
     251             :  * there won't be an SMgrRelation hashtable entry anymore.
     252             :  *
     253             :  * forknum can be a fork number to delete a specific fork, or InvalidForkNumber
     254             :  * to delete all forks.
     255             :  *
     256             :  * For regular relations, we don't unlink the first segment file of the rel,
     257             :  * but just truncate it to zero length, and record a request to unlink it after
     258             :  * the next checkpoint.  Additional segments can be unlinked immediately,
     259             :  * however.  Leaving the empty file in place prevents that relfilenumber
     260             :  * from being reused.  The scenario this protects us from is:
     261             :  * 1. We delete a relation (and commit, and actually remove its file).
     262             :  * 2. We create a new relation, which by chance gets the same relfilenumber as
     263             :  *    the just-deleted one (OIDs must've wrapped around for that to happen).
     264             :  * 3. We crash before another checkpoint occurs.
     265             :  * During replay, we would delete the file and then recreate it, which is fine
     266             :  * if the contents of the file were repopulated by subsequent WAL entries.
     267             :  * But if we didn't WAL-log insertions, but instead relied on fsyncing the
     268             :  * file after populating it (as we do at wal_level=minimal), the contents of
     269             :  * the file would be lost forever.  By leaving the empty file until after the
     270             :  * next checkpoint, we prevent reassignment of the relfilenumber until it's
     271             :  * safe, because relfilenumber assignment skips over any existing file.
     272             :  *
     273             :  * Additional segments, if any, are truncated and then unlinked.  The reason
     274             :  * for truncating is that other backends may still hold open FDs for these at
     275             :  * the smgr level, so that the kernel can't remove the file yet.  We want to
     276             :  * reclaim the disk space right away despite that.
     277             :  *
     278             :  * We do not need to go through this dance for temp relations, though, because
     279             :  * we never make WAL entries for temp rels, and so a temp rel poses no threat
     280             :  * to the health of a regular rel that has taken over its relfilenumber.
     281             :  * The fact that temp rels and regular rels have different file naming
     282             :  * patterns provides additional safety.  Other backends shouldn't have open
     283             :  * FDs for them, either.
     284             :  *
     285             :  * We also don't do it while performing a binary upgrade.  There is no reuse
     286             :  * hazard in that case, since after a crash or even a simple ERROR, the
     287             :  * upgrade fails and the whole cluster must be recreated from scratch.
     288             :  * Furthermore, it is important to remove the files from disk immediately,
     289             :  * because we may be about to reuse the same relfilenumber.
     290             :  *
     291             :  * All the above applies only to the relation's main fork; other forks can
     292             :  * just be removed immediately, since they are not needed to prevent the
     293             :  * relfilenumber from being recycled.  Also, we do not carefully
     294             :  * track whether other forks have been created or not, but just attempt to
     295             :  * unlink them unconditionally; so we should never complain about ENOENT.
     296             :  *
     297             :  * If isRedo is true, it's unsurprising for the relation to be already gone.
     298             :  * Also, we should remove the file immediately instead of queuing a request
     299             :  * for later, since during redo there's no possibility of creating a
     300             :  * conflicting relation.
     301             :  *
     302             :  * Note: we currently just never warn about ENOENT at all.  We could warn in
     303             :  * the main-fork, non-isRedo case, but it doesn't seem worth the trouble.
     304             :  *
     305             :  * Note: any failure should be reported as WARNING not ERROR, because
     306             :  * we are usually not in a transaction anymore when this is called.
     307             :  */
     308             : void
     309      301928 : mdunlink(RelFileLocatorBackend rlocator, ForkNumber forknum, bool isRedo)
     310             : {
     311             :     /* Now do the per-fork work */
     312      301928 :     if (forknum == InvalidForkNumber)
     313             :     {
     314           0 :         for (forknum = 0; forknum <= MAX_FORKNUM; forknum++)
     315           0 :             mdunlinkfork(rlocator, forknum, isRedo);
     316             :     }
     317             :     else
     318      301928 :         mdunlinkfork(rlocator, forknum, isRedo);
     319      301928 : }
     320             : 
     321             : /*
     322             :  * Truncate a file to release disk space.
     323             :  */
     324             : static int
     325      352198 : do_truncate(const char *path)
     326             : {
     327             :     int         save_errno;
     328             :     int         ret;
     329             : 
     330      352198 :     ret = pg_truncate(path, 0);
     331             : 
     332             :     /* Log a warning here to avoid repetition in callers. */
     333      352198 :     if (ret < 0 && errno != ENOENT)
     334             :     {
     335           0 :         save_errno = errno;
     336           0 :         ereport(WARNING,
     337             :                 (errcode_for_file_access(),
     338             :                  errmsg("could not truncate file \"%s\": %m", path)));
     339           0 :         errno = save_errno;
     340             :     }
     341             : 
     342      352198 :     return ret;
     343             : }
     344             : 
     345             : static void
     346      301928 : mdunlinkfork(RelFileLocatorBackend rlocator, ForkNumber forknum, bool isRedo)
     347             : {
     348             :     char       *path;
     349             :     int         ret;
     350             :     int         save_errno;
     351             : 
     352      301928 :     path = relpath(rlocator, forknum);
     353             : 
     354             :     /*
     355             :      * Truncate and then unlink the first segment, or just register a request
     356             :      * to unlink it later, as described in the comments for mdunlink().
     357             :      */
     358      301928 :     if (isRedo || IsBinaryUpgrade || forknum != MAIN_FORKNUM ||
     359       63290 :         RelFileLocatorBackendIsTemp(rlocator))
     360             :     {
     361      244294 :         if (!RelFileLocatorBackendIsTemp(rlocator))
     362             :         {
     363             :             /* Prevent other backends' fds from holding on to the disk space */
     364      221670 :             ret = do_truncate(path);
     365             : 
     366             :             /* Forget any pending sync requests for the first segment */
     367      221670 :             save_errno = errno;
     368      221670 :             register_forget_request(rlocator, forknum, 0 /* first seg */ );
     369      221670 :             errno = save_errno;
     370             :         }
     371             :         else
     372       22624 :             ret = 0;
     373             : 
     374             :         /* Next unlink the file, unless it was already found to be missing */
     375      244294 :         if (ret >= 0 || errno != ENOENT)
     376             :         {
     377       37892 :             ret = unlink(path);
     378       37892 :             if (ret < 0 && errno != ENOENT)
     379             :             {
     380           0 :                 save_errno = errno;
     381           0 :                 ereport(WARNING,
     382             :                         (errcode_for_file_access(),
     383             :                          errmsg("could not remove file \"%s\": %m", path)));
     384           0 :                 errno = save_errno;
     385             :             }
     386             :         }
     387             :     }
     388             :     else
     389             :     {
     390             :         /* Prevent other backends' fds from holding on to the disk space */
     391       57634 :         ret = do_truncate(path);
     392             : 
     393             :         /* Register request to unlink first segment later */
     394       57634 :         save_errno = errno;
     395       57634 :         register_unlink_segment(rlocator, forknum, 0 /* first seg */ );
     396       57634 :         errno = save_errno;
     397             :     }
     398             : 
     399             :     /*
     400             :      * Delete any additional segments.
     401             :      *
     402             :      * Note that because we loop until getting ENOENT, we will correctly
     403             :      * remove all inactive segments as well as active ones.  Ideally we'd
     404             :      * continue the loop until getting exactly that errno, but that risks an
     405             :      * infinite loop if the problem is directory-wide (for instance, if we
     406             :      * suddenly can't read the data directory itself).  We compromise by
     407             :      * continuing after a non-ENOENT truncate error, but stopping after any
     408             :      * unlink error.  If there is indeed a directory-wide problem, additional
     409             :      * unlink attempts wouldn't work anyway.
     410             :      */
     411      301928 :     if (ret >= 0 || errno != ENOENT)
     412             :     {
     413       78812 :         char       *segpath = (char *) palloc(strlen(path) + 12);
     414             :         BlockNumber segno;
     415             : 
     416       78812 :         for (segno = 1;; segno++)
     417             :         {
     418       78812 :             sprintf(segpath, "%s.%u", path, segno);
     419             : 
     420       78812 :             if (!RelFileLocatorBackendIsTemp(rlocator))
     421             :             {
     422             :                 /*
     423             :                  * Prevent other backends' fds from holding on to the disk
     424             :                  * space.  We're done if we see ENOENT, though.
