diff options
Diffstat (limited to 'src/backend/storage/smgr')
| -rw-r--r-- | src/backend/storage/smgr/Makefile | 19 | ||||
| -rw-r--r-- | src/backend/storage/smgr/README | 52 | ||||
| -rw-r--r-- | src/backend/storage/smgr/md.c | 1409 | ||||
| -rw-r--r-- | src/backend/storage/smgr/smgr.c | 695 |
4 files changed, 2175 insertions, 0 deletions
diff --git a/src/backend/storage/smgr/Makefile b/src/backend/storage/smgr/Makefile new file mode 100644 index 0000000..596b564 --- /dev/null +++ b/src/backend/storage/smgr/Makefile @@ -0,0 +1,19 @@ +#------------------------------------------------------------------------- +# +# Makefile-- +# Makefile for storage/smgr +# +# IDENTIFICATION +# src/backend/storage/smgr/Makefile +# +#------------------------------------------------------------------------- + +subdir = src/backend/storage/smgr +top_builddir = ../../../.. +include $(top_builddir)/src/Makefile.global + +OBJS = \ + md.o \ + smgr.o + +include $(top_srcdir)/src/backend/common.mk diff --git a/src/backend/storage/smgr/README b/src/backend/storage/smgr/README new file mode 100644 index 0000000..e1cfc6c --- /dev/null +++ b/src/backend/storage/smgr/README @@ -0,0 +1,52 @@ +src/backend/storage/smgr/README + +Storage Managers +================ + +In the original Berkeley Postgres system, there were several storage managers, +of which only the "magnetic disk" manager remains. (At Berkeley there were +also managers for the Sony WORM optical disk jukebox and persistent main +memory, but these were never supported in any externally released Postgres, +nor in any version of PostgreSQL.) The "magnetic disk" manager is itself +seriously misnamed, because actually it supports any kind of device for +which the operating system provides standard filesystem operations; which +these days is pretty much everything of interest. However, we retain the +notion of a storage manager switch in case anyone ever wants to reintroduce +other kinds of storage managers. Removing the switch layer would save +nothing noticeable anyway, since storage-access operations are surely far +more expensive than one extra layer of C function calls. + +In Berkeley Postgres each relation was tagged with the ID of the storage +manager to use for it. This is gone. It would be probably more reasonable +to associate storage managers with tablespaces, should we ever re-introduce +multiple storage managers into the system catalogs. + +The files in this directory, and their contents, are + + smgr.c The storage manager switch dispatch code. The routines in + this file call the appropriate storage manager to do storage + accesses requested by higher-level code. smgr.c also manages + the file handle cache (SMgrRelation table). + + md.c The "magnetic disk" storage manager, which is really just + an interface to the kernel's filesystem operations. + +Note that md.c in turn relies on src/backend/storage/file/fd.c. + + +Relation Forks +============== + +Since 8.4, a single smgr relation can be comprised of multiple physical +files, called relation forks. This allows storing additional metadata like +Free Space information in additional forks, which can be grown and truncated +independently of the main data file, while still treating it all as a single +physical relation in system catalogs. + +It is assumed that the main fork, fork number 0 or MAIN_FORKNUM, always +exists. Fork numbers are assigned in src/include/common/relpath.h. +Functions in smgr.c and md.c take an extra fork number argument, in addition +to relfilenode and block number, to identify which relation fork you want to +access. Since most code wants to access the main fork, a shortcut version of +ReadBuffer that accesses MAIN_FORKNUM is provided in the buffer manager for +convenience. diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c new file mode 100644 index 0000000..b4bca7e --- /dev/null +++ b/src/backend/storage/smgr/md.c @@ -0,0 +1,1409 @@ +/*------------------------------------------------------------------------- + * + * 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) 1996-2021, 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/relfilenode.