LCOV - code coverage report
Current view: top level - src/backend/storage/smgr - md.c (source / functions) Hit Total Coverage
Test: PostgreSQL 11devel Lines: 325 451 72.1 %
Date: 2018-05-21 18:20:01 Functions: 27 29 93.1 %
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) 1996-2018, 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 "miscadmin.h"
      29             : #include "access/xlog.h"
      30             : #include "pgstat.h"
      31             : #include "portability/instr_time.h"
      32             : #include "postmaster/bgwriter.h"
      33             : #include "storage/fd.h"
      34             : #include "storage/bufmgr.h"
      35             : #include "storage/relfilenode.h"
      36             : #include "storage/smgr.h"
      37             : #include "utils/hsearch.h"
      38             : #include "utils/memutils.h"
      39             : #include "pg_trace.h"
      40             : 
      41             : 
      42             : /* intervals for calling AbsorbFsyncRequests in mdsync and mdpostckpt */
      43             : #define FSYNCS_PER_ABSORB       10
      44             : #define UNLINKS_PER_ABSORB      10
      45             : 
      46             : /*
      47             :  * Special values for the segno arg to RememberFsyncRequest.
      48             :  *
      49             :  * Note that CompactCheckpointerRequestQueue assumes that it's OK to remove an
      50             :  * fsync request from the queue if an identical, subsequent request is found.
      51             :  * See comments there before making changes here.
      52             :  */
      53             : #define FORGET_RELATION_FSYNC   (InvalidBlockNumber)
      54             : #define FORGET_DATABASE_FSYNC   (InvalidBlockNumber-1)
      55             : #define UNLINK_RELATION_REQUEST (InvalidBlockNumber-2)
      56             : 
      57             : /*
      58             :  * On Windows, we have to interpret EACCES as possibly meaning the same as
      59             :  * ENOENT, because if a file is unlinked-but-not-yet-gone on that platform,
      60             :  * that's what you get.  Ugh.  This code is designed so that we don't
      61             :  * actually believe these cases are okay without further evidence (namely,
      62             :  * a pending fsync request getting canceled ... see mdsync).
      63             :  */
      64             : #ifndef WIN32
      65             : #define FILE_POSSIBLY_DELETED(err)  ((err) == ENOENT)
      66             : #else
      67             : #define FILE_POSSIBLY_DELETED(err)  ((err) == ENOENT || (err) == EACCES)
      68             : #endif
      69             : 
      70             : /*
      71             :  *  The magnetic disk storage manager keeps track of open file
      72             :  *  descriptors in its own descriptor pool.  This is done to make it
      73             :  *  easier to support relations that are larger than the operating
      74             :  *  system's file size limit (often 2GBytes).  In order to do that,
      75             :  *  we break relations up into "segment" files that are each shorter than
      76             :  *  the OS file size limit.  The segment size is set by the RELSEG_SIZE
      77             :  *  configuration constant in pg_config.h.
      78             :  *
      79             :  *  On disk, a relation must consist of consecutively numbered segment
      80             :  *  files in the pattern
      81             :  *      -- Zero or more full segments of exactly RELSEG_SIZE blocks each
      82             :  *      -- Exactly one partial segment of size 0 <= size < RELSEG_SIZE blocks
      83             :  *      -- Optionally, any number of inactive segments of size 0 blocks.
      84             :  *  The full and partial segments are collectively the "active" segments.
      85             :  *  Inactive segments are those that once contained data but are currently
      86             :  *  not needed because of an mdtruncate() operation.  The reason for leaving
      87             :  *  them present at size zero, rather than unlinking them, is that other
      88             :  *  backends and/or the checkpointer might be holding open file references to
      89             :  *  such segments.  If the relation expands again after mdtruncate(), such
      90             :  *  that a deactivated segment becomes active again, it is important that
      91             :  *  such file references still be valid --- else data might get written
      92             :  *  out to an unlinked old copy of a segment file that will eventually
      93             :  *  disappear.
      94             :  *
      95             :  *  File descriptors are stored in the per-fork md_seg_fds arrays inside
      96             :  *  SMgrRelation. The length of these arrays is stored in md_num_open_segs.
      97             :  *  Note that a fork's md_num_open_segs having a specific value does not
      98             :  *  necessarily mean the relation doesn't have additional segments; we may
      99             :  *  just not have opened the next segment yet.  (We could not have "all
     100             :  *  segments are in the array" as an invariant anyway, since another backend
     101             :  *  could extend the relation while we aren't looking.)  We do not have
     102             :  *  entries for inactive segments, however; as soon as we find a partial
     103             :  *  segment, we assume that any subsequent segments are inactive.
     104             :  *
     105             :  *  The entire MdfdVec array is palloc'd in the MdCxt memory context.
     106             :  */
     107             : 
     108             : typedef struct _MdfdVec
     109             : {
     110             :     File        mdfd_vfd;       /* fd number in fd.c's pool */
     111             :     BlockNumber mdfd_segno;     /* segment number, from 0 */
     112             : } MdfdVec;
     113             : 
     114             : static MemoryContext MdCxt;     /* context for all MdfdVec objects */
     115             : 
     116             : 
     117             : /*
     118             :  * In some contexts (currently, standalone backends and the checkpointer)
     119             :  * we keep track of pending fsync operations: we need to remember all relation
     120             :  * segments that have been written since the last checkpoint, so that we can
     121             :  * fsync them down to disk before completing the next checkpoint.  This hash
     122             :  * table remembers the pending operations.  We use a hash table mostly as
     123             :  * a convenient way of merging duplicate requests.
     124             :  *
     125             :  * We use a similar mechanism to remember no-longer-needed files that can
     126             :  * be deleted after the next checkpoint, but we use a linked list instead of
     127             :  * a hash table, because we don't expect there to be any duplicate requests.
     128             :  *
     129             :  * These mechanisms are only used for non-temp relations; we never fsync
     130             :  * temp rels, nor do we need to postpone their deletion (see comments in
     131             :  * mdunlink).
     132             :  *
     133             :  * (Regular backends do not track pending operations locally, but forward
     134             :  * them to the checkpointer.)
     135             :  */
     136             : typedef uint16 CycleCtr;        /* can be any convenient integer size */
     137             : 
     138             : typedef struct
     139             : {
     140             :     RelFileNode rnode;          /* hash table key (must be first!) */
     141             :     CycleCtr    cycle_ctr;      /* mdsync_cycle_ctr of oldest request */
     142             :     /* requests[f] has bit n set if we need to fsync segment n of fork f */
     143             :     Bitmapset  *requests[MAX_FORKNUM + 1];
     144             :     /* canceled[f] is true if we canceled fsyncs for fork "recently" */
     145             :     bool        canceled[MAX_FORKNUM + 1];
     146             : } PendingOperationEntry;
     147             : 
     148             : typedef struct
     149             : {
     150             :     RelFileNode rnode;          /* the dead relation to delete */
     151             :     CycleCtr    cycle_ctr;      /* mdckpt_cycle_ctr when request was made */
     152             : } PendingUnlinkEntry;
     153             : 
     154             : static HTAB *pendingOpsTable = NULL;
     155             : static List *pendingUnlinks = NIL;
     156             : static MemoryContext pendingOpsCxt; /* context for the above  */
     157             : 
     158             : static CycleCtr mdsync_cycle_ctr = 0;
     159             : static CycleCtr mdckpt_cycle_ctr = 0;
     160             : 
     161             : 
     162             : /*** behavior for mdopen & _mdfd_getseg ***/
     163             : /* ereport if segment not present */
     164             : #define EXTENSION_FAIL              (1 << 0)
     165             : /* return NULL if segment not present */
     166             : #define EXTENSION_RETURN_NULL       (1 << 1)
     167             : /* create new segments as needed */
     168             : #define EXTENSION_CREATE            (1 << 2)
     169             : /* create new segments if needed during recovery */
     170             : #define EXTENSION_CREATE_RECOVERY   (1 << 3)
     171             : /*
     172             :  * Allow opening segments which are preceded by segments smaller than
     173             :  * RELSEG_SIZE, e.g. inactive segments (see above). Note that this is breaks
     174             :  * mdnblocks() and related functionality henceforth - which currently is ok,
     175             :  * because this is only required in the checkpointer which never uses
     176             :  * mdnblocks().
     177             :  */
     178             : #define EXTENSION_DONT_CHECK_SIZE   (1 << 4)
     179             : 
     180             : 
     181             : /* local routines */
     182             : static void mdunlinkfork(RelFileNodeBackend rnode, ForkNumber forkNum,
     183             :              bool isRedo);
     184             : static MdfdVec *mdopen(SMgrRelation reln, ForkNumber forknum, int behavior);
     185             : static void register_dirty_segment(SMgrRelation reln, ForkNumber forknum,
     186             :                        MdfdVec *seg);
     187             : static void register_unlink(RelFileNodeBackend rnode);
     188             : static void _fdvec_resize(SMgrRelation reln,
     189             :               ForkNumber forknum,
     190             :               int nseg);
     191             : static char *_mdfd_segpath(SMgrRelation reln, ForkNumber forknum,
     192             :               BlockNumber segno);
     193             : static MdfdVec *_mdfd_openseg(SMgrRelation reln, ForkNumber forkno,
     194             :               BlockNumber segno, int oflags);
     195             : static MdfdVec *_mdfd_getseg(SMgrRelation reln, ForkNumber forkno,
     196             :              BlockNumber blkno, bool skipFsync, int behavior);
     197             : static BlockNumber _mdnblocks(SMgrRelation reln, ForkNumber forknum,
     198             :            MdfdVec *seg);
     199             : 
     200             : 
     201             : /*
     202             :  *  mdinit() -- Initialize private state for magnetic disk storage manager.
     203             :  */
     204             : void
     205       11840 : mdinit(void)
     206             : {
     207       11840 :     MdCxt = AllocSetContextCreate(TopMemoryContext,
     208             :                                   "MdSmgr",
     209             :                                   ALLOCSET_DEFAULT_SIZES);
     210             : 
     211             :     /*
     212             :      * Create pending-operations hashtable if we need it.  Currently, we need
     213             :      * it if we are standalone (not under a postmaster) or if we are a startup
     214             :      * or checkpointer auxiliary process.
     215             :      */
     216       11840 :     if (!IsUnderPostmaster || AmStartupProcess() || AmCheckpointerProcess())
     217             :     {
     218             :         HASHCTL     hash_ctl;
     219             : 
     220             :         /*
     221             :          * XXX: The checkpointer needs to add entries to the pending ops table
     222             :          * when absorbing fsync requests.  That is done within a critical
     223             :          * section, which isn't usually allowed, but we make an exception. It
     224             :          * means that there's a theoretical possibility that you run out of
     225             :          * memory while absorbing fsync requests, which leads to a PANIC.
     226             :          * Fortunately the hash table is small so that's unlikely to happen in
     227             :          * practice.
     228             :          */
     229        2180 :         pendingOpsCxt = AllocSetContextCreate(MdCxt,
     230             :                                               "Pending ops context",
     231             :                                               ALLOCSET_DEFAULT_SIZES);
     232        2180 :         MemoryContextAllowInCriticalSection(pendingOpsCxt, true);
     233             : 
     234        2180 :         MemSet(&hash_ctl, 0, sizeof(hash_ctl));
     235        2180 :         hash_ctl.keysize = sizeof(RelFileNode);
     236        2180 :         hash_ctl.entrysize = sizeof(PendingOperationEntry);
     237        2180 :         hash_ctl.hcxt = pendingOpsCxt;
     238        2180 :         pendingOpsTable = hash_create("Pending Ops Table",
     239             :                                       100L,
     240             :                                       &hash_ctl,
     241             :                                       HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
     242        2180 :         pendingUnlinks = NIL;
     243             :     }
     244       11840 : }
     245             : 
     246             : /*
     247             :  * In archive recovery, we rely on checkpointer to do fsyncs, but we will have
     248             :  * already created the pendingOpsTable during initialization of the startup
     249             :  * process.  Calling this function drops the local pendingOpsTable so that
     250             :  * subsequent requests will be forwarded to checkpointer.
