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 3 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, see <http://www.gnu.org/licenses/>.
28 #include "tdb_private.h"
30 #define TDB_MARK_LOCK 0x80000000
32 /* a byte range locking function - return 0 on success
33 this functions locks/unlocks 1 byte at the specified offset.
35 On error, errno is also set so that errors are passed back properly
38 note that a len of zero means lock to end of file
40 int tdb_brlock(struct tdb_context *tdb, tdb_off_t offset,
41 int rw_type, int lck_type, int probe, size_t len)
46 if (tdb->flags & TDB_NOLOCK) {
50 if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) {
51 tdb->ecode = TDB_ERR_RDONLY;
56 fl.l_whence = SEEK_SET;
62 ret = fcntl(tdb->fd,lck_type,&fl);
63 } while (ret == -1 && errno == EINTR);
66 /* Generic lock error. errno set by fcntl.
67 * EAGAIN is an expected return from non-blocking
69 if (!probe && lck_type != F_SETLK) {
70 /* Ensure error code is set for log fun to examine. */
71 tdb->ecode = TDB_ERR_LOCK;
72 TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock failed (fd=%d) at offset %d rw_type=%d lck_type=%d len=%d\n",
73 tdb->fd, offset, rw_type, lck_type, (int)len));
75 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
82 upgrade a read lock to a write lock. This needs to be handled in a
83 special way as some OSes (such as solaris) have too conservative
84 deadlock detection and claim a deadlock when progress can be
85 made. For those OSes we may loop for a while.
87 int tdb_brlock_upgrade(struct tdb_context *tdb, tdb_off_t offset, size_t len)
92 if (tdb_brlock(tdb, offset, F_WRLCK, F_SETLKW, 1, len) == 0) {
95 if (errno != EDEADLK) {
98 /* sleep for as short a time as we can - more portable than usleep() */
101 select(0, NULL, NULL, NULL, &tv);
103 TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock_upgrade failed at offset %d\n", offset));
108 /* lock a list in the database. list -1 is the alloc list */
109 static int _tdb_lock(struct tdb_context *tdb, int list, int ltype, int op)
111 struct tdb_lock_type *new_lck;
113 bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
115 ltype &= ~TDB_MARK_LOCK;
117 /* a global lock allows us to avoid per chain locks */
118 if (tdb->global_lock.count &&
119 (ltype == tdb->global_lock.ltype || ltype == F_RDLCK)) {
123 if (tdb->global_lock.count) {
124 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
127 if (list < -1 || list >= (int)tdb->header.hash_size) {
128 TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid list %d for ltype=%d\n",
132 if (tdb->flags & TDB_NOLOCK)
135 for (i=0; i<tdb->num_lockrecs; i++) {
136 if (tdb->lockrecs[i].list == list) {
137 if (tdb->lockrecs[i].count == 0) {
139 * Can't happen, see tdb_unlock(). It should
142 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock: "
143 "lck->count == 0 for list %d", list));
146 * Just increment the in-memory struct, posix locks
149 tdb->lockrecs[i].count++;
154 new_lck = (struct tdb_lock_type *)realloc(
156 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
157 if (new_lck == NULL) {
161 tdb->lockrecs = new_lck;
163 /* Since fcntl locks don't nest, we do a lock for the first one,
164 and simply bump the count for future ones */
166 tdb->methods->tdb_brlock(tdb,FREELIST_TOP+4*list, ltype, op,
173 tdb->lockrecs[tdb->num_lockrecs].list = list;
174 tdb->lockrecs[tdb->num_lockrecs].count = 1;
175 tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
176 tdb->num_lockrecs += 1;
181 /* lock a list in the database. list -1 is the alloc list */
182 int tdb_lock(struct tdb_context *tdb, int list, int ltype)
185 ret = _tdb_lock(tdb, list, ltype, F_SETLKW);
187 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock failed on list %d "
188 "ltype=%d (%s)\n", list, ltype, strerror(errno)));
193 /* lock a list in the database. list -1 is the alloc list. non-blocking lock */
194 int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype)
196 return _tdb_lock(tdb, list, ltype, F_SETLK);