     425             :                  */
     426       72894 :                 if (do_truncate(segpath) < 0 && errno == ENOENT)
     427       72894 :                     break;
     428             : 
     429             :                 /*
     430             :                  * Forget any pending sync requests for this segment before we
     431             :                  * try to unlink.
     432             :                  */
     433           0 :                 register_forget_request(rlocator, forknum, segno);
     434             :             }
     435             : 
     436        5918 :             if (unlink(segpath) < 0)
     437             :             {
     438             :                 /* ENOENT is expected after the last segment... */
     439        5918 :                 if (errno != ENOENT)
     440           0 :                     ereport(WARNING,
     441             :                             (errcode_for_file_access(),
     442             :                              errmsg("could not remove file \"%s\": %m", segpath)));
     443        5918 :                 break;
     444             :             }
     445             :         }
     446       78812 :         pfree(segpath);
     447             :     }
     448             : 
     449      301928 :     pfree(path);
     450      301928 : }
     451             : 
     452             : /*
     453             :  * mdextend() -- Add a block to the specified relation.
     454             :  *
     455             :  * The semantics are nearly the same as mdwrite(): write at the
     456             :  * specified position.  However, this is to be used for the case of
     457             :  * extending a relation (i.e., blocknum is at or beyond the current
     458             :  * EOF).  Note that we assume writing a block beyond current EOF
     459             :  * causes intervening file space to become filled with zeroes.
     460             :  */
     461             : void
     462      195370 : mdextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
     463             :          const void *buffer, bool skipFsync)
     464             : {
     465             :     off_t       seekpos;
     466             :     int         nbytes;
     467             :     MdfdVec    *v;
     468             : 
     469             :     /* If this build supports direct I/O, the buffer must be I/O aligned. */
     470             :     if (PG_O_DIRECT != 0 && PG_IO_ALIGN_SIZE <= BLCKSZ)
     471             :         Assert((uintptr_t) buffer == TYPEALIGN(PG_IO_ALIGN_SIZE, buffer));
     472             : 
     473             :     /* This assert is too expensive to have on normally ... */
     474             : #ifdef CHECK_WRITE_VS_EXTEND
     475             :     Assert(blocknum >= mdnblocks(reln, forknum));
     476             : #endif
     477             : 
     478             :     /*
     479             :      * If a relation manages to grow to 2^32-1 blocks, refuse to extend it any
     480             :      * more --- we mustn't create a block whose number actually is
     481             :      * InvalidBlockNumber.  (Note that this failure should be unreachable
     482             :      * because of upstream checks in bufmgr.c.)
     483             :      */
     484      195370 :     if (blocknum == InvalidBlockNumber)
     485           0 :         ereport(ERROR,
     486             :                 (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
     487             :                  errmsg("cannot extend file \"%s\" beyond %u blocks",
     488             :                         relpath(reln->smgr_rlocator, forknum),
     489             :                         InvalidBlockNumber)));
     490             : 
     491      195370 :     v = _mdfd_getseg(reln, forknum, blocknum, skipFsync, EXTENSION_CREATE);
     492             : 
     493      195370 :     seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
     494             : 
     495             :     Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
     496             : 
     497      195370 :     if ((nbytes = FileWrite(v->mdfd_vfd, buffer, BLCKSZ, seekpos, WAIT_EVENT_DATA_FILE_EXTEND)) != BLCKSZ)
     498             :     {
     499           0 :         if (nbytes < 0)
     500           0 :             ereport(ERROR,
     501             :                     (errcode_for_file_access(),
     502             :                      errmsg("could not extend file \"%s\": %m",
     503             :                             FilePathName(v->mdfd_vfd)),
     504             :                      errhint("Check free disk space.")));
     505             :         /* short write: complain appropriately */
     506           0 :         ereport(ERROR,
     507             :                 (errcode(ERRCODE_DISK_FULL),
     508             :                  errmsg("could not extend file \"%s\": wrote only %d of %d bytes at block %u",
     509             :                         FilePathName(v->mdfd_vfd),
     510             :                         nbytes, BLCKSZ, blocknum),
     511             :                  errhint("Check free disk space.")));
     512             :     }
     513             : 
     514      195370 :     if (!skipFsync && !SmgrIsTemp(reln))
     515          54 :         register_dirty_segment(reln, forknum, v);
     516             : 
     517             :     Assert(_mdnblocks(reln, forknum, v) <= ((BlockNumber) RELSEG_SIZE));
     518      195370 : }
     519             : 
     520             : /*
     521             :  * mdzeroextend() -- Add new zeroed out blocks to the specified relation.
     522             :  *
     523             :  * Similar to mdextend(), except the relation can be extended by multiple
     524             :  * blocks at once and the added blocks will be filled with zeroes.
     525             :  */
     526             : void
     527      350086 : mdzeroextend(SMgrRelation reln, ForkNumber forknum,
     528             :              BlockNumber blocknum, int nblocks, bool skipFsync)
     529             : {
     530             :     MdfdVec    *v;
     531      350086 :     BlockNumber curblocknum = blocknum;
     532      350086 :     int         remblocks = nblocks;
     533             : 
     534             :     Assert(nblocks > 0);
     535             : 
     536             :     /* This assert is too expensive to have on normally ... */
     537             : #ifdef CHECK_WRITE_VS_EXTEND
     538             :     Assert(blocknum >= mdnblocks(reln, forknum));
     539             : #endif
     540             : 
     541             :     /*
     542             :      * If a relation manages to grow to 2^32-1 blocks, refuse to extend it any
     543             :      * more --- we mustn't create a block whose number actually is
     544             :      * InvalidBlockNumber or larger.
     545             :      */
     546      350086 :     if ((uint64) blocknum + nblocks >= (uint64) InvalidBlockNumber)
     547           0 :         ereport(ERROR,
     548             :                 (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
     549             :                  errmsg("cannot extend file \"%s\" beyond %u blocks",
     550             :                         relpath(reln->smgr_rlocator, forknum),
     551             :                         InvalidBlockNumber)));
     552             : 
     553      700172 :     while (remblocks > 0)
     554             :     {
     555      350086 :         BlockNumber segstartblock = curblocknum % ((BlockNumber) RELSEG_SIZE);
     556      350086 :         off_t       seekpos = (off_t) BLCKSZ * segstartblock;
     557             :         int         numblocks;
     558             : 
     559      350086 :         if (segstartblock + remblocks > RELSEG_SIZE)
     560           0 :             numblocks = RELSEG_SIZE - segstartblock;
     561             :         else
     562      350086 :             numblocks = remblocks;
     563             : 
     564      350086 :         v = _mdfd_getseg(reln, forknum, curblocknum, skipFsync, EXTENSION_CREATE);
     565             : 
     566             :         Assert(segstartblock < RELSEG_SIZE);
     567             :         Assert(segstartblock + numblocks <= RELSEG_SIZE);
     568             : 
     569             :         /*
     570             :          * If available and useful, use posix_fallocate() (via
     571             :          * FileFallocate()) to extend the relation. That's often more
     572             :          * efficient than using write(), as it commonly won't cause the kernel
     573             :          * to allocate page cache space for the extended pages.
     574             :          *
     575             :          * However, we don't use FileFallocate() for small extensions, as it
     576             :          * defeats delayed allocation on some filesystems. Not clear where
     577             :          * that decision should be made though? For now just use a cutoff of
     578             :          * 8, anything between 4 and 8 worked OK in some local testing.
     579             :          */
     580      350086 :         if (numblocks > 8)
     581             :         {
     582             :             int         ret;
     583             : 
     584        1002 :             ret = FileFallocate(v->mdfd_vfd,
     585             :                                 seekpos, (off_t) BLCKSZ * numblocks,
     586             :                                 WAIT_EVENT_DATA_FILE_EXTEND);
     587        1002 :             if (ret != 0)
     588             :             {
     589           0 :                 ereport(ERROR,
     590             :                         errcode_for_file_access(),
     591             :                         errmsg("could not extend file \"%s\" with FileFallocate(): %m",
     592             :                                FilePathName(v->mdfd_vfd)),
     593             :                         errhint("Check free disk space."));
     594             :             }
     595             :         }
     596             :         else
     597             :         {
     598             :             int         ret;
     599             : 
     600             :             /*
     601             :              * Even if we don't want to use fallocate, we can still extend a
     602             :              * bit more efficiently than writing each 8kB block individually.
