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postgresql/src/backend/storage/smgr/md.c

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/*-------------------------------------------------------------------------
*
* md.c
* This code manages relations that reside on magnetic disk.
*
* Or at least, that was what the Berkeley folk had in mind when they named
* this file. In reality, what this code provides is an interface from
* the smgr API to Unix-like filesystem APIs, so it will work with any type
* of device for which the operating system provides filesystem support.
* It doesn't matter whether the bits are on spinning rust or some other
* storage technology.
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/storage/smgr/md.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <unistd.h>
#include <fcntl.h>
#include <sys/file.h>
#include "access/xlog.h"
#include "access/xlogutils.h"
#include "commands/tablespace.h"
#include "miscadmin.h"
#include "pg_trace.h"
#include "pgstat.h"
#include "postmaster/bgwriter.h"
#include "storage/bufmgr.h"
#include "storage/fd.h"
#include "storage/md.h"
#include "storage/relfilelocator.h"
#include "storage/smgr.h"
#include "storage/sync.h"
#include "utils/hsearch.h"
#include "utils/memutils.h"
/*
* The magnetic disk storage manager keeps track of open file
* descriptors in its own descriptor pool. This is done to make it
* easier to support relations that are larger than the operating
* system's file size limit (often 2GBytes). In order to do that,
* we break relations up into "segment" files that are each shorter than
* the OS file size limit. The segment size is set by the RELSEG_SIZE
* configuration constant in pg_config.h.
*
* On disk, a relation must consist of consecutively numbered segment
* files in the pattern
* -- Zero or more full segments of exactly RELSEG_SIZE blocks each
* -- Exactly one partial segment of size 0 <= size < RELSEG_SIZE blocks
* -- Optionally, any number of inactive segments of size 0 blocks.
* The full and partial segments are collectively the "active" segments.
* Inactive segments are those that once contained data but are currently
* not needed because of an mdtruncate() operation. The reason for leaving
* them present at size zero, rather than unlinking them, is that other
* backends and/or the checkpointer might be holding open file references to
* such segments. If the relation expands again after mdtruncate(), such
* that a deactivated segment becomes active again, it is important that
* such file references still be valid --- else data might get written
* out to an unlinked old copy of a segment file that will eventually
* disappear.
*
* File descriptors are stored in the per-fork md_seg_fds arrays inside
* SMgrRelation. The length of these arrays is stored in md_num_open_segs.
* Note that a fork's md_num_open_segs having a specific value does not
* necessarily mean the relation doesn't have additional segments; we may
* just not have opened the next segment yet. (We could not have "all
* segments are in the array" as an invariant anyway, since another backend
* could extend the relation while we aren't looking.) We do not have
* entries for inactive segments, however; as soon as we find a partial
* segment, we assume that any subsequent segments are inactive.
*
* The entire MdfdVec array is palloc'd in the MdCxt memory context.
*/
typedef struct _MdfdVec
{
File mdfd_vfd; /* fd number in fd.c's pool */
BlockNumber mdfd_segno; /* segment number, from 0 */
} MdfdVec;
static MemoryContext MdCxt; /* context for all MdfdVec objects */
/* Populate a file tag describing an md.c segment file. */
#define INIT_MD_FILETAG(a,xx_rlocator,xx_forknum,xx_segno) \
( \
memset(&(a), 0, sizeof(FileTag)), \
(a).handler = SYNC_HANDLER_MD, \
(a).rlocator = (xx_rlocator), \
(a).forknum = (xx_forknum), \
(a).segno = (xx_segno) \
)
/*** behavior for mdopen & _mdfd_getseg ***/
/* ereport if segment not present */
#define EXTENSION_FAIL (1 << 0)
/* return NULL if segment not present */
#define EXTENSION_RETURN_NULL (1 << 1)
/* create new segments as needed */
#define EXTENSION_CREATE (1 << 2)
/* create new segments if needed during recovery */
#define EXTENSION_CREATE_RECOVERY (1 << 3)
/*
* Allow opening segments which are preceded by segments smaller than
* RELSEG_SIZE, e.g. inactive segments (see above). Note that this breaks
* mdnblocks() and related functionality henceforth - which currently is ok,
* because this is only required in the checkpointer which never uses
* mdnblocks().
*/
#define EXTENSION_DONT_CHECK_SIZE (1 << 4)
/* don't try to open a segment, if not already open */
#define EXTENSION_DONT_OPEN (1 << 5)
/* local routines */
static void mdunlinkfork(RelFileLocatorBackend rlocator, ForkNumber forknum,
bool isRedo);
static MdfdVec *mdopenfork(SMgrRelation reln, ForkNumber forknum, int behavior);
static void register_dirty_segment(SMgrRelation reln, ForkNumber forknum,
MdfdVec *seg);
static void register_unlink_segment(RelFileLocatorBackend rlocator, ForkNumber forknum,
BlockNumber segno);
static void register_forget_request(RelFileLocatorBackend rlocator, ForkNumber forknum,
BlockNumber segno);
static void _fdvec_resize(SMgrRelation reln,
ForkNumber forknum,
int nseg);
static char *_mdfd_segpath(SMgrRelation reln, ForkNumber forknum,
BlockNumber segno);
static MdfdVec *_mdfd_openseg(SMgrRelation reln, ForkNumber forknum,
BlockNumber segno, int oflags);
static MdfdVec *_mdfd_getseg(SMgrRelation reln, ForkNumber forknum,
BlockNumber blkno, bool skipFsync, int behavior);
static BlockNumber _mdnblocks(SMgrRelation reln, ForkNumber forknum,
MdfdVec *seg);
static inline int
_mdfd_open_flags(void)
{
int flags = O_RDWR | PG_BINARY;
if (io_direct_flags & IO_DIRECT_DATA)
flags |= PG_O_DIRECT;
return flags;
}
/*
* mdinit() -- Initialize private state for magnetic disk storage manager.
*/
void
mdinit(void)
{
MdCxt = AllocSetContextCreate(TopMemoryContext,
"MdSmgr",
ALLOCSET_DEFAULT_SIZES);
}
/*
* mdexists() -- Does the physical file exist?
*
* Note: this will return true for lingering files, with pending deletions
*/
bool
mdexists(SMgrRelation reln, ForkNumber forknum)
{
/*
* Close it first, to ensure that we notice if the fork has been unlinked
* since we opened it. As an optimization, we can skip that in recovery,
* which already closes relations when dropping them.
