mp_bh.c
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上传日期:2022-05-23
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文件大小:17k
- /*-
- * 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_bh.c,v 11.71 2002/09/04 19:06:45 margo Exp $";
- #endif /* not lint */
- #ifndef NO_SYSTEM_INCLUDES
- #include <sys/types.h>
- #include <string.h>
- #include <unistd.h>
- #endif
- #include "db_int.h"
- #include "dbinc/db_shash.h"
- #include "dbinc/mp.h"
- #include "dbinc/log.h"
- #include "dbinc/db_page.h"
- static int __memp_pgwrite
- __P((DB_MPOOL *, DB_MPOOLFILE *, DB_MPOOL_HASH *, BH *));
- static int __memp_upgrade __P((DB_MPOOL *, DB_MPOOLFILE *, MPOOLFILE *));
- /*
- * __memp_bhwrite --
- * Write the page associated with a given buffer header.
- *
- * PUBLIC: int __memp_bhwrite __P((DB_MPOOL *,
- * PUBLIC: DB_MPOOL_HASH *, MPOOLFILE *, BH *, int));
- */
- int
- __memp_bhwrite(dbmp, hp, mfp, bhp, open_extents)
- DB_MPOOL *dbmp;
- DB_MPOOL_HASH *hp;
- MPOOLFILE *mfp;
- BH *bhp;
- int open_extents;
- {
- DB_ENV *dbenv;
- DB_MPOOLFILE *dbmfp;
- DB_MPREG *mpreg;
- int local_open, incremented, ret;
- dbenv = dbmp->dbenv;
- local_open = incremented = 0;
- /*
- * If the file has been removed or is a closed temporary file, jump
- * right ahead and pretend that we've found the file we want -- the
- * page-write function knows how to handle the fact that we don't have
- * (or need!) any real file descriptor information.
- */
- if (F_ISSET(mfp, MP_DEADFILE)) {
- dbmfp = NULL;
- goto found;
- }
- /*
- * Walk the process' DB_MPOOLFILE list and find a file descriptor for
- * the file. We also check that the descriptor is open for writing.
- * If we find a descriptor on the file that's not open for writing, we
- * try and upgrade it to make it writeable. If that fails, we're done.
- */
- MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
- for (dbmfp = TAILQ_FIRST(&dbmp->dbmfq);
- dbmfp != NULL; dbmfp = TAILQ_NEXT(dbmfp, q))
- if (dbmfp->mfp == mfp) {
- if (F_ISSET(dbmfp, MP_READONLY) &&
- !F_ISSET(dbmfp, MP_UPGRADE) &&
- (F_ISSET(dbmfp, MP_UPGRADE_FAIL) ||
- __memp_upgrade(dbmp, dbmfp, mfp))) {
- MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- return (EPERM);
- }
- /*
- * Increment the reference count -- see the comment in
- * __memp_fclose_int().
- */
- ++dbmfp->ref;
- incremented = 1;
- break;
- }
- MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- if (dbmfp != NULL)
- goto found;
- /*
- * !!!
- * It's the caller's choice if we're going to open extent files.
- */
- if (!open_extents && F_ISSET(mfp, MP_EXTENT))
- return (EPERM);
- /*
- * !!!
- * Don't try to attach to temporary files. There are two problems in
- * trying to do that. First, if we have different privileges than the
- * process that "owns" the temporary file, we might create the backing
- * disk file such that the owning process couldn't read/write its own
- * buffers, e.g., memp_trickle running as root creating a file owned
- * as root, mode 600. Second, if the temporary file has already been
- * created, we don't have any way of finding out what its real name is,
- * and, even if we did, it was already unlinked (so that it won't be
- * left if the process dies horribly). This decision causes a problem,
- * however: if the temporary file consumes the entire buffer cache,
- * and the owner doesn't flush the buffers to disk, we could end up
- * with resource starvation, and the memp_trickle thread couldn't do
- * anything about it. That's a pretty unlikely scenario, though.
- *
- * Note we should never get here when the temporary file in question
- * has already been closed in another process, in which case it should
- * be marked MP_DEADFILE.
- */
- if (F_ISSET(mfp, MP_TEMP))
- return (EPERM);
- /*
- * It's not a page from a file we've opened. If the file requires
- * input/output processing, see if this process has ever registered
- * information as to how to write this type of file. If not, there's
- * nothing we can do.
