mp_sync.c
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上传日期:2022-05-23
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文件大小:16k
- /*-
- * See the file LICENSE for redistribution information.
- *
- * Copyright (c) 1996-2002
- * Sleepycat Software. All rights reserved.
- */
- #include "db_config.h"
- #ifndef lint
- static const char revid[] = "$Id: mp_sync.c,v 11.64 2002/08/25 16:00:27 bostic Exp $";
- #endif /* not lint */
- #ifndef NO_SYSTEM_INCLUDES
- #include <sys/types.h>
- #include <stdlib.h>
- #endif
- #include "db_int.h"
- #include "dbinc/db_shash.h"
- #include "dbinc/mp.h"
- typedef struct {
- DB_MPOOL_HASH *track_hp; /* Hash bucket. */
- roff_t track_off; /* Page file offset. */
- db_pgno_t track_pgno; /* Page number. */
- } BH_TRACK;
- static int __bhcmp __P((const void *, const void *));
- static int __memp_close_flush_files __P((DB_ENV *, DB_MPOOL *));
- static int __memp_sync_files __P((DB_ENV *, DB_MPOOL *));
- /*
- * __memp_sync --
- * Mpool sync function.
- *
- * PUBLIC: int __memp_sync __P((DB_ENV *, DB_LSN *));
- */
- int
- __memp_sync(dbenv, lsnp)
- DB_ENV *dbenv;
- DB_LSN *lsnp;
- {
- DB_MPOOL *dbmp;
- MPOOL *mp;
- int ret;
- PANIC_CHECK(dbenv);
- ENV_REQUIRES_CONFIG(dbenv,
- dbenv->mp_handle, "memp_sync", DB_INIT_MPOOL);
- /*
- * If no LSN is provided, flush the entire cache (reasonable usage
- * even if there's no log subsystem configured).
- */
- if (lsnp != NULL)
- ENV_REQUIRES_CONFIG(dbenv,
- dbenv->lg_handle, "memp_sync", DB_INIT_LOG);
- dbmp = dbenv->mp_handle;
- mp = dbmp->reginfo[0].primary;
- /* If we've flushed to the requested LSN, return that information. */
- if (lsnp != NULL) {
- R_LOCK(dbenv, dbmp->reginfo);
- if (log_compare(lsnp, &mp->lsn) <= 0) {
- *lsnp = mp->lsn;
- R_UNLOCK(dbenv, dbmp->reginfo);
- return (0);
- }
- R_UNLOCK(dbenv, dbmp->reginfo);
- }
- if ((ret = __memp_sync_int(dbenv, NULL, 0, DB_SYNC_CACHE, NULL)) != 0)
- return (ret);
- if (lsnp != NULL) {
- R_LOCK(dbenv, dbmp->reginfo);
- if (log_compare(lsnp, &mp->lsn) > 0)
- mp->lsn = *lsnp;
- R_UNLOCK(dbenv, dbmp->reginfo);
- }
- return (0);
- }
- /*
- * __memp_fsync --
- * Mpool file sync function.
- *
- * PUBLIC: int __memp_fsync __P((DB_MPOOLFILE *));
- */
- int
- __memp_fsync(dbmfp)
- DB_MPOOLFILE *dbmfp;
- {
- DB_ENV *dbenv;
- DB_MPOOL *dbmp;
- dbmp = dbmfp->dbmp;
- dbenv = dbmp->dbenv;
- PANIC_CHECK(dbenv);
- /*
- * If this handle doesn't have a file descriptor that's open for
- * writing, or if the file is a temporary, there's no reason to
- * proceed further.
- */
- if (F_ISSET(dbmfp, MP_READONLY))
- return (0);
- if (F_ISSET(dbmfp->mfp, MP_TEMP))
- return (0);
- return (__memp_sync_int(dbenv, dbmfp, 0, DB_SYNC_FILE, NULL));
- }
- /*
- * __mp_xxx_fh --
- * Return a file descriptor for DB 1.85 compatibility locking.
- *
- * PUBLIC: int __mp_xxx_fh __P((DB_MPOOLFILE *, DB_FH **));
- */
- int
- __mp_xxx_fh(dbmfp, fhp)
- DB_MPOOLFILE *dbmfp;
- DB_FH **fhp;
- {
- DB_ENV *dbenv;
- /*
- * This is a truly spectacular layering violation, intended ONLY to
- * support compatibility for the DB 1.85 DB->fd call.