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_rnode,xx_forknum,xx_segno) \ +( \ + memset(&(a), 0, sizeof(FileTag)), \ + (a).handler = SYNC_HANDLER_MD, \ + (a).rnode = (xx_rnode), \ + (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) + + +/* local routines */ +static void mdunlinkfork(RelFileNodeBackend rnode, 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(RelFileNodeBackend rnode, ForkNumber forknum, + BlockNumber segno); +static void register_forget_request(RelFileNodeBackend rnode, 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 forkno, + BlockNumber segno, int oflags); +static MdfdVec *_mdfd_getseg(SMgrRelation reln, ForkNumber forkno, + BlockNumber blkno, bool skipFsync, int behavior); +static BlockNumber _mdnblocks(SMgrRelation reln, ForkNumber forknum, + MdfdVec *seg); + + +/* + * 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. + */ + 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_rnode.node.spcNode, + reln->smgr_rnode.node.dbNode, + isRedo); + + path = relpath(reln->smgr_rnode, forkNum); + + fd = PathNameOpenFile(path, O_RDWR | O_CREAT | O_EXCL | PG_BINARY); + + if (fd < 0) + { + int save_errno = errno; + + if (isRedo) + fd = PathNameOpenFile(path, O_RDWR | PG_BINARY); + 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 RelFileNodeBackend --- 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 relfilenode + * number 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 relfilenode 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 relfilenode number until + * it's safe, because relfilenode assignment skips over any existing file. + * + * 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 relfilenode number. + * The fact that temp rels and regular rels have different file naming + * patterns provides additional safety. + * + * 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 + * relfilenode number 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: any failure should be reported as WARNING not ERROR, because + * we are usually not in a transaction anymore when this is called. + */ +void +mdunlink(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo) +{ + /* Now do the per-fork work */ + if (forkNum == InvalidForkNumber) + { + for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++) + mdunlinkfork(rnode, forkNum, isRedo); + } + else + mdunlinkfork(rnode, 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(RelFileNodeBackend rnode, ForkNumber forkNum, bool isRedo) +{ + char *path; + int ret; + + path = relpath(rnode, forkNum); + + /* + * Delete or truncate the first segment. + */ + if (isRedo || forkNum != MAIN_FORKNUM || RelFileNodeBackendIsTemp(rnode)) + { + if (!RelFileNodeBackendIsTemp(rnode)) + { + /* Prevent other backends' fds from holding on to the disk space */ + ret = do_truncate(path); + + /* Forget any pending sync requests for the first segment */ + register_forget_request(rnode, forkNum, 0 /* first seg */ ); + } + 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) + ereport(WARNING, + (errcode_for_file_access(), + errmsg("could not remove file \"%s\": %m", path))); + } + } + else + { + /* Prevent other backends' fds from holding on to the disk space */ + ret = do_truncate(path); + + /* Register request to unlink first segment later */ + register_unlink_segment(rnode, forkNum, 0 /* first seg */ ); + } + + /* + * Delete any additional segments. + */ + if (ret >= 0) + { + char *segpath = (char *) palloc(strlen(path) + 12); + BlockNumber segno; + + /* + * Note that because we loop until getting ENOENT, we will correctly + * remove all inactive segments as well as active ones. + */ + for (segno = 1;; segno++) + { + sprintf(segpath, "%s.