/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1996-2004
* Sleepycat Software. All rights reserved.
*
* $Id: mp_sync.c,v 1.1.1.1 2005/06/24 22:42:42 ca Exp $
*/
#include "db_config.h"
#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#include <stdlib.h>
#endif
#include "db_int.h"
#include "dbinc/db_shash.h"
#include "dbinc/log.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 *, int));
static int __memp_sync_files __P((DB_ENV *, DB_MPOOL *));
/*
* __memp_sync_pp --
* DB_ENV->memp_sync pre/post processing.
*
* PUBLIC: int __memp_sync_pp __P((DB_ENV *, DB_LSN *));
*/
int
__memp_sync_pp(dbenv, lsnp)
DB_ENV *dbenv;
DB_LSN *lsnp;
{
int rep_check, 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);
rep_check = IS_ENV_REPLICATED(dbenv) ? 1 : 0;
if (rep_check)
__env_rep_enter(dbenv);
ret = __memp_sync(dbenv, lsnp);
if (rep_check)
__env_db_rep_exit(dbenv);
return (ret);
}
/*
* __memp_sync --
* DB_ENV->memp_sync.
*
* 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;
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_pp --
* DB_MPOOLFILE->sync pre/post processing.
*
* PUBLIC: int __memp_fsync_pp __P((DB_MPOOLFILE *));
*/
int
__memp_fsync_pp(dbmfp)
DB_MPOOLFILE *dbmfp;
{
DB_ENV *dbenv;
int rep_check, ret;
dbenv = dbmfp->dbenv;
PANIC_CHECK(dbenv);
MPF_ILLEGAL_BEFORE_OPEN(dbmfp, "DB_MPOOLFILE->sync");
rep_check = IS_ENV_REPLICATED(dbenv) ? 1 : 0;
if (rep_check)
__env_rep_enter(dbenv);
ret = __memp_fsync(dbmfp);
if (rep_check)
__env_db_rep_exit(dbenv);
return (ret);
}
/*
* __memp_fsync --
* DB_MPOOLFILE->sync.
*
* PUBLIC: int __memp_fsync __P((DB_MPOOLFILE *));
*/
int
__memp_fsync(dbmfp)
DB_MPOOLFILE *dbmfp;
{
MPOOLFILE *mfp;
mfp = dbmfp->mfp;
/*
* If this handle doesn't have a file descriptor that's open for
* writing, or if the file is a temporary, or if the file hasn't
* been written since it was flushed, there's no reason to proceed
* further.
*/
if (F_ISSET(dbmfp, MP_READONLY))
return (0);
if (F_ISSET(mfp, MP_TEMP))
return (0);
if (mfp->file_written == 0)
return (0);
return (__memp_sync_int(dbmfp->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;
{
/*
* 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.
*/
if ((*fhp = dbmfp->fhp) != NULL)
return (0);
return (__memp_sync_int(dbmfp->dbenv, dbmfp, 0, DB_SYNC_FILE, NULL));
}
/*
* __memp_sync_int --
* Mpool sync internal function.
*
* PUBLIC: int __memp_sync_int __P((DB_ENV *,
* PUBLIC: DB_MPOOLFILE *, u_int32_t, db_sync_op, u_int32_t *));
*/
int
__memp_sync_int(dbenv, dbmfp, trickle_max, op, wrotep)
DB_ENV *dbenv;
DB_MPOOLFILE *dbmfp;
u_int32_t trickle_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;
roff_t last_mf_offset;
u_int32_t ar_cnt, ar_max, i, n_cache, remaining, wrote;
int filecnt, hb_lock, maxopenfd, maxwrite, maxwrite_sleep;
int pass, ret, t_ret, wait_cnt, write_cnt;
dbmp = dbenv->mp_handle;
mp = dbmp->reginfo[0].primary;
last_mf_offset = INVALID_ROFF;
filecnt = pass = wrote = 0;
/* Get shared configuration information. */
R_LOCK(dbenv, dbmp->reginfo);
maxopenfd = mp->mp_maxopenfd;
maxwrite = mp->mp_maxwrite;
maxwrite_sleep = mp->mp_maxwrite_sleep;
R_UNLOCK(dbenv, dbmp->reginfo);
/* Assume one dirty page per bucket. */
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 we run out of space, double and continue.
* Don't stop at trickle_max, we want to sort
* as large a sample set as possible in order
* to minimize disk seeks.
*/
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.
*/
if (op == DB_SYNC_TRICKLE && ar_cnt > trickle_max)
ar_cnt = trickle_max;
/*
* 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 = __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 (i = pass = write_cnt = 0, remaining = ar_cnt; 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 we've switched files, check to see if we're configured
* to close file descriptors.