     603             :              * pg_pwrite_zeros() (via FileZero()) uses pg_pwritev_with_retry()
     604             :              * to avoid multiple writes or needing a zeroed buffer for the
     605             :              * whole length of the extension.
     606             :              */
     607      349084 :             ret = FileZero(v->mdfd_vfd,
     608             :                            seekpos, (off_t) BLCKSZ * numblocks,
     609             :                            WAIT_EVENT_DATA_FILE_EXTEND);
     610      349084 :             if (ret < 0)
     611           0 :                 ereport(ERROR,
     612             :                         errcode_for_file_access(),
     613             :                         errmsg("could not extend file \"%s\": %m",
     614             :                                FilePathName(v->mdfd_vfd)),
     615             :                         errhint("Check free disk space."));
     616             :         }
     617             : 
     618      350086 :         if (!skipFsync && !SmgrIsTemp(reln))
     619      332634 :             register_dirty_segment(reln, forknum, v);
     620             : 
     621             :         Assert(_mdnblocks(reln, forknum, v) <= ((BlockNumber) RELSEG_SIZE));
     622             : 
     623      350086 :         remblocks -= numblocks;
     624      350086 :         curblocknum += numblocks;
     625             :     }
     626      350086 : }
     627             : 
     628             : /*
     629             :  * mdopenfork() -- Open one fork of the specified relation.
     630             :  *
     631             :  * Note we only open the first segment, when there are multiple segments.
     632             :  *
     633             :  * If first segment is not present, either ereport or return NULL according
     634             :  * to "behavior".  We treat EXTENSION_CREATE the same as EXTENSION_FAIL;
     635             :  * EXTENSION_CREATE means it's OK to extend an existing relation, not to
     636             :  * invent one out of whole cloth.
     637             :  */
     638             : static MdfdVec *
     639     5313164 : mdopenfork(SMgrRelation reln, ForkNumber forknum, int behavior)
     640             : {
     641             :     MdfdVec    *mdfd;
     642             :     char       *path;
     643             :     File        fd;
     644             : 
     645             :     /* No work if already open */
     646     5313164 :     if (reln->md_num_open_segs[forknum] > 0)
     647     3726696 :         return &reln->md_seg_fds[forknum][0];
     648             : 
     649     1586468 :     path = relpath(reln->smgr_rlocator, forknum);
     650             : 
     651     1586468 :     fd = PathNameOpenFile(path, _mdfd_open_flags());
     652             : 
     653     1586468 :     if (fd < 0)
     654             :     {
     655      573736 :         if ((behavior & EXTENSION_RETURN_NULL) &&
     656      573692 :             FILE_POSSIBLY_DELETED(errno))
     657             :         {
     658      573692 :             pfree(path);
     659      573692 :             return NULL;
     660             :         }
     661          44 :         ereport(ERROR,
     662             :                 (errcode_for_file_access(),
     663             :                  errmsg("could not open file \"%s\": %m", path)));
     664             :     }
     665             : 
     666     1012732 :     pfree(path);
     667             : 
     668     1012732 :     _fdvec_resize(reln, forknum, 1);
     669     1012732 :     mdfd = &reln->md_seg_fds[forknum][0];
     670     1012732 :     mdfd->mdfd_vfd = fd;
     671     1012732 :     mdfd->mdfd_segno = 0;
     672             : 
     673             :     Assert(_mdnblocks(reln, forknum, mdfd) <= ((BlockNumber) RELSEG_SIZE));
     674             : 
     675     1012732 :     return mdfd;
     676             : }
     677             : 
     678             : /*
     679             :  * mdopen() -- Initialize newly-opened relation.
     680             :  */
     681             : void
     682     1709092 : mdopen(SMgrRelation reln)
     683             : {
     684             :     /* mark it not open */
     685     8545460 :     for (int forknum = 0; forknum <= MAX_FORKNUM; forknum++)
     686     6836368 :         reln->md_num_open_segs[forknum] = 0;
     687     1709092 : }
     688             : 
     689             : /*
     690             :  * mdclose() -- Close the specified relation, if it isn't closed already.
     691             :  */
     692             : void
     693     4270954 : mdclose(SMgrRelation reln, ForkNumber forknum)
     694             : {
     695     4270954 :     int         nopensegs = reln->md_num_open_segs[forknum];
     696             : 
     697             :     /* No work if already closed */
     698     4270954 :     if (nopensegs == 0)
     699     3477440 :         return;
     700             : 
     701             :     /* close segments starting from the end */
     702     1587028 :     while (nopensegs > 0)
     703             :     {
     704      793514 :         MdfdVec    *v = &reln->md_seg_fds[forknum][nopensegs - 1];
     705             : 
     706      793514 :         FileClose(v->mdfd_vfd);
     707      793514 :         _fdvec_resize(reln, forknum, nopensegs - 1);
     708      793514 :         nopensegs--;
     709             :     }
     710             : }
     711             : 
     712             : /*
     713             :  * mdprefetch() -- Initiate asynchronous read of the specified block of a relation
     714             :  */
     715             : bool
     716      248790 : mdprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum)
     717             : {
     718             : #ifdef USE_PREFETCH
     719             :     off_t       seekpos;
     720             :     MdfdVec    *v;
     721             : 
     722             :     Assert((io_direct_flags & IO_DIRECT_DATA) == 0);
     723             : 
     724      248790 :     v = _mdfd_getseg(reln, forknum, blocknum, false,
     725      248790 :                      InRecovery ? EXTENSION_RETURN_NULL : EXTENSION_FAIL);
     726      248790 :     if (v == NULL)
     727           0 :         return false;
     728             : 
     729      248790 :     seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
     730             : 
     731             :     Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
     732             : 
     733      248790 :     (void) FilePrefetch(v->mdfd_vfd, seekpos, BLCKSZ, WAIT_EVENT_DATA_FILE_PREFETCH);
     734             : #endif                          /* USE_PREFETCH */
     735             : 
     736      248790 :     return true;
     737             : }
     738             : 
     739             : /*
     740             :  * mdread() -- Read the specified block from a relation.
     741             :  */
     742             : void
     743     2044574 : mdread(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
     744             :        void *buffer)
     745             : {
     746             :     off_t       seekpos;
     747             :     int         nbytes;
     748             :     MdfdVec    *v;
     749             : 
     750             :     /* If this build supports direct I/O, the buffer must be I/O aligned. */
     751             :     if (PG_O_DIRECT != 0 && PG_IO_ALIGN_SIZE <= BLCKSZ)
     752             :         Assert((uintptr_t) buffer == TYPEALIGN(PG_IO_ALIGN_SIZE, buffer));
     753             : 
     754             :     TRACE_POSTGRESQL_SMGR_MD_READ_START(forknum, blocknum,
     755             :                                         reln->smgr_rlocator.locator.spcOid,
     756             :                                         reln->smgr_rlocator.locator.dbOid,
     757             :                                         reln->smgr_rlocator.locator.relNumber,
     758             :                                         reln->smgr_rlocator.backend);
     759             : 
     760     2044574 :     v = _mdfd_getseg(reln, forknum, blocknum, false,
     761             :                      EXTENSION_FAIL | EXTENSION_CREATE_RECOVERY);
     762             : 
     763     2044544 :     seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
     764             : 
     765             :     Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
     766             : 
     767     2044544 :     nbytes = FileRead(v->mdfd_vfd, buffer, BLCKSZ, seekpos, WAIT_EVENT_DATA_FILE_READ);
     768             : 
     769             :     TRACE_POSTGRESQL_SMGR_MD_READ_DONE(forknum, blocknum,
     770             :                                        reln->smgr_rlocator.locator.spcOid,
     771             :                                        reln->smgr_rlocator.locator.dbOid,
     772             :                                        reln->smgr_rlocator.locator.relNumber,
     773             :                                        reln->smgr_rlocator.backend,
     774             :                                        nbytes,
     775             :                                        BLCKSZ);
     776             : 
     777     2044544 :     if (nbytes != BLCKSZ)
     778             :     {
     779           0 :         if (nbytes < 0)
     780           0 :             ereport(ERROR,
     781             :                     (errcode_for_file_access(),
     782             :                      errmsg("could not read block %u in file \"%s\": %m",
     783             :                             blocknum, FilePathName(v->mdfd_vfd))));
     784             : 
     785             :         /*
     786             :          * Short read: we are at or past EOF, or we read a partial block at
     787             :          * EOF.  Normally this is an error; upper levels should never try to
     788             :          * read a nonexistent block.  However, if zero_damaged_pages is ON or
     789             :          * we are InRecovery, we should instead return zeroes without
     790             :          * complaining.  This allows, for example, the case of trying to
     791             :          * update a block that was later truncated away.