200 /* unlock the database: returns void because it's too late for errors. */
201 /* changed to return int it may be interesting to know there
202 has been an error --simo */
203 int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
207 struct tdb_lock_type *lck = NULL;
208 bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
210 ltype &= ~TDB_MARK_LOCK;
212 /* a global lock allows us to avoid per chain locks */
213 if (tdb->global_lock.count &&
214 (ltype == tdb->global_lock.ltype || ltype == F_RDLCK)) {
218 if (tdb->global_lock.count) {
219 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
222 if (tdb->flags & TDB_NOLOCK)
226 if (list < -1 || list >= (int)tdb->header.hash_size) {
227 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: list %d invalid (%d)\n", list, tdb->header.hash_size));
231 for (i=0; i<tdb->num_lockrecs; i++) {
232 if (tdb->lockrecs[i].list == list) {
233 lck = &tdb->lockrecs[i];
238 if ((lck == NULL) || (lck->count == 0)) {
239 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: count is 0\n"));
243 if (lck->count > 1) {
249 * This lock has count==1 left, so we need to unlock it in the
250 * kernel. We don't bother with decrementing the in-memory array
251 * element, we're about to overwrite it with the last array element
258 ret = tdb->methods->tdb_brlock(tdb, FREELIST_TOP+4*list, F_UNLCK,
264 * Shrink the array by overwriting the element just unlocked with the
265 * last array element.
268 if (tdb->num_lockrecs > 1) {
269 *lck = tdb->lockrecs[tdb->num_lockrecs-1];
271 tdb->num_lockrecs -= 1;
274 * We don't bother with realloc when the array shrinks, but if we have
275 * a completely idle tdb we should get rid of the locked array.
278 if (tdb->num_lockrecs == 0) {
279 SAFE_FREE(tdb->lockrecs);
283 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: An error occurred unlocking!\n"));
288 get the transaction lock
290 int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
292 if (tdb->have_transaction_lock || tdb->global_lock.count) {
295 if (tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, ltype,
296 F_SETLKW, 0, 1) == -1) {
297 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_lock: failed to get transaction lock\n"));
298 tdb->ecode = TDB_ERR_LOCK;
301 tdb->have_transaction_lock = 1;
306 release the transaction lock
308 int tdb_transaction_unlock(struct tdb_context *tdb)
311 if (!tdb->have_transaction_lock) {
314 ret = tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
316 tdb->have_transaction_lock = 0;
324 /* lock/unlock entire database */
325 static int _tdb_lockall(struct tdb_context *tdb, int ltype, int op)
327 bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
329 ltype &= ~TDB_MARK_LOCK;
331 /* There are no locks on read-only dbs */
332 if (tdb->read_only || tdb->traverse_read)
333 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
335 if (tdb->global_lock.count && tdb->global_lock.ltype == ltype) {
336 tdb->global_lock.count++;
340 if (tdb->global_lock.count) {
341 /* a global lock of a different type exists */
342 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
345 if (tdb->num_locks != 0) {
346 /* can't combine global and chain locks */
347 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
351 tdb->methods->tdb_brlock(tdb, FREELIST_TOP, ltype, op,
352 0, 4*tdb->header.hash_size)) {
353 if (op == F_SETLKW) {
354 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lockall failed (%s)\n", strerror(errno)));
359 tdb->global_lock.count = 1;
360 tdb->global_lock.ltype = ltype;
367 /* unlock entire db */
368 static int _tdb_unlockall(struct tdb_context *tdb, int ltype)
370 bool mark_lock = ((ltype & TDB_MARK_LOCK) == TDB_MARK_LOCK);
372 ltype &= ~TDB_MARK_LOCK;
374 /* There are no locks on read-only dbs */
375 if (tdb->read_only || tdb->traverse_read) {
376 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
379 if (tdb->global_lock.ltype != ltype || tdb->global_lock.count == 0) {
380 return TDB_ERRCODE(TDB_ERR_LOCK, -1);
383 if (tdb->global_lock.count > 1) {
384 tdb->global_lock.count--;