     251             :  */
     252             : void
     253         124 : SetForwardFsyncRequests(void)
     254             : {
     255             :     /* Perform any pending fsyncs we may have queued up, then drop table */
     256         124 :     if (pendingOpsTable)
     257             :     {
     258         124 :         mdsync();
     259         124 :         hash_destroy(pendingOpsTable);
     260             :     }
     261         124 :     pendingOpsTable = NULL;
     262             : 
     263             :     /*
     264             :      * We should not have any pending unlink requests, since mdunlink doesn't
     265             :      * queue unlink requests when isRedo.
     266             :      */
     267             :     Assert(pendingUnlinks == NIL);
     268         124 : }
     269             : 
     270             : /*
     271             :  *  mdexists() -- Does the physical file exist?
     272             :  *
     273             :  * Note: this will return true for lingering files, with pending deletions
     274             :  */
     275             : bool
     276      293308 : mdexists(SMgrRelation reln, ForkNumber forkNum)
     277             : {
     278             :     /*
     279             :      * Close it first, to ensure that we notice if the fork has been unlinked
     280             :      * since we opened it.
     281             :      */
     282      293308 :     mdclose(reln, forkNum);
     283             : 
     284      293308 :     return (mdopen(reln, forkNum, EXTENSION_RETURN_NULL) != NULL);
     285             : }
     286             : 
     287             : /*
     288             :  *  mdcreate() -- Create a new relation on magnetic disk.
     289             :  *
     290             :  * If isRedo is true, it's okay for the relation to exist already.
     291             :  */
     292             : void
     293      117388 : mdcreate(SMgrRelation reln, ForkNumber forkNum, bool isRedo)
     294             : {
     295             :     MdfdVec    *mdfd;
     296             :     char       *path;
     297             :     File        fd;
     298             : 
     299      117388 :     if (isRedo && reln->md_num_open_segs[forkNum] > 0)
     300           0 :         return;                 /* created and opened already... */
     301             : 
     302             :     Assert(reln->md_num_open_segs[forkNum] == 0);
     303             : 
     304      117388 :     path = relpath(reln->smgr_rnode, forkNum);
     305             : 
     306      117388 :     fd = PathNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
     307             : 
     308      117388 :     if (fd < 0)
     309             :     {
     310        1000 :         int         save_errno = errno;
     311             : 
     312             :         /*
     313             :          * During bootstrap, there are cases where a system relation will be
     314             :          * accessed (by internal backend processes) before the bootstrap
     315             :          * script nominally creates it.  Therefore, allow the file to exist
     316             :          * already, even if isRedo is not set.  (See also mdopen)
     317             :          */
     318        1000 :         if (isRedo || IsBootstrapProcessingMode())
     319        1000 :             fd = PathNameOpenFile(path, O_RDWR | PG_BINARY);
     320        1000 :         if (fd < 0)
     321             :         {
     322             :             /* be sure to report the error reported by create, not open */
     323           0 :             errno = save_errno;
     324           0 :             ereport(ERROR,
     325             :                     (errcode_for_file_access(),
     326             :                      errmsg("could not create file \"%s\": %m", path)));
     327             :         }
     328             :     }
     329             : 
     330      117388 :     pfree(path);
     331             : 
     332      117388 :     _fdvec_resize(reln, forkNum, 1);
     333      117388 :     mdfd = &reln->md_seg_fds[forkNum][0];
     334      117388 :     mdfd->mdfd_vfd = fd;
     335      117388 :     mdfd->mdfd_segno = 0;
     336             : }
     337             : 
     338             : /*
     339             :  *  mdunlink() -- Unlink a relation.
     340             :  *
     341             :  * Note that we're passed a RelFileNodeBackend --- by the time this is called,
     342             :  * there won't be an SMgrRelation hashtable entry anymore.
     343             :  *
     344             :  * forkNum can be a fork number to delete a specific fork, or InvalidForkNumber
     345             :  * to delete all forks.
     346             :  *
     347             :  * For regular relations, we don't unlink the first segment file of the rel,
     348             :  * but just truncate it to zero length, and record a request to unlink it after
     349             :  * the next checkpoint.  Additional segments can be unlinked immediately,
     350             :  * however.  Leaving the empty file in place prevents that relfilenode
     351             :  * number from being reused.  The scenario this protects us from is:
     352             :  * 1. We delete a relation (and commit, and actually remove its file).
     353             :  * 2. We create a new relation, which by chance gets the same relfilenode as
     354             :  *    the just-deleted one (OIDs must've wrapped around for that to happen).
     355             :  * 3. We crash before another checkpoint occurs.
     356             :  * During replay, we would delete the file and then recreate it, which is fine
     357             :  * if the contents of the file were repopulated by subsequent WAL entries.
     358             :  * But if we didn't WAL-log insertions, but instead relied on fsyncing the
     359             :  * file after populating it (as for instance CLUSTER and CREATE INDEX do),
     360             :  * the contents of the file would be lost forever.  By leaving the empty file
     361             :  * until after the next checkpoint, we prevent reassignment of the relfilenode
     362             :  * number until it's safe, because relfilenode assignment skips over any
     363             :  * existing file.
     364             :  *
     365             :  * We do not need to go through this dance for temp relations, though, because
     366             :  * we never make WAL entries for temp rels, and so a temp rel poses no threat
     367             :  * to the health of a regular rel that has taken over its relfilenode number.
     368             :  * The fact that temp rels and regular rels have different file naming
     369             :  * patterns provides additional safety.
     370             :  *
     371             :  * All the above applies only to the relation's main fork; other forks can
     372             :  * just be removed immediately, since they are not needed to prevent the
     373             :  * relfilenode number from being recycled.  Also, we do not carefully
     374             :  * track whether other forks have been created or not, but just attempt to
     375             :  * unlink them unconditionally; so we should never complain about ENOENT.
     376             :  *
     377             :  * If isRedo is true, it's unsurprising for the relation to be already gone.
     378             :  * Also, we should remove the file immediately instead of queuing a request
     379             :  * for later, since during redo there's no possibility of creating a
     380             :  * conflicting relation.
     381             :  *
     382             :  * Note: any failure should be reported as WARNING not ERROR, because
     383             :  * we are usually not in a transaction anymore when this is called.
     384             :  */
     385             : void
     386      136258 : mdunlink(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
     387             : {
     388             :     /*
     389             :      * We have to clean out any pending fsync requests for the doomed
     390             :      * relation, else the next mdsync() will fail.  There can't be any such
     391             :      * requests for a temp relation, though.  We can send just one request
     392             :      * even when deleting multiple forks, since the fsync queuing code accepts
     393             :      * the "InvalidForkNumber = all forks" convention.
     394             :      */
     395      136258 :     if (!RelFileNodeBackendIsTemp(rnode))
     396      119154 :         ForgetRelationFsyncRequests(rnode.node, forkNum);
     397             : 
     398             :     /* Now do the per-fork work */
     399      136258 :     if (forkNum == InvalidForkNumber)
     400             :     {
     401          10 :         for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++)
     402           8 :             mdunlinkfork(rnode, forkNum, isRedo);
     403             :     }
     404             :     else
     405      136256 :         mdunlinkfork(rnode, forkNum, isRedo);
     406      136258 : }
     407             : 
     408             : static void
     409      136264 : mdunlinkfork(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo)
     410             : {
     411             :     char       *path;
     412             :     int         ret;
     413             : 
     414      136264 :     path = relpath(rnode, forkNum);
     415             : 
     416             :     /*
     417             :      * Delete or truncate the first segment.
     418             :      */
     419      136264 :     if (isRedo || forkNum != MAIN_FORKNUM || RelFileNodeBackendIsTemp(rnode))
     420             :     {
     421      106474 :         ret = unlink(path);
     422      212948 :         if (ret < 0 && errno != ENOENT)
     423           0 :             ereport(WARNING,
     424             :                     (errcode_for_file_access(),
     425             :                      errmsg("could not remove file \"%s\": %m", path)));
     426             :     }
     427             :     else
     428             :     {
     429             :         /* truncate(2) would be easier here, but Windows hasn't got it */
     430             :         int         fd;
     431             : 
     432       29790 :         fd = OpenTransientFile(path, O_RDWR | PG_BINARY);
     433       29790 :         if (fd >= 0)
     434             :         {
     435             :             int         save_errno;
     436             : 
     437       29790 :             ret = ftruncate(fd, 0);
     438       29790 :             save_errno = errno;
     439       29790 :             CloseTransientFile(fd);
     440       29790 :             errno = save_errno;
     441             :         }
     442             :         else
     443           0 :             ret = -1;
     444       29790 :         if (ret < 0 && errno != ENOENT)
     445           0 :             ereport(WARNING,
     446             :                     (errcode_for_file_access(),
     447             :                      errmsg("could not truncate file \"%s\": %m", path)));
     448             : 
     449             :         /* Register request to unlink first segment later */
     450       29790 :         register_unlink(rnode);
     451             :     }
     452             : 
     453             :     /*
     454             :      * Delete any additional segments.
     455             :      */
     456      136264 :     if (ret >= 0)
     457             :     {
     458       35902 :         char       *segpath = (char *) palloc(strlen(path) + 12);
     459             :         BlockNumber segno;
     460             : 
     461             :         /*
     462             :          * Note that because we loop until getting ENOENT, we will correctly
     463             :          * remove all inactive segments as well as active ones.
     464             :          */
     465       35902 :         for (segno = 1;; segno++)
     466             :         {
     467       35902 :             sprintf(segpath, "%s.%u", path, segno);
     468       35902 :             if (unlink(segpath) < 0)
     469             :             {
     470             :                 /* ENOENT is expected after the last segment... */
     471       35902 :                 if (errno != ENOENT)
     472           0 :                     ereport(WARNING,
     473             :                             (errcode_for_file_access(),
     474             :                              errmsg("could not remove file \"%s\": %m", segpath)));
     475       35902 :                 break;
     476             :             }
     477             :         }
     478       35902 :         pfree(segpath);
     479             :     }
     480             : 
     481      136264 :     pfree(path);
     482      136264 : }
     483             : 
     484             : /*
     485             :  *  mdextend() -- Add a block to the specified relation.
     486             :  *
     487             :  *      The semantics are nearly the same as mdwrite(): write at the
     488             :  *      specified position.  However, this is to be used for the case of
     489             :  *      extending a relation (i.e., blocknum is at or beyond the current
     490             :  *      EOF).  Note that we assume writing a block beyond current EOF
     491             :  *      causes intervening file space to become filled with zeroes.
     492             :  */
     493             : void
     494      514226 : mdextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
     495             :          char *buffer, bool skipFsync)
     496             : {
     497             :     off_t       seekpos;
     498             :     int         nbytes;
     499             :     MdfdVec    *v;
     500             : 
     501             :     /* This assert is too expensive to have on normally ... */
     502             : #ifdef CHECK_WRITE_VS_EXTEND
     503             :     Assert(blocknum >= mdnblocks(reln, forknum));
     504             : #endif
     505             : 
     506             :     /*
     507             :      * If a relation manages to grow to 2^32-1 blocks, refuse to extend it any
     508             :      * more --- we mustn't create a block whose number actually is
     509             :      * InvalidBlockNumber.