- */
- if (mfp->ftype != 0) {
- MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
- for (mpreg = LIST_FIRST(&dbmp->dbregq);
- mpreg != NULL; mpreg = LIST_NEXT(mpreg, q))
- if (mpreg->ftype == mfp->ftype)
- break;
- MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- if (mpreg == NULL)
- return (EPERM);
- }
- /*
- * Try and open the file, attaching to the underlying shared area.
- * Ignore any error, assume it's a permissions problem.
- *
- * XXX
- * There's no negative cache, so we may repeatedly try and open files
- * that we have previously tried (and failed) to open.
- */
- if ((ret = dbenv->memp_fcreate(dbenv, &dbmfp, 0)) != 0)
- return (ret);
- if ((ret = __memp_fopen_int(dbmfp, mfp,
- R_ADDR(dbmp->reginfo, mfp->path_off),
- 0, 0, mfp->stat.st_pagesize)) != 0) {
- (void)dbmfp->close(dbmfp, 0);
- return (ret);
- }
- local_open = 1;
- found: ret = __memp_pgwrite(dbmp, dbmfp, hp, bhp);
- MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
- if (incremented)
- --dbmfp->ref;
- else if (local_open)
- F_SET(dbmfp, MP_FLUSH);
- MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- return (ret);
- }
- /*
- * __memp_pgread --
- * Read a page from a file.
- *
- * PUBLIC: int __memp_pgread __P((DB_MPOOLFILE *, DB_MUTEX *, BH *, int));
- */
- int
- __memp_pgread(dbmfp, mutexp, bhp, can_create)
- DB_MPOOLFILE *dbmfp;
- DB_MUTEX *mutexp;
- BH *bhp;
- int can_create;
- {
- DB_IO db_io;
- DB_ENV *dbenv;
- DB_MPOOL *dbmp;
- MPOOLFILE *mfp;
- size_t len, nr, pagesize;
- int ret;
- dbmp = dbmfp->dbmp;
- dbenv = dbmp->dbenv;
- mfp = dbmfp->mfp;
- pagesize = mfp->stat.st_pagesize;
- /* We should never be called with a dirty or a locked buffer. */
- DB_ASSERT(!F_ISSET(bhp, BH_DIRTY | BH_DIRTY_CREATE | BH_LOCKED));
- /* Lock the buffer and swap the hash bucket lock for the buffer lock. */
- F_SET(bhp, BH_LOCKED | BH_TRASH);
- MUTEX_LOCK(dbenv, &bhp->mutex);
- MUTEX_UNLOCK(dbenv, mutexp);
- /*
- * Temporary files may not yet have been created. We don't create
- * them now, we create them when the pages have to be flushed.
- */
- nr = 0;
- if (F_ISSET(dbmfp->fhp, DB_FH_VALID)) {
- db_io.fhp = dbmfp->fhp;
- db_io.mutexp = dbmfp->mutexp;
- db_io.pagesize = db_io.bytes = pagesize;
- db_io.pgno = bhp->pgno;
- db_io.buf = bhp->buf;
- /*
- * The page may not exist; if it doesn't, nr may well be 0,
- * but we expect the underlying OS calls not to return an
- * error code in this case.
- */
- if ((ret = __os_io(dbenv, &db_io, DB_IO_READ, &nr)) != 0)
- goto err;
- }
- if (nr < pagesize) {
- /*
- * Don't output error messages for short reads. In particular,
- * DB recovery processing may request pages never written to
- * disk or for which only some part have been written to disk,
- * in which case we won't find the page. The caller must know
- * how to handle the error.
- */
- if (can_create == 0) {
- ret = DB_PAGE_NOTFOUND;
- goto err;
- }
- /* Clear any bytes that need to be cleared. */
- len = mfp->clear_len == 0 ? pagesize : mfp->clear_len;
- memset(bhp->buf, 0, len);
- #if defined(DIAGNOSTIC) || defined(UMRW)
- /*
- * If we're running in diagnostic mode, corrupt any bytes on
- * the page that are unknown quantities for the caller.
- */
- if (len < pagesize)
- memset(bhp->buf + len, CLEAR_BYTE, pagesize - len);
- #endif
- ++mfp->stat.st_page_create;
- } else
- ++mfp->stat.st_page_in;
- /* Call any pgin function. */
- ret = mfp->ftype == 0 ? 0 : __memp_pg(dbmfp, bhp, 1);
- /* Unlock the buffer and reacquire the hash bucket lock. */
- err: MUTEX_UNLOCK(dbenv, &bhp->mutex);
- MUTEX_LOCK(dbenv, mutexp);
- /*
- * If no errors occurred, the data is now valid, clear the BH_TRASH
- * flag; regardless, clear the lock bit and let other threads proceed.