389 tdb->methods->tdb_brlock(tdb, FREELIST_TOP, F_UNLCK, F_SETLKW,
390 0, 4*tdb->header.hash_size)) {
391 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed (%s)\n", strerror(errno)));
395 tdb->global_lock.count = 0;
396 tdb->global_lock.ltype = 0;
401 /* lock entire database with write lock */
402 int tdb_lockall(struct tdb_context *tdb)
404 return _tdb_lockall(tdb, F_WRLCK, F_SETLKW);
407 /* lock entire database with write lock - mark only */
408 int tdb_lockall_mark(struct tdb_context *tdb)
410 return _tdb_lockall(tdb, F_WRLCK | TDB_MARK_LOCK, F_SETLKW);
413 /* unlock entire database with write lock - unmark only */
414 int tdb_lockall_unmark(struct tdb_context *tdb)
416 return _tdb_unlockall(tdb, F_WRLCK | TDB_MARK_LOCK);
419 /* lock entire database with write lock - nonblocking varient */
420 int tdb_lockall_nonblock(struct tdb_context *tdb)
422 return _tdb_lockall(tdb, F_WRLCK, F_SETLK);
425 /* unlock entire database with write lock */
426 int tdb_unlockall(struct tdb_context *tdb)
428 return _tdb_unlockall(tdb, F_WRLCK);
431 /* lock entire database with read lock */
432 int tdb_lockall_read(struct tdb_context *tdb)
434 return _tdb_lockall(tdb, F_RDLCK, F_SETLKW);
437 /* lock entire database with read lock - nonblock varient */
438 int tdb_lockall_read_nonblock(struct tdb_context *tdb)
440 return _tdb_lockall(tdb, F_RDLCK, F_SETLK);
443 /* unlock entire database with read lock */
444 int tdb_unlockall_read(struct tdb_context *tdb)
446 return _tdb_unlockall(tdb, F_RDLCK);
449 /* lock/unlock one hash chain. This is meant to be used to reduce
450 contention - it cannot guarantee how many records will be locked */
451 int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
453 return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
456 /* lock/unlock one hash chain, non-blocking. This is meant to be used
457 to reduce contention - it cannot guarantee how many records will be
459 int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)
461 return tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
464 /* mark a chain as locked without actually locking it. Warning! use with great caution! */
465 int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key)
467 return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK | TDB_MARK_LOCK);
470 /* unmark a chain as locked without actually locking it. Warning! use with great caution! */
471 int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key)
473 return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK | TDB_MARK_LOCK);
476 int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
478 return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
481 int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
483 return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
486 int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
488 return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
493 /* record lock stops delete underneath */
494 int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
496 return off ? tdb->methods->tdb_brlock(tdb, off, F_RDLCK, F_SETLKW, 0, 1) : 0;
500 Write locks override our own fcntl readlocks, so check it here.
501 Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
502 an error to fail to get the lock here.
504 int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
506 struct tdb_traverse_lock *i;
507 for (i = &tdb->travlocks; i; i = i->next)
510 return tdb->methods->tdb_brlock(tdb, off, F_WRLCK, F_SETLK, 1, 1);
514 Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
515 an error to fail to get the lock here.
517 int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
519 return tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLK, 0, 1);
522 /* fcntl locks don't stack: avoid unlocking someone else's */
523 int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
525 struct tdb_traverse_lock *i;
530 for (i = &tdb->travlocks; i; i = i->next)
533 return (count == 1 ? tdb->methods->tdb_brlock(tdb, off, F_UNLCK, F_SETLKW, 0, 1) : 0);