- *
- * Sync the database file to disk, creating the file as necessary.
- *
- * We skip the MP_READONLY and MP_TEMP tests done by memp_fsync(3).
- * The MP_READONLY test isn't interesting because we will either
- * already have a file descriptor (we opened the database file for
- * reading) or we aren't readonly (we created the database which
- * requires write privileges). The MP_TEMP test isn't interesting
- * because we want to write to the backing file regardless so that
- * we get a file descriptor to return.
- */
- *fhp = dbmfp->fhp;
- if (F_ISSET(dbmfp->fhp, DB_FH_VALID))
- return (0);
- dbenv = dbmfp->dbmp->dbenv;
- return (__memp_sync_int(dbenv, dbmfp, 0, DB_SYNC_FILE, NULL));
- }
- /*
- * __memp_sync_int --
- * Mpool sync internal function.
- *
- * PUBLIC: int __memp_sync_int
- * PUBLIC: __P((DB_ENV *, DB_MPOOLFILE *, int, db_sync_op, int *));
- */
- int
- __memp_sync_int(dbenv, dbmfp, ar_max, op, wrotep)
- DB_ENV *dbenv;
- DB_MPOOLFILE *dbmfp;
- int ar_max, *wrotep;
- db_sync_op op;
- {
- BH *bhp;
- BH_TRACK *bharray;
- DB_MPOOL *dbmp;
- DB_MPOOL_HASH *hp;
- DB_MUTEX *mutexp;
- MPOOL *c_mp, *mp;
- MPOOLFILE *mfp;
- u_int32_t n_cache;
- int ar_cnt, hb_lock, i, pass, remaining, ret, t_ret, wait_cnt, wrote;
- dbmp = dbenv->mp_handle;
- mp = dbmp->reginfo[0].primary;
- pass = wrote = 0;
- /*
- * If the caller does not specify how many pages assume one
- * per bucket.
- */
- if (ar_max == 0)
- ar_max = mp->nreg * mp->htab_buckets;
- if ((ret =
- __os_malloc(dbenv, ar_max * sizeof(BH_TRACK), &bharray)) != 0)
- return (ret);
- /*
- * Walk each cache's list of buffers and mark all dirty buffers to be
- * written and all pinned buffers to be potentially written, depending
- * on our flags.
- */
- for (ar_cnt = 0, n_cache = 0; n_cache < mp->nreg; ++n_cache) {
- c_mp = dbmp->reginfo[n_cache].primary;
- hp = R_ADDR(&dbmp->reginfo[n_cache], c_mp->htab);
- for (i = 0; i < c_mp->htab_buckets; i++, hp++) {
- /*
- * We can check for empty buckets before locking as we
- * only care if the pointer is zero or non-zero. We
- * can ignore empty buckets because we only need write
- * buffers that were dirty before we started.
- */
- if (SH_TAILQ_FIRST(&hp->hash_bucket, __bh) == NULL)
- continue;
- MUTEX_LOCK(dbenv, &hp->hash_mutex);
- for (bhp = SH_TAILQ_FIRST(&hp->hash_bucket, __bh);
- bhp != NULL; bhp = SH_TAILQ_NEXT(bhp, hq, __bh)) {
- /* Always ignore unreferenced, clean pages. */
- if (bhp->ref == 0 && !F_ISSET(bhp, BH_DIRTY))
- continue;
- /*
- * Checkpoints have to wait on all pinned pages,
- * as pages may be marked dirty when returned to
- * the cache.
- *
- * File syncs only wait on pages both pinned and
- * dirty. (We don't care if pages are marked
- * dirty when returned to the cache, that means
- * there's another writing thread and flushing
- * the cache for this handle is meaningless.)
- */
- if (op == DB_SYNC_FILE &&
- !F_ISSET(bhp, BH_DIRTY))
- continue;
- mfp = R_ADDR(dbmp->reginfo, bhp->mf_offset);
- /*
- * Ignore temporary files -- this means you
- * can't even flush temporary files by handle.
- * (Checkpoint doesn't require temporary files
- * be flushed and the underlying buffer write
- * write routine may not be able to write it
- * anyway.)
- */
- if (F_ISSET(mfp, MP_TEMP))
- continue;
- /*
- * If we're flushing a specific file, see if
- * this page is from that file.