- */
- F_CLR(bhp, BH_LOCKED);
- if (ret == 0)
- F_CLR(bhp, BH_TRASH);
- return (ret);
- }
- /*
- * __memp_pgwrite --
- * Write a page to a file.
- */
- static int
- __memp_pgwrite(dbmp, dbmfp, hp, bhp)
- DB_MPOOL *dbmp;
- DB_MPOOLFILE *dbmfp;
- DB_MPOOL_HASH *hp;
- BH *bhp;
- {
- DB_ENV *dbenv;
- DB_IO db_io;
- DB_LSN lsn;
- MPOOLFILE *mfp;
- size_t nw;
- int callpgin, ret;
- dbenv = dbmp->dbenv;
- mfp = dbmfp == NULL ? NULL : dbmfp->mfp;
- callpgin = ret = 0;
- /*
- * We should never be called with a clean or trash buffer.
- * The sync code does call us with already locked buffers.
- */
- DB_ASSERT(F_ISSET(bhp, BH_DIRTY));
- DB_ASSERT(!F_ISSET(bhp, BH_TRASH));
- /*
- * If we have not already traded the hash bucket lock for the buffer
- * lock, do so now.
- */
- if (!F_ISSET(bhp, BH_LOCKED)) {
- F_SET(bhp, BH_LOCKED);
- MUTEX_LOCK(dbenv, &bhp->mutex);
- MUTEX_UNLOCK(dbenv, &hp->hash_mutex);
- }
- /*
- * It's possible that the underlying file doesn't exist, either
- * because of an outright removal or because it was a temporary
- * file that's been closed.
- *
- * !!!
- * Once we pass this point, we know that dbmfp and mfp aren't NULL,
- * and that we have a valid file reference.
- */
- if (mfp == NULL || F_ISSET(mfp, MP_DEADFILE))
- goto file_dead;
- /*
- * If the page is in a file for which we have LSN information, we have
- * to ensure the appropriate log records are on disk.
- */
- if (LOGGING_ON(dbenv) && mfp->lsn_off != -1) {
- memcpy(&lsn, bhp->buf + mfp->lsn_off, sizeof(DB_LSN));
- if ((ret = dbenv->log_flush(dbenv, &lsn)) != 0)
- goto err;
- }
- #ifdef DIAGNOSTIC
- /*
- * Verify write-ahead logging semantics.
- *
- * !!!
- * One special case. There is a single field on the meta-data page,
- * the last-page-number-in-the-file field, for which we do not log
- * changes. If the page was originally created in a database that
- * didn't have logging turned on, we can see a page marked dirty but
- * for which no corresponding log record has been written. However,
- * the only way that a page can be created for which there isn't a
- * previous log record and valid LSN is when the page was created
- * without logging turned on, and so we check for that special-case
- * LSN value.
- */
- if (LOGGING_ON(dbenv) && !IS_NOT_LOGGED_LSN(LSN(bhp->buf))) {
- /*
- * There is a potential race here. If we are in the midst of
- * switching log files, it's possible we could test against the
- * old file and the new offset in the log region's LSN. If we
- * fail the first test, acquire the log mutex and check again.
- */
- DB_LOG *dblp;
- LOG *lp;
- dblp = dbenv->lg_handle;
- lp = dblp->reginfo.primary;
- if (!IS_NOT_LOGGED_LSN(LSN(bhp->buf)) &&
- log_compare(&lp->s_lsn, &LSN(bhp->buf)) <= 0) {
- R_LOCK(dbenv, &dblp->reginfo);
- DB_ASSERT(log_compare(&lp->s_lsn, &LSN(bhp->buf)) > 0);
- R_UNLOCK(dbenv, &dblp->reginfo);
- }
- }
- #endif
- /*
- * Call any pgout function. We set the callpgin flag so that we flag
- * that the contents of the buffer will need to be passed through pgin
- * before they are reused.