     510             :      */
     511      514226 :     if (blocknum == InvalidBlockNumber)
     512           0 :         ereport(ERROR,
     513             :                 (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
     514             :                  errmsg("cannot extend file \"%s\" beyond %u blocks",
     515             :                         relpath(reln->smgr_rnode, forknum),
     516             :                         InvalidBlockNumber)));
     517             : 
     518      514226 :     v = _mdfd_getseg(reln, forknum, blocknum, skipFsync, EXTENSION_CREATE);
     519             : 
     520      514226 :     seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
     521             : 
     522             :     Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
     523             : 
     524             :     /*
     525             :      * Note: because caller usually obtained blocknum by calling mdnblocks,
     526             :      * which did a seek(SEEK_END), this seek is often redundant and will be
     527             :      * optimized away by fd.c.  It's not redundant, however, if there is a
     528             :      * partial page at the end of the file. In that case we want to try to
     529             :      * overwrite the partial page with a full page.  It's also not redundant
     530             :      * if bufmgr.c had to dump another buffer of the same file to make room
     531             :      * for the new page's buffer.
     532             :      */
     533      514226 :     if (FileSeek(v->mdfd_vfd, seekpos, SEEK_SET) != seekpos)
     534           0 :         ereport(ERROR,
     535             :                 (errcode_for_file_access(),
     536             :                  errmsg("could not seek to block %u in file \"%s\": %m",
     537             :                         blocknum, FilePathName(v->mdfd_vfd))));
     538             : 
     539      514226 :     if ((nbytes = FileWrite(v->mdfd_vfd, buffer, BLCKSZ, WAIT_EVENT_DATA_FILE_EXTEND)) != BLCKSZ)
     540             :     {
     541           0 :         if (nbytes < 0)
     542           0 :             ereport(ERROR,
     543             :                     (errcode_for_file_access(),
     544             :                      errmsg("could not extend file \"%s\": %m",
     545             :                             FilePathName(v->mdfd_vfd)),
     546             :                      errhint("Check free disk space.")));
     547             :         /* short write: complain appropriately */
     548           0 :         ereport(ERROR,
     549             :                 (errcode(ERRCODE_DISK_FULL),
     550             :                  errmsg("could not extend file \"%s\": wrote only %d of %d bytes at block %u",
     551             :                         FilePathName(v->mdfd_vfd),
     552             :                         nbytes, BLCKSZ, blocknum),
     553             :                  errhint("Check free disk space.")));
     554             :     }
     555             : 
     556      514226 :     if (!skipFsync && !SmgrIsTemp(reln))
     557      376764 :         register_dirty_segment(reln, forknum, v);
     558             : 
     559             :     Assert(_mdnblocks(reln, forknum, v) <= ((BlockNumber) RELSEG_SIZE));
     560      514226 : }
     561             : 
     562             : /*
     563             :  *  mdopen() -- Open the specified relation.
     564             :  *
     565             :  * Note we only open the first segment, when there are multiple segments.
     566             :  *
     567             :  * If first segment is not present, either ereport or return NULL according
     568             :  * to "behavior".  We treat EXTENSION_CREATE the same as EXTENSION_FAIL;
     569             :  * EXTENSION_CREATE means it's OK to extend an existing relation, not to
     570             :  * invent one out of whole cloth.
     571             :  */
     572             : static MdfdVec *
     573     3460494 : mdopen(SMgrRelation reln, ForkNumber forknum, int behavior)
     574             : {
     575             :     MdfdVec    *mdfd;
     576             :     char       *path;
     577             :     File        fd;
     578             : 
     579             :     /* No work if already open */
     580     3460494 :     if (reln->md_num_open_segs[forknum] > 0)
     581     2800914 :         return &reln->md_seg_fds[forknum][0];
     582             : 
     583      659580 :     path = relpath(reln->smgr_rnode, forknum);
     584             : 
     585      659580 :     fd = PathNameOpenFile(path, O_RDWR | PG_BINARY);
     586             : 
     587      659580 :     if (fd < 0)
     588             :     {
     589             :         /*
     590             :          * During bootstrap, there are cases where a system relation will be
     591             :          * accessed (by internal backend processes) before the bootstrap
     592             :          * script nominally creates it.  Therefore, accept mdopen() as a
     593             :          * substitute for mdcreate() in bootstrap mode only. (See mdcreate)
     594             :          */
     595      179142 :         if (IsBootstrapProcessingMode())
     596       28800 :             fd = PathNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
     597      179142 :         if (fd < 0)
     598             :         {
     599      300684 :             if ((behavior & EXTENSION_RETURN_NULL) &&
     600      150342 :                 FILE_POSSIBLY_DELETED(errno))
     601             :             {
     602      150342 :                 pfree(path);
     603      150342 :                 return NULL;
     604             :             }
     605           0 :             ereport(ERROR,
     606             :                     (errcode_for_file_access(),
     607             :                      errmsg("could not open file \"%s\": %m", path)));
     608             :         }
     609             :     }
     610             : 
     611      509238 :     pfree(path);
     612             : 
     613      509238 :     _fdvec_resize(reln, forknum, 1);
     614      509238 :     mdfd = &reln->md_seg_fds[forknum][0];
     615      509238 :     mdfd->mdfd_vfd = fd;
     616      509238 :     mdfd->mdfd_segno = 0;
     617             : 
     618             :     Assert(_mdnblocks(reln, forknum, mdfd) <= ((BlockNumber) RELSEG_SIZE));
     619             : 
     620      509238 :     return mdfd;
     621             : }
     622             : 
     623             : /*
     624             :  *  mdclose() -- Close the specified relation, if it isn't closed already.
     625             :  */
     626             : void
     627     1871788 : mdclose(SMgrRelation reln, ForkNumber forknum)
     628             : {
     629     1871788 :     int         nopensegs = reln->md_num_open_segs[forknum];
     630             : 
     631             :     /* No work if already closed */
     632     1871788 :     if (nopensegs == 0)
     633     1461772 :         return;
     634             : 
     635             :     /* close segments starting from the end */
     636     1230048 :     while (nopensegs > 0)
     637             :     {
     638      410016 :         MdfdVec    *v = &reln->md_seg_fds[forknum][nopensegs - 1];
     639             : 
     640             :         /* if not closed already */
     641      410016 :         if (v->mdfd_vfd >= 0)
     642             :         {
     643      410016 :             FileClose(v->mdfd_vfd);
     644      410016 :             v->mdfd_vfd = -1;
     645             :         }
     646             : 
     647      410016 :         nopensegs--;
     648             :     }
     649             : 
     650             :     /* resize just once, avoids pointless reallocations */
     651      410016 :     _fdvec_resize(reln, forknum, 0);
     652             : }
     653             : 
     654             : /*
     655             :  *  mdprefetch() -- Initiate asynchronous read of the specified block of a relation
     656             :  */
     657             : void
     658         118 : mdprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum)
     659             : {
     660             : #ifdef USE_PREFETCH
     661             :     off_t       seekpos;
     662             :     MdfdVec    *v;
     663             : 
     664         118 :     v = _mdfd_getseg(reln, forknum, blocknum, false, EXTENSION_FAIL);
     665             : 
     666         118 :     seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
     667             : 
     668             :     Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
     669             : 
     670         118 :     (void) FilePrefetch(v->mdfd_vfd, seekpos, BLCKSZ, WAIT_EVENT_DATA_FILE_PREFETCH);
     671             : #endif                          /* USE_PREFETCH */
     672         118 : }
     673             : 
     674             : /*
     675             :  * mdwriteback() -- Tell the kernel to write pages back to storage.
     676             :  *
     677             :  * This accepts a range of blocks because flushing several pages at once is
     678             :  * considerably more efficient than doing so individually.
     679             :  */
     680             : void
     681      129280 : mdwriteback(SMgrRelation reln, ForkNumber forknum,
     682             :             BlockNumber blocknum, BlockNumber nblocks)
     683             : {
     684             :     /*
     685             :      * Issue flush requests in as few requests as possible; have to split at
     686             :      * segment boundaries though, since those are actually separate files.
     687             :      */
     688      387840 :     while (nblocks > 0)
     689             :     {
     690      129280 :         BlockNumber nflush = nblocks;
     691             :         off_t       seekpos;
     692             :         MdfdVec    *v;
     693             :         int         segnum_start,
     694             :                     segnum_end;
     695             : 
     696      129280 :         v = _mdfd_getseg(reln, forknum, blocknum, true /* not used */ ,
     697             :                          EXTENSION_RETURN_NULL);
     698             : 
     699             :         /*
     700             :          * We might be flushing buffers of already removed relations, that's
     701             :          * ok, just ignore that case.
     702             :          */
     703      129280 :         if (!v)
     704           0 :             return;
     705             : 
     706             :         /* compute offset inside the current segment */
     707      129280 :         segnum_start = blocknum / RELSEG_SIZE;
     708             : 
     709             :         /* compute number of desired writes within the current segment */
     710      129280 :         segnum_end = (blocknum + nblocks - 1) / RELSEG_SIZE;
     711      129280 :         if (segnum_start != segnum_end)
     712           0 :             nflush = RELSEG_SIZE - (blocknum % ((BlockNumber) RELSEG_SIZE));
     713             : 
     714             :         Assert(nflush >= 1);
     715             :         Assert(nflush <= nblocks);
     716             : 
     717      129280 :         seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
     718             : 
     719      129280 :         FileWriteback(v->mdfd_vfd, seekpos, (off_t) BLCKSZ * nflush, WAIT_EVENT_DATA_FILE_FLUSH);
     720             : 
     721      129280 :         nblocks -= nflush;
     722      129280 :         blocknum += nflush;
     723             :     }
     724             : }
     725             : 
     726             : /*
     727             :  *  mdread() -- Read the specified block from a relation.
     728             :  */
     729             : void
     730      418418 : mdread(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
     731             :        char *buffer)
     732             : {
     733             :     off_t       seekpos;
     734             :     int         nbytes;
     735             :     MdfdVec    *v;
     736             : 
     737             :     TRACE_POSTGRESQL_SMGR_MD_READ_START(forknum, blocknum,
     738             :                                         reln->smgr_rnode.node.spcNode,
     739             :                                         reln->smgr_rnode.node.dbNode,
     740             :                                         reln->smgr_rnode.node.relNode,
     741             :                                         reln->smgr_rnode.backend);
     742             : 
     743      418418 :     v = _mdfd_getseg(reln, forknum, blocknum, false,
     744             :                      EXTENSION_FAIL | EXTENSION_CREATE_RECOVERY);
     745             : 
     746      418418 :     seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
     747             : 
     748             :     Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
     749             : 
     750      418418 :     if (FileSeek(v->mdfd_vfd, seekpos, SEEK_SET) != seekpos)
     751           0 :         ereport(ERROR,
     752             :                 (errcode_for_file_access(),
     753             :                  errmsg("could not seek to block %u in file \"%s\": %m",
     754             :                         blocknum, FilePathName(v->mdfd_vfd))));
     755             : 
     756      418418 :     nbytes = FileRead(v->mdfd_vfd, buffer, BLCKSZ, WAIT_EVENT_DATA_FILE_READ);
     757             : 
     758             :     TRACE_POSTGRESQL_SMGR_MD_READ_DONE(forknum, blocknum,
     759             :                                        reln->smgr_rnode.node.spcNode,
     760             :                                        reln->smgr_rnode.node.dbNode,
     761             :                                        reln->smgr_rnode.node.relNode,
     762             :                                        reln->smgr_rnode.backend,
     763             :                                        nbytes,
     764             :                                        BLCKSZ);
     765             : 
     766      418418 :     if (nbytes != BLCKSZ)
     767             :     {
     768           0 :         if (nbytes < 0)
     769           0 :             ereport(ERROR,
     770             :                     (errcode_for_file_access(),
     771             :                      errmsg("could not read block %u in file \"%s\": %m",
     772             :                             blocknum, FilePathName(v->mdfd_vfd))));
     773             : 
     774             :         /*
     775             :          * Short read: we are at or past EOF, or we read a partial block at
     776             :          * EOF.  Normally this is an error; upper levels should never try to
     777             :          * read a nonexistent block.  However, if zero_damaged_pages is ON or
     778             :          * we are InRecovery, we should instead return zeroes without
     779             :          * complaining.  This allows, for example, the case of trying to
     780             :          * update a block that was later truncated away.