     792             :          */
     793           0 :         if (zero_damaged_pages || InRecovery)
     794           0 :             MemSet(buffer, 0, BLCKSZ);
     795             :         else
     796           0 :             ereport(ERROR,
     797             :                     (errcode(ERRCODE_DATA_CORRUPTED),
     798             :                      errmsg("could not read block %u in file \"%s\": read only %d of %d bytes",
     799             :                             blocknum, FilePathName(v->mdfd_vfd),
     800             :                             nbytes, BLCKSZ)));
     801             :     }
     802     2044544 : }
     803             : 
     804             : /*
     805             :  * mdwrite() -- Write the supplied block at the appropriate location.
     806             :  *
     807             :  * This is to be used only for updating already-existing blocks of a
     808             :  * relation (ie, those before the current EOF).  To extend a relation,
     809             :  * use mdextend().
     810             :  */
     811             : void
     812      846244 : mdwrite(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
     813             :         const void *buffer, bool skipFsync)
     814             : {
     815             :     off_t       seekpos;
     816             :     int         nbytes;
     817             :     MdfdVec    *v;
     818             : 
     819             :     /* If this build supports direct I/O, the buffer must be I/O aligned. */
     820             :     if (PG_O_DIRECT != 0 && PG_IO_ALIGN_SIZE <= BLCKSZ)
     821             :         Assert((uintptr_t) buffer == TYPEALIGN(PG_IO_ALIGN_SIZE, buffer));
     822             : 
     823             :     /* This assert is too expensive to have on normally ... */
     824             : #ifdef CHECK_WRITE_VS_EXTEND
     825             :     Assert(blocknum < mdnblocks(reln, forknum));
     826             : #endif
     827             : 
     828             :     TRACE_POSTGRESQL_SMGR_MD_WRITE_START(forknum, blocknum,
     829             :                                          reln->smgr_rlocator.locator.spcOid,
     830             :                                          reln->smgr_rlocator.locator.dbOid,
     831             :                                          reln->smgr_rlocator.locator.relNumber,
     832             :                                          reln->smgr_rlocator.backend);
     833             : 
     834      846244 :     v = _mdfd_getseg(reln, forknum, blocknum, skipFsync,
     835             :                      EXTENSION_FAIL | EXTENSION_CREATE_RECOVERY);
     836             : 
     837      846244 :     seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
     838             : 
     839             :     Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
     840             : 
     841      846244 :     nbytes = FileWrite(v->mdfd_vfd, buffer, BLCKSZ, seekpos, WAIT_EVENT_DATA_FILE_WRITE);
     842             : 
     843             :     TRACE_POSTGRESQL_SMGR_MD_WRITE_DONE(forknum, blocknum,
     844             :                                         reln->smgr_rlocator.locator.spcOid,
     845             :                                         reln->smgr_rlocator.locator.dbOid,
     846             :                                         reln->smgr_rlocator.locator.relNumber,
     847             :                                         reln->smgr_rlocator.backend,
     848             :                                         nbytes,
     849             :                                         BLCKSZ);
     850             : 
     851      846244 :     if (nbytes != BLCKSZ)
     852             :     {
     853           0 :         if (nbytes < 0)
     854           0 :             ereport(ERROR,
     855             :                     (errcode_for_file_access(),
     856             :                      errmsg("could not write block %u in file \"%s\": %m",
     857             :                             blocknum, FilePathName(v->mdfd_vfd))));
     858             :         /* short write: complain appropriately */
     859           0 :         ereport(ERROR,
     860             :                 (errcode(ERRCODE_DISK_FULL),
     861             :                  errmsg("could not write block %u in file \"%s\": wrote only %d of %d bytes",
     862             :                         blocknum,
     863             :                         FilePathName(v->mdfd_vfd),
     864             :                         nbytes, BLCKSZ),
     865             :                  errhint("Check free disk space.")));
     866             :     }
     867             : 
     868      846244 :     if (!skipFsync && !SmgrIsTemp(reln))
     869      836114 :         register_dirty_segment(reln, forknum, v);
     870      846244 : }
     871             : 
     872             : /*
     873             :  * mdwriteback() -- Tell the kernel to write pages back to storage.
     874             :  *
     875             :  * This accepts a range of blocks because flushing several pages at once is
     876             :  * considerably more efficient than doing so individually.
     877             :  */
     878             : void
     879      125648 : mdwriteback(SMgrRelation reln, ForkNumber forknum,
     880             :             BlockNumber blocknum, BlockNumber nblocks)
     881             : {
     882             :     Assert((io_direct_flags & IO_DIRECT_DATA) == 0);
     883             : 
     884             :     /*
     885             :      * Issue flush requests in as few requests as possible; have to split at
     886             :      * segment boundaries though, since those are actually separate files.
     887             :      */
     888      250610 :     while (nblocks > 0)
     889             :     {
     890      125648 :         BlockNumber nflush = nblocks;
     891             :         off_t       seekpos;
     892             :         MdfdVec    *v;
     893             :         int         segnum_start,
     894             :                     segnum_end;
     895             : 
     896      125648 :         v = _mdfd_getseg(reln, forknum, blocknum, true /* not used */ ,
     897             :                          EXTENSION_DONT_OPEN);
     898             : 
     899             :         /*
     900             :          * We might be flushing buffers of already removed relations, that's
     901             :          * ok, just ignore that case.  If the segment file wasn't open already
     902             :          * (ie from a recent mdwrite()), then we don't want to re-open it, to
     903             :          * avoid a race with PROCSIGNAL_BARRIER_SMGRRELEASE that might leave
     904             :          * us with a descriptor to a file that is about to be unlinked.
     905             :          */
     906      125648 :         if (!v)
     907         686 :             return;
     908             : 
     909             :         /* compute offset inside the current segment */
     910      124962 :         segnum_start = blocknum / RELSEG_SIZE;
     911             : 
     912             :         /* compute number of desired writes within the current segment */
     913      124962 :         segnum_end = (blocknum + nblocks - 1) / RELSEG_SIZE;
     914      124962 :         if (segnum_start != segnum_end)
     915           0 :             nflush = RELSEG_SIZE - (blocknum % ((BlockNumber) RELSEG_SIZE));
     916             : 
     917             :         Assert(nflush >= 1);
     918             :         Assert(nflush <= nblocks);
     919             : 
     920      124962 :         seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
     921             : 
     922      124962 :         FileWriteback(v->mdfd_vfd, seekpos, (off_t) BLCKSZ * nflush, WAIT_EVENT_DATA_FILE_FLUSH);
     923             : 
     924      124962 :         nblocks -= nflush;
     925      124962 :         blocknum += nflush;
     926             :     }
     927             : }
     928             : 
     929             : /*
     930             :  * mdnblocks() -- Get the number of blocks stored in a relation.
     931             :  *
     932             :  * Important side effect: all active segments of the relation are opened
     933             :  * and added to the md_seg_fds array.  If this routine has not been
     934             :  * called, then only segments up to the last one actually touched
     935             :  * are present in the array.