%u", path, segno); + + if (!RelFileNodeBackendIsTemp(rnode)) + { + /* + * Prevent other backends' fds from holding on to the disk + * space. + */ + if (do_truncate(segpath) < 0 && errno == ENOENT) + break; + + /* + * Forget any pending sync requests for this segment before we + * try to unlink. + */ + register_forget_request(rnode, 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, + char *buffer, bool skipFsync) +{ + off_t seekpos; + int nbytes; + MdfdVec *v; + + /* 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_rnode, 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)); +} + +/* + * 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_rnode, forknum); + + fd = PathNameOpenFile(path, O_RDWR | PG_BINARY); + + 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; + + 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; +} + +/* + * 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) +{ + /* + * 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_RETURN_NULL); + + /* + * We might be flushing buffers of already removed relations, that's + * ok, just ignore that case. + */ + 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; + } +} + +/* + * mdread() -- Read the specified block from a relation. + */ +void +mdread(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, + char *buffer) +{ + off_t seekpos; + int nbytes; + MdfdVec *v; + + TRACE_POSTGRESQL_SMGR_MD_READ_START(forknum, blocknum, + reln->smgr_rnode.node.spcNode, + reln->smgr_rnode.node.dbNode, + reln->smgr_rnode.node.relNode, + reln->smgr_rnode.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_rnode.node.spcNode, + reln->smgr_rnode.node.dbNode, + reln->smgr_rnode.node.relNode, + reln->smgr_rnode.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, + char *buffer, bool skipFsync) +{ + off_t seekpos; + int nbytes; + MdfdVec *v; + + /* 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_rnode.node.spcNode, + reln->smgr_rnode.node.dbNode, + reln->smgr_rnode.node.relNode, + reln->smgr_rnode.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_rnode.node.spcNode, + reln->smgr_rnode.node.dbNode, + reln->smgr_rnode.node.relNode, + reln->smgr_rnode.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); +} + +/* + * 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_rnode, 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]; + + 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_rnode.node, forknum, seg->mdfd_segno); + + /* Temp relations should never be fsync'd */ + Assert(!SmgrIsTemp(reln)); + + if (!RegisterSyncRequest(&tag, SYNC_REQUEST, false /* retryOnError */ )) + { + ereport(DEBUG1, + (errmsg_internal("could not forward fsync request because request queue is full"))); + + 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)))); + } +} + +/* + * register_unlink_segment() -- Schedule a file to be deleted after next checkpoint + */ +static void +register_unlink_segment(RelFileNodeBackend rnode, ForkNumber forknum, + BlockNumber segno) +{ + FileTag tag; + + INIT_MD_FILETAG(tag, rnode.node, forknum, segno); + + /* Should never be used with temp relations */ + Assert(!RelFileNodeBackendIsTemp(rnode)); + + RegisterSyncRequest(&tag, SYNC_UNLINK_REQUEST, true /* retryOnError */ ); +} + +/* + * register_forget_request() -- forget any fsyncs for a relation fork's segment + */ +static void +register_forget_request(RelFileNodeBackend rnode, ForkNumber forknum, + BlockNumber segno) +{ + FileTag tag; + + INIT_MD_FILETAG(tag, rnode.node, forknum, segno); + + RegisterSyncRequest(&tag, SYNC_FORGET_REQUEST, true /* retryOnError */ ); +} + +/* + * ForgetDatabaseSyncRequests -- forget any fsyncs and unlinks for a DB + */ +void +ForgetDatabaseSyncRequests(Oid dbid) +{ + FileTag tag; + RelFileNode rnode; + + rnode.dbNode = dbid; + rnode.spcNode = 0; + rnode.relNode = 0; + + INIT_MD_FILETAG(tag, rnode, InvalidForkNumber, InvalidBlockNumber); + + RegisterSyncRequest(&tag, SYNC_FILTER_REQUEST, true /* retryOnError */ ); +} + +/* + * DropRelationFiles -- drop files of all given relations + */ +void +DropRelationFiles(RelFileNode *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_rnode, 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, O_RDWR | PG_BINARY | 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)); + + 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 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 = palloc0(BLCKSZ); + + 