     781             :          */
     782           0 :         if (zero_damaged_pages || InRecovery)
     783           0 :             MemSet(buffer, 0, BLCKSZ);
     784             :         else
     785           0 :             ereport(ERROR,
     786             :                     (errcode(ERRCODE_DATA_CORRUPTED),
     787             :                      errmsg("could not read block %u in file \"%s\": read only %d of %d bytes",
     788             :                             blocknum, FilePathName(v->mdfd_vfd),
     789             :                             nbytes, BLCKSZ)));
     790             :     }
     791      418418 : }
     792             : 
     793             : /*
     794             :  *  mdwrite() -- Write the supplied block at the appropriate location.
     795             :  *
     796             :  *      This is to be used only for updating already-existing blocks of a
     797             :  *      relation (ie, those before the current EOF).  To extend a relation,
     798             :  *      use mdextend().
     799             :  */
     800             : void
     801      426554 : mdwrite(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
     802             :         char *buffer, bool skipFsync)
     803             : {
     804             :     off_t       seekpos;
     805             :     int         nbytes;
     806             :     MdfdVec    *v;
     807             : 
     808             :     /* This assert is too expensive to have on normally ... */
     809             : #ifdef CHECK_WRITE_VS_EXTEND
     810             :     Assert(blocknum < mdnblocks(reln, forknum));
     811             : #endif
     812             : 
     813             :     TRACE_POSTGRESQL_SMGR_MD_WRITE_START(forknum, blocknum,
     814             :                                          reln->smgr_rnode.node.spcNode,
     815             :                                          reln->smgr_rnode.node.dbNode,
     816             :                                          reln->smgr_rnode.node.relNode,
     817             :                                          reln->smgr_rnode.backend);
     818             : 
     819      426554 :     v = _mdfd_getseg(reln, forknum, blocknum, skipFsync,
     820             :                      EXTENSION_FAIL | EXTENSION_CREATE_RECOVERY);
     821             : 
     822      426554 :     seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
     823             : 
     824             :     Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
     825             : 
     826      426554 :     if (FileSeek(v->mdfd_vfd, seekpos, SEEK_SET) != seekpos)
     827           0 :         ereport(ERROR,
     828             :                 (errcode_for_file_access(),
     829             :                  errmsg("could not seek to block %u in file \"%s\": %m",
     830             :                         blocknum, FilePathName(v->mdfd_vfd))));
     831             : 
     832      426554 :     nbytes = FileWrite(v->mdfd_vfd, buffer, BLCKSZ, WAIT_EVENT_DATA_FILE_WRITE);
     833             : 
     834             :     TRACE_POSTGRESQL_SMGR_MD_WRITE_DONE(forknum, blocknum,
     835             :                                         reln->smgr_rnode.node.spcNode,
     836             :                                         reln->smgr_rnode.node.dbNode,
     837             :                                         reln->smgr_rnode.node.relNode,
     838             :                                         reln->smgr_rnode.backend,
     839             :                                         nbytes,
     840             :                                         BLCKSZ);
     841             : 
     842      426554 :     if (nbytes != BLCKSZ)
     843             :     {
     844           0 :         if (nbytes < 0)
     845           0 :             ereport(ERROR,
     846             :                     (errcode_for_file_access(),
     847             :                      errmsg("could not write block %u in file \"%s\": %m",
     848             :                             blocknum, FilePathName(v->mdfd_vfd))));
     849             :         /* short write: complain appropriately */
     850           0 :         ereport(ERROR,
     851             :                 (errcode(ERRCODE_DISK_FULL),
     852             :                  errmsg("could not write block %u in file \"%s\": wrote only %d of %d bytes",
     853             :                         blocknum,
     854             :                         FilePathName(v->mdfd_vfd),
     855             :                         nbytes, BLCKSZ),
     856             :                  errhint("Check free disk space.")));
     857             :     }
     858             : 
     859      426554 :     if (!skipFsync && !SmgrIsTemp(reln))
     860      405994 :         register_dirty_segment(reln, forknum, v);
     861      426554 : }
     862             : 
     863             : /*
     864             :  *  mdnblocks() -- Get the number of blocks stored in a relation.
     865             :  *
     866             :  *      Important side effect: all active segments of the relation are opened
     867             :  *      and added to the mdfd_seg_fds array.  If this routine has not been
     868             :  *      called, then only segments up to the last one actually touched
     869             :  *      are present in the array.
     870             :  */
     871             : BlockNumber
     872     3042290 : mdnblocks(SMgrRelation reln, ForkNumber forknum)
     873             : {
     874     3042290 :     MdfdVec    *v = mdopen(reln, forknum, EXTENSION_FAIL);
     875             :     BlockNumber nblocks;
     876     3042290 :     BlockNumber segno = 0;
     877             : 
     878             :     /* mdopen has opened the first segment */
     879             :     Assert(reln->md_num_open_segs[forknum] > 0);
     880             : 
     881             :     /*
     882             :      * Start from the last open segments, to avoid redundant seeks.  We have
     883             :      * previously verified that these segments are exactly RELSEG_SIZE long,
     884             :      * and it's useless to recheck that each time.
     885             :      *
     886             :      * NOTE: this assumption could only be wrong if another backend has
     887             :      * truncated the relation.  We rely on higher code levels to handle that
     888             :      * scenario by closing and re-opening the md fd, which is handled via
     889             :      * relcache flush.  (Since the checkpointer doesn't participate in
     890             :      * relcache flush, it could have segment entries for inactive segments;
     891             :      * that's OK because the checkpointer never needs to compute relation
     892             :      * size.)
     893             :      */
     894     3042290 :     segno = reln->md_num_open_segs[forknum] - 1;
     895     3042290 :     v = &reln->md_seg_fds[forknum][segno];
     896             : 
     897             :     for (;;)
     898             :     {
     899     3042290 :         nblocks = _mdnblocks(reln, forknum, v);
     900     3042290 :         if (nblocks > ((BlockNumber) RELSEG_SIZE))
     901           0 :             elog(FATAL, "segment too big");
     902     3042290 :         if (nblocks < ((BlockNumber) RELSEG_SIZE))
     903     3042290 :             return (segno * ((BlockNumber) RELSEG_SIZE)) + nblocks;
     904             : 
     905             :         /*
     906             :          * If segment is exactly RELSEG_SIZE, advance to next one.
     907             :          */
     908           0 :         segno++;
     909             : 
     910             :         /*
     911             :          * We used to pass O_CREAT here, but that's has the disadvantage that
     912             :          * it might create a segment which has vanished through some operating
     913             :          * system misadventure.  In such a case, creating the segment here
     914             :          * undermines _mdfd_getseg's attempts to notice and report an error
     915             :          * upon access to a missing segment.
     916             :          */
     917           0 :         v = _mdfd_openseg(reln, forknum, segno, 0);
     918           0 :         if (v == NULL)
     919           0 :             return segno * ((BlockNumber) RELSEG_SIZE);
     920             :     }
     921             : }
     922             : 
     923             : /*
     924             :  *  mdtruncate() -- Truncate relation to specified number of blocks.
     925             :  */
     926             : void
     927         344 : mdtruncate(SMgrRelation reln, ForkNumber forknum, BlockNumber nblocks)
     928             : {
     929             :     BlockNumber curnblk;
     930             :     BlockNumber priorblocks;
     931             :     int         curopensegs;
     932             : 
     933             :     /*
     934             :      * NOTE: mdnblocks makes sure we have opened all active segments, so that
     935             :      * truncation loop will get them all!
     936             :      */
     937         344 :     curnblk = mdnblocks(reln, forknum);
     938         344 :     if (nblocks > curnblk)
     939             :     {
     940             :         /* Bogus request ... but no complaint if InRecovery */
     941           0 :         if (InRecovery)
     942           0 :             return;
     943           0 :         ereport(ERROR,
     944             :                 (errmsg("could not truncate file \"%s\" to %u blocks: it's only %u blocks now",
     945             :                         relpath(reln->smgr_rnode, forknum),
     946             :                         nblocks, curnblk)));
     947             :     }
     948         344 :     if (nblocks == curnblk)
     949         118 :         return;                 /* no work */
     950             : 
     951             :     /*
     952             :      * Truncate segments, starting at the last one. Starting at the end makes
     953             :      * managing the memory for the fd array easier, should there be errors.
     954             :      */
     955         226 :     curopensegs = reln->md_num_open_segs[forknum];
     956         678 :     while (curopensegs > 0)
     957             :     {
     958             :         MdfdVec    *v;
     959             : 
     960         226 :         priorblocks = (curopensegs - 1) * RELSEG_SIZE;
     961             : 
     962         226 :         v = &reln->md_seg_fds[forknum][curopensegs - 1];
     963             : 
     964         226 :         if (priorblocks > nblocks)
     965             :         {
     966             :             /*
     967             :              * This segment is no longer active. We truncate the file, but do
     968             :              * not delete it, for reasons explained in the header comments.
     969             :              */
     970           0 :             if (FileTruncate(v->mdfd_vfd, 0, WAIT_EVENT_DATA_FILE_TRUNCATE) < 0)
     971           0 :                 ereport(ERROR,
     972             :                         (errcode_for_file_access(),
     973             :                          errmsg("could not truncate file \"%s\": %m",
     974             :                                 FilePathName(v->mdfd_vfd))));
     975             : 
     976           0 :             if (!SmgrIsTemp(reln))
     977           0 :                 register_dirty_segment(reln, forknum, v);
     978             : 
     979             :             /* we never drop the 1st segment */
     980             :             Assert(v != &reln->md_seg_fds[forknum][0]);
     981             : 
     982           0 :             FileClose(v->mdfd_vfd);
     983           0 :             _fdvec_resize(reln, forknum, curopensegs - 1);
     984             :         }
     985         226 :         else if (priorblocks + ((BlockNumber) RELSEG_SIZE) > nblocks)
     986             :         {
     987             :             /*
     988             :              * This is the last segment we want to keep. Truncate the file to
     989             :              * the right length. NOTE: if nblocks is exactly a multiple K of
     990             :              * RELSEG_SIZE, we will truncate the K+1st segment to 0 length but
     991             :              * keep it. This adheres to the invariant given in the header
     992             :              * comments.