*/
if (!InRecovery)
mdclose(reln, forknum);
return (mdopenfork(reln, forknum, EXTENSION_RETURN_NULL) != NULL);
}
/*
* mdcreate() -- Create a new relation on magnetic disk.
*
* If isRedo is true, it's okay for the relation to exist already.
*/
void
mdcreate(SMgrRelation reln, ForkNumber forknum, bool isRedo)
{
MdfdVec *mdfd;
char *path;
File fd;
if (isRedo && reln->md_num_open_segs[forknum] > 0)
return; /* created and opened already... */
Assert(reln->md_num_open_segs[forknum] == 0);
/*
* We may be using the target table space for the first time in this
* database, so create a per-database subdirectory if needed.
*
* XXX this is a fairly ugly violation of module layering, but this seems
* to be the best place to put the check. Maybe TablespaceCreateDbspace
* should be here and not in commands/tablespace.c? But that would imply
* importing a lot of stuff that smgr.c oughtn't know, either.
*/
TablespaceCreateDbspace(reln->smgr_rlocator.locator.spcOid,
reln->smgr_rlocator.locator.dbOid,
isRedo);
path = relpath(reln->smgr_rlocator, forknum);
fd = PathNameOpenFile(path, _mdfd_open_flags() | O_CREAT | O_EXCL);
if (fd < 0)
{
int save_errno = errno;
if (isRedo)
fd = PathNameOpenFile(path, _mdfd_open_flags());
if (fd < 0)
{
/* be sure to report the error reported by create, not open */
errno = save_errno;
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not create file \"%s\": %m", path)));
}
}
pfree(path);
_fdvec_resize(reln, forknum, 1);
mdfd = &reln->md_seg_fds[forknum][0];
mdfd->mdfd_vfd = fd;
mdfd->mdfd_segno = 0;
}
/*
* mdunlink() -- Unlink a relation.
*
* Note that we're passed a RelFileLocatorBackend --- by the time this is called,
* there won't be an SMgrRelation hashtable entry anymore.
*
* forknum can be a fork number to delete a specific fork, or InvalidForkNumber
* to delete all forks.
*
* For regular relations, we don't unlink the first segment file of the rel,
* but just truncate it to zero length, and record a request to unlink it after
* the next checkpoint. Additional segments can be unlinked immediately,
* however. Leaving the empty file in place prevents that relfilenumber
* from being reused. The scenario this protects us from is:
* 1. We delete a relation (and commit, and actually remove its file).
* 2. We create a new relation, which by chance gets the same relfilenumber as
* the just-deleted one (OIDs must've wrapped around for that to happen).
* 3. We crash before another checkpoint occurs.
* During replay, we would delete the file and then recreate it, which is fine
* if the contents of the file were repopulated by subsequent WAL entries.
* But if we didn't WAL-log insertions, but instead relied on fsyncing the
* file after populating it (as we do at wal_level=minimal), the contents of
* the file would be lost forever. By leaving the empty file until after the
* next checkpoint, we prevent reassignment of the relfilenumber until it's
* safe, because relfilenumber assignment skips over any existing file.
*
* Additional segments, if any, are truncated and then unlinked. The reason
* for truncating is that other backends may still hold open FDs for these at
* the smgr level, so that the kernel can't remove the file yet. We want to
* reclaim the disk space right away despite that.
*
* We do not need to go through this dance for temp relations, though, because
* we never make WAL entries for temp rels, and so a temp rel poses no threat
* to the health of a regular rel that has taken over its relfilenumber.
* The fact that temp rels and regular rels have different file naming
* patterns provides additional safety. Other backends shouldn't have open
* FDs for them, either.
*
* We also don't do it while performing a binary upgrade. There is no reuse
* hazard in that case, since after a crash or even a simple ERROR, the
* upgrade fails and the whole cluster must be recreated from scratch.
* Furthermore, it is important to remove the files from disk immediately,
* because we may be about to reuse the same relfilenumber.
*
* All the above applies only to the relation's main fork; other forks can
* just be removed immediately, since they are not needed to prevent the
* relfilenumber from being recycled. Also, we do not carefully
* track whether other forks have been created or not, but just attempt to
* unlink them unconditionally; so we should never complain about ENOENT.
*
* If isRedo is true, it's unsurprising for the relation to be already gone.
* Also, we should remove the file immediately instead of queuing a request
* for later, since during redo there's no possibility of creating a
* conflicting relation.
*
* Note: we currently just never warn about ENOENT at all. We could warn in
* the main-fork, non-isRedo case, but it doesn't seem worth the trouble.
*
* Note: any failure should be reported as WARNING not ERROR, because
* we are usually not in a transaction anymore when this is called.
*/
void
mdunlink(RelFileLocatorBackend rlocator, ForkNumber forknum, bool isRedo)
{
/* Now do the per-fork work */
if (forknum == InvalidForkNumber)
{
for (forknum = 0; forknum <= MAX_FORKNUM; forknum++)
mdunlinkfork(rlocator, forknum, isRedo);
}
else
mdunlinkfork(rlocator, forknum, isRedo);
}
/*
* Truncate a file to release disk space.
*/
static int
do_truncate(const char *path)
{
int save_errno;
int ret;
ret = pg_truncate(path, 0);
/* Log a warning here to avoid repetition in callers. */
if (ret < 0 && errno != ENOENT)
{
save_errno = errno;
ereport(WARNING,
(errcode_for_file_access(),
errmsg("could not truncate file \"%s\": %m", path)));
errno = save_errno;
}
return ret;
}
static void
mdunlinkfork(RelFileLocatorBackend rlocator, ForkNumber forknum, bool isRedo)
{
char *path;
int ret;
int save_errno;
path = relpath(rlocator, forknum);
/*
* Truncate and then unlink the first segment, or just register a request
* to unlink it later, as described in the comments for mdunlink().
*/
if (isRedo || IsBinaryUpgrade || forknum != MAIN_FORKNUM ||
RelFileLocatorBackendIsTemp(rlocator))
{
if (!RelFileLocatorBackendIsTemp(rlocator))
{
/* Prevent other backends' fds from holding on to the disk space */
ret = do_truncate(path);
/* Forget any pending sync requests for the first segment */
save_errno = errno;
register_forget_request(rlocator, forknum, 0 /* first seg */ );
errno = save_errno;
}
else
ret = 0;
/* Next unlink the file, unless it was already found to be missing */
if (ret >= 0 || errno != ENOENT)
{
ret = unlink(path);
if (ret < 0 && errno != ENOENT)
{
save_errno = errno;
ereport(WARNING,
(errcode_for_file_access(),
errmsg("could not remove file \"%s\": %m", path)));
errno = save_errno;
}
}
}
else
{
/* Prevent other backends' fds from holding on to the disk space */
ret = do_truncate(path);
/* Register request to unlink first segment later */
save_errno = errno;
register_unlink_segment(rlocator, forknum, 0 /* first seg */ );
errno = save_errno;
}
/*
* Delete any additional segments.