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->rnode, InvalidBackendId); + File file; + 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, O_RDWR | PG_BINARY); + if (file < 0) + return -1; + need_to_close = true; + } + + /* Sync the file. */ + result = FileSync(file, WAIT_EVENT_DATA_FILE_SYNC); + save_errno = errno; + + if (need_to_close) + FileClose(file); + + 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->rnode, 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->rnode.dbNode == candidate->rnode.dbNode; +} diff --git a/src/backend/storage/smgr/smgr.c b/src/backend/storage/smgr/smgr.c new file mode 100644 index 0000000..4dc2464 --- /dev/null +++ b/src/backend/storage/smgr/smgr.c @@ -0,0 +1,695 @@ +/*------------------------------------------------------------------------- + * + * smgr.c + * public interface routines to storage manager switch. + * + * All file system operations in POSTGRES dispatch through these + * routines. + * + * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * + * IDENTIFICATION + * src/backend/storage/smgr/smgr.c + * + *------------------------------------------------------------------------- + */ +#include "postgres.h" + +#include "access/xlog.h" +#include "lib/ilist.h" +#include "storage/bufmgr.h" +#include "storage/ipc.h" +#include "storage/md.h" +#include "storage/smgr.h" +#include "utils/hsearch.h" +#include "utils/inval.h" + + +/* + * This struct of function pointers defines the API between smgr.c and + * any individual storage manager module. Note that smgr subfunctions are + * generally expected to report problems via elog(ERROR). An exception is + * that smgr_unlink should use elog(WARNING), rather than erroring out, + * because we normally unlink relations during post-commit/abort cleanup, + * and so it's too late to raise an error. Also, various conditions that + * would normally be errors should be allowed during bootstrap and/or WAL + * recovery --- see comments in md.c for details. + */ +typedef struct f_smgr +{ + void (*smgr_init) (void); /* may be NULL */ + void (*smgr_shutdown) (void); /* may be NULL */ + void (*smgr_open) (SMgrRelation reln); + void (*smgr_close) (SMgrRelation reln, ForkNumber forknum); + void (*smgr_create) (SMgrRelation reln, ForkNumber forknum, + bool isRedo); + bool (*smgr_exists) (SMgrRelation reln, ForkNumber forknum); + void (*smgr_unlink) (RelFileNodeBackend rnode, ForkNumber forknum, + bool isRedo); + void (*smgr_extend) (SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum, char *buffer, bool skipFsync); + bool (*smgr_prefetch) (SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum); + void (*smgr_read) (SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum, char *buffer); + void (*smgr_write) (SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum, char *buffer, bool skipFsync); + void (*smgr_writeback) (SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum, BlockNumber nblocks); + BlockNumber (*smgr_nblocks) (SMgrRelation reln, ForkNumber forknum); + void (*smgr_truncate) (SMgrRelation reln, ForkNumber forknum, + BlockNumber nblocks); + void (*smgr_immedsync) (SMgrRelation reln, ForkNumber forknum); +} f_smgr; + +static const f_smgr smgrsw[] = { + /* magnetic disk */ + { + .smgr_init = mdinit, + .smgr_shutdown = NULL, + .smgr_open = mdopen, + .smgr_close = mdclose, + .smgr_create = mdcreate, + .smgr_exists = mdexists, + .smgr_unlink = mdunlink, + .smgr_extend = mdextend, + .smgr_prefetch = mdprefetch, + .smgr_read = mdread, + .smgr_write = mdwrite, + .smgr_writeback = mdwriteback, + .smgr_nblocks = mdnblocks, + .smgr_truncate = mdtruncate, + .smgr_immedsync = mdimmedsync, + } +}; + +static const int NSmgr = lengthof(smgrsw); + +/* + * Each backend has a hashtable that stores all extant SMgrRelation objects. + * In addition, "unowned" SMgrRelation objects are chained together in a list. + */ +static HTAB *SMgrRelationHash = NULL; + +static dlist_head unowned_relns; + +/* local function prototypes */ +static void smgrshutdown(int code, Datum arg); + + +/* + * smgrinit(), smgrshutdown() -- Initialize or shut down storage + * managers. + * + * Note: smgrinit is called during backend startup (normal or standalone + * case), *not* during postmaster start. Therefore, any resources created + * here or destroyed in smgrshutdown are backend-local. + */ +void +smgrinit(void) +{ + int i; + + for (i = 0; i < NSmgr; i++) + { + if (smgrsw[i].smgr_init) + smgrsw[i].smgr_init(); + } + + /* register the shutdown proc */ + on_proc_exit(smgrshutdown, 0); +} + +/* + * on_proc_exit hook for smgr cleanup during backend shutdown + */ +static void +smgrshutdown(int code, Datum arg) +{ + int i; + + for (i = 0; i < NSmgr; i++) + { + if (smgrsw[i].smgr_shutdown) + smgrsw[i].smgr_shutdown(); + } +} + +/* + * smgropen() -- Return an SMgrRelation object, creating it if need be. + * + * This does not attempt to actually open the underlying file. + */ +SMgrRelation +smgropen(RelFileNode rnode, BackendId backend) +{ + RelFileNodeBackend brnode; + SMgrRelation reln; + bool found; + + if (SMgrRelationHash == NULL) + { + /* First time through: initialize the hash table */ + HASHCTL ctl; + + ctl.keysize = sizeof(RelFileNodeBackend); + ctl.entrysize = sizeof(SMgrRelationData); + SMgrRelationHash = hash_create("smgr relation table", 400, + &ctl, HASH_ELEM | HASH_BLOBS); + dlist_init(&unowned_relns); + } + + /* Look up or create an entry */ + brnode.node = rnode; + brnode.backend = backend; + reln = (SMgrRelation) hash_search(SMgrRelationHash, + (void *) &brnode, + HASH_ENTER, &found); + + /* Initialize it if not present before */ + if (!found) + { + /* hash_search already filled in the lookup key */ + reln->smgr_owner = NULL; + reln->smgr_targblock = InvalidBlockNumber; + for (int i = 0; i <= MAX_FORKNUM; ++i) + reln->smgr_cached_nblocks[i] = InvalidBlockNumber; + reln->smgr_which = 0; /* we only have md.c at present */ + + /* implementation-specific initialization */ + smgrsw[reln->smgr_which].smgr_open(reln); + + /* it has no owner yet */ + dlist_push_tail(&unowned_relns, &reln->node); + } + + return reln; +} + +/* + * smgrsetowner() -- Establish a long-lived reference to an SMgrRelation object + * + * There can be only one owner at a time; this is sufficient since currently + * the only such owners exist in the relcache. + */ +void +smgrsetowner(SMgrRelation *owner, SMgrRelation reln) +{ + /* We don't support "disowning" an SMgrRelation here, use smgrclearowner */ + Assert(owner != NULL); + + /* + * First, unhook any old owner. (Normally there shouldn't be any, but it + * seems possible that this can happen during swap_relation_files() + * depending on the order of processing. It's ok to close the old + * relcache entry early in that case.) + * + * If there isn't an old owner, then the reln should be in the unowned + * list, and we need to remove it. + */ + if (reln->smgr_owner) + *(reln->smgr_owner) = NULL; + else + dlist_delete(&reln->node); + + /* Now establish the ownership relationship. */ + reln->smgr_owner = owner; + *owner = reln; +} + +/* + * smgrclearowner() -- Remove long-lived reference to an SMgrRelation object + * if one exists + */ +void +smgrclearowner(SMgrRelation *owner, SMgrRelation reln) +{ + /* Do nothing if the SMgrRelation object is not owned by the owner */ + if (reln->smgr_owner != owner) + return; + + /* unset the owner's reference */ + *owner = NULL; + + /* unset our reference to the owner */ + reln->smgr_owner = NULL; + + /* add to list of unowned relations */ + dlist_push_tail(&unowned_relns, &reln->node); +} + +/* + * smgrexists() -- Does the underlying file for a fork exist? + */ +bool +smgrexists(SMgrRelation reln, ForkNumber forknum) +{ + return smgrsw[reln->smgr_which].smgr_exists(reln, forknum); +} + +/* + * smgrclose() -- Close and delete an SMgrRelation object. + */ +void +smgrclose(SMgrRelation reln) +{ + SMgrRelation *owner; + ForkNumber forknum; + + for (forknum = 0; forknum <= MAX_FORKNUM; forknum++) + smgrsw[reln->smgr_which].smgr_close(reln, forknum); + + owner = reln->smgr_owner; + + if (!owner) + dlist_delete(&reln->node); + + if (hash_search(SMgrRelationHash, + (void *) &(reln->smgr_rnode), + HASH_REMOVE, NULL) == NULL) + elog(ERROR, "SMgrRelation