2 Unix SMB/CIFS implementation.
4 trivial database library
6 Copyright (C) Andrew Tridgell 2005
8 ** NOTE! The following LGPL license applies to the tdb
9 ** library. This does NOT imply that all of Samba is released
12 This library is free software; you can redistribute it and/or
13 modify it under the terms of the GNU Lesser General Public
14 License as published by the Free Software Foundation; either
15 version 3 of the License, or (at your option) any later version.
17 This library is distributed in the hope that it will be useful,
18 but WITHOUT ANY WARRANTY; without even the implied warranty of
19 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 Lesser General Public License for more details.
22 You should have received a copy of the GNU Lesser General Public
23 License along with this library; if not, see <http://www.gnu.org/licenses/>.
26 #include "tdb_private.h"
31 - only allow a single transaction at a time per database. This makes
32 using the transaction API simpler, as otherwise the caller would
33 have to cope with temporary failures in transactions that conflict
34 with other current transactions
36 - keep the transaction recovery information in the same file as the
37 database, using a special 'transaction recovery' record pointed at
38 by the header. This removes the need for extra journal files as
39 used by some other databases
41 - dynamically allocated the transaction recover record, re-using it
42 for subsequent transactions. If a larger record is needed then
43 tdb_free() the old record to place it on the normal tdb freelist
44 before allocating the new record
46 - during transactions, keep a linked list of writes all that have
47 been performed by intercepting all tdb_write() calls. The hooked
48 transaction versions of tdb_read() and tdb_write() check this
49 linked list and try to use the elements of the list in preference
52 - don't allow any locks to be held when a transaction starts,
53 otherwise we can end up with deadlock (plus lack of lock nesting
54 in posix locks would mean the lock is lost)
56 - if the caller gains a lock during the transaction but doesn't
57 release it then fail the commit
59 - allow for nested calls to tdb_transaction_start(), re-using the
60 existing transaction record. If the inner transaction is cancelled
61 then a subsequent commit will fail
63 - keep a mirrored copy of the tdb hash chain heads to allow for the
64 fast hash heads scan on traverse, updating the mirrored copy in
65 the transaction version of tdb_write
67 - allow callers to mix transaction and non-transaction use of tdb,
68 although once a transaction is started then an exclusive lock is
69 gained until the transaction is committed or cancelled
71 - the commit stategy involves first saving away all modified data
72 into a linearised buffer in the transaction recovery area, then
73 marking the transaction recovery area with a magic value to
74 indicate a valid recovery record. In total 4 fsync/msync calls are
75 needed per commit to prevent race conditions. It might be possible
76 to reduce this to 3 or even 2 with some more work.
78 - check for a valid recovery record on open of the tdb, while the
79 global lock is held. Automatically recover from the transaction
80 recovery area if needed, then continue with the open as
81 usual. This allows for smooth crash recovery with no administrator
84 - if TDB_NOSYNC is passed to flags in tdb_open then transactions are
85 still available, but no transaction recovery area is used and no
86 fsync/msync calls are made.
88 - if TDB_ALLOW_NESTING is passed to flags in tdb open, or added using
89 tdb_add_flags() transaction nesting is enabled.
90 It resets the TDB_DISALLOW_NESTING flag, as both cannot be used together.
91 The default is that transaction nesting is allowed.
92 Note: this default may change in future versions of tdb.
94 Beware. when transactions are nested a transaction successfully
95 completed with tdb_transaction_commit() can be silently unrolled later.
97 - if TDB_DISALLOW_NESTING is passed to flags in tdb open, or added using
98 tdb_add_flags() transaction nesting is disabled.