*
* Note that because we loop until getting ENOENT, we will correctly
* remove all inactive segments as well as active ones. Ideally we'd
* continue the loop until getting exactly that errno, but that risks an
* infinite loop if the problem is directory-wide (for instance, if we
* suddenly can't read the data directory itself). We compromise by
* continuing after a non-ENOENT truncate error, but stopping after any
* unlink error. If there is indeed a directory-wide problem, additional
* unlink attempts wouldn't work anyway.
*/
if (ret >= 0 || errno != ENOENT)
{
char *segpath = (char *) palloc(strlen(path) + 12);
BlockNumber segno;
for (segno = 1;; segno++)
{
sprintf(segpath, "%s.%u", path, segno);
if (!RelFileLocatorBackendIsTemp(rlocator))
{
/*
* Prevent other backends' fds from holding on to the disk
* space. We're done if we see ENOENT, though.
*/
if (do_truncate(segpath) < 0 && errno == ENOENT)
break;
/*
* Forget any pending sync requests for this segment before we
* try to unlink.
*/
register_forget_request(rlocator, forknum, segno);
}
if (unlink(segpath) < 0)
{
/* ENOENT is expected after the last segment... */
if (errno != ENOENT)
ereport(WARNING,
(errcode_for_file_access(),
errmsg("could not remove file \"%s\": %m", segpath)));
break;
}
}
pfree(segpath);
}
pfree(path);
}
/*
* mdextend() -- Add a block to the specified relation.
*
* The semantics are nearly the same as mdwrite(): write at the
* specified position. However, this is to be used for the case of
* extending a relation (i.e., blocknum is at or beyond the current
* EOF). Note that we assume writing a block beyond current EOF
* causes intervening file space to become filled with zeroes.
*/
void
mdextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
const void *buffer, bool skipFsync)
{
off_t seekpos;
int nbytes;
MdfdVec *v;
/* If this build supports direct I/O, the buffer must be I/O aligned. */
if (PG_O_DIRECT != 0 && PG_IO_ALIGN_SIZE <= BLCKSZ)
Assert((uintptr_t) buffer == TYPEALIGN(PG_IO_ALIGN_SIZE, buffer));
/* This assert is too expensive to have on normally ... */
#ifdef CHECK_WRITE_VS_EXTEND
Assert(blocknum >= mdnblocks(reln, forknum));
#endif
/*
* If a relation manages to grow to 2^32-1 blocks, refuse to extend it any
* more --- we mustn't create a block whose number actually is
* InvalidBlockNumber. (Note that this failure should be unreachable
* because of upstream checks in bufmgr.c.)
*/
if (blocknum == InvalidBlockNumber)
ereport(ERROR,
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("cannot extend file \"%s\" beyond %u blocks",
relpath(reln->smgr_rlocator, forknum),
InvalidBlockNumber)));
v = _mdfd_getseg(reln, forknum, blocknum, skipFsync, EXTENSION_CREATE);
seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
if ((nbytes = FileWrite(v->mdfd_vfd, buffer, BLCKSZ, seekpos, WAIT_EVENT_DATA_FILE_EXTEND)) != BLCKSZ)
{
if (nbytes < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not extend file \"%s\": %m",
FilePathName(v->mdfd_vfd)),
errhint("Check free disk space.")));
/* short write: complain appropriately */
ereport(ERROR,
(errcode(ERRCODE_DISK_FULL),
errmsg("could not extend file \"%s\": wrote only %d of %d bytes at block %u",
FilePathName(v->mdfd_vfd),
nbytes, BLCKSZ, blocknum),
errhint("Check free disk space.")));
}
if (!skipFsync && !SmgrIsTemp(reln))
register_dirty_segment(reln, forknum, v);
Assert(_mdnblocks(reln, forknum, v) <= ((BlockNumber) RELSEG_SIZE));
}
/*
* mdzeroextend() -- Add new zeroed out blocks to the specified relation.
*
* Similar to mdextend(), except the relation can be extended by multiple
* blocks at once and the added blocks will be filled with zeroes.
*/
void
mdzeroextend(SMgrRelation reln, ForkNumber forknum,
BlockNumber blocknum, int nblocks, bool skipFsync)
{
MdfdVec *v;
BlockNumber curblocknum = blocknum;
int remblocks = nblocks;
Assert(nblocks > 0);
/* This assert is too expensive to have on normally ... */
#ifdef CHECK_WRITE_VS_EXTEND
Assert(blocknum >= mdnblocks(reln, forknum));
#endif
/*
* If a relation manages to grow to 2^32-1 blocks, refuse to extend it any
* more --- we mustn't create a block whose number actually is
* InvalidBlockNumber or larger.
*/
if ((uint64) blocknum + nblocks >= (uint64) InvalidBlockNumber)
ereport(ERROR,
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("cannot extend file \"%s\" beyond %u blocks",
relpath(reln->smgr_rlocator, forknum),
InvalidBlockNumber)));
while (remblocks > 0)
{
BlockNumber segstartblock = curblocknum % ((BlockNumber) RELSEG_SIZE);
off_t seekpos = (off_t) BLCKSZ * segstartblock;
int numblocks;
if (segstartblock + remblocks > RELSEG_SIZE)
numblocks = RELSEG_SIZE - segstartblock;
else
numblocks = remblocks;
v = _mdfd_getseg(reln, forknum, curblocknum, skipFsync, EXTENSION_CREATE);
Assert(segstartblock < RELSEG_SIZE);
Assert(segstartblock + numblocks <= RELSEG_SIZE);
/*
* If available and useful, use posix_fallocate() (via FileAllocate())
* to extend the relation. That's often more efficient than using
* write(), as it commonly won't cause the kernel to allocate page
* cache space for the extended pages.
*
* However, we don't use FileAllocate() for small extensions, as it
* defeats delayed allocation on some filesystems. Not clear where
* that decision should be made though? For now just use a cutoff of
* 8, anything between 4 and 8 worked OK in some local testing.