     936             :  */
     937             : BlockNumber
     938     3248606 : mdnblocks(SMgrRelation reln, ForkNumber forknum)
     939             : {
     940             :     MdfdVec    *v;
     941             :     BlockNumber nblocks;
     942             :     BlockNumber segno;
     943             : 
     944     3248606 :     mdopenfork(reln, forknum, EXTENSION_FAIL);
     945             : 
     946             :     /* mdopen has opened the first segment */
     947             :     Assert(reln->md_num_open_segs[forknum] > 0);
     948             : 
     949             :     /*
     950             :      * Start from the last open segments, to avoid redundant seeks.  We have
     951             :      * previously verified that these segments are exactly RELSEG_SIZE long,
     952             :      * and it's useless to recheck that each time.
     953             :      *
     954             :      * NOTE: this assumption could only be wrong if another backend has
     955             :      * truncated the relation.  We rely on higher code levels to handle that
     956             :      * scenario by closing and re-opening the md fd, which is handled via
     957             :      * relcache flush.  (Since the checkpointer doesn't participate in
     958             :      * relcache flush, it could have segment entries for inactive segments;
     959             :      * that's OK because the checkpointer never needs to compute relation
     960             :      * size.)
     961             :      */
     962     3248568 :     segno = reln->md_num_open_segs[forknum] - 1;
     963     3248568 :     v = &reln->md_seg_fds[forknum][segno];
     964             : 
     965             :     for (;;)
     966             :     {
     967     3248568 :         nblocks = _mdnblocks(reln, forknum, v);
     968     3248568 :         if (nblocks > ((BlockNumber) RELSEG_SIZE))
     969           0 :             elog(FATAL, "segment too big");
     970     3248568 :         if (nblocks < ((BlockNumber) RELSEG_SIZE))
     971     3248568 :             return (segno * ((BlockNumber) RELSEG_SIZE)) + nblocks;
     972             : 
     973             :         /*
     974             :          * If segment is exactly RELSEG_SIZE, advance to next one.
     975             :          */
     976           0 :         segno++;
     977             : 
     978             :         /*
     979             :          * We used to pass O_CREAT here, but that has the disadvantage that it
     980             :          * might create a segment which has vanished through some operating
     981             :          * system misadventure.  In such a case, creating the segment here
     982             :          * undermines _mdfd_getseg's attempts to notice and report an error
     983             :          * upon access to a missing segment.
     984             :          */
     985           0 :         v = _mdfd_openseg(reln, forknum, segno, 0);
     986           0 :         if (v == NULL)
     987           0 :             return segno * ((BlockNumber) RELSEG_SIZE);
     988             :     }
     989             : }
     990             : 
     991             : /*
     992             :  * mdtruncate() -- Truncate relation to specified number of blocks.
     993             :  */
     994             : void
     995        1586 : mdtruncate(SMgrRelation reln, ForkNumber forknum, BlockNumber nblocks)
     996             : {
     997             :     BlockNumber curnblk;
     998             :     BlockNumber priorblocks;
     999             :     int         curopensegs;
    1000             : 
    1001             :     /*
    1002             :      * NOTE: mdnblocks makes sure we have opened all active segments, so that
    1003             :      * truncation loop will get them all!
    1004             :      */
    1005        1586 :     curnblk = mdnblocks(reln, forknum);
    1006        1586 :     if (nblocks > curnblk)
    1007             :     {
    1008             :         /* Bogus request ... but no complaint if InRecovery */
    1009           0 :         if (InRecovery)
    1010           0 :             return;
    1011           0 :         ereport(ERROR,
    1012             :                 (errmsg("could not truncate file \"%s\" to %u blocks: it's only %u blocks now",
    1013             :                         relpath(reln->smgr_rlocator, forknum),
    1014             :                         nblocks, curnblk)));
    1015             :     }
    1016        1586 :     if (nblocks == curnblk)
    1017         666 :         return;                 /* no work */
    1018             : 
    1019             :     /*
    1020             :      * Truncate segments, starting at the last one. Starting at the end makes
    1021             :      * managing the memory for the fd array easier, should there be errors.
    1022             :      */
    1023         920 :     curopensegs = reln->md_num_open_segs[forknum];
    1024        1840 :     while (curopensegs > 0)
    1025             :     {
    1026             :         MdfdVec    *v;
    1027             : 
    1028         920 :         priorblocks = (curopensegs - 1) * RELSEG_SIZE;
    1029             : 
    1030         920 :         v = &reln->md_seg_fds[forknum][curopensegs - 1];
    1031             : 
    1032         920 :         if (priorblocks > nblocks)
    1033             :         {
    1034             :             /*
    1035             :              * This segment is no longer active. We truncate the file, but do
    1036             :              * not delete it, for reasons explained in the header comments.
    1037             :              */
    1038           0 :             if (FileTruncate(v->mdfd_vfd, 0, WAIT_EVENT_DATA_FILE_TRUNCATE) < 0)
    1039           0 :                 ereport(ERROR,
    1040             :                         (errcode_for_file_access(),
    1041             :                          errmsg("could not truncate file \"%s\": %m",
    1042             :                                 FilePathName(v->mdfd_vfd))));
    1043             : 
    1044           0 :             if (!SmgrIsTemp(reln))
    1045           0 :                 register_dirty_segment(reln, forknum, v);
    1046             : 
    1047             :             /* we never drop the 1st segment */
    1048             :             Assert(v != &reln->md_seg_fds[forknum][0]);
    1049             : 
    1050           0 :             FileClose(v->mdfd_vfd);
    1051           0 :             _fdvec_resize(reln, forknum, curopensegs - 1);
    1052             :         }
    1053         920 :         else if (priorblocks + ((BlockNumber) RELSEG_SIZE) > nblocks)
    1054             :         {
    1055             :             /*
    1056             :              * This is the last segment we want to keep. Truncate the file to
    1057             :              * the right length. NOTE: if nblocks is exactly a multiple K of
    1058             :              * RELSEG_SIZE, we will truncate the K+1st segment to 0 length but
    1059             :              * keep it. This adheres to the invariant given in the header
    1060             :              * comments.
    1061             :              */
    1062         920 :             BlockNumber lastsegblocks = nblocks - priorblocks;
    1063             : 
    1064         920 :             if (FileTruncate(v->mdfd_vfd, (off_t) lastsegblocks * BLCKSZ, WAIT_EVENT_DATA_FILE_TRUNCATE) < 0)
    1065           0 :                 ereport(ERROR,
    1066             :                         (errcode_for_file_access(),
    1067             :                          errmsg("could not truncate file \"%s\" to %u blocks: %m",
    1068             :                                 FilePathName(v->mdfd_vfd),
    1069             :                                 nblocks)));
    1070         920 :             if (!SmgrIsTemp(reln))
    1071         646 :                 register_dirty_segment(reln, forknum, v);
    1072             :         }
    1073             :         else
    1074             :         {
    1075             :             /*
    1076             :              * We still need this segment, so nothing to do for this and any
    1077             :              * earlier segment.
    1078             :              */
    1079           0 :             break;
    1080             :         }
    1081         920 :         curopensegs--;
    1082             :     }
    1083             : }
    1084             : 
    1085             : /*
    1086             :  * mdimmedsync() -- Immediately sync a relation to stable storage.
    1087             :  *
    1088             :  * Note that only writes already issued are synced; this routine knows
    1089             :  * nothing of dirty buffers that may exist inside the buffer manager.  We
    1090             :  * sync active and inactive segments; smgrDoPendingSyncs() relies on this.
    1091             :  * Consider a relation skipping WAL.  Suppose a checkpoint syncs blocks of
    1092             :  * some segment, then mdtruncate() renders that segment inactive.  If we
    1093             :  * crash before the next checkpoint syncs the newly-inactive segment, that
    1094             :  * segment may survive recovery, reintroducing unwanted data into the table.
    1095             :  */
    1096             : void
    1097       29060 : mdimmedsync(SMgrRelation reln, ForkNumber forknum)
    1098             : {
    1099             :     int         segno;
    1100             :     int         min_inactive_seg;
    1101             : 
    1102             :     /*
    1103             :      * NOTE: mdnblocks makes sure we have opened all active segments, so that
    1104             :      * fsync loop will get them all!