hashtable corrupted"); + + /* + * Unhook the owner pointer, if any. We do this last since in the remote + * possibility of failure above, the SMgrRelation object will still exist. + */ + if (owner) + *owner = NULL; +} + +/* + * smgrcloseall() -- Close all existing SMgrRelation objects. + */ +void +smgrcloseall(void) +{ + HASH_SEQ_STATUS status; + SMgrRelation reln; + + /* Nothing to do if hashtable not set up */ + if (SMgrRelationHash == NULL) + return; + + hash_seq_init(&status, SMgrRelationHash); + + while ((reln = (SMgrRelation) hash_seq_search(&status)) != NULL) + smgrclose(reln); +} + +/* + * smgrclosenode() -- Close SMgrRelation object for given RelFileNode, + * if one exists. + * + * This has the same effects as smgrclose(smgropen(rnode)), but it avoids + * uselessly creating a hashtable entry only to drop it again when no + * such entry exists already. + */ +void +smgrclosenode(RelFileNodeBackend rnode) +{ + SMgrRelation reln; + + /* Nothing to do if hashtable not set up */ + if (SMgrRelationHash == NULL) + return; + + reln = (SMgrRelation) hash_search(SMgrRelationHash, + (void *) &rnode, + HASH_FIND, NULL); + if (reln != NULL) + smgrclose(reln); +} + +/* + * smgrcreate() -- Create a new relation. + * + * Given an already-created (but presumably unused) SMgrRelation, + * cause the underlying disk file or other storage for the fork + * to be created. + */ +void +smgrcreate(SMgrRelation reln, ForkNumber forknum, bool isRedo) +{ + smgrsw[reln->smgr_which].smgr_create(reln, forknum, isRedo); +} + +/* + * smgrdosyncall() -- Immediately sync all forks of all given relations + * + * All forks of all given relations are synced out to the store. + * + * This is equivalent to FlushRelationBuffers() for each smgr relation, + * then calling smgrimmedsync() for all forks of each relation, but it's + * significantly quicker so should be preferred when possible. + */ +void +smgrdosyncall(SMgrRelation *rels, int nrels) +{ + int i = 0; + ForkNumber forknum; + + if (nrels == 0) + return; + + FlushRelationsAllBuffers(rels, nrels); + + /* + * Sync the physical file(s). + */ + for (i = 0; i < nrels; i++) + { + int which = rels[i]->smgr_which; + + for (forknum = 0; forknum <= MAX_FORKNUM; forknum++) + { + if (smgrsw[which].smgr_exists(rels[i], forknum)) + smgrsw[which].smgr_immedsync(rels[i], forknum); + } + } +} + +/* + * smgrdounlinkall() -- Immediately unlink all forks of all given relations + * + * All forks of all given relations are removed from the store. This + * should not be used during transactional operations, since it can't be + * undone. + * + * If isRedo is true, it is okay for the underlying file(s) to be gone + * already. + */ +void +smgrdounlinkall(SMgrRelation *rels, int nrels, bool isRedo) +{ + int i = 0; + RelFileNodeBackend *rnodes; + ForkNumber forknum; + + if (nrels == 0) + return; + + /* + * Get rid of any remaining buffers for the relations. bufmgr will just + * drop them without bothering to write the contents. + */ + DropRelFileNodesAllBuffers(rels, nrels); + + /* + * create an array which contains all relations to be dropped, and close + * each relation's forks at the smgr level while at it + */ + rnodes = palloc(sizeof(RelFileNodeBackend) * nrels); + for (i = 0; i < nrels; i++) + { + RelFileNodeBackend rnode = rels[i]->smgr_rnode; + int which = rels[i]->smgr_which; + + rnodes[i] = rnode; + + /* Close the forks at smgr level */ + for (forknum = 0; forknum <= MAX_FORKNUM; forknum++) + smgrsw[which].smgr_close(rels[i], forknum); + } + + /* + * It'd be nice to tell the stats collector to forget them immediately, + * too. But we can't because we don't know the OIDs. + */ + + /* + * Send a shared-inval message to force other backends to close any + * dangling smgr references they may have for these rels. We should do + * this before starting the actual unlinking, in case we fail partway + * through that step. Note that the sinval messages will eventually come + * back to this backend, too, and thereby provide a backstop that we + * closed our own smgr rel. + */ + for (i = 0; i < nrels; i++) + CacheInvalidateSmgr(rnodes[i]); + + /* + * Delete the physical file(s). + * + * Note: smgr_unlink must treat deletion failure as a WARNING, not an + * ERROR, because we've already decided to commit or abort the current + * xact. + */ + + for (i = 0; i < nrels; i++) + { + int which = rels[i]->smgr_which; + + for (forknum = 0; forknum <= MAX_FORKNUM; forknum++) + smgrsw[which].smgr_unlink(rnodes[i], forknum, isRedo); + } + + pfree(rnodes); +} + + +/* + * smgrextend() -- Add a new block to a file. + * + * The semantics are nearly the same as smgrwrite(): 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 +smgrextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, + char *buffer, bool skipFsync) +{ + smgrsw[reln->smgr_which].smgr_extend(reln, forknum, blocknum, + buffer, skipFsync); + + /* + * Normally we expect this to increase nblocks by one, but if the cached + * value isn't as expected, just invalidate it so the next call asks the + * kernel. + */ + if (reln->smgr_cached_nblocks[forknum] == blocknum) + reln->smgr_cached_nblocks[forknum] = blocknum + 1; + else + reln->smgr_cached_nblocks[forknum] = InvalidBlockNumber; +} + +/* + * smgrprefetch() -- Initiate asynchronous read of the specified block of a relation. + * + * In recovery only, this can return false to indicate that a file + * doesn't exist (presumably it has been dropped by a later WAL + * record). + */ +bool +smgrprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum) +{ + return smgrsw[reln->smgr_which].smgr_prefetch(reln, forknum, blocknum); +} + +/* + * smgrread() -- read a particular block from a relation into the supplied + * buffer. + * + * This routine is called from the buffer manager in order to + * instantiate pages in the shared buffer cache. All storage managers + * return pages in the format that POSTGRES expects. + */ +void +smgrread(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, + char *buffer) +{ + smgrsw[reln->smgr_which].smgr_read(reln, forknum, blocknum, buffer); +} + +/* + * smgrwrite() -- Write the supplied buffer out. + * + * 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 smgrextend(). + * + * This is not a synchronous write -- the block is not necessarily + * on disk at return, only dumped out to the kernel. However, + * provisions will be made to fsync the write before the next checkpoint. + * + * skipFsync indicates that the caller will make other provisions to + * fsync the relation, so we needn't bother. Temporary relations also + * do not require fsync. + */ +void +smgrwrite(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, + char *buffer, bool skipFsync) +{ + smgrsw[reln->smgr_which].smgr_write(reln, forknum, blocknum, + buffer, skipFsync); +} + + +/* + * smgrwriteback() -- Trigger kernel writeback for the supplied range of + * blocks. + */ +void +smgrwriteback(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, + BlockNumber nblocks) +{ + smgrsw[reln->smgr_which].smgr_writeback(reln, forknum, blocknum, + nblocks); +} + +/* + * smgrnblocks() -- Calculate the number of blocks in the + * supplied relation. + */ +BlockNumber +smgrnblocks(SMgrRelation reln, ForkNumber forknum) +{ + BlockNumber result; + + /* Check and return if we get the cached value for the number of blocks. */ + result = smgrnblocks_cached(reln, forknum); + if (result != InvalidBlockNumber) + return result; + + result = smgrsw[reln->smgr_which].smgr_nblocks(reln, forknum); + + reln->smgr_cached_nblocks[forknum] = result; + + return result; +} + +/* + * smgrnblocks_cached() -- Get the cached number of blocks in the supplied + * relation. + * + * Returns an InvalidBlockNumber when not in recovery and when the relation + * fork size is not cached. + */ +BlockNumber +smgrnblocks_cached(SMgrRelation reln, ForkNumber forknum) +{ + /* + * For now, we only use cached values in recovery due to lack of a shared + * invalidation mechanism for changes in file size. + */ + if (InRecovery && reln->smgr_cached_nblocks[forknum] != InvalidBlockNumber) + return reln->smgr_cached_nblocks[forknum]; + + return