*/
if (numblocks > 8)
{
int ret;
ret = FileFallocate(v->mdfd_vfd,
seekpos, (off_t) BLCKSZ * numblocks,
WAIT_EVENT_DATA_FILE_EXTEND);
if (ret != 0)
{
ereport(ERROR,
errcode_for_file_access(),
errmsg("could not extend file \"%s\" with FileFallocate(): %m",
FilePathName(v->mdfd_vfd)),
errhint("Check free disk space."));
}
}
else
{
int ret;
/*
* Even if we don't want to use fallocate, we can still extend a
* bit more efficiently than writing each 8kB block individually.
* pg_pwrite_zeros() (via FileZero()) uses pg_pwritev_with_retry()
* to avoid multiple writes or needing a zeroed buffer for the
* whole length of the extension.
*/
ret = FileZero(v->mdfd_vfd,
seekpos, (off_t) BLCKSZ * numblocks,
WAIT_EVENT_DATA_FILE_EXTEND);
if (ret < 0)
ereport(ERROR,
errcode_for_file_access(),
errmsg("could not extend file \"%s\": %m",
FilePathName(v->mdfd_vfd)),
errhint("Check free disk space."));
}
if (!skipFsync && !SmgrIsTemp(reln))
register_dirty_segment(reln, forknum, v);
Assert(_mdnblocks(reln, forknum, v) <= ((BlockNumber) RELSEG_SIZE));
remblocks -= numblocks;
curblocknum += numblocks;
}
}
/*
* mdopenfork() -- Open one fork of the specified relation.
*
* Note we only open the first segment, when there are multiple segments.
*
* If first segment is not present, either ereport or return NULL according
* to "behavior". We treat EXTENSION_CREATE the same as EXTENSION_FAIL;
* EXTENSION_CREATE means it's OK to extend an existing relation, not to
* invent one out of whole cloth.
*/
static MdfdVec *
mdopenfork(SMgrRelation reln, ForkNumber forknum, int behavior)
{
MdfdVec *mdfd;
char *path;
File fd;
/* No work if already open */
if (reln->md_num_open_segs[forknum] > 0)
return &reln->md_seg_fds[forknum][0];
path = relpath(reln->smgr_rlocator, forknum);
fd = PathNameOpenFile(path, _mdfd_open_flags());
if (fd < 0)
{
if ((behavior & EXTENSION_RETURN_NULL) &&
FILE_POSSIBLY_DELETED(errno))
{
pfree(path);
return NULL;
}
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open file \"%s\": %m", path)));
}
pfree(path);
_fdvec_resize(reln, forknum, 1);
mdfd = &reln->md_seg_fds[forknum][0];
mdfd->mdfd_vfd = fd;
mdfd->mdfd_segno = 0;
Assert(_mdnblocks(reln, forknum, mdfd) <= ((BlockNumber) RELSEG_SIZE));
return mdfd;
}
/*
* mdopen() -- Initialize newly-opened relation.
*/
void
mdopen(SMgrRelation reln)
{
/* mark it not open */
for (int forknum = 0; forknum <= MAX_FORKNUM; forknum++)
reln->md_num_open_segs[forknum] = 0;
}
/*
* mdclose() -- Close the specified relation, if it isn't closed already.
*/
void
mdclose(SMgrRelation reln, ForkNumber forknum)
{
int nopensegs = reln->md_num_open_segs[forknum];
/* No work if already closed */
if (nopensegs == 0)
return;
/* close segments starting from the end */
while (nopensegs > 0)
{
MdfdVec *v = &reln->md_seg_fds[forknum][nopensegs - 1];
FileClose(v->mdfd_vfd);
_fdvec_resize(reln, forknum, nopensegs - 1);
nopensegs--;
}
}
/*
* mdprefetch() -- Initiate asynchronous read of the specified block of a relation
*/
bool
mdprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum)
{
#ifdef USE_PREFETCH
off_t seekpos;
MdfdVec *v;
Assert((io_direct_flags & IO_DIRECT_DATA) == 0);
v = _mdfd_getseg(reln, forknum, blocknum, false,
InRecovery ? EXTENSION_RETURN_NULL : EXTENSION_FAIL);
if (v == NULL)
return false;
seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
(void) FilePrefetch(v->mdfd_vfd, seekpos, BLCKSZ, WAIT_EVENT_DATA_FILE_PREFETCH);
#endif /* USE_PREFETCH */
return true;
}
/*
* mdread() -- Read the specified block from a relation.
*/
void
mdread(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
void *buffer)
{
off_t seekpos;
int nbytes;
MdfdVec *v;
/* If this build supports direct I/O, the buffer must be I/O aligned. */
if (PG_O_DIRECT != 0 && PG_IO_ALIGN_SIZE <= BLCKSZ)
Assert((uintptr_t) buffer == TYPEALIGN(PG_IO_ALIGN_SIZE, buffer));
TRACE_POSTGRESQL_SMGR_MD_READ_START(forknum, blocknum,
reln->smgr_rlocator.locator.spcOid,
reln->smgr_rlocator.locator.dbOid,
reln->smgr_rlocator.locator.relNumber,
reln->smgr_rlocator.backend);
v = _mdfd_getseg(reln, forknum, blocknum, false,
EXTENSION_FAIL | EXTENSION_CREATE_RECOVERY);
seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
nbytes = FileRead(v->mdfd_vfd, buffer, BLCKSZ, seekpos, WAIT_EVENT_DATA_FILE_READ);
TRACE_POSTGRESQL_SMGR_MD_READ_DONE(forknum, blocknum,
reln->smgr_rlocator.locator.spcOid,
reln->smgr_rlocator.locator.dbOid,
reln->smgr_rlocator.locator.relNumber,
reln->smgr_rlocator.backend,
nbytes,
BLCKSZ);
if (nbytes != BLCKSZ)
{
if (nbytes < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not read block %u in file \"%s\": %m",
blocknum, FilePathName(v->mdfd_vfd))));
/*
* Short read: we are at or past EOF, or we read a partial block at
* EOF. Normally this is an error; upper levels should never try to
* read a nonexistent block. However, if zero_damaged_pages is ON or
* we are InRecovery, we should instead return zeroes without
* complaining. This allows, for example, the case of trying to
* update a block that was later truncated away.
*/
if (zero_damaged_pages || InRecovery)
MemSet(buffer, 0, BLCKSZ);
else
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg("could not read block %u in file \"%s\": read only %d of %d bytes",
blocknum, FilePathName(v->mdfd_vfd),
nbytes, BLCKSZ)));
}
}
/*
* mdwrite() -- Write the supplied block at the appropriate location.