- */
- if (dbmfp != NULL && mfp != dbmfp->mfp)
- continue;
- /*
- * Ignore files that aren't involved in DB's
- * transactional operations during checkpoints.
- */
- if (dbmfp == NULL && mfp->lsn_off == -1)
- continue;
- /* Track the buffer, we want it. */
- bharray[ar_cnt].track_hp = hp;
- bharray[ar_cnt].track_pgno = bhp->pgno;
- bharray[ar_cnt].track_off = bhp->mf_offset;
- ar_cnt++;
- if (ar_cnt >= ar_max) {
- if ((ret = __os_realloc(dbenv,
- (ar_max * 2) * sizeof(BH_TRACK),
- &bharray)) != 0)
- break;
- ar_max *= 2;
- }
- }
- MUTEX_UNLOCK(dbenv, &hp->hash_mutex);
- if (ret != 0)
- goto err;
- }
- }
- /* If there no buffers to write, we're done. */
- if (ar_cnt == 0)
- goto done;
- /*
- * Write the buffers in file/page order, trying to reduce seeks by the
- * filesystem and, when pages are smaller than filesystem block sizes,
- * reduce the actual number of writes.
- */
- if (ar_cnt > 1)
- qsort(bharray, ar_cnt, sizeof(BH_TRACK), __bhcmp);
- /*
- * If we're trickling buffers, only write enough to reach the correct
- * percentage for this region. We may not write enough if the dirty
- * buffers have an unbalanced distribution among the regions, but that
- * seems unlikely.
- */
- if (op == DB_SYNC_TRICKLE && ar_cnt > ar_max / (int)mp->nreg)
- ar_cnt = ar_max / (int)mp->nreg;
- /*
- * Flush the log. We have to ensure the log records reflecting the
- * changes on the database pages we're writing have already made it
- * to disk. We still have to check the log each time we write a page
- * (because pages we are about to write may be modified after we have
- * flushed the log), but in general this will at least avoid any I/O
- * on the log's part.
- */
- if (LOGGING_ON(dbenv) && (ret = dbenv->log_flush(dbenv, NULL)) != 0)
- goto err;
- /*
- * Walk the array, writing buffers. When we write a buffer, we NULL
- * out its hash bucket pointer so we don't process a slot more than
- * once.
- */
- for (remaining = ar_cnt, i = pass = 0; remaining > 0; ++i) {
- if (i >= ar_cnt) {
- i = 0;
- ++pass;
- __os_sleep(dbenv, 1, 0);
- }
- if ((hp = bharray[i].track_hp) == NULL)
- continue;
- /* Lock the hash bucket and find the buffer. */
- mutexp = &hp->hash_mutex;
- MUTEX_LOCK(dbenv, mutexp);
- for (bhp = SH_TAILQ_FIRST(&hp->hash_bucket, __bh);
- bhp != NULL; bhp = SH_TAILQ_NEXT(bhp, hq, __bh))
- if (bhp->pgno == bharray[i].track_pgno &&
- bhp->mf_offset == bharray[i].track_off)
- break;
- /*
- * If we can't find the buffer we're done, somebody else had
- * to have written it.
- *
- * If the buffer isn't pinned or dirty, we're done, there's
- * no work needed.
- */
- if (bhp == NULL || (bhp->ref == 0 && !F_ISSET(bhp, BH_DIRTY))) {
- MUTEX_UNLOCK(dbenv, mutexp);
- --remaining;
- bharray[i].track_hp = NULL;
- continue;
- }
- /*
- * If the buffer is locked by another thread, ignore it, we'll
- * come back to it.
- *
- * If the buffer is pinned and it's only the first or second
- * time we have looked at it, ignore it, we'll come back to
- * it.
- *
- * In either case, skip the buffer if we're not required to
- * write it.
- */
- if (F_ISSET(bhp, BH_LOCKED) || (bhp->ref != 0 && pass < 2)) {
- MUTEX_UNLOCK(dbenv, mutexp);
- if (op != DB_SYNC_CACHE && op != DB_SYNC_FILE) {
- --remaining;
- bharray[i].track_hp = NULL;
- }
- continue;
- }
- /*
- * The buffer is either pinned or dirty.
- *
- * Set the sync wait-for count, used to count down outstanding
- * references to this buffer as they are returned to the cache.