     993             :              */
     994         226 :             BlockNumber lastsegblocks = nblocks - priorblocks;
     995             : 
     996         226 :             if (FileTruncate(v->mdfd_vfd, (off_t) lastsegblocks * BLCKSZ, WAIT_EVENT_DATA_FILE_TRUNCATE) < 0)
     997           0 :                 ereport(ERROR,
     998             :                         (errcode_for_file_access(),
     999             :                          errmsg("could not truncate file \"%s\" to %u blocks: %m",
    1000             :                                 FilePathName(v->mdfd_vfd),
    1001             :                                 nblocks)));
    1002         226 :             if (!SmgrIsTemp(reln))
    1003         202 :                 register_dirty_segment(reln, forknum, v);
    1004             :         }
    1005             :         else
    1006             :         {
    1007             :             /*
    1008             :              * We still need this segment, so nothing to do for this and any
    1009             :              * earlier segment.
    1010             :              */
    1011           0 :             break;
    1012             :         }
    1013         226 :         curopensegs--;
    1014             :     }
    1015             : }
    1016             : 
    1017             : /*
    1018             :  *  mdimmedsync() -- Immediately sync a relation to stable storage.
    1019             :  *
    1020             :  * Note that only writes already issued are synced; this routine knows
    1021             :  * nothing of dirty buffers that may exist inside the buffer manager.
    1022             :  */
    1023             : void
    1024       54882 : mdimmedsync(SMgrRelation reln, ForkNumber forknum)
    1025             : {
    1026             :     int         segno;
    1027             : 
    1028             :     /*
    1029             :      * NOTE: mdnblocks makes sure we have opened all active segments, so that
    1030             :      * fsync loop will get them all!
    1031             :      */
    1032       54882 :     mdnblocks(reln, forknum);
    1033             : 
    1034       54882 :     segno = reln->md_num_open_segs[forknum];
    1035             : 
    1036      164646 :     while (segno > 0)
    1037             :     {
    1038       54882 :         MdfdVec    *v = &reln->md_seg_fds[forknum][segno - 1];
    1039             : 
    1040       54882 :         if (FileSync(v->mdfd_vfd, WAIT_EVENT_DATA_FILE_IMMEDIATE_SYNC) < 0)
    1041           0 :             ereport(ERROR,
    1042             :                     (errcode_for_file_access(),
    1043             :                      errmsg("could not fsync file \"%s\": %m",
    1044             :                             FilePathName(v->mdfd_vfd))));
    1045       54882 :         segno--;
    1046             :     }
    1047       54882 : }
    1048             : 
    1049             : /*
    1050             :  *  mdsync() -- Sync previous writes to stable storage.
    1051             :  */
    1052             : void
    1053        2874 : mdsync(void)
    1054             : {
    1055             :     static bool mdsync_in_progress = false;
    1056             : 
    1057             :     HASH_SEQ_STATUS hstat;
    1058             :     PendingOperationEntry *entry;
    1059             :     int         absorb_counter;
    1060             : 
    1061             :     /* Statistics on sync times */
    1062        2874 :     int         processed = 0;
    1063             :     instr_time  sync_start,
    1064             :                 sync_end,
    1065             :                 sync_diff;
    1066             :     uint64      elapsed;
    1067        2874 :     uint64      longest = 0;
    1068        2874 :     uint64      total_elapsed = 0;
    1069             : 
    1070             :     /*
    1071             :      * This is only called during checkpoints, and checkpoints should only
    1072             :      * occur in processes that have created a pendingOpsTable.
    1073             :      */
    1074        2874 :     if (!pendingOpsTable)
    1075           0 :         elog(ERROR, "cannot sync without a pendingOpsTable");
    1076             : 
    1077             :     /*
    1078             :      * If we are in the checkpointer, the sync had better include all fsync
    1079             :      * requests that were queued by backends up to this point.  The tightest
    1080             :      * race condition that could occur is that a buffer that must be written
    1081             :      * and fsync'd for the checkpoint could have been dumped by a backend just
    1082             :      * before it was visited by BufferSync().  We know the backend will have
    1083             :      * queued an fsync request before clearing the buffer's dirtybit, so we
    1084             :      * are safe as long as we do an Absorb after completing BufferSync().
    1085             :      */
    1086        2874 :     AbsorbFsyncRequests();
    1087             : 
    1088             :     /*
    1089             :      * To avoid excess fsync'ing (in the worst case, maybe a never-terminating
    1090             :      * checkpoint), we want to ignore fsync requests that are entered into the
    1091             :      * hashtable after this point --- they should be processed next time,
    1092             :      * instead.  We use mdsync_cycle_ctr to tell old entries apart from new
    1093             :      * ones: new ones will have cycle_ctr equal to the incremented value of
    1094             :      * mdsync_cycle_ctr.
    1095             :      *
    1096             :      * In normal circumstances, all entries present in the table at this point
    1097             :      * will have cycle_ctr exactly equal to the current (about to be old)
    1098             :      * value of mdsync_cycle_ctr.  However, if we fail partway through the
    1099             :      * fsync'ing loop, then older values of cycle_ctr might remain when we
    1100             :      * come back here to try again.  Repeated checkpoint failures would
    1101             :      * eventually wrap the counter around to the point where an old entry
    1102             :      * might appear new, causing us to skip it, possibly allowing a checkpoint
    1103             :      * to succeed that should not have.  To forestall wraparound, any time the
    1104             :      * previous mdsync() failed to complete, run through the table and
    1105             :      * forcibly set cycle_ctr = mdsync_cycle_ctr.
    1106             :      *
    1107             :      * Think not to merge this loop with the main loop, as the problem is
    1108             :      * exactly that that loop may fail before having visited all the entries.
    1109             :      * From a performance point of view it doesn't matter anyway, as this path
    1110             :      * will never be taken in a system that's functioning normally.
    1111             :      */
    1112        2874 :     if (mdsync_in_progress)
    1113             :     {
    1114             :         /* prior try failed, so update any stale cycle_ctr values */
    1115           0 :         hash_seq_init(&hstat, pendingOpsTable);
    1116           0 :         while ((entry = (PendingOperationEntry *) hash_seq_search(&hstat)) != NULL)
    1117             :         {
    1118           0 :             entry->cycle_ctr = mdsync_cycle_ctr;
    1119             :         }
    1120             :     }
    1121             : 
    1122             :     /* Advance counter so that new hashtable entries are distinguishable */
    1123        2874 :     mdsync_cycle_ctr++;
    1124             : 
    1125             :     /* Set flag to detect failure if we don't reach the end of the loop */
    1126        2874 :     mdsync_in_progress = true;
    1127             : 
    1128             :     /* Now scan the hashtable for fsync requests to process */
    1129        2874 :     absorb_counter = FSYNCS_PER_ABSORB;
    1130        2874 :     hash_seq_init(&hstat, pendingOpsTable);
    1131        2874 :     while ((entry = (PendingOperationEntry *) hash_seq_search(&hstat)) != NULL)
    1132             :     {
    1133             :         ForkNumber  forknum;
    1134             : 
    1135             :         /*
    1136             :          * If the entry is new then don't process it this time; it might
    1137             :          * contain multiple fsync-request bits, but they are all new.  Note
    1138             :          * "continue" bypasses the hash-remove call at the bottom of the loop.
    1139             :          */
    1140       88352 :         if (entry->cycle_ctr == mdsync_cycle_ctr)
    1141           0 :             continue;
    1142             : 
    1143             :         /* Else assert we haven't missed it */
    1144             :         Assert((CycleCtr) (entry->cycle_ctr + 1) == mdsync_cycle_ctr);
    1145             : 
    1146             :         /*
    1147             :          * Scan over the forks and segments represented by the entry.
    1148             :          *
    1149             :          * The bitmap manipulations are slightly tricky, because we can call
    1150             :          * AbsorbFsyncRequests() inside the loop and that could result in
    1151             :          * bms_add_member() modifying and even re-palloc'ing the bitmapsets.
    1152             :          * This is okay because we unlink each bitmapset from the hashtable
    1153             :          * entry before scanning it.  That means that any incoming fsync
    1154             :          * requests will be processed now if they reach the table before we
    1155             :          * begin to scan their fork.
    1156             :          */
    1157      441760 :         for (forknum = 0; forknum <= MAX_FORKNUM; forknum++)
    1158             :         {
    1159      353408 :             Bitmapset  *requests = entry->requests[forknum];
    1160             :             int         segno;
    1161             : 
    1162      353408 :             entry->requests[forknum] = NULL;
    1163      353408 :             entry->canceled[forknum] = false;
    1164             : 
    1165      818218 :             while ((segno = bms_first_member(requests)) >= 0)
    1166             :             {
    1167             :                 int         failures;
    1168             : 
    1169             :                 /*
    1170             :                  * If fsync is off then we don't have to bother opening the
    1171             :                  * file at all.  (We delay checking until this point so that
    1172             :                  * changing fsync on the fly behaves sensibly.)
    1173             :                  */
    1174      111402 :                 if (!enableFsync)
    1175      111294 :                     continue;
    1176             : 
    1177             :                 /*
    1178             :                  * If in checkpointer, we want to absorb pending requests
    1179             :                  * every so often to prevent overflow of the fsync request
    1180             :                  * queue.  It is unspecified whether newly-added entries will
    1181             :                  * be visited by hash_seq_search, but we don't care since we
    1182             :                  * don't need to process them anyway.
    1183             :                  */
    1184         108 :                 if (--absorb_counter <= 0)
    1185             :                 {
    1186           8 :                     AbsorbFsyncRequests();
    1187           8 :                     absorb_counter = FSYNCS_PER_ABSORB;
    1188             :                 }
    1189             : 
    1190             :                 /*
    1191             :                  * The fsync table could contain requests to fsync segments
    1192             :                  * that have been deleted (unlinked) by the time we get to
    1193             :                  * them. Rather than just hoping an ENOENT (or EACCES on
    1194             :                  * Windows) error can be ignored, what we do on error is
    1195             :                  * absorb pending requests and then retry.  Since mdunlink()
    1196             :                  * queues a "cancel" message before actually unlinking, the
    1197             :                  * fsync request is guaranteed to be marked canceled after the
    1198             :                  * absorb if it really was this case. DROP DATABASE likewise
    1199             :                  * has to tell us to forget fsync requests before it starts
    1200             :                  * deletions.
    1201             :                  */
    1202         108 :                 for (failures = 0;; failures++) /* loop exits at "break" */
    1203           0 :                 {
    1204             :                     SMgrRelation reln;
    1205             :                     MdfdVec    *seg;
    1206             :                     char       *path;
    1207             :                     int         save_errno;
    1208             : 
    1209             :                     /*
    1210             :                      * Find or create an smgr hash entry for this relation.
    1211             :                      * This may seem a bit unclean -- md calling smgr?  But
    1212             :                      * it's really the best solution.  It ensures that the
    1213             :                      * open file reference isn't permanently leaked if we get
    1214             :                      * an error here. (You may say "but an unreferenced
    1215             :                      * SMgrRelation is still a leak!" Not really, because the
    1216             :                      * only case in which a checkpoint is done by a process
    1217             :                      * that isn't about to shut down is in the checkpointer,
    1218             :                      * and it will periodically do smgrcloseall(). This fact
    1219             :                      * justifies our not closing the reln in the success path
    1220             :                      * either, which is a good thing since in non-checkpointer
    1221             :                      * cases we couldn't safely do that.)