*
* This is to be used only for updating already-existing blocks of a
* relation (ie, those before the current EOF). To extend a relation,
* use mdextend().
*/
void
mdwrite(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
const void *buffer, bool skipFsync)
{
off_t seekpos;
int nbytes;
MdfdVec *v;
/* If this build supports direct I/O, the buffer must be I/O aligned. */
if (PG_O_DIRECT != 0 && PG_IO_ALIGN_SIZE <= BLCKSZ)
Assert((uintptr_t) buffer == TYPEALIGN(PG_IO_ALIGN_SIZE, buffer));
/* This assert is too expensive to have on normally ... */
#ifdef CHECK_WRITE_VS_EXTEND
Assert(blocknum < mdnblocks(reln, forknum));
#endif
TRACE_POSTGRESQL_SMGR_MD_WRITE_START(forknum, blocknum,
reln->smgr_rlocator.locator.spcOid,
reln->smgr_rlocator.locator.dbOid,
reln->smgr_rlocator.locator.relNumber,
reln->smgr_rlocator.backend);
v = _mdfd_getseg(reln, forknum, blocknum, skipFsync,
EXTENSION_FAIL | EXTENSION_CREATE_RECOVERY);
seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
Assert(seekpos < (off_t) BLCKSZ * RELSEG_SIZE);
nbytes = FileWrite(v->mdfd_vfd, buffer, BLCKSZ, seekpos, WAIT_EVENT_DATA_FILE_WRITE);
TRACE_POSTGRESQL_SMGR_MD_WRITE_DONE(forknum, blocknum,
reln->smgr_rlocator.locator.spcOid,
reln->smgr_rlocator.locator.dbOid,
reln->smgr_rlocator.locator.relNumber,
reln->smgr_rlocator.backend,
nbytes,
BLCKSZ);
if (nbytes != BLCKSZ)
{
if (nbytes < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not write block %u in file \"%s\": %m",
blocknum, FilePathName(v->mdfd_vfd))));
/* short write: complain appropriately */
ereport(ERROR,
(errcode(ERRCODE_DISK_FULL),
errmsg("could not write block %u in file \"%s\": wrote only %d of %d bytes",
blocknum,
FilePathName(v->mdfd_vfd),
nbytes, BLCKSZ),
errhint("Check free disk space.")));
}
if (!skipFsync && !SmgrIsTemp(reln))
register_dirty_segment(reln, forknum, v);
}
/*
* mdwriteback() -- Tell the kernel to write pages back to storage.
*
* This accepts a range of blocks because flushing several pages at once is
* considerably more efficient than doing so individually.
*/
void
mdwriteback(SMgrRelation reln, ForkNumber forknum,
BlockNumber blocknum, BlockNumber nblocks)
{
Assert((io_direct_flags & IO_DIRECT_DATA) == 0);
/*
* Issue flush requests in as few requests as possible; have to split at
* segment boundaries though, since those are actually separate files.
*/
while (nblocks > 0)
{
BlockNumber nflush = nblocks;
off_t seekpos;
MdfdVec *v;
int segnum_start,
segnum_end;
v = _mdfd_getseg(reln, forknum, blocknum, true /* not used */ ,
EXTENSION_DONT_OPEN);
/*
* We might be flushing buffers of already removed relations, that's
* ok, just ignore that case. If the segment file wasn't open already
* (ie from a recent mdwrite()), then we don't want to re-open it, to
* avoid a race with PROCSIGNAL_BARRIER_SMGRRELEASE that might leave
* us with a descriptor to a file that is about to be unlinked.
*/
if (!v)
return;
/* compute offset inside the current segment */
segnum_start = blocknum / RELSEG_SIZE;
/* compute number of desired writes within the current segment */
segnum_end = (blocknum + nblocks - 1) / RELSEG_SIZE;
if (segnum_start != segnum_end)
nflush = RELSEG_SIZE - (blocknum % ((BlockNumber) RELSEG_SIZE));
Assert(nflush >= 1);
Assert(nflush <= nblocks);
seekpos = (off_t) BLCKSZ * (blocknum % ((BlockNumber) RELSEG_SIZE));
FileWriteback(v->mdfd_vfd, seekpos, (off_t) BLCKSZ * nflush, WAIT_EVENT_DATA_FILE_FLUSH);
nblocks -= nflush;
blocknum += nflush;
}
}
/*
* mdnblocks() -- Get the number of blocks stored in a relation.
*
* Important side effect: all active segments of the relation are opened
* and added to the md_seg_fds array. If this routine has not been
* called, then only segments up to the last one actually touched
* are present in the array.
*/
BlockNumber
mdnblocks(SMgrRelation reln, ForkNumber forknum)
{
MdfdVec *v;
BlockNumber nblocks;
BlockNumber segno;
mdopenfork(reln, forknum, EXTENSION_FAIL);
/* mdopen has opened the first segment */
Assert(reln->md_num_open_segs[forknum] > 0);
/*
* Start from the last open segments, to avoid redundant seeks. We have
* previously verified that these segments are exactly RELSEG_SIZE long,
* and it's useless to recheck that each time.
*
* NOTE: this assumption could only be wrong if another backend has
* truncated the relation. We rely on higher code levels to handle that
* scenario by closing and re-opening the md fd, which is handled via
* relcache flush. (Since the checkpointer doesn't participate in
* relcache flush, it could have segment entries for inactive segments;
* that's OK because the checkpointer never needs to compute relation
* size.)
*/
segno = reln->md_num_open_segs[forknum] - 1;
v = &reln->md_seg_fds[forknum][segno];
for (;;)
{
nblocks = _mdnblocks(reln, forknum, v);
if (nblocks > ((BlockNumber) RELSEG_SIZE))
elog(FATAL, "segment too big");
if (nblocks < ((BlockNumber) RELSEG_SIZE))
return (segno * ((BlockNumber) RELSEG_SIZE)) + nblocks;
/*
* If segment is exactly RELSEG_SIZE, advance to next one.
*/
segno++;
/*
* We used to pass O_CREAT here, but that has the disadvantage that it
* might create a segment which has vanished through some operating
* system misadventure. In such a case, creating the segment here
* undermines _mdfd_getseg's attempts to notice and report an error
* upon access to a missing segment.