- */
- if (mfp->ftype != 0) {
- callpgin = 1;
- if ((ret = __memp_pg(dbmfp, bhp, 0)) != 0)
- goto err;
- }
- /* Temporary files may not yet have been created. */
- if (!F_ISSET(dbmfp->fhp, DB_FH_VALID)) {
- MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
- ret = F_ISSET(dbmfp->fhp, DB_FH_VALID) ? 0 :
- __db_appname(dbenv, DB_APP_TMP, NULL,
- F_ISSET(dbenv, DB_ENV_DIRECT_DB) ? DB_OSO_DIRECT : 0,
- dbmfp->fhp, NULL);
- MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- if (ret != 0) {
- __db_err(dbenv,
- "unable to create temporary backing file");
- goto err;
- }
- }
- /* Write the page. */
- db_io.fhp = dbmfp->fhp;
- db_io.mutexp = dbmfp->mutexp;
- db_io.pagesize = db_io.bytes = mfp->stat.st_pagesize;
- db_io.pgno = bhp->pgno;
- db_io.buf = bhp->buf;
- if ((ret = __os_io(dbenv, &db_io, DB_IO_WRITE, &nw)) != 0) {
- __db_err(dbenv, "%s: write failed for page %lu",
- __memp_fn(dbmfp), (u_long)bhp->pgno);
- goto err;
- }
- ++mfp->stat.st_page_out;
- err:
- file_dead:
- /*
- * !!!
- * Once we pass this point, dbmfp and mfp may be NULL, we may not have
- * a valid file reference.
- *
- * Unlock the buffer and reacquire the hash lock.
- */
- MUTEX_UNLOCK(dbenv, &bhp->mutex);
- MUTEX_LOCK(dbenv, &hp->hash_mutex);
- /*
- * If we rewrote the page, it will need processing by the pgin
- * routine before reuse.
- */
- if (callpgin)
- F_SET(bhp, BH_CALLPGIN);
- /*
- * Update the hash bucket statistics, reset the flags.
- * If we were successful, the page is no longer dirty.
- */
- if (ret == 0) {
- DB_ASSERT(hp->hash_page_dirty != 0);
- --hp->hash_page_dirty;
- F_CLR(bhp, BH_DIRTY | BH_DIRTY_CREATE);
- }
- /* Regardless, clear any sync wait-for count and remove our lock. */
- bhp->ref_sync = 0;
- F_CLR(bhp, BH_LOCKED);
- return (ret);
- }
- /*
- * __memp_pg --
- * Call the pgin/pgout routine.
- *
- * PUBLIC: int __memp_pg __P((DB_MPOOLFILE *, BH *, int));
- */
- int
- __memp_pg(dbmfp, bhp, is_pgin)
- DB_MPOOLFILE *dbmfp;
- BH *bhp;
- int is_pgin;
- {
- DBT dbt, *dbtp;
- DB_ENV *dbenv;
- DB_MPOOL *dbmp;
- DB_MPREG *mpreg;
- MPOOLFILE *mfp;
- int ftype, ret;
- dbmp = dbmfp->dbmp;
- dbenv = dbmp->dbenv;
- mfp = dbmfp->mfp;
- MUTEX_THREAD_LOCK(dbenv, dbmp->mutexp);
- ftype = mfp->ftype;
- for (mpreg = LIST_FIRST(&dbmp->dbregq);
- mpreg != NULL; mpreg = LIST_NEXT(mpreg, q)) {
- if (ftype != mpreg->ftype)
- continue;
- if (mfp->pgcookie_len == 0)
- dbtp = NULL;
- else {
- dbt.size = mfp->pgcookie_len;
- dbt.data = R_ADDR(dbmp->reginfo, mfp->pgcookie_off);
- dbtp = &dbt;
- }
- MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- if (is_pgin) {
- if (mpreg->pgin != NULL &&
- (ret = mpreg->pgin(dbenv,
- bhp->pgno, bhp->buf, dbtp)) != 0)
- goto err;
- } else
- if (mpreg->pgout != NULL &&
- (ret = mpreg->pgout(dbenv,
- bhp->pgno, bhp->buf, dbtp)) != 0)
- goto err;
- break;
- }
- if (mpreg == NULL)
- MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- return (0);
- err: MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
- __db_err(dbenv, "%s: %s failed for page %lu",
- __memp_fn(dbmfp), is_pgin ? "pgin" : "pgout", (u_long)bhp->pgno);
- return (ret);
- }
- /*
- * __memp_bhfree --
- * Free a bucket header and its referenced data.
- *
- * PUBLIC: void __memp_bhfree __P((DB_MPOOL *, DB_MPOOL_HASH *, BH *, int));
- */
- void
- __memp_bhfree(dbmp, hp, bhp, free_mem)
- DB_MPOOL *dbmp;
- DB_MPOOL_HASH *hp;
- BH *bhp;
- int free_mem;
- {
- DB_ENV *dbenv;
- MPOOL *c_mp, *mp;
- MPOOLFILE *mfp;
- u_int32_t n_cache;
- /*
- * Assumes the hash bucket is locked and the MPOOL is not.