InvalidBlockNumber; +} + +/* + * smgrtruncate() -- Truncate the given forks of supplied relation to + * each specified numbers of blocks + * + * The truncation is done immediately, so this can't be rolled back. + * + * The caller must hold AccessExclusiveLock on the relation, to ensure that + * other backends receive the smgr invalidation event that this function sends + * before they access any forks of the relation again. + */ +void +smgrtruncate(SMgrRelation reln, ForkNumber *forknum, int nforks, BlockNumber *nblocks) +{ + int i; + + /* + * Get rid of any buffers for the about-to-be-deleted blocks. bufmgr will + * just drop them without bothering to write the contents. + */ + DropRelFileNodeBuffers(reln, forknum, nforks, nblocks); + + /* + * Send a shared-inval message to force other backends to close any smgr + * references they may have for this rel. This is useful because they + * might have open file pointers to segments that got removed, and/or + * smgr_targblock variables pointing past the new rel end. (The inval + * message will come back to our backend, too, causing a + * probably-unnecessary local smgr flush. But we don't expect that this + * is a performance-critical path.) As in the unlink code, we want to be + * sure the message is sent before we start changing things on-disk. + */ + CacheInvalidateSmgr(reln->smgr_rnode); + + /* Do the truncation */ + for (i = 0; i < nforks; i++) + { + /* Make the cached size is invalid if we encounter an error. */ + reln->smgr_cached_nblocks[forknum[i]] = InvalidBlockNumber; + + smgrsw[reln->smgr_which].smgr_truncate(reln, forknum[i], nblocks[i]); + + /* + * We might as well update the local smgr_cached_nblocks values. The + * smgr cache inval message that this function sent will cause other + * backends to invalidate their copies of smgr_fsm_nblocks and + * smgr_vm_nblocks, and these ones too at the next command boundary. + * But these ensure they aren't outright wrong until then. + */ + reln->smgr_cached_nblocks[forknum[i]] = nblocks[i]; + } +} + +/* + * smgrimmedsync() -- Force the specified relation to stable storage. + * + * Synchronously force all previous writes to the specified relation + * down to disk. + * + * This is useful for building completely new relations (eg, new + * indexes). Instead of incrementally WAL-logging the index build + * steps, we can just write completed index pages to disk with smgrwrite + * or smgrextend, and then fsync the completed index file before + * committing the transaction. (This is sufficient for purposes of + * crash recovery, since it effectively duplicates forcing a checkpoint + * for the completed index. But it is *not* sufficient if one wishes + * to use the WAL log for PITR or replication purposes: in that case + * we have to make WAL entries as well.) + * + * The preceding writes should specify skipFsync = true to avoid + * duplicative fsyncs. + * + * Note that you need to do FlushRelationBuffers() first if there is + * any possibility that there are dirty buffers for the relation; + * otherwise the sync is not very meaningful. + */ +void +smgrimmedsync(SMgrRelation reln, ForkNumber forknum) +{ + smgrsw[reln->smgr_which].smgr_immedsync(reln, forknum); +} + +/* + * AtEOXact_SMgr + * + * This routine is called during transaction commit or abort (it doesn't + * particularly care which). All transient SMgrRelation objects are closed. + * + * We do this as a compromise between wanting transient SMgrRelations to + * live awhile (to amortize the costs of blind writes of multiple blocks) + * and needing them to not live forever (since we're probably holding open + * a kernel file descriptor for the underlying file, and we need to ensure + * that gets closed reasonably soon if the file gets deleted). + */ +void +AtEOXact_SMgr(void) +{ + dlist_mutable_iter iter; + + /* + * Zap all unowned SMgrRelations. We rely on smgrclose() to remove each + * one from the list. + */ + dlist_foreach_modify(iter, &unowned_relns) + { + SMgrRelation rel = dlist_container(SMgrRelationData, node, + iter.cur); + + Assert(rel->smgr_owner == NULL); + + smgrclose(rel); + } +} |