*/
v = _mdfd_openseg(reln, forknum, segno, 0);
if (v == NULL)
return segno * ((BlockNumber) RELSEG_SIZE);
}
}
/*
* mdtruncate() -- Truncate relation to specified number of blocks.
*/
void
mdtruncate(SMgrRelation reln, ForkNumber forknum, BlockNumber nblocks)
{
BlockNumber curnblk;
BlockNumber priorblocks;
int curopensegs;
/*
* NOTE: mdnblocks makes sure we have opened all active segments, so that
* truncation loop will get them all!
*/
curnblk = mdnblocks(reln, forknum);
if (nblocks > curnblk)
{
/* Bogus request ... but no complaint if InRecovery */
if (InRecovery)
return;
ereport(ERROR,
(errmsg("could not truncate file \"%s\" to %u blocks: it's only %u blocks now",
relpath(reln->smgr_rlocator, forknum),
nblocks, curnblk)));
}
if (nblocks == curnblk)
return; /* no work */
/*
* Truncate segments, starting at the last one. Starting at the end makes
* managing the memory for the fd array easier, should there be errors.
*/
curopensegs = reln->md_num_open_segs[forknum];
while (curopensegs > 0)
{
MdfdVec *v;
priorblocks = (curopensegs - 1) * RELSEG_SIZE;
v = &reln->md_seg_fds[forknum][curopensegs - 1];
if (priorblocks > nblocks)
{
/*
* This segment is no longer active. We truncate the file, but do
* not delete it, for reasons explained in the header comments.
*/
if (FileTruncate(v->mdfd_vfd, 0, WAIT_EVENT_DATA_FILE_TRUNCATE) < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not truncate file \"%s\": %m",
FilePathName(v->mdfd_vfd))));
if (!SmgrIsTemp(reln))
register_dirty_segment(reln, forknum, v);
/* we never drop the 1st segment */
Assert(v != &reln->md_seg_fds[forknum][0]);
FileClose(v->mdfd_vfd);
_fdvec_resize(reln, forknum, curopensegs - 1);
}
else if (priorblocks + ((BlockNumber) RELSEG_SIZE) > nblocks)
{
/*
* This is the last segment we want to keep. Truncate the file to
* the right length. NOTE: if nblocks is exactly a multiple K of
* RELSEG_SIZE, we will truncate the K+1st segment to 0 length but
* keep it. This adheres to the invariant given in the header
* comments.
*/
BlockNumber lastsegblocks = nblocks - priorblocks;
if (FileTruncate(v->mdfd_vfd, (off_t) lastsegblocks * BLCKSZ, WAIT_EVENT_DATA_FILE_TRUNCATE) < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not truncate file \"%s\" to %u blocks: %m",
FilePathName(v->mdfd_vfd),
nblocks)));
if (!SmgrIsTemp(reln))
register_dirty_segment(reln, forknum, v);
}
else
{
/*
* We still need this segment, so nothing to do for this and any
* earlier segment.
*/
break;
}
curopensegs--;
}
}
/*
* mdimmedsync() -- Immediately sync a relation to stable storage.
*
* Note that only writes already issued are synced; this routine knows
* nothing of dirty buffers that may exist inside the buffer manager. We
* sync active and inactive segments; smgrDoPendingSyncs() relies on this.
* Consider a relation skipping WAL. Suppose a checkpoint syncs blocks of
* some segment, then mdtruncate() renders that segment inactive. If we
* crash before the next checkpoint syncs the newly-inactive segment, that
* segment may survive recovery, reintroducing unwanted data into the table.
*/
void
mdimmedsync(SMgrRelation reln, ForkNumber forknum)
{
int segno;
int min_inactive_seg;
/*
* NOTE: mdnblocks makes sure we have opened all active segments, so that
* fsync loop will get them all!
*/
mdnblocks(reln, forknum);
min_inactive_seg = segno = reln->md_num_open_segs[forknum];
/*
* Temporarily open inactive segments, then close them after sync. There
* may be some inactive segments left opened after fsync() error, but that
* is harmless. We don't bother to clean them up and take a risk of
* further trouble. The next mdclose() will soon close them.
*/
while (_mdfd_openseg(reln, forknum, segno, 0) != NULL)
segno++;
while (segno > 0)
{
MdfdVec *v = &reln->md_seg_fds[forknum][segno - 1];
/*
* fsyncs done through mdimmedsync() should be tracked in a separate
* IOContext than those done through mdsyncfiletag() to differentiate
* between unavoidable client backend fsyncs (e.g. those done during
* index build) and those which ideally would have been done by the
* checkpointer. Since other IO operations bypassing the buffer
* manager could also be tracked in such an IOContext, wait until
* these are also tracked to track immediate fsyncs.
*/
if (FileSync(v->mdfd_vfd, WAIT_EVENT_DATA_FILE_IMMEDIATE_SYNC) < 0)
ereport(data_sync_elevel(ERROR),
(errcode_for_file_access(),
errmsg("could not fsync file \"%s\": %m",
FilePathName(v->mdfd_vfd))));
/* Close inactive segments immediately */
if (segno > min_inactive_seg)
{
FileClose(v->mdfd_vfd);
_fdvec_resize(reln, forknum, segno - 1);
}
segno--;
}
}
/*
* register_dirty_segment() -- Mark a relation segment as needing fsync
*
* If there is a local pending-ops table, just make an entry in it for
* ProcessSyncRequests to process later. Otherwise, try to pass off the
* fsync request to the checkpointer process. If that fails, just do the
* fsync locally before returning (we hope this will not happen often
* enough to be a performance problem).
*/
static void
register_dirty_segment(SMgrRelation reln, ForkNumber forknum, MdfdVec *seg)
{
FileTag tag;
INIT_MD_FILETAG(tag, reln->smgr_rlocator.locator, forknum, seg->mdfd_segno);
/* Temp relations should never be fsync'd */
Assert(!SmgrIsTemp(reln));
if (!RegisterSyncRequest(&tag, SYNC_REQUEST, false /* retryOnError */ ))
{
instr_time io_start;
ereport(DEBUG1,
(errmsg_internal("could not forward fsync request because request queue is full")));
io_start = pgstat_prepare_io_time();
if (FileSync(seg->mdfd_vfd, WAIT_EVENT_DATA_FILE_SYNC) < 0)
ereport(data_sync_elevel(ERROR),
(errcode_for_file_access(),
errmsg("could not fsync file \"%s\": %m",
FilePathName(seg->mdfd_vfd))));
/*
* We have no way of knowing if the current IOContext is
* IOCONTEXT_NORMAL or IOCONTEXT_[BULKREAD, BULKWRITE, VACUUM] at this
* point, so count the fsync as being in the IOCONTEXT_NORMAL
* IOContext. This is probably okay, because the number of backend
* fsyncs doesn't say anything about the efficacy of the
* BufferAccessStrategy. And counting both fsyncs done in
* IOCONTEXT_NORMAL and IOCONTEXT_[BULKREAD, BULKWRITE, VACUUM] under
* IOCONTEXT_NORMAL is likely clearer when investigating the number of
* backend fsyncs.