- */
- bhp->ref_sync = bhp->ref;
- /* Pin the buffer into memory and lock it. */
- ++bhp->ref;
- F_SET(bhp, BH_LOCKED);
- MUTEX_LOCK(dbenv, &bhp->mutex);
- /*
- * Unlock the hash bucket and wait for the wait-for count to
- * go to 0. No new thread can acquire the buffer because we
- * have it locked.
- *
- * If a thread attempts to re-pin a page, the wait-for count
- * will never go to 0 (the thread spins on our buffer lock,
- * while we spin on the thread's ref count). Give up if we
- * don't get the buffer in 3 seconds, we can try again later.
- *
- * If, when the wait-for count goes to 0, the buffer is found
- * to be dirty, write it.
- */
- MUTEX_UNLOCK(dbenv, mutexp);
- for (wait_cnt = 1;
- bhp->ref_sync != 0 && wait_cnt < 4; ++wait_cnt)
- __os_sleep(dbenv, 1, 0);
- MUTEX_LOCK(dbenv, mutexp);
- hb_lock = 1;
- /*
- * If the ref_sync count has gone to 0, we're going to be done
- * with this buffer no matter what happens.
- */
- if (bhp->ref_sync == 0) {
- --remaining;
- bharray[i].track_hp = NULL;
- }
- /*
- * If the ref_sync count has gone to 0 and the buffer is still
- * dirty, we write it. We only try to write the buffer once.
- * Any process checkpointing or trickle-flushing the pool
- * must be able to write any underlying file -- if the write
- * fails, error out. It would be very strange if file sync
- * failed to write, but we don't care if it happens.
- */
- if (bhp->ref_sync == 0 && F_ISSET(bhp, BH_DIRTY)) {
- hb_lock = 0;
- MUTEX_UNLOCK(dbenv, mutexp);
- mfp = R_ADDR(dbmp->reginfo, bhp->mf_offset);
- if ((ret = __memp_bhwrite(dbmp, hp, mfp, bhp, 1)) == 0)
- ++wrote;
- else if (op == DB_SYNC_CACHE || op == DB_SYNC_TRICKLE)
- __db_err(dbenv, "%s: unable to flush page: %lu",
- __memp_fns(dbmp, mfp), (u_long)bhp->pgno);
- else
- ret = 0;
- }
- /*
- * If ref_sync count never went to 0, the buffer was written
- * by another thread, or the write failed, we still have the
- * buffer locked.
- *
- * We may or may not currently hold the hash bucket mutex. If
- * the __memp_bhwrite -> __memp_pgwrite call was successful,
- * then __memp_pgwrite will have swapped the buffer lock for
- * the hash lock. All other call paths will leave us without
- * the hash bucket lock.
- *
- * The order of mutexes above was to acquire the buffer lock
- * while holding the hash bucket lock. Don't deadlock here,
- * release the buffer lock and then acquire the hash bucket
- * lock.
- */
- if (F_ISSET(bhp, BH_LOCKED)) {
- F_CLR(bhp, BH_LOCKED);
- MUTEX_UNLOCK(dbenv, &bhp->mutex);
- if (!hb_lock)
- MUTEX_LOCK(dbenv, mutexp);
- }
- /*
- * Reset the ref_sync count regardless of our success, we're
- * done with this buffer for now.
- */
- bhp->ref_sync = 0;
- /* Discard our reference and unlock the bucket. */
- --bhp->ref;
- MUTEX_UNLOCK(dbenv, mutexp);
- if (ret != 0)
- break;
- }
- done: /* If we've opened files to flush pages, close them. */
- if ((t_ret = __memp_close_flush_files(dbenv, dbmp)) != 0 && ret == 0)
- ret = t_ret;
- /*
- * If doing a checkpoint or flushing a file for the application, we
- * have to force the pages to disk. We don't do this as we go along
- * because we want to give the OS as much time as possible to lazily
- * flush, and because we have to flush files that might not even have
- * had dirty buffers in the cache, so we have to walk the files list.
- */
- if (ret == 0 && (op == DB_SYNC_CACHE || op == DB_SYNC_FILE)) {
- if (dbmfp == NULL)
- ret = __memp_sync_files(dbenv, dbmp);
- else
- ret = __os_fsync(dbenv, dbmfp->fhp);
- }
- err: __os_free(dbenv, bharray);
- if (wrotep != NULL)
- *wrotep = wrote;
- return (ret);
- }
- /*
- * __memp_sync_files --
- * Sync all the files in the environment, open or not.