    1222             :                      */
    1223         108 :                     reln = smgropen(entry->rnode, InvalidBackendId);
    1224             : 
    1225             :                     /* Attempt to open and fsync the target segment */
    1226         108 :                     seg = _mdfd_getseg(reln, forknum,
    1227         108 :                                        (BlockNumber) segno * (BlockNumber) RELSEG_SIZE,
    1228             :                                        false,
    1229             :                                        EXTENSION_RETURN_NULL
    1230             :                                        | EXTENSION_DONT_CHECK_SIZE);
    1231             : 
    1232         108 :                     INSTR_TIME_SET_CURRENT(sync_start);
    1233             : 
    1234         216 :                     if (seg != NULL &&
    1235         108 :                         FileSync(seg->mdfd_vfd, WAIT_EVENT_DATA_FILE_SYNC) >= 0)
    1236             :                     {
    1237             :                         /* Success; update statistics about sync timing */
    1238         108 :                         INSTR_TIME_SET_CURRENT(sync_end);
    1239         108 :                         sync_diff = sync_end;
    1240         108 :                         INSTR_TIME_SUBTRACT(sync_diff, sync_start);
    1241         108 :                         elapsed = INSTR_TIME_GET_MICROSEC(sync_diff);
    1242         108 :                         if (elapsed > longest)
    1243          18 :                             longest = elapsed;
    1244         108 :                         total_elapsed += elapsed;
    1245         108 :                         processed++;
    1246         108 :                         if (log_checkpoints)
    1247           0 :                             elog(DEBUG1, "checkpoint sync: number=%d file=%s time=%.3f msec",
    1248             :                                  processed,
    1249             :                                  FilePathName(seg->mdfd_vfd),
    1250             :                                  (double) elapsed / 1000);
    1251             : 
    1252         108 :                         break;  /* out of retry loop */
    1253             :                     }
    1254             : 
    1255             :                     /* Compute file name for use in message */
    1256           0 :                     save_errno = errno;
    1257           0 :                     path = _mdfd_segpath(reln, forknum, (BlockNumber) segno);
    1258           0 :                     errno = save_errno;
    1259             : 
    1260             :                     /*
    1261             :                      * It is possible that the relation has been dropped or
    1262             :                      * truncated since the fsync request was entered.
    1263             :                      * Therefore, allow ENOENT, but only if we didn't fail
    1264             :                      * already on this file.  This applies both for
    1265             :                      * _mdfd_getseg() and for FileSync, since fd.c might have
    1266             :                      * closed the file behind our back.
    1267             :                      *
    1268             :                      * XXX is there any point in allowing more than one retry?
    1269             :                      * Don't see one at the moment, but easy to change the
    1270             :                      * test here if so.
    1271             :                      */
    1272           0 :                     if (!FILE_POSSIBLY_DELETED(errno) ||
    1273             :                         failures > 0)
    1274           0 :                         ereport(ERROR,
    1275             :                                 (errcode_for_file_access(),
    1276             :                                  errmsg("could not fsync file \"%s\": %m",
    1277             :                                         path)));
    1278             :                     else
    1279           0 :                         ereport(DEBUG1,
    1280             :                                 (errcode_for_file_access(),
    1281             :                                  errmsg("could not fsync file \"%s\" but retrying: %m",
    1282             :                                         path)));
    1283           0 :                     pfree(path);
    1284             : 
    1285             :                     /*
    1286             :                      * Absorb incoming requests and check to see if a cancel
    1287             :                      * arrived for this relation fork.
    1288             :                      */
    1289           0 :                     AbsorbFsyncRequests();
    1290           0 :                     absorb_counter = FSYNCS_PER_ABSORB; /* might as well... */
    1291             : 
    1292           0 :                     if (entry->canceled[forknum])
    1293           0 :                         break;
    1294             :                 }               /* end retry loop */
    1295             :             }
    1296      353408 :             bms_free(requests);
    1297             :         }
    1298             : 
    1299             :         /*
    1300             :          * We've finished everything that was requested before we started to
    1301             :          * scan the entry.  If no new requests have been inserted meanwhile,
    1302             :          * remove the entry.  Otherwise, update its cycle counter, as all the
    1303             :          * requests now in it must have arrived during this cycle.
    1304             :          */
    1305      441760 :         for (forknum = 0; forknum <= MAX_FORKNUM; forknum++)
    1306             :         {
    1307      353408 :             if (entry->requests[forknum] != NULL)
    1308           0 :                 break;
    1309             :         }
    1310       88352 :         if (forknum <= MAX_FORKNUM)
    1311           0 :             entry->cycle_ctr = mdsync_cycle_ctr;
    1312             :         else
    1313             :         {
    1314             :             /* Okay to remove it */
    1315       88352 :             if (hash_search(pendingOpsTable, &entry->rnode,
    1316             :                             HASH_REMOVE, NULL) == NULL)
    1317           0 :                 elog(ERROR, "pendingOpsTable corrupted");
    1318             :         }
    1319             :     }                           /* end loop over hashtable entries */
    1320             : 
    1321             :     /* Return sync performance metrics for report at checkpoint end */
    1322        2874 :     CheckpointStats.ckpt_sync_rels = processed;
    1323        2874 :     CheckpointStats.ckpt_longest_sync = longest;
    1324        2874 :     CheckpointStats.ckpt_agg_sync_time = total_elapsed;
    1325             : 
    1326             :     /* Flag successful completion of mdsync */
    1327        2874 :     mdsync_in_progress = false;
    1328        2874 : }
    1329             : 
    1330             : /*
    1331             :  * mdpreckpt() -- Do pre-checkpoint work
    1332             :  *
    1333             :  * To distinguish unlink requests that arrived before this checkpoint
    1334             :  * started from those that arrived during the checkpoint, we use a cycle
    1335             :  * counter similar to the one we use for fsync requests. That cycle
    1336             :  * counter is incremented here.
    1337             :  *
    1338             :  * This must be called *before* the checkpoint REDO point is determined.
    1339             :  * That ensures that we won't delete files too soon.
    1340             :  *
    1341             :  * Note that we can't do anything here that depends on the assumption
    1342             :  * that the checkpoint will be completed.
    1343             :  */
    1344             : void
    1345        2734 : mdpreckpt(void)
    1346             : {
    1347             :     /*
    1348             :      * Any unlink requests arriving after this point will be assigned the next
    1349             :      * cycle counter, and won't be unlinked until next checkpoint.
    1350             :      */
    1351        2734 :     mdckpt_cycle_ctr++;
    1352        2734 : }
    1353             : 
    1354             : /*
    1355             :  * mdpostckpt() -- Do post-checkpoint work
    1356             :  *
    1357             :  * Remove any lingering files that can now be safely removed.
    1358             :  */
    1359             : void
    1360        2732 : mdpostckpt(void)
    1361             : {
    1362             :     int         absorb_counter;
    1363             : 
    1364        2732 :     absorb_counter = UNLINKS_PER_ABSORB;
    1365       31258 :     while (pendingUnlinks != NIL)
    1366             :     {
    1367       25804 :         PendingUnlinkEntry *entry = (PendingUnlinkEntry *) linitial(pendingUnlinks);
    1368             :         char       *path;
    1369             : 
    1370             :         /*
    1371             :          * New entries are appended to the end, so if the entry is new we've
    1372             :          * reached the end of old entries.
    1373             :          *
    1374             :          * Note: if just the right number of consecutive checkpoints fail, we
    1375             :          * could be fooled here by cycle_ctr wraparound.  However, the only
    1376             :          * consequence is that we'd delay unlinking for one more checkpoint,
    1377             :          * which is perfectly tolerable.
    1378             :          */
    1379       25804 :         if (entry->cycle_ctr == mdckpt_cycle_ctr)
    1380          10 :             break;
    1381             : 
    1382             :         /* Unlink the file */
    1383       25794 :         path = relpathperm(entry->rnode, MAIN_FORKNUM);
    1384       25794 :         if (unlink(path) < 0)
    1385             :         {
    1386             :             /*
    1387             :              * There's a race condition, when the database is dropped at the
    1388             :              * same time that we process the pending unlink requests. If the
    1389             :              * DROP DATABASE deletes the file before we do, we will get ENOENT
    1390             :              * here. rmtree() also has to ignore ENOENT errors, to deal with
    1391             :              * the possibility that we delete the file first.
    1392             :              */
    1393           0 :             if (errno != ENOENT)
    1394           0 :                 ereport(WARNING,
    1395             :                         (errcode_for_file_access(),
    1396             :                          errmsg("could not remove file \"%s\": %m", path)));
    1397             :         }
    1398       25794 :         pfree(path);
    1399             : 
    1400             :         /* And remove the list entry */
    1401       25794 :         pendingUnlinks = list_delete_first(pendingUnlinks);
    1402       25794 :         pfree(entry);
    1403             : 
    1404             :         /*
    1405             :          * As in mdsync, we don't want to stop absorbing fsync requests for a
    1406             :          * long time when there are many deletions to be done.  We can safely
    1407             :          * call AbsorbFsyncRequests() at this point in the loop (note it might
    1408             :          * try to delete list entries).
    1409             :          */
    1410       25794 :         if (--absorb_counter <= 0)
    1411             :         {
    1412        2540 :             AbsorbFsyncRequests();
    1413        2540 :             absorb_counter = UNLINKS_PER_ABSORB;
    1414             :         }
    1415             :     }
    1416        2732 : }
    1417             : 
    1418             : /*
    1419             :  * register_dirty_segment() -- Mark a relation segment as needing fsync
    1420             :  *
    1421             :  * If there is a local pending-ops table, just make an entry in it for
    1422             :  * mdsync to process later.  Otherwise, try to pass off the fsync request
    1423             :  * to the checkpointer process.  If that fails, just do the fsync
    1424             :  * locally before returning (we hope this will not happen often enough
    1425             :  * to be a performance problem).
    1426             :  */
    1427             : static void
    1428      782960 : register_dirty_segment(SMgrRelation reln, ForkNumber forknum, MdfdVec *seg)
    1429             : {
    1430             :     /* Temp relations should never be fsync'd */
    1431             :     Assert(!SmgrIsTemp(reln));
    1432             : 
    1433      782960 :     if (pendingOpsTable)
    1434             :     {
    1435             :         /* push it into local pending-ops table */
    1436      606372 :         RememberFsyncRequest(reln->smgr_rnode.node, forknum, seg->mdfd_segno);
    1437             :     }
    1438             :     else
    1439             :     {
    1440      176588 :         if (ForwardFsyncRequest(reln->smgr_rnode.node, forknum, seg->mdfd_segno))
    1441      176444 :             return;             /* passed it off successfully */
    1442             : 
    1443         144 :         ereport(DEBUG1,
    1444             :                 (errmsg("could not forward fsync request because request queue is full")));
    1445             : 
    1446         144 :         if (FileSync(seg->mdfd_vfd, WAIT_EVENT_DATA_FILE_SYNC) < 0)
    1447           0 :             ereport(ERROR,
    1448             :                     (errcode_for_file_access(),
    1449             :                      errmsg("could not fsync file \"%s\": %m",
    1450             :                             FilePathName(seg->mdfd_vfd))));
    1451             :     }
    1452             : }
    1453             : 
    1454             : /*
    1455             :  * register_unlink() -- Schedule a file to be deleted after next checkpoint
    1456             :  *
    1457             :  * We don't bother passing in the fork number, because this is only used
    1458             :  * with main forks.
    1459             :  *
    1460             :  * As with register_dirty_segment, this could involve either a local or
    1461             :  * a remote pending-ops table.