*/
pgstat_count_io_op_time(IOOBJECT_RELATION, IOCONTEXT_NORMAL,
IOOP_FSYNC, io_start, 1);
}
}
/*
* register_unlink_segment() -- Schedule a file to be deleted after next checkpoint
*/
static void
register_unlink_segment(RelFileLocatorBackend rlocator, ForkNumber forknum,
BlockNumber segno)
{
FileTag tag;
INIT_MD_FILETAG(tag, rlocator.locator, forknum, segno);
/* Should never be used with temp relations */
Assert(!RelFileLocatorBackendIsTemp(rlocator));
RegisterSyncRequest(&tag, SYNC_UNLINK_REQUEST, true /* retryOnError */ );
}
/*
* register_forget_request() -- forget any fsyncs for a relation fork's segment
*/
static void
register_forget_request(RelFileLocatorBackend rlocator, ForkNumber forknum,
BlockNumber segno)
{
FileTag tag;
INIT_MD_FILETAG(tag, rlocator.locator, forknum, segno);
RegisterSyncRequest(&tag, SYNC_FORGET_REQUEST, true /* retryOnError */ );
}
/*
* ForgetDatabaseSyncRequests -- forget any fsyncs and unlinks for a DB
*/
void
ForgetDatabaseSyncRequests(Oid dbid)
{
FileTag tag;
RelFileLocator rlocator;
rlocator.dbOid = dbid;
rlocator.spcOid = 0;
rlocator.relNumber = 0;
INIT_MD_FILETAG(tag, rlocator, InvalidForkNumber, InvalidBlockNumber);
RegisterSyncRequest(&tag, SYNC_FILTER_REQUEST, true /* retryOnError */ );
}
/*
* DropRelationFiles -- drop files of all given relations
*/
void
DropRelationFiles(RelFileLocator *delrels, int ndelrels, bool isRedo)
{
SMgrRelation *srels;
int i;
srels = palloc(sizeof(SMgrRelation) * ndelrels);
for (i = 0; i < ndelrels; i++)
{
SMgrRelation srel = smgropen(delrels[i], InvalidBackendId);
if (isRedo)
{
ForkNumber fork;
for (fork = 0; fork <= MAX_FORKNUM; fork++)
XLogDropRelation(delrels[i], fork);
}
srels[i] = srel;
}
smgrdounlinkall(srels, ndelrels, isRedo);
for (i = 0; i < ndelrels; i++)
smgrclose(srels[i]);
pfree(srels);
}
/*
* _fdvec_resize() -- Resize the fork's open segments array
*/
static void
_fdvec_resize(SMgrRelation reln,
ForkNumber forknum,
int nseg)
{
if (nseg == 0)
{
if (reln->md_num_open_segs[forknum] > 0)
{
pfree(reln->md_seg_fds[forknum]);
reln->md_seg_fds[forknum] = NULL;
}
}
else if (reln->md_num_open_segs[forknum] == 0)
{
reln->md_seg_fds[forknum] =
MemoryContextAlloc(MdCxt, sizeof(MdfdVec) * nseg);
}
else
{
/*
* It doesn't seem worthwhile complicating the code to amortize
* repalloc() calls. Those are far faster than PathNameOpenFile() or
* FileClose(), and the memory context internally will sometimes avoid
* doing an actual reallocation.
*/
reln->md_seg_fds[forknum] =
repalloc(reln->md_seg_fds[forknum],
sizeof(MdfdVec) * nseg);
}
reln->md_num_open_segs[forknum] = nseg;
}
/*
* Return the filename for the specified segment of the relation. The
* returned string is palloc'd.
*/
static char *
_mdfd_segpath(SMgrRelation reln, ForkNumber forknum, BlockNumber segno)
{
char *path,
*fullpath;
path = relpath(reln->smgr_rlocator, forknum);
if (segno > 0)
{
fullpath = psprintf("%s.%u", path, segno);
pfree(path);
}
else
fullpath = path;
return fullpath;
}
/*
* Open the specified segment of the relation,
* and make a MdfdVec object for it. Returns NULL on failure.
*/
static MdfdVec *
_mdfd_openseg(SMgrRelation reln, ForkNumber forknum, BlockNumber segno,
int oflags)
{
MdfdVec *v;
File fd;
char *fullpath;
fullpath = _mdfd_segpath(reln, forknum, segno);
/* open the file */
fd = PathNameOpenFile(fullpath, _mdfd_open_flags() | oflags);
pfree(fullpath);
if (fd < 0)
return NULL;
/*
* Segments are always opened in order from lowest to highest, so we must
* be adding a new one at the end.
*/
Assert(segno == reln->md_num_open_segs[forknum]);
_fdvec_resize(reln, forknum, segno + 1);
/* fill the entry */
v = &reln->md_seg_fds[forknum][segno];
v->mdfd_vfd = fd;
v->mdfd_segno = segno;
Assert(_mdnblocks(reln, forknum, v) <= ((BlockNumber) RELSEG_SIZE));
/* all done */
return v;
}
/*
* _mdfd_getseg() -- Find the segment of the relation holding the
* specified block.
*
* If the segment doesn't exist, we ereport, return NULL, or create the
* segment, according to "behavior". Note: skipFsync is only used in the
* EXTENSION_CREATE case.
*/
static MdfdVec *
_mdfd_getseg(SMgrRelation reln, ForkNumber forknum, BlockNumber blkno,
bool skipFsync, int behavior)
{
MdfdVec *v;
BlockNumber targetseg;
BlockNumber nextsegno;
/* some way to handle non-existent segments needs to be specified */
Assert(behavior &
(EXTENSION_FAIL | EXTENSION_CREATE | EXTENSION_RETURN_NULL |
EXTENSION_DONT_OPEN));
targetseg = blkno / ((BlockNumber) RELSEG_SIZE);
/* if an existing and opened segment, we're done */
if (targetseg < reln->md_num_open_segs[forknum])
{
v = &reln->md_seg_fds[forknum][targetseg];
return v;
}
/* The caller only wants the segment if we already had it open. */
if (behavior & EXTENSION_DONT_OPEN)
return NULL;
/*
* The target segment is not yet open. Iterate over all the segments
* between the last opened and the target segment. This way missing
* segments either raise an error, or get created (according to
* 'behavior'). Start with either the last opened, or the first segment if
* none was opened before.