    1105             :      */
    1106       29060 :     mdnblocks(reln, forknum);
    1107             : 
    1108       29060 :     min_inactive_seg = segno = reln->md_num_open_segs[forknum];
    1109             : 
    1110             :     /*
    1111             :      * Temporarily open inactive segments, then close them after sync.  There
    1112             :      * may be some inactive segments left opened after fsync() error, but that
    1113             :      * is harmless.  We don't bother to clean them up and take a risk of
    1114             :      * further trouble.  The next mdclose() will soon close them.
    1115             :      */
    1116       29060 :     while (_mdfd_openseg(reln, forknum, segno, 0) != NULL)
    1117           0 :         segno++;
    1118             : 
    1119       58120 :     while (segno > 0)
    1120             :     {
    1121       29060 :         MdfdVec    *v = &reln->md_seg_fds[forknum][segno - 1];
    1122             : 
    1123             :         /*
    1124             :          * fsyncs done through mdimmedsync() should be tracked in a separate
    1125             :          * IOContext than those done through mdsyncfiletag() to differentiate
    1126             :          * between unavoidable client backend fsyncs (e.g. those done during
    1127             :          * index build) and those which ideally would have been done by the
    1128             :          * checkpointer. Since other IO operations bypassing the buffer
    1129             :          * manager could also be tracked in such an IOContext, wait until
    1130             :          * these are also tracked to track immediate fsyncs.
    1131             :          */
    1132       29060 :         if (FileSync(v->mdfd_vfd, WAIT_EVENT_DATA_FILE_IMMEDIATE_SYNC) < 0)
    1133           0 :             ereport(data_sync_elevel(ERROR),
    1134             :                     (errcode_for_file_access(),
    1135             :                      errmsg("could not fsync file \"%s\": %m",
    1136             :                             FilePathName(v->mdfd_vfd))));
    1137             : 
    1138             :         /* Close inactive segments immediately */
    1139       29060 :         if (segno > min_inactive_seg)
    1140             :         {
    1141           0 :             FileClose(v->mdfd_vfd);
    1142           0 :             _fdvec_resize(reln, forknum, segno - 1);
    1143             :         }
    1144             : 
    1145       29060 :         segno--;
    1146             :     }
    1147       29060 : }
    1148             : 
    1149             : /*
    1150             :  * register_dirty_segment() -- Mark a relation segment as needing fsync
    1151             :  *
    1152             :  * If there is a local pending-ops table, just make an entry in it for
    1153             :  * ProcessSyncRequests to process later.  Otherwise, try to pass off the
    1154             :  * fsync request to the checkpointer process.  If that fails, just do the
    1155             :  * fsync locally before returning (we hope this will not happen often
    1156             :  * enough to be a performance problem).
    1157             :  */
    1158             : static void
    1159     1418760 : register_dirty_segment(SMgrRelation reln, ForkNumber forknum, MdfdVec *seg)
    1160             : {
    1161             :     FileTag     tag;
    1162             : 
    1163     1418760 :     INIT_MD_FILETAG(tag, reln->smgr_rlocator.locator, forknum, seg->mdfd_segno);
    1164             : 
    1165             :     /* Temp relations should never be fsync'd */
    1166             :     Assert(!SmgrIsTemp(reln));
    1167             : 
    1168     1418760 :     if (!RegisterSyncRequest(&tag, SYNC_REQUEST, false /* retryOnError */ ))
    1169             :     {
    1170             :         instr_time  io_start;
    1171             : 
    1172          54 :         ereport(DEBUG1,
    1173             :                 (errmsg_internal("could not forward fsync request because request queue is full")));
    1174             : 
    1175          54 :         io_start = pgstat_prepare_io_time();
    1176             : 
    1177          54 :         if (FileSync(seg->mdfd_vfd, WAIT_EVENT_DATA_FILE_SYNC) < 0)
    1178           0 :             ereport(data_sync_elevel(ERROR),
    1179             :                     (errcode_for_file_access(),
    1180             :                      errmsg("could not fsync file \"%s\": %m",
    1181             :                             FilePathName(seg->mdfd_vfd))));
    1182             : 
    1183             :         /*
    1184             :          * We have no way of knowing if the current IOContext is
    1185             :          * IOCONTEXT_NORMAL or IOCONTEXT_[BULKREAD, BULKWRITE, VACUUM] at this
    1186             :          * point, so count the fsync as being in the IOCONTEXT_NORMAL
    1187             :          * IOContext. This is probably okay, because the number of backend
    1188             :          * fsyncs doesn't say anything about the efficacy of the
    1189             :          * BufferAccessStrategy. And counting both fsyncs done in
    1190             :          * IOCONTEXT_NORMAL and IOCONTEXT_[BULKREAD, BULKWRITE, VACUUM] under
    1191             :          * IOCONTEXT_NORMAL is likely clearer when investigating the number of
    1192             :          * backend fsyncs.
    1193             :          */
    1194          54 :         pgstat_count_io_op_time(IOOBJECT_RELATION, IOCONTEXT_NORMAL,
    1195             :                                 IOOP_FSYNC, io_start, 1);
    1196             :     }
    1197     1418760 : }
    1198             : 
    1199             : /*
    1200             :  * register_unlink_segment() -- Schedule a file to be deleted after next checkpoint
    1201             :  */
    1202             : static void
    1203       57634 : register_unlink_segment(RelFileLocatorBackend rlocator, ForkNumber forknum,
    1204             :                         BlockNumber segno)
    1205             : {
    1206             :     FileTag     tag;
    1207             : 
    1208       57634 :     INIT_MD_FILETAG(tag, rlocator.locator, forknum, segno);
    1209             : 
    1210             :     /* Should never be used with temp relations */
    1211             :     Assert(!RelFileLocatorBackendIsTemp(rlocator));
    1212             : 
    1213       57634 :     RegisterSyncRequest(&tag, SYNC_UNLINK_REQUEST, true /* retryOnError */ );
    1214       57634 : }
    1215             : 
    1216             : /*
    1217             :  * register_forget_request() -- forget any fsyncs for a relation fork's segment
    1218             :  */
    1219             : static void
    1220      221670 : register_forget_request(RelFileLocatorBackend rlocator, ForkNumber forknum,
    1221             :                         BlockNumber segno)
    1222             : {
    1223             :     FileTag     tag;
    1224             : 
    1225      221670 :     INIT_MD_FILETAG(tag, rlocator.locator, forknum, segno);
    1226             : 
    1227      221670 :     RegisterSyncRequest(&tag, SYNC_FORGET_REQUEST, true /* retryOnError */ );
    1228      221670 : }
    1229             : 
    1230             : /*
    1231             :  * ForgetDatabaseSyncRequests -- forget any fsyncs and unlinks for a DB
    1232             :  */
    1233             : void
    1234          70 : ForgetDatabaseSyncRequests(Oid dbid)
    1235             : {
    1236             :     FileTag     tag;
    1237             :     RelFileLocator rlocator;
    1238             : 
    1239          70 :     rlocator.dbOid = dbid;
    1240          70 :     rlocator.spcOid = 0;
    1241          70 :     rlocator.relNumber = 0;
    1242             : 
    1243          70 :     INIT_MD_FILETAG(tag, rlocator, InvalidForkNumber, InvalidBlockNumber);
    1244             : 
    1245          70 :     RegisterSyncRequest(&tag, SYNC_FILTER_REQUEST, true /* retryOnError */ );
    1246          70 : }
    1247             : 
    1248             : /*
    1249             :  * DropRelationFiles -- drop files of all given relations
    1250             :  */
    1251             : void
    1252        4544 : DropRelationFiles(RelFileLocator *delrels, int ndelrels, bool isRedo)
    1253             : {
    1254             :     SMgrRelation *srels;
    1255             :     int         i;
    1256             : 
    1257        4544 :     srels = palloc(sizeof(SMgrRelation) * ndelrels);
    1258       16752 :     for (i = 0; i < ndelrels; i++)
    1259             :     {
    1260       12208 :         SMgrRelation srel = smgropen(delrels[i], InvalidBackendId);
    1261             : 
    1262       12208 :         if (isRedo)
    1263             :         {
    1264             :             ForkNumber  fork;
    1265             : 
    1266       60800 :             for (fork = 0; fork <= MAX_FORKNUM; fork++)
    1267       48640 :                 XLogDropRelation(delrels[i], fork);
    1268             :         }
    1269       12208 :         srels[i] = srel;
    1270             :     }
    1271             : 
    1272        4544 :     smgrdounlinkall(srels, ndelrels, isRedo);
    1273             : 
    1274       16752 :     for (i = 0; i < ndelrels; i++)
    1275       12208 :         smgrclose(srels[i]);
    1276        4544 :     pfree(srels);
    1277        4544 : }
    1278             : 
    1279             : 
    1280             : /*
    1281             :  * _fdvec_resize() -- Resize the fork's open segments array
    1282             :  */
    1283             : static void
    1284     2061476 : _fdvec_resize(SMgrRelation reln,
    1285             :               ForkNumber forknum,
    1286             :               int nseg)
    1287             : {
    1288     2061476 :     if (nseg == 0)
    1289             :     {
    1290      793514 :         if (reln->md_num_open_segs[forknum] > 0)
    1291             :         {
    1292      793514 :             pfree(reln->md_seg_fds[forknum]);
    1293      793514 :             reln->md_seg_fds[forknum] = NULL;
    1294             :         }
    1295             :     }
    1296     1267962 :     else if (reln->md_num_open_segs[forknum] == 0)
    1297             :     {
    1298     1267962 :         reln->md_seg_fds[forknum] =
    1299     1267962 :             MemoryContextAlloc(MdCxt, sizeof(MdfdVec) * nseg);
    1300             :     }
    1301             :     else
    1302             :     {
    1303             :         /*
    1304             :          * It doesn't seem worthwhile complicating the code to amortize
    1305             :          * repalloc() calls.  Those are far faster than PathNameOpenFile() or
    1306             :          * FileClose(), and the memory context internally will sometimes avoid
    1307             :          * doing an actual reallocation.
