2 Unix SMB/CIFS implementation.
4 trivial database library
6 Copyright (C) Andrew Tridgell 1999-2005
7 Copyright (C) Paul `Rusty' Russell 2000
8 Copyright (C) Jeremy Allison 2000-2003
10 ** NOTE! The following LGPL license applies to the tdb
11 ** library. This does NOT imply that all of Samba is released
14 This library is free software; you can redistribute it and/or
15 modify it under the terms of the GNU Lesser General Public
16 License as published by the Free Software Foundation; either
17 version 2 of the License, or (at your option) any later version.
19 This library is distributed in the hope that it will be useful,
20 but WITHOUT ANY WARRANTY; without even the implied warranty of
21 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
22 Lesser General Public License for more details.
24 You should have received a copy of the GNU Lesser General Public
25 License along with this library; if not, write to the Free Software
26 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
29 #include "tdb_private.h"
31 #define TDB_MARK_LOCK 0x80000000
33 /* a byte range locking function - return 0 on success
34 this functions locks/unlocks 1 byte at the specified offset.
36 On error, errno is also set so that errors are passed back properly
39 note that a len of zero means lock to end of file
41 int tdb_brlock(struct tdb_context *tdb, tdb_off_t offset,
42 int rw_type, int lck_type, int probe, size_t len)
47 if (tdb->flags & TDB_NOLOCK) {
51 if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) {
52 tdb->ecode = TDB_ERR_RDONLY;
57 fl.l_whence = SEEK_SET;
63 ret = fcntl(tdb->fd,lck_type,&fl);
64 } while (ret == -1 && errno == EINTR);
67 /* Generic lock error. errno set by fcntl.
68 * EAGAIN is an expected return from non-blocking
70 if (!probe && lck_type != F_SETLK) {
71 /* Ensure error code is set for log fun to examine. */
72 tdb->ecode = TDB_ERR_LOCK;
73 TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock failed (fd=%d) at offset %d rw_type=%d lck_type=%d len=%d\n",
74 tdb->fd, offset, rw_type, lck_type, (int)len));
76 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
83 upgrade a read lock to a write lock. This needs to be handled in a
84 special way as some OSes (such as solaris) have too conservative
85 deadlock detection and claim a deadlock when progress can be
86 made. For those OSes we may loop for a while.
88 int tdb_brlock_upgrade(struct tdb_context *tdb, tdb_off_t offset, size_t len)
93 if (tdb_brlock(tdb, offset, F_WRLCK, F_SETLKW, 1, len) == 0) {
96 if (errno != EDEADLK) {
99 /* sleep for as short a time as we can - more portable than usleep() */
102 select(0, NULL, NULL, NULL, &tv);
104 TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock_upgrade failed at offset %d\n", offset));
109 /* lock a list in the database. list -1 is the alloc list */
110 static int _tdb_lock(struct tdb_context *tdb, int list, int ltype, int op)
112 struct tdb_lock_type *new_lck;
114 bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
116 ltype &= ~TDB_MARK_LOCK;
118 /* a global lock allows us to avoid per chain locks */
119 if (tdb->global_lock.count &&
120 (ltype == tdb->global_lock.ltype || ltype == F_RDLCK)) {
124 if (tdb->global_lock.count) {
125 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
128 if (list < -1 || list >= (int)tdb->header.hash_size) {
129 TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid list %d for ltype=%d\n",
133 if (tdb->flags & TDB_NOLOCK)
136 for (i=0; i<tdb->num_lockrecs; i++) {
137 if (tdb->lockrecs[i].list == list) {
138 if (tdb->lockrecs[i].count == 0) {
140 * Can't happen, see tdb_unlock(). It should
143 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock: "
144 "lck->count == 0 for list %d", list));
147 * Just increment the in-memory struct, posix locks
150 tdb->lockrecs[i].count++;
155 new_lck = (struct tdb_lock_type *)realloc(
157 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
158 if (new_lck == NULL) {
162 tdb->lockrecs = new_lck;
164 /* Since fcntl locks don't nest, we do a lock for the first one,
165 and simply bump the count for future ones */
167 tdb->methods->tdb_brlock(tdb,FREELIST_TOP+4*list, ltype, op,
174 tdb->lockrecs[tdb->num_lockrecs].list = list;
175 tdb->lockrecs[tdb->num_lockrecs].count = 1;
176 tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
177 tdb->num_lockrecs += 1;