*/
if (reln->md_num_open_segs[forknum] > 0)
v = &reln->md_seg_fds[forknum][reln->md_num_open_segs[forknum] - 1];
else
{
v = mdopenfork(reln, forknum, behavior);
if (!v)
return NULL; /* if behavior & EXTENSION_RETURN_NULL */
}
for (nextsegno = reln->md_num_open_segs[forknum];
nextsegno <= targetseg; nextsegno++)
{
BlockNumber nblocks = _mdnblocks(reln, forknum, v);
int flags = 0;
Assert(nextsegno == v->mdfd_segno + 1);
if (nblocks > ((BlockNumber) RELSEG_SIZE))
elog(FATAL, "segment too big");
if ((behavior & EXTENSION_CREATE) ||
(InRecovery && (behavior & EXTENSION_CREATE_RECOVERY)))
{
/*
* Normally we will create new segments only if authorized by the
* caller (i.e., we are doing mdextend()). But when doing WAL
* recovery, create segments anyway; this allows cases such as
* replaying WAL data that has a write into a high-numbered
* segment of a relation that was later deleted. We want to go
* ahead and create the segments so we can finish out the replay.
*
* We have to maintain the invariant that segments before the last
* active segment are of size RELSEG_SIZE; therefore, if
* extending, pad them out with zeroes if needed. (This only
* matters if in recovery, or if the caller is extending the
* relation discontiguously, but that can happen in hash indexes.)
*/
if (nblocks < ((BlockNumber) RELSEG_SIZE))
{
char *zerobuf = palloc_aligned(BLCKSZ, PG_IO_ALIGN_SIZE,
MCXT_ALLOC_ZERO);
mdextend(reln, forknum,
nextsegno * ((BlockNumber) RELSEG_SIZE) - 1,
zerobuf, skipFsync);
pfree(zerobuf);
}
flags = O_CREAT;
}
else if (!(behavior & EXTENSION_DONT_CHECK_SIZE) &&
nblocks < ((BlockNumber) RELSEG_SIZE))
{
/*
* When not extending (or explicitly including truncated
* segments), only open the next segment if the current one is
* exactly RELSEG_SIZE. If not (this branch), either return NULL
* or fail.
*/
if (behavior & EXTENSION_RETURN_NULL)
{
/*
* Some callers discern between reasons for _mdfd_getseg()
* returning NULL based on errno. As there's no failing
* syscall involved in this case, explicitly set errno to
* ENOENT, as that seems the closest interpretation.
*/
errno = ENOENT;
return NULL;
}
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open file \"%s\" (target block %u): previous segment is only %u blocks",
_mdfd_segpath(reln, forknum, nextsegno),
blkno, nblocks)));
}
v = _mdfd_openseg(reln, forknum, nextsegno, flags);
if (v == NULL)
{
if ((behavior & EXTENSION_RETURN_NULL) &&
FILE_POSSIBLY_DELETED(errno))
return NULL;
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not open file \"%s\" (target block %u): %m",
_mdfd_segpath(reln, forknum, nextsegno),
blkno)));
}
}
return v;
}
/*
* Get number of blocks present in a single disk file
*/
static BlockNumber
_mdnblocks(SMgrRelation reln, ForkNumber forknum, MdfdVec *seg)
{
off_t len;
len = FileSize(seg->mdfd_vfd);
if (len < 0)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not seek to end of file \"%s\": %m",
FilePathName(seg->mdfd_vfd))));
/* note that this calculation will ignore any partial block at EOF */
return (BlockNumber) (len / BLCKSZ);
}
/*
* Sync a file to disk, given a file tag. Write the path into an output
* buffer so the caller can use it in error messages.
*
* Return 0 on success, -1 on failure, with errno set.
*/
int
mdsyncfiletag(const FileTag *ftag, char *path)
{
SMgrRelation reln = smgropen(ftag->rlocator, InvalidBackendId);
File file;
instr_time io_start;
bool need_to_close;
int result,
save_errno;
/* See if we already have the file open, or need to open it. */
if (ftag->segno < reln->md_num_open_segs[ftag->forknum])
{
file = reln->md_seg_fds[ftag->forknum][ftag->segno].mdfd_vfd;
strlcpy(path, FilePathName(file), MAXPGPATH);
need_to_close = false;
}
else
{
char *p;
p = _mdfd_segpath(reln, ftag->forknum, ftag->segno);
strlcpy(path, p, MAXPGPATH);
pfree(p);
file = PathNameOpenFile(path, _mdfd_open_flags());
if (file < 0)
return -1;
need_to_close = true;
}
io_start = pgstat_prepare_io_time();
/* Sync the file. */
result = FileSync(file, WAIT_EVENT_DATA_FILE_SYNC);
save_errno = errno;
if (need_to_close)
FileClose(file);
pgstat_count_io_op_time(IOOBJECT_RELATION, IOCONTEXT_NORMAL,
IOOP_FSYNC, io_start, 1);
errno = save_errno;
return result;
}
/*
* Unlink a file, given a file tag. Write the path into an output
* buffer so the caller can use it in error messages.
*
* Return 0 on success, -1 on failure, with errno set.
*/
int
mdunlinkfiletag(const FileTag *ftag, char *path)
{
char *p;
/* Compute the path. */
p = relpathperm(ftag->rlocator, MAIN_FORKNUM);
strlcpy(path, p, MAXPGPATH);
pfree(p);
/* Try to unlink the file. */
return unlink(path);
}
/*
* Check if a given candidate request matches a given tag, when processing
* a SYNC_FILTER_REQUEST request. This will be called for all pending
* requests to find out whether to forget them.
*/
bool
mdfiletagmatches(const FileTag *ftag, const FileTag *candidate)
{
/*
* For now we only use filter requests as a way to drop all scheduled
* callbacks relating to a given database, when dropping the database.
* We'll return true for all candidates that have the same database OID as
* the ftag from the SYNC_FILTER_REQUEST request, so they're forgotten.
*/
return ftag->rlocator.dbOid == candidate->rlocator.dbOid;
}
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