    1308             :          */
    1309           0 :         reln->md_seg_fds[forknum] =
    1310           0 :             repalloc(reln->md_seg_fds[forknum],
    1311             :                      sizeof(MdfdVec) * nseg);
    1312             :     }
    1313             : 
    1314     2061476 :     reln->md_num_open_segs[forknum] = nseg;
    1315     2061476 : }
    1316             : 
    1317             : /*
    1318             :  * Return the filename for the specified segment of the relation. The
    1319             :  * returned string is palloc'd.
    1320             :  */
    1321             : static char *
    1322       29084 : _mdfd_segpath(SMgrRelation reln, ForkNumber forknum, BlockNumber segno)
    1323             : {
    1324             :     char       *path,
    1325             :                *fullpath;
    1326             : 
    1327       29084 :     path = relpath(reln->smgr_rlocator, forknum);
    1328             : 
    1329       29084 :     if (segno > 0)
    1330             :     {
    1331       29084 :         fullpath = psprintf("%s.%u", path, segno);
    1332       29084 :         pfree(path);
    1333             :     }
    1334             :     else
    1335           0 :         fullpath = path;
    1336             : 
    1337       29084 :     return fullpath;
    1338             : }
    1339             : 
    1340             : /*
    1341             :  * Open the specified segment of the relation,
    1342             :  * and make a MdfdVec object for it.  Returns NULL on failure.
    1343             :  */
    1344             : static MdfdVec *
    1345       29060 : _mdfd_openseg(SMgrRelation reln, ForkNumber forknum, BlockNumber segno,
    1346             :               int oflags)
    1347             : {
    1348             :     MdfdVec    *v;
    1349             :     File        fd;
    1350             :     char       *fullpath;
    1351             : 
    1352       29060 :     fullpath = _mdfd_segpath(reln, forknum, segno);
    1353             : 
    1354             :     /* open the file */
    1355       29060 :     fd = PathNameOpenFile(fullpath, _mdfd_open_flags() | oflags);
    1356             : 
    1357       29060 :     pfree(fullpath);
    1358             : 
    1359       29060 :     if (fd < 0)
    1360       29060 :         return NULL;
    1361             : 
    1362             :     /*
    1363             :      * Segments are always opened in order from lowest to highest, so we must
    1364             :      * be adding a new one at the end.
    1365             :      */
    1366             :     Assert(segno == reln->md_num_open_segs[forknum]);
    1367             : 
    1368           0 :     _fdvec_resize(reln, forknum, segno + 1);
    1369             : 
    1370             :     /* fill the entry */
    1371           0 :     v = &reln->md_seg_fds[forknum][segno];
    1372           0 :     v->mdfd_vfd = fd;
    1373           0 :     v->mdfd_segno = segno;
    1374             : 
    1375             :     Assert(_mdnblocks(reln, forknum, v) <= ((BlockNumber) RELSEG_SIZE));
    1376             : 
    1377             :     /* all done */
    1378           0 :     return v;
    1379             : }
    1380             : 
    1381             : /*
    1382             :  * _mdfd_getseg() -- Find the segment of the relation holding the
    1383             :  *                   specified block.
    1384             :  *
    1385             :  * If the segment doesn't exist, we ereport, return NULL, or create the
    1386             :  * segment, according to "behavior".  Note: skipFsync is only used in the
    1387             :  * EXTENSION_CREATE case.
    1388             :  */
    1389             : static MdfdVec *
    1390     3810712 : _mdfd_getseg(SMgrRelation reln, ForkNumber forknum, BlockNumber blkno,
    1391             :              bool skipFsync, int behavior)
    1392             : {
    1393             :     MdfdVec    *v;
    1394             :     BlockNumber targetseg;
    1395             :     BlockNumber nextsegno;
    1396             : 
    1397             :     /* some way to handle non-existent segments needs to be specified */
    1398             :     Assert(behavior &
    1399             :            (EXTENSION_FAIL | EXTENSION_CREATE | EXTENSION_RETURN_NULL |
    1400             :             EXTENSION_DONT_OPEN));
    1401             : 
    1402     3810712 :     targetseg = blkno / ((BlockNumber) RELSEG_SIZE);
    1403             : 
    1404             :     /* if an existing and opened segment, we're done */
    1405     3810712 :     if (targetseg < reln->md_num_open_segs[forknum])
    1406             :     {
    1407     3476668 :         v = &reln->md_seg_fds[forknum][targetseg];
    1408     3476668 :         return v;
    1409             :     }
    1410             : 
    1411             :     /* The caller only wants the segment if we already had it open. */
    1412      334044 :     if (behavior & EXTENSION_DONT_OPEN)
    1413         686 :         return NULL;
    1414             : 
    1415             :     /*
    1416             :      * The target segment is not yet open. Iterate over all the segments
    1417             :      * between the last opened and the target segment. This way missing
    1418             :      * segments either raise an error, or get created (according to
    1419             :      * 'behavior'). Start with either the last opened, or the first segment if
    1420             :      * none was opened before.
    1421             :      */
    1422      333358 :     if (reln->md_num_open_segs[forknum] > 0)
    1423          24 :         v = &reln->md_seg_fds[forknum][reln->md_num_open_segs[forknum] - 1];
    1424             :     else
    1425             :     {
    1426      333334 :         v = mdopenfork(reln, forknum, behavior);
    1427      333328 :         if (!v)
    1428           0 :             return NULL;        /* if behavior & EXTENSION_RETURN_NULL */
    1429             :     }
    1430             : 
    1431      333352 :     for (nextsegno = reln->md_num_open_segs[forknum];
    1432           0 :          nextsegno <= targetseg; nextsegno++)
    1433             :     {
    1434          24 :         BlockNumber nblocks = _mdnblocks(reln, forknum, v);
    1435          24 :         int         flags = 0;
    1436             : 
    1437             :         Assert(nextsegno == v->mdfd_segno + 1);
    1438             : 
    1439          24 :         if (nblocks > ((BlockNumber) RELSEG_SIZE))
    1440           0 :             elog(FATAL, "segment too big");
    1441             : 
    1442          24 :         if ((behavior & EXTENSION_CREATE) ||
    1443          24 :             (InRecovery && (behavior & EXTENSION_CREATE_RECOVERY)))
    1444             :         {
    1445             :             /*
    1446             :              * Normally we will create new segments only if authorized by the
    1447             :              * caller (i.e., we are doing mdextend()).  But when doing WAL
    1448             :              * recovery, create segments anyway; this allows cases such as
    1449             :              * replaying WAL data that has a write into a high-numbered
    1450             :              * segment of a relation that was later deleted. We want to go
    1451             :              * ahead and create the segments so we can finish out the replay.