*/
if (maxopenfd != 0 && bhp->mf_offset != last_mf_offset) {
if (++filecnt >= maxopenfd) {
filecnt = 0;
if ((ret = __memp_close_flush_files(
dbenv, dbmp, 1)) != 0)
break;
}
last_mf_offset = bhp->mf_offset;
}
/*
* 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.
*/
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
__db_err(dbenv, "%s: unable to flush page: %lu",
__memp_fns(dbmp, mfp), (u_long)bhp->pgno);
/*
* Avoid saturating the disk, sleep once we've done
* some number of writes.
*/
if (maxwrite != 0 && ++write_cnt >= maxwrite) {
write_cnt = 0;
__os_sleep(dbenv, 0, (u_long)maxwrite_sleep);
}
}
/*
* 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 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);
}
/* If we've opened files to flush pages, close them. */
if ((t_ret = __memp_close_flush_files(dbenv, dbmp, 0)) != 0 && ret == 0)
ret = t_ret;
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 final_ret, ret;
final_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->file_written ||
mfp->deadfile || F_ISSET(mfp, MP_TEMP))
continue;
/*
* Look for an already open, writeable handle (fsync doesn't
* work on read-only Windows handles).
*/
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 || F_ISSET(dbmfp, MP_READONLY))
continue;
ret = __os_fsync(dbenv, dbmfp->fhp);
break;
}
MUTEX_THREAD_UNLOCK(dbenv, dbmp->mutexp);
/* If we don't find one, open one. */
if (dbmfp == NULL)
ret = __memp_mf_sync(dbmp, mfp);
if (ret != 0) {
__db_err(dbenv, "%s: unable to flush: %s",
(char *)R_ADDR(dbmp->reginfo, mfp->path_off),
db_strerror(ret));
if (final_ret == 0)
final_ret = ret;
continue;
}
/*
* If we wrote the file and there are no open handles (or there
* is a single open handle, and it's the one we opened to write
* buffers during checkpoint), clear the file_written flag. We
* do this so that applications opening thousands of files don't
* loop here opening and flushing those files during checkpoint.
*
* The danger here is if a buffer were to be written as part of
* a checkpoint, and then not be flushed to disk. This cannot
* happen because we only clear file_written when there are no
* other users of the MPOOLFILE in the system, and, as we hold
* the region lock, no possibility of another thread of control
* racing with us to open a MPOOLFILE.
*/
if (mfp->mpf_cnt == 0 || (mfp->mpf_cnt == 1 &&
dbmfp != NULL && F_ISSET(dbmfp, MP_FLUSH)))
mfp->file_written = 0;
}
R_UNLOCK(dbenv, dbmp->reginfo);
return (final_ret);
}
/*
* __memp_mf_sync --
* Flush an MPOOLFILE.
*
* Should only be used when the file is not already open in this process.
*
* PUBLIC: int __memp_mf_sync __P((DB_MPOOL *, MPOOLFILE *));
*/
int
__memp_mf_sync(dbmp, mfp)
DB_MPOOL *dbmp;
MPOOLFILE *mfp;
{
DB_ENV *dbenv;
DB_FH *fhp;
int ret, t_ret;
char *rpath;
dbenv = dbmp->dbenv;
/*
* Expects caller to be holding the region lock: we're using the path
* name and __memp_nameop might try and rename the file.
*/
if ((ret = __db_appname(dbenv, DB_APP_DATA,
R_ADDR(dbmp->reginfo, mfp->path_off), 0, NULL,
&rpath)) == 0) {
if ((ret = __os_open(dbenv, rpath, 0, 0, &fhp)) == 0) {
ret = __os_fsync(dbenv, fhp);
if ((t_ret =
__os_closehandle(dbenv, fhp)) != 0 && ret == 0)
ret = t_ret;
}
__os_free(dbenv, rpath);
}
return (ret);
}
/*
* __memp_close_flush_files --
* Close files opened only to flush buffers.
*/
static int
__memp_close_flush_files(dbenv, dbmp, dosync)
DB_ENV *dbenv;
DB_MPOOL *dbmp;
int dosync;
{
DB_MPOOLFILE *dbmfp;
MPOOLFILE *mfp;
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, an 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 (dosync) {
if ((ret = __os_fsync(dbenv, dbmfp->fhp)) != 0)
return (ret);
/*
* If the file is clean and we have the only
* open handle on the file, clear the dirty
* flag so we don't re-open and sync it again.
*/
mfp = dbmfp->mfp;
if (mfp->mpf_cnt == 1) {
R_LOCK(dbenv, dbmp->reginfo);
if (mfp->mpf_cnt == 1)
mfp->file_written = 0;
R_UNLOCK(dbenv, dbmp->reginfo);
}
}
if ((ret = __memp_fclose(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);
}
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