/*------------------------------------------------------------------------- * * smgr.c * public interface routines to storage manager switch. * * All file system operations in POSTGRES dispatch through these * routines. * * Portions Copyright (c) 1996-2023, 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/xlogutils.h" #include "lib/ilist.h" #include "storage/bufmgr.h" #include "storage/fd.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) (RelFileLocatorBackend rlocator, ForkNumber forknum, bool isRedo); void (*smgr_extend) (SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, const void *buffer, bool skipFsync); void (*smgr_zeroextend) (SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks, bool skipFsync); bool (*smgr_prefetch) (SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum); void (*smgr_read) (SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, void *buffer); void (*smgr_write) (SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, const void *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_zeroextend = mdzeroextend, .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(RelFileLocator rlocator, BackendId backend) { RelFileLocatorBackend brlocator; SMgrRelation reln; bool found; if (SMgrRelationHash == NULL) { /* First time through: initialize the hash table */ HASHCTL ctl; ctl.keysize = sizeof(RelFileLocatorBackend); 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 */ brlocator.locator = rlocator; brlocator.backend = backend; reln = (SMgrRelation) hash_search(SMgrRelationHash, &brlocator, 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, &(reln->smgr_rlocator), 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; } /* * smgrrelease() -- Release all resources used by this object. * * The object remains valid. */ void smgrrelease(SMgrRelation reln) { for (ForkNumber forknum = 0; forknum <= MAX_FORKNUM; forknum++) { smgrsw[reln->smgr_which].smgr_close(reln, forknum); reln->smgr_cached_nblocks[forknum] = InvalidBlockNumber; } } /* * smgrreleaseall() -- Release resources used by all objects. * * This is called for PROCSIGNAL_BARRIER_SMGRRELEASE. */ void smgrreleaseall(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) smgrrelease(reln); } /* * 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); } /* * smgrcloserellocator() -- Close SMgrRelation object for given RelFileLocator, * if one exists. * * This has the same effects as smgrclose(smgropen(rlocator)), but it avoids * uselessly creating a hashtable entry only to drop it again when no * such entry exists already. */ void smgrcloserellocator(RelFileLocatorBackend rlocator) { SMgrRelation reln; /* Nothing to do if hashtable not set up */ if (SMgrRelationHash == NULL) return; reln = (SMgrRelation) hash_search(SMgrRelationHash, &rlocator, 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; RelFileLocatorBackend *rlocators; 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. */ DropRelationsAllBuffers(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 */ rlocators = palloc(sizeof(RelFileLocatorBackend) * nrels); for (i = 0; i < nrels; i++) { RelFileLocatorBackend rlocator = rels[i]->smgr_rlocator; int which = rels[i]->smgr_which; rlocators[i] = rlocator; /* Close the forks at smgr level */ for (forknum = 0; forknum <= MAX_FORKNUM; forknum++) smgrsw[which].smgr_close(rels[i], forknum); } /* * 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(rlocators[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(rlocators[i], forknum, isRedo); } pfree(rlocators); } /* * 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, const void *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; } /* * smgrzeroextend() -- Add new zeroed out blocks to a file. * * Similar to smgrextend(), except the relation can be extended by * multiple blocks at once and the added blocks will be filled with * zeroes. */ void smgrzeroextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks, bool skipFsync) { smgrsw[reln->smgr_which].smgr_zeroextend(reln, forknum, blocknum, nblocks, skipFsync); /* * Normally we expect this to increase the fork size by nblocks, 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 + nblocks; 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, void *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, const void *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. */ DropRelationBuffers(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_rlocator); /* 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); } } /* * This routine is called when we are ordered to release all open files by a * ProcSignalBarrier. */ bool ProcessBarrierSmgrRelease(void) { smgrreleaseall(); return true; }