    1452             :              *
    1453             :              * We have to maintain the invariant that segments before the last
    1454             :              * active segment are of size RELSEG_SIZE; therefore, if
    1455             :              * extending, pad them out with zeroes if needed.  (This only
    1456             :              * matters if in recovery, or if the caller is extending the
    1457             :              * relation discontiguously, but that can happen in hash indexes.)
    1458             :              */
    1459           0 :             if (nblocks < ((BlockNumber) RELSEG_SIZE))
    1460             :             {
    1461           0 :                 char       *zerobuf = palloc_aligned(BLCKSZ, PG_IO_ALIGN_SIZE,
    1462             :                                                      MCXT_ALLOC_ZERO);
    1463             : 
    1464           0 :                 mdextend(reln, forknum,
    1465           0 :                          nextsegno * ((BlockNumber) RELSEG_SIZE) - 1,
    1466             :                          zerobuf, skipFsync);
    1467           0 :                 pfree(zerobuf);
    1468             :             }
    1469           0 :             flags = O_CREAT;
    1470             :         }
    1471          24 :         else if (!(behavior & EXTENSION_DONT_CHECK_SIZE) &&
    1472             :                  nblocks < ((BlockNumber) RELSEG_SIZE))
    1473             :         {
    1474             :             /*
    1475             :              * When not extending (or explicitly including truncated
    1476             :              * segments), only open the next segment if the current one is
    1477             :              * exactly RELSEG_SIZE.  If not (this branch), either return NULL
    1478             :              * or fail.
    1479             :              */
    1480          24 :             if (behavior & EXTENSION_RETURN_NULL)
    1481             :             {
    1482             :                 /*
    1483             :                  * Some callers discern between reasons for _mdfd_getseg()
    1484             :                  * returning NULL based on errno. As there's no failing
    1485             :                  * syscall involved in this case, explicitly set errno to
    1486             :                  * ENOENT, as that seems the closest interpretation.
    1487             :                  */
    1488           0 :                 errno = ENOENT;
    1489           0 :                 return NULL;
    1490             :             }
    1491             : 
    1492          24 :             ereport(ERROR,
    1493             :                     (errcode_for_file_access(),
    1494             :                      errmsg("could not open file \"%s\" (target block %u): previous segment is only %u blocks",
    1495             :                             _mdfd_segpath(reln, forknum, nextsegno),
    1496             :                             blkno, nblocks)));
    1497             :         }
    1498             : 
    1499           0 :         v = _mdfd_openseg(reln, forknum, nextsegno, flags);
    1500             : 
    1501           0 :         if (v == NULL)
    1502             :         {
    1503           0 :             if ((behavior & EXTENSION_RETURN_NULL) &&
    1504           0 :                 FILE_POSSIBLY_DELETED(errno))
    1505           0 :                 return NULL;
    1506           0 :             ereport(ERROR,
    1507             :                     (errcode_for_file_access(),
    1508             :                      errmsg("could not open file \"%s\" (target block %u): %m",
    1509             :                             _mdfd_segpath(reln, forknum, nextsegno),
    1510             :                             blkno)));
    1511             :         }
    1512             :     }
    1513             : 
    1514      333328 :     return v;
    1515             : }
    1516             : 
    1517             : /*
    1518             :  * Get number of blocks present in a single disk file
    1519             :  */
    1520             : static BlockNumber
    1521     3248592 : _mdnblocks(SMgrRelation reln, ForkNumber forknum, MdfdVec *seg)
    1522             : {
    1523             :     off_t       len;
    1524             : 
    1525     3248592 :     len = FileSize(seg->mdfd_vfd);
    1526     3248592 :     if (len < 0)
    1527           0 :         ereport(ERROR,
    1528             :                 (errcode_for_file_access(),
    1529             :                  errmsg("could not seek to end of file \"%s\": %m",
    1530             :                         FilePathName(seg->mdfd_vfd))));
    1531             :     /* note that this calculation will ignore any partial block at EOF */
    1532     3248592 :     return (BlockNumber) (len / BLCKSZ);
    1533             : }
    1534             : 
    1535             : /*
    1536             :  * Sync a file to disk, given a file tag.  Write the path into an output
    1537             :  * buffer so the caller can use it in error messages.
    1538             :  *
    1539             :  * Return 0 on success, -1 on failure, with errno set.
    1540             :  */
    1541             : int
    1542           0 : mdsyncfiletag(const FileTag *ftag, char *path)
    1543             : {
    1544           0 :     SMgrRelation reln = smgropen(ftag->rlocator, InvalidBackendId);
    1545             :     File        file;
    1546             :     instr_time  io_start;
    1547             :     bool        need_to_close;
    1548             :     int         result,
    1549             :                 save_errno;
    1550             : 
    1551             :     /* See if we already have the file open, or need to open it. */
    1552           0 :     if (ftag->segno < reln->md_num_open_segs[ftag->forknum])
    1553             :     {
    1554           0 :         file = reln->md_seg_fds[ftag->forknum][ftag->segno].mdfd_vfd;
    1555           0 :         strlcpy(path, FilePathName(file), MAXPGPATH);
    1556           0 :         need_to_close = false;
    1557             :     }
    1558             :     else
    1559             :     {
    1560             :         char       *p;
    1561             : 
    1562           0 :         p = _mdfd_segpath(reln, ftag->forknum, ftag->segno);
    1563           0 :         strlcpy(path, p, MAXPGPATH);
    1564           0 :         pfree(p);
    1565             : 
    1566           0 :         file = PathNameOpenFile(path, _mdfd_open_flags());
    1567           0 :         if (file < 0)
    1568           0 :             return -1;
    1569           0 :         need_to_close = true;
    1570             :     }
    1571             : 
    1572           0 :     io_start = pgstat_prepare_io_time();
    1573             : 
    1574             :     /* Sync the file. */
    1575           0 :     result = FileSync(file, WAIT_EVENT_DATA_FILE_SYNC);
    1576           0 :     save_errno = errno;
    1577             : 
    1578           0 :     if (need_to_close)
    1579           0 :         FileClose(file);
    1580             : 
    1581           0 :     pgstat_count_io_op_time(IOOBJECT_RELATION, IOCONTEXT_NORMAL,
    1582             :                             IOOP_FSYNC, io_start, 1);
    1583             : 
    1584           0 :     errno = save_errno;
    1585           0 :     return result;
    1586             : }
    1587             : 
    1588             : /*
    1589             :  * Unlink a file, given a file tag.  Write the path into an output
    1590             :  * buffer so the caller can use it in error messages.
    1591             :  *
    1592             :  * Return 0 on success, -1 on failure, with errno set.
    1593             :  */
    1594             : int
    1595       55520 : mdunlinkfiletag(const FileTag *ftag, char *path)
    1596             : {
    1597             :     char       *p;
    1598             : 
    1599             :     /* Compute the path. */
    1600       55520 :     p = relpathperm(ftag->rlocator, MAIN_FORKNUM);
    1601       55520 :     strlcpy(path, p, MAXPGPATH);
    1602       55520 :     pfree(p);
    1603             : 
    1604             :     /* Try to unlink the file. */
    1605       55520 :     return unlink(path);
    1606             : }
    1607             : 
    1608             : /*
    1609             :  * Check if a given candidate request matches a given tag, when processing
    1610             :  * a SYNC_FILTER_REQUEST request.  This will be called for all pending
    1611             :  * requests to find out whether to forget them.
    1612             :  */
    1613             : bool
    1614       12314 : mdfiletagmatches(const FileTag *ftag, const FileTag *candidate)
    1615             : {
    1616             :     /*
    1617             :      * For now we only use filter requests as a way to drop all scheduled
    1618             :      * callbacks relating to a given database, when dropping the database.
    1619             :      * We'll return true for all candidates that have the same database OID as
    1620             :      * the ftag from the SYNC_FILTER_REQUEST request, so they're forgotten.
    1621             :      */
    1622       12314 :     return ftag->rlocator.dbOid == candidate->rlocator.dbOid;
    1623             : }

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