- */
- static
- int __memp_sync_files(dbenv, dbmp)
- DB_ENV *dbenv;
- DB_MPOOL *dbmp;
- {
- DB_MPOOLFILE *dbmfp;
- MPOOL *mp;
- MPOOLFILE *mfp;
- int ret, t_ret;
- ret = 0;
- mp = dbmp->reginfo[0].primary;
- R_LOCK(dbenv, dbmp->reginfo);
- for (mfp = SH_TAILQ_FIRST(&mp->mpfq, __mpoolfile);
- mfp != NULL; mfp = SH_TAILQ_NEXT(mfp, q, __mpoolfile)) {
- if (mfp->stat.st_page_out == 0 ||
- F_ISSET(mfp, MP_DEADFILE | MP_TEMP))
- continue;
- /* Look for an already open handle. */
- ret = 0;
- MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
- for (dbmfp = TAILQ_FIRST(&dbmp->dbmfq);
- dbmfp != NULL; dbmfp = TAILQ_NEXT(dbmfp, q))
- if (dbmfp->mfp == mfp) {
- ret = __os_fsync(dbenv, dbmfp->fhp);
- break;
- }
- MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- if (ret != 0)
- goto err;
- /* If we don't find one, open one. */
- if (dbmfp == NULL) {
- if ((ret = dbenv->memp_fcreate(dbenv, &dbmfp, 0)) != 0)
- goto err;
- ret = __memp_fopen_int(
- dbmfp, mfp, R_ADDR(dbmp->reginfo, mfp->path_off),
- 0, 0, mfp->stat.st_pagesize);
- if (ret == 0)
- ret = __os_fsync(dbenv, dbmfp->fhp);
- if ((t_ret =
- __memp_fclose_int(dbmfp, 0)) != 0 && ret == 0)
- ret = t_ret;
- if (ret != 0)
- goto err;
- }
- }
- if (0) {
- err: __db_err(dbenv, "%s: cannot sync: %s",
- R_ADDR(dbmp->reginfo, mfp->path_off), db_strerror(ret));
- }
- R_UNLOCK(dbenv, dbmp->reginfo);
- return (ret);
- }
- /*
- * __memp_close_flush_files --
- * Close files opened only to flush buffers.
- */
- static int
- __memp_close_flush_files(dbenv, dbmp)
- DB_ENV *dbenv;
- DB_MPOOL *dbmp;
- {
- DB_MPOOLFILE *dbmfp;
- int ret;
- /*
- * The routine exists because we must close files opened by sync to
- * flush buffers. There are two cases: first, extent files have to
- * be closed so they may be removed when empty. Second, regular
- * files have to be closed so we don't run out of descriptors (for
- * example, and application partitioning its data into databases
- * based on timestamps, so there's a continually increasing set of
- * files).
- *
- * We mark files opened in the __memp_bhwrite() function with the
- * MP_FLUSH flag. Here we walk through our file descriptor list,
- * and, if a file was opened by __memp_bhwrite(), we close it.
- */
- retry: MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
- for (dbmfp = TAILQ_FIRST(&dbmp->dbmfq);
- dbmfp != NULL; dbmfp = TAILQ_NEXT(dbmfp, q))
- if (F_ISSET(dbmfp, MP_FLUSH)) {
- F_CLR(dbmfp, MP_FLUSH);
- MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- if ((ret = __memp_fclose_int(dbmfp, 0)) != 0)
- return (ret);
- goto retry;
- }
- MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- return (0);
- }
- static int
- __bhcmp(p1, p2)
- const void *p1, *p2;
- {
- BH_TRACK *bhp1, *bhp2;
- bhp1 = (BH_TRACK *)p1;
- bhp2 = (BH_TRACK *)p2;
- /* Sort by file (shared memory pool offset). */
- if (bhp1->track_off < bhp2->track_off)
- return (-1);
- if (bhp1->track_off > bhp2->track_off)
- return (1);
- /*
- * !!!
- * Defend against badly written quicksort code calling the comparison
- * function with two identical pointers (e.g., WATCOM C++ (Power++)).
- */
- if (bhp1->track_pgno < bhp2->track_pgno)
- return (-1);
- if (bhp1->track_pgno > bhp2->track_pgno)
- return (1);
- return (0);
- }