182 /* lock a list in the database. list -1 is the alloc list */
183 int tdb_lock(struct tdb_context *tdb, int list, int ltype)
186 ret = _tdb_lock(tdb, list, ltype, F_SETLKW);
188 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock failed on list %d "
189 "ltype=%d (%s)\n", list, ltype, strerror(errno)));
194 /* lock a list in the database. list -1 is the alloc list. non-blocking lock */
195 int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype)
197 return _tdb_lock(tdb, list, ltype, F_SETLK);
201 /* unlock the database: returns void because it's too late for errors. */
202 /* changed to return int it may be interesting to know there
203 has been an error --simo */
204 int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
208 struct tdb_lock_type *lck = NULL;
209 bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
211 ltype &= ~TDB_MARK_LOCK;
213 /* a global lock allows us to avoid per chain locks */
214 if (tdb->global_lock.count &&
215 (ltype == tdb->global_lock.ltype || ltype == F_RDLCK)) {
219 if (tdb->global_lock.count) {
220 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
223 if (tdb->flags & TDB_NOLOCK)
227 if (list < -1 || list >= (int)tdb->header.hash_size) {
228 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: list %d invalid (%d)\n", list, tdb->header.hash_size));
232 for (i=0; i<tdb->num_lockrecs; i++) {
233 if (tdb->lockrecs[i].list == list) {
234 lck = &tdb->lockrecs[i];
239 if ((lck == NULL) || (lck->count == 0)) {
240 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: count is 0\n"));
244 if (lck->count > 1) {
250 * This lock has count==1 left, so we need to unlock it in the
251 * kernel. We don't bother with decrementing the in-memory array
252 * element, we're about to overwrite it with the last array element
259 ret = tdb->methods->tdb_brlock(tdb, FREELIST_TOP+4*list, F_UNLCK,
265 * Shrink the array by overwriting the element just unlocked with the
266 * last array element.
269 if (tdb->num_lockrecs > 1) {
270 *lck = tdb->lockrecs[tdb->num_lockrecs-1];
272 tdb->num_lockrecs -= 1;
275 * We don't bother with realloc when the array shrinks, but if we have
276 * a completely idle tdb we should get rid of the locked array.
279 if (tdb->num_lockrecs == 0) {
280 SAFE_FREE(tdb->lockrecs);
284 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: An error occurred unlocking!\n"));
289 get the transaction lock
291 int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
293 if (tdb->have_transaction_lock || tdb->global_lock.count) {
296 if (tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, ltype,
297 F_SETLKW, 0, 1) == -1) {
298 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_lock: failed to get transaction lock\n"));
299 tdb->ecode = TDB_ERR_LOCK;
302 tdb->have_transaction_lock = 1;
307 release the transaction lock
309 int tdb_transaction_unlock(struct tdb_context *tdb)
312 if (!tdb->have_transaction_lock) {
315 ret = tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
317 tdb->have_transaction_lock = 0;
325 /* lock/unlock entire database */
326 static int _tdb_lockall(struct tdb_context *tdb, int ltype, int op)
328 bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
330 ltype &= ~TDB_MARK_LOCK;
332 /* There are no locks on read-only dbs */
333 if (tdb->read_only || tdb->traverse_read)
334 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
336 if (tdb->global_lock.count && tdb->global_lock.ltype == ltype) {
337 tdb->global_lock.count++;
341 if (tdb->global_lock.count) {
342 /* a global lock of a different type exists */
343 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
346 if (tdb->num_locks != 0) {
347 /* can't combine global and chain locks */
348 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
352 tdb->methods->tdb_brlock(tdb, FREELIST_TOP, ltype, op,
353 0, 4*tdb->header.hash_size)) {
354 if (op == F_SETLKW) {
355 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lockall failed (%s)\n", strerror(errno)));
360 tdb->global_lock.count = 1;
361 tdb->global_lock.ltype = ltype;
368 /* unlock entire db */
369 static int _tdb_unlockall(struct tdb_context *tdb, int ltype)
371 bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
373 ltype &= ~TDB_MARK_LOCK;
375 /* There are no locks on read-only dbs */
376 if (tdb->read_only || tdb->traverse_read) {