    1462             :  */
    1463             : static void
    1464       29790 : register_unlink(RelFileNodeBackend rnode)
    1465             : {
    1466             :     /* Should never be used with temp relations */
    1467             :     Assert(!RelFileNodeBackendIsTemp(rnode));
    1468             : 
    1469       29790 :     if (pendingOpsTable)
    1470             :     {
    1471             :         /* push it into local pending-ops table */
    1472           0 :         RememberFsyncRequest(rnode.node, MAIN_FORKNUM,
    1473             :                              UNLINK_RELATION_REQUEST);
    1474             :     }
    1475             :     else
    1476             :     {
    1477             :         /*
    1478             :          * Notify the checkpointer about it.  If we fail to queue the request
    1479             :          * message, we have to sleep and try again, because we can't simply
    1480             :          * delete the file now.  Ugly, but hopefully won't happen often.
    1481             :          *
    1482             :          * XXX should we just leave the file orphaned instead?
    1483             :          */
    1484             :         Assert(IsUnderPostmaster);
    1485       59580 :         while (!ForwardFsyncRequest(rnode.node, MAIN_FORKNUM,
    1486             :                                     UNLINK_RELATION_REQUEST))
    1487           0 :             pg_usleep(10000L);  /* 10 msec seems a good number */
    1488             :     }
    1489       29790 : }
    1490             : 
    1491             : /*
    1492             :  * RememberFsyncRequest() -- callback from checkpointer side of fsync request
    1493             :  *
    1494             :  * We stuff fsync requests into the local hash table for execution
    1495             :  * during the checkpointer's next checkpoint.  UNLINK requests go into a
    1496             :  * separate linked list, however, because they get processed separately.
    1497             :  *
    1498             :  * The range of possible segment numbers is way less than the range of
    1499             :  * BlockNumber, so we can reserve high values of segno for special purposes.
    1500             :  * We define three:
    1501             :  * - FORGET_RELATION_FSYNC means to cancel pending fsyncs for a relation,
    1502             :  *   either for one fork, or all forks if forknum is InvalidForkNumber
    1503             :  * - FORGET_DATABASE_FSYNC means to cancel pending fsyncs for a whole database
    1504             :  * - UNLINK_RELATION_REQUEST is a request to delete the file after the next
    1505             :  *   checkpoint.
    1506             :  * Note also that we're assuming real segment numbers don't exceed INT_MAX.
    1507             :  *
    1508             :  * (Handling FORGET_DATABASE_FSYNC requests is a tad slow because the hash
    1509             :  * table has to be searched linearly, but dropping a database is a pretty
    1510             :  * heavyweight operation anyhow, so we'll live with it.)
    1511             :  */
    1512             : void
    1513      910276 : RememberFsyncRequest(RelFileNode rnode, ForkNumber forknum, BlockNumber segno)
    1514             : {
    1515             :     Assert(pendingOpsTable);
    1516             : 
    1517      910276 :     if (segno == FORGET_RELATION_FSYNC)
    1518             :     {
    1519             :         /* Remove any pending requests for the relation (one or all forks) */
    1520             :         PendingOperationEntry *entry;
    1521             : 
    1522      103268 :         entry = (PendingOperationEntry *) hash_search(pendingOpsTable,
    1523             :                                                       &rnode,
    1524             :                                                       HASH_FIND,
    1525             :                                                       NULL);
    1526      103268 :         if (entry)
    1527             :         {
    1528             :             /*
    1529             :              * We can't just delete the entry since mdsync could have an
    1530             :              * active hashtable scan.  Instead we delete the bitmapsets; this
    1531             :              * is safe because of the way mdsync is coded.  We also set the
    1532             :              * "canceled" flags so that mdsync can tell that a cancel arrived
    1533             :              * for the fork(s).
    1534             :              */
    1535       47336 :             if (forknum == InvalidForkNumber)
    1536             :             {
    1537             :                 /* remove requests for all forks */
    1538           0 :                 for (forknum = 0; forknum <= MAX_FORKNUM; forknum++)
    1539             :                 {
    1540           0 :                     bms_free(entry->requests[forknum]);
    1541           0 :                     entry->requests[forknum] = NULL;
    1542           0 :                     entry->canceled[forknum] = true;
    1543             :                 }
    1544             :             }
    1545             :             else
    1546             :             {
    1547             :                 /* remove requests for single fork */
    1548       47336 :                 bms_free(entry->requests[forknum]);
    1549       47336 :                 entry->requests[forknum] = NULL;
    1550       47336 :                 entry->canceled[forknum] = true;
    1551             :             }
    1552             :         }
    1553             :     }
    1554      807008 :     else if (segno == FORGET_DATABASE_FSYNC)
    1555             :     {
    1556             :         /* Remove any pending requests for the entire database */
    1557             :         HASH_SEQ_STATUS hstat;
    1558             :         PendingOperationEntry *entry;
    1559             :         ListCell   *cell,
    1560             :                    *prev,
    1561             :                    *next;
    1562             : 
    1563             :         /* Remove fsync requests */
    1564          18 :         hash_seq_init(&hstat, pendingOpsTable);
    1565          42 :         while ((entry = (PendingOperationEntry *) hash_seq_search(&hstat)) != NULL)
    1566             :         {
    1567           6 :             if (entry->rnode.dbNode == rnode.dbNode)
    1568             :             {
    1569             :                 /* remove requests for all forks */
    1570          10 :                 for (forknum = 0; forknum <= MAX_FORKNUM; forknum++)
    1571             :                 {
    1572           8 :                     bms_free(entry->requests[forknum]);
    1573           8 :                     entry->requests[forknum] = NULL;
    1574           8 :                     entry->canceled[forknum] = true;
    1575             :                 }
    1576             :             }
    1577             :         }
    1578             : 
    1579             :         /* Remove unlink requests */
    1580          18 :         prev = NULL;
    1581          20 :         for (cell = list_head(pendingUnlinks); cell; cell = next)
    1582             :         {
    1583           2 :             PendingUnlinkEntry *entry = (PendingUnlinkEntry *) lfirst(cell);
    1584             : 
    1585           2 :             next = lnext(cell);
    1586           2 :             if (entry->rnode.dbNode == rnode.dbNode)
    1587             :             {
    1588           0 :                 pendingUnlinks = list_delete_cell(pendingUnlinks, cell, prev);
    1589           0 :                 pfree(entry);
    1590             :             }
    1591             :             else
    1592           2 :                 prev = cell;
    1593             :         }
    1594             :     }
    1595      806990 :     else if (segno == UNLINK_RELATION_REQUEST)
    1596             :     {
    1597             :         /* Unlink request: put it in the linked list */
    1598       25818 :         MemoryContext oldcxt = MemoryContextSwitchTo(pendingOpsCxt);
    1599             :         PendingUnlinkEntry *entry;
    1600             : 
    1601             :         /* PendingUnlinkEntry doesn't store forknum, since it's always MAIN */
    1602             :         Assert(forknum == MAIN_FORKNUM);
    1603             : 
    1604       25818 :         entry = palloc(sizeof(PendingUnlinkEntry));
    1605       25818 :         entry->rnode = rnode;
    1606       25818 :         entry->cycle_ctr = mdckpt_cycle_ctr;
    1607             : 
    1608       25818 :         pendingUnlinks = lappend(pendingUnlinks, entry);
    1609             : 
    1610       25818 :         MemoryContextSwitchTo(oldcxt);
    1611             :     }
    1612             :     else
    1613             :     {
    1614             :         /* Normal case: enter a request to fsync this segment */
    1615      781172 :         MemoryContext oldcxt = MemoryContextSwitchTo(pendingOpsCxt);
    1616             :         PendingOperationEntry *entry;
    1617             :         bool        found;
    1618             : 
    1619      781172 :         entry = (PendingOperationEntry *) hash_search(pendingOpsTable,
    1620             :                                                       &rnode,
    1621             :                                                       HASH_ENTER,
    1622             :                                                       &found);
    1623             :         /* if new entry, initialize it */
    1624      781172 :         if (!found)
    1625             :         {
    1626       88534 :             entry->cycle_ctr = mdsync_cycle_ctr;
    1627       88534 :             MemSet(entry->requests, 0, sizeof(entry->requests));
    1628       88534 :             MemSet(entry->canceled, 0, sizeof(entry->canceled));
    1629             :         }
    1630             : 
    1631             :         /*
    1632             :          * NB: it's intentional that we don't change cycle_ctr if the entry
    1633             :          * already exists.  The cycle_ctr must represent the oldest fsync
    1634             :          * request that could be in the entry.
    1635             :          */
    1636             : 
    1637      781172 :         entry->requests[forknum] = bms_add_member(entry->requests[forknum],
    1638             :                                                   (int) segno);
    1639             : 
    1640      781172 :         MemoryContextSwitchTo(oldcxt);
    1641             :     }
    1642      910276 : }
    1643             : 
    1644             : /*
    1645             :  * ForgetRelationFsyncRequests -- forget any fsyncs for a relation fork
    1646             :  *
    1647             :  * forknum == InvalidForkNumber means all forks, although this code doesn't
    1648             :  * actually know that, since it's just forwarding the request elsewhere.
    1649             :  */
    1650             : void
    1651      119154 : ForgetRelationFsyncRequests(RelFileNode rnode, ForkNumber forknum)
    1652             : {
    1653      119154 :     if (pendingOpsTable)
    1654             :     {
    1655             :         /* standalone backend or startup process: fsync state is local */
    1656           0 :         RememberFsyncRequest(rnode, forknum, FORGET_RELATION_FSYNC);
    1657             :     }
    1658      119154 :     else if (IsUnderPostmaster)
    1659             :     {
    1660             :         /*
    1661             :          * Notify the checkpointer about it.  If we fail to queue the cancel
    1662             :          * message, we have to sleep and try again ... ugly, but hopefully
    1663             :          * won't happen often.
    1664             :          *
    1665             :          * XXX should we CHECK_FOR_INTERRUPTS in this loop?  Escaping with an
    1666             :          * error would leave the no-longer-used file still present on disk,
    1667             :          * which would be bad, so I'm inclined to assume that the checkpointer
    1668             :          * will always empty the queue soon.
    1669             :          */
    1670      238308 :         while (!ForwardFsyncRequest(rnode, forknum, FORGET_RELATION_FSYNC))
    1671           0 :             pg_usleep(10000L);  /* 10 msec seems a good number */
    1672             : 
    1673             :         /*
    1674             :          * Note we don't wait for the checkpointer to actually absorb the
    1675             :          * cancel message; see mdsync() for the implications.
    1676             :          */
    1677             :     }
    1678      119154 : }
    1679             : 
    1680             : /*
    1681             :  * ForgetDatabaseFsyncRequests -- forget any fsyncs and unlinks for a DB
    1682             :  */
    1683             : void
    1684          18 : ForgetDatabaseFsyncRequests(Oid dbid)
    1685             : {
    1686             :     RelFileNode rnode;
    1687             : 
    1688          18 :     rnode.dbNode = dbid;
    1689          18 :     rnode.spcNode = 0;
    1690          18 :     rnode.relNode = 0;
    1691             : 
    1692          18 :     if (pendingOpsTable)
    1693             :     {
    1694             :         /* standalone backend or startup process: fsync state is local */
    1695           0 :         RememberFsyncRequest(rnode, InvalidForkNumber, FORGET_DATABASE_FSYNC);
    1696             :     }
    1697          18 :     else if (IsUnderPostmaster)
    1698             :     {
    1699             :         /* see notes in ForgetRelationFsyncRequests */
    1700          36 :         while (!ForwardFsyncRequest(rnode, InvalidForkNumber,
    1701             :                                     FORGET_DATABASE_FSYNC))
    1702           0 :             pg_usleep(10000L);  /* 10 msec seems a good number */
    1703             :     }
    1704          18 : }
    1705             : 
    1706             : 
    1707             : /*
    1708             :  *  _fdvec_resize() -- Resize the fork's open segments array
    1709             :  */
    1710             : static void
    1711     1036642 : _fdvec_resize(SMgrRelation reln,
    1712             :               ForkNumber forknum,
    1713             :               int nseg)
    1714             : {
    1715     1036642 :     if (nseg == 0)
    1716             :     {
    1717      410016 :         if (reln->md_num_open_segs[forknum] > 0)
    1718             :         {
    1719      410016 :             pfree(reln->md_seg_fds[forknum]);
    1720      410016 :             reln->md_seg_fds[forknum] = NULL;
    1721             :         }
    1722             :     }
    1723      626626 :     else if (reln->md_num_open_segs[forknum] == 0)
    1724             :     {
    1725      626626 :         reln->md_seg_fds[forknum] =
    1726      626626 :             MemoryContextAlloc(MdCxt, sizeof(MdfdVec) * nseg);
    1727             :     }
    1728             :     else
    1729             :     {
    1730             :         /*
    1731             :          * It doesn't seem worthwhile complicating the code by having a more
    1732             :          * aggressive growth strategy here; the number of segments doesn't
    1733             :          * grow that fast, and the memory context internally will sometimes
    1734             :          * avoid doing an actual reallocation.