- */
- dbenv = dbmp->dbenv;
- mp = dbmp->reginfo[0].primary;
- n_cache = NCACHE(mp, bhp->mf_offset, bhp->pgno);
- /*
- * Delete the buffer header from the hash bucket queue and reset
- * the hash bucket's priority, if necessary.
- */
- SH_TAILQ_REMOVE(&hp->hash_bucket, bhp, hq, __bh);
- if (bhp->priority == hp->hash_priority)
- hp->hash_priority =
- SH_TAILQ_FIRST(&hp->hash_bucket, __bh) == NULL ?
- 0 : SH_TAILQ_FIRST(&hp->hash_bucket, __bh)->priority;
- /*
- * Discard the hash bucket's mutex, it's no longer needed, and
- * we don't want to be holding it when acquiring other locks.
- */
- MUTEX_UNLOCK(dbenv, &hp->hash_mutex);
- /*
- * Find the underlying MPOOLFILE and decrement its reference count.
- * If this is its last reference, remove it.
- */
- mfp = R_ADDR(dbmp->reginfo, bhp->mf_offset);
- MUTEX_LOCK(dbenv, &mfp->mutex);
- if (--mfp->block_cnt == 0 && mfp->mpf_cnt == 0)
- __memp_mf_discard(dbmp, mfp);
- else
- MUTEX_UNLOCK(dbenv, &mfp->mutex);
- R_LOCK(dbenv, &dbmp->reginfo[n_cache]);
- /*
- * Clear the mutex this buffer recorded; requires the region lock
- * be held.
- */
- __db_shlocks_clear(&bhp->mutex, &dbmp->reginfo[n_cache],
- (REGMAINT *)R_ADDR(&dbmp->reginfo[n_cache], mp->maint_off));
- /*
- * If we're not reusing the buffer immediately, free the buffer header
- * and data for real.
- */
- if (free_mem) {
- __db_shalloc_free(dbmp->reginfo[n_cache].addr, bhp);
- c_mp = dbmp->reginfo[n_cache].primary;
- c_mp->stat.st_pages--;
- }
- R_UNLOCK(dbenv, &dbmp->reginfo[n_cache]);
- }
- /*
- * __memp_upgrade --
- * Upgrade a file descriptor from read-only to read-write.
- */
- static int
- __memp_upgrade(dbmp, dbmfp, mfp)
- DB_MPOOL *dbmp;
- DB_MPOOLFILE *dbmfp;
- MPOOLFILE *mfp;
- {
- DB_ENV *dbenv;
- DB_FH *fhp, *tfhp;
- int ret;
- char *rpath;
- dbenv = dbmp->dbenv;
- fhp = NULL;
- rpath = NULL;
- /*
- * Calculate the real name for this file and try to open it read/write.
- * We know we have a valid pathname for the file because it's the only
- * way we could have gotten a file descriptor of any kind.
- */
- if ((ret = __os_calloc(dbenv, 1, sizeof(DB_FH), &fhp)) != 0)
- goto err;
- if ((ret = __db_appname(dbenv, DB_APP_DATA,
- R_ADDR(dbmp->reginfo, mfp->path_off), 0, NULL, &rpath)) != 0)
- goto err;
- if (__os_open(dbenv, rpath,
- F_ISSET(mfp, MP_DIRECT) ? DB_OSO_DIRECT : 0, 0, fhp) != 0) {
- F_SET(dbmfp, MP_UPGRADE_FAIL);
- goto err;
- }
- /*
- * Swap the descriptors and set the upgrade flag.
- *
- * XXX
- * There is a race here. If another process schedules a read using the
- * existing file descriptor and is swapped out before making the system
- * call, this code could theoretically close the file descriptor out
- * from under it. While it's very unlikely, this code should still be
- * rewritten.
- */
- tfhp = dbmfp->fhp;
- dbmfp->fhp = fhp;
- fhp = tfhp;
- (void)__os_closehandle(dbenv, fhp);
- F_SET(dbmfp, MP_UPGRADE);
- ret = 0;
- if (0) {
- err: ret = 1;
- }
- if (fhp != NULL)
- __os_free(dbenv, fhp);
- if (rpath != NULL)
- __os_free(dbenv, rpath);
- return (ret);
- }