377 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
380 if (tdb->global_lock.ltype != ltype || tdb->global_lock.count == 0) {
381 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
384 if (tdb->global_lock.count > 1) {
385 tdb->global_lock.count--;
390 tdb->methods->tdb_brlock(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW,
391 0, 4*tdb->header.hash_size)) {
392 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed (%s)\n", strerror(errno)));
396 tdb->global_lock.count = 0;
397 tdb->global_lock.ltype = 0;
402 /* lock entire database with write lock */
403 int tdb_lockall(struct tdb_context *tdb)
405 return _tdb_lockall(tdb, F_WRLCK, F_SETLKW);
408 /* lock entire database with write lock - mark only */
409 int tdb_lockall_mark(struct tdb_context *tdb)
411 return _tdb_lockall(tdb, F_WRLCK | TDB_MARK_LOCK, F_SETLKW);
414 /* unlock entire database with write lock - unmark only */
415 int tdb_lockall_unmark(struct tdb_context *tdb)
417 return _tdb_unlockall(tdb, F_WRLCK | TDB_MARK_LOCK);
420 /* lock entire database with write lock - nonblocking varient */
421 int tdb_lockall_nonblock(struct tdb_context *tdb)
423 return _tdb_lockall(tdb, F_WRLCK, F_SETLK);
426 /* unlock entire database with write lock */
427 int tdb_unlockall(struct tdb_context *tdb)
429 return _tdb_unlockall(tdb, F_WRLCK);
432 /* lock entire database with read lock */
433 int tdb_lockall_read(struct tdb_context *tdb)
435 return _tdb_lockall(tdb, F_RDLCK, F_SETLKW);
438 /* lock entire database with read lock - nonblock varient */
439 int tdb_lockall_read_nonblock(struct tdb_context *tdb)
441 return _tdb_lockall(tdb, F_RDLCK, F_SETLK);
444 /* unlock entire database with read lock */
445 int tdb_unlockall_read(struct tdb_context *tdb)
447 return _tdb_unlockall(tdb, F_RDLCK);
450 /* lock/unlock one hash chain. This is meant to be used to reduce
451 contention - it cannot guarantee how many records will be locked */
452 int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
454 return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
457 /* lock/unlock one hash chain, non-blocking. This is meant to be used
458 to reduce contention - it cannot guarantee how many records will be
460 int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)
462 return tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
465 /* mark a chain as locked without actually locking it. Warning! use with great caution! */
466 int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key)
468 return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK | TDB_MARK_LOCK);
471 /* unmark a chain as locked without actually locking it. Warning! use with great caution! */
472 int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key)
474 return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK | TDB_MARK_LOCK);
477 int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
479 return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
482 int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
484 return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
487 int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
489 return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
494 /* record lock stops delete underneath */
495 int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
497 if (tdb->global_lock.count) {
500 return off ? tdb->methods->tdb_brlock(tdb, off, F_RDLCK, F_SETLKW, 0, 1) : 0;
504 Write locks override our own fcntl readlocks, so check it here.
505 Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
506 an error to fail to get the lock here.
508 int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
510 struct tdb_traverse_lock *i;
511 for (i = &tdb->travlocks; i; i = i->next)
514 return tdb->methods->tdb_brlock(tdb, off, F_WRLCK, F_SETLK, 1, 1);
518 Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
519 an error to fail to get the lock here.
521 int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
523 return tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLK, 0, 1);
526 /* fcntl locks don't stack: avoid unlocking someone else's */
527 int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
529 struct tdb_traverse_lock *i;
532 if (tdb->global_lock.count) {
538 for (i = &tdb->travlocks; i; i = i->next)
541 return (count == 1 ? tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLKW, 0, 1) : 0);