    1735             :          */
    1736           0 :         reln->md_seg_fds[forknum] =
    1737           0 :             repalloc(reln->md_seg_fds[forknum],
    1738             :                      sizeof(MdfdVec) * nseg);
    1739             :     }
    1740             : 
    1741     1036642 :     reln->md_num_open_segs[forknum] = nseg;
    1742     1036642 : }
    1743             : 
    1744             : /*
    1745             :  * Return the filename for the specified segment of the relation. The
    1746             :  * returned string is palloc'd.
    1747             :  */
    1748             : static char *
    1749           0 : _mdfd_segpath(SMgrRelation reln, ForkNumber forknum, BlockNumber segno)
    1750             : {
    1751             :     char       *path,
    1752             :                *fullpath;
    1753             : 
    1754           0 :     path = relpath(reln->smgr_rnode, forknum);
    1755             : 
    1756           0 :     if (segno > 0)
    1757             :     {
    1758           0 :         fullpath = psprintf("%s.%u", path, segno);
    1759           0 :         pfree(path);
    1760             :     }
    1761             :     else
    1762           0 :         fullpath = path;
    1763             : 
    1764           0 :     return fullpath;
    1765             : }
    1766             : 
    1767             : /*
    1768             :  * Open the specified segment of the relation,
    1769             :  * and make a MdfdVec object for it.  Returns NULL on failure.
    1770             :  */
    1771             : static MdfdVec *
    1772           0 : _mdfd_openseg(SMgrRelation reln, ForkNumber forknum, BlockNumber segno,
    1773             :               int oflags)
    1774             : {
    1775             :     MdfdVec    *v;
    1776             :     int         fd;
    1777             :     char       *fullpath;
    1778             : 
    1779           0 :     fullpath = _mdfd_segpath(reln, forknum, segno);
    1780             : 
    1781             :     /* open the file */
    1782           0 :     fd = PathNameOpenFile(fullpath, O_RDWR | PG_BINARY | oflags);
    1783             : 
    1784           0 :     pfree(fullpath);
    1785             : 
    1786           0 :     if (fd < 0)
    1787           0 :         return NULL;
    1788             : 
    1789           0 :     if (segno <= reln->md_num_open_segs[forknum])
    1790           0 :         _fdvec_resize(reln, forknum, segno + 1);
    1791             : 
    1792             :     /* fill the entry */
    1793           0 :     v = &reln->md_seg_fds[forknum][segno];
    1794           0 :     v->mdfd_vfd = fd;
    1795           0 :     v->mdfd_segno = segno;
    1796             : 
    1797             :     Assert(_mdnblocks(reln, forknum, v) <= ((BlockNumber) RELSEG_SIZE));
    1798             : 
    1799             :     /* all done */
    1800           0 :     return v;
    1801             : }
    1802             : 
    1803             : /*
    1804             :  *  _mdfd_getseg() -- Find the segment of the relation holding the
    1805             :  *      specified block.
    1806             :  *
    1807             :  * If the segment doesn't exist, we ereport, return NULL, or create the
    1808             :  * segment, according to "behavior".  Note: skipFsync is only used in the
    1809             :  * EXTENSION_CREATE case.
    1810             :  */
    1811             : static MdfdVec *
    1812     1488704 : _mdfd_getseg(SMgrRelation reln, ForkNumber forknum, BlockNumber blkno,
    1813             :              bool skipFsync, int behavior)
    1814             : {
    1815             :     MdfdVec    *v;
    1816             :     BlockNumber targetseg;
    1817             :     BlockNumber nextsegno;
    1818             : 
    1819             :     /* some way to handle non-existent segments needs to be specified */
    1820             :     Assert(behavior &
    1821             :            (EXTENSION_FAIL | EXTENSION_CREATE | EXTENSION_RETURN_NULL));
    1822             : 
    1823     1488704 :     targetseg = blkno / ((BlockNumber) RELSEG_SIZE);
    1824             : 
    1825             :     /* if an existing and opened segment, we're done */
    1826     1488704 :     if (targetseg < reln->md_num_open_segs[forknum])
    1827             :     {
    1828     1363808 :         v = &reln->md_seg_fds[forknum][targetseg];
    1829     1363808 :         return v;
    1830             :     }
    1831             : 
    1832             :     /*
    1833             :      * The target segment is not yet open. Iterate over all the segments
    1834             :      * between the last opened and the target segment. This way missing
    1835             :      * segments either raise an error, or get created (according to
    1836             :      * 'behavior'). Start with either the last opened, or the first segment if
    1837             :      * none was opened before.
    1838             :      */
    1839      124896 :     if (reln->md_num_open_segs[forknum] > 0)
    1840           0 :         v = &reln->md_seg_fds[forknum][reln->md_num_open_segs[forknum] - 1];
    1841             :     else
    1842             :     {
    1843      124896 :         v = mdopen(reln, forknum, behavior);
    1844      124896 :         if (!v)
    1845           0 :             return NULL;        /* if behavior & EXTENSION_RETURN_NULL */
    1846             :     }
    1847             : 
    1848      249792 :     for (nextsegno = reln->md_num_open_segs[forknum];
    1849           0 :          nextsegno <= targetseg; nextsegno++)
    1850             :     {
    1851           0 :         BlockNumber nblocks = _mdnblocks(reln, forknum, v);
    1852           0 :         int         flags = 0;
    1853             : 
    1854             :         Assert(nextsegno == v->mdfd_segno + 1);
    1855             : 
    1856           0 :         if (nblocks > ((BlockNumber) RELSEG_SIZE))
    1857           0 :             elog(FATAL, "segment too big");
    1858             : 
    1859           0 :         if ((behavior & EXTENSION_CREATE) ||
    1860           0 :             (InRecovery && (behavior & EXTENSION_CREATE_RECOVERY)))
    1861             :         {
    1862             :             /*
    1863             :              * Normally we will create new segments only if authorized by the
    1864             :              * caller (i.e., we are doing mdextend()).  But when doing WAL
    1865             :              * recovery, create segments anyway; this allows cases such as
    1866             :              * replaying WAL data that has a write into a high-numbered
    1867             :              * segment of a relation that was later deleted. We want to go
    1868             :              * ahead and create the segments so we can finish out the replay.
    1869             :              * However if the caller has specified
    1870             :              * EXTENSION_REALLY_RETURN_NULL, then extension is not desired
    1871             :              * even in recovery; we won't reach this point in that case.
    1872             :              *
    1873             :              * We have to maintain the invariant that segments before the last
    1874             :              * active segment are of size RELSEG_SIZE; therefore, if
    1875             :              * extending, pad them out with zeroes if needed.  (This only
    1876             :              * matters if in recovery, or if the caller is extending the
    1877             :              * relation discontiguously, but that can happen in hash indexes.)
    1878             :              */
    1879           0 :             if (nblocks < ((BlockNumber) RELSEG_SIZE))
    1880             :             {
    1881           0 :                 char       *zerobuf = palloc0(BLCKSZ);
    1882             : 
    1883           0 :                 mdextend(reln, forknum,
    1884           0 :                          nextsegno * ((BlockNumber) RELSEG_SIZE) - 1,
    1885             :                          zerobuf, skipFsync);
    1886           0 :                 pfree(zerobuf);
    1887             :             }
    1888           0 :             flags = O_CREAT;
    1889             :         }
    1890           0 :         else if (!(behavior & EXTENSION_DONT_CHECK_SIZE) &&
    1891             :                  nblocks < ((BlockNumber) RELSEG_SIZE))
    1892             :         {
    1893             :             /*
    1894             :              * When not extending (or explicitly including truncated
    1895             :              * segments), only open the next segment if the current one is
    1896             :              * exactly RELSEG_SIZE.  If not (this branch), either return NULL
    1897             :              * or fail.
    1898             :              */
    1899           0 :             if (behavior & EXTENSION_RETURN_NULL)
    1900             :             {
    1901             :                 /*
    1902             :                  * Some callers discern between reasons for _mdfd_getseg()
    1903             :                  * returning NULL based on errno. As there's no failing
    1904             :                  * syscall involved in this case, explicitly set errno to
    1905             :                  * ENOENT, as that seems the closest interpretation.
    1906             :                  */
    1907           0 :                 errno = ENOENT;
    1908           0 :                 return NULL;
    1909             :             }
    1910             : 
    1911           0 :             ereport(ERROR,
    1912             :                     (errcode_for_file_access(),
    1913             :                      errmsg("could not open file \"%s\" (target block %u): previous segment is only %u blocks",
    1914             :                             _mdfd_segpath(reln, forknum, nextsegno),
    1915             :                             blkno, nblocks)));
    1916             :         }
    1917             : 
    1918           0 :         v = _mdfd_openseg(reln, forknum, nextsegno, flags);
    1919             : 
    1920           0 :         if (v == NULL)
    1921             :         {
    1922           0 :             if ((behavior & EXTENSION_RETURN_NULL) &&
    1923           0 :                 FILE_POSSIBLY_DELETED(errno))
    1924           0 :                 return NULL;
    1925           0 :             ereport(ERROR,
    1926             :                     (errcode_for_file_access(),
    1927             :                      errmsg("could not open file \"%s\" (target block %u): %m",
    1928             :                             _mdfd_segpath(reln, forknum, nextsegno),
    1929             :                             blkno)));
    1930             :         }
    1931             :     }
    1932             : 
    1933      124896 :     return v;
    1934             : }
    1935             : 
    1936             : /*
    1937             :  * Get number of blocks present in a single disk file
    1938             :  */
    1939             : static BlockNumber
    1940     3042290 : _mdnblocks(SMgrRelation reln, ForkNumber forknum, MdfdVec *seg)
    1941             : {
    1942             :     off_t       len;
    1943             : 
    1944     3042290 :     len = FileSeek(seg->mdfd_vfd, 0L, SEEK_END);
    1945     3042290 :     if (len < 0)
    1946           0 :         ereport(ERROR,
    1947             :                 (errcode_for_file_access(),
    1948             :                  errmsg("could not seek to end of file \"%s\": %m",
    1949             :                         FilePathName(seg->mdfd_vfd))));
    1950             :     /* note that this calculation will ignore any partial block at EOF */
    1951     3042290 :     return (BlockNumber) (len / BLCKSZ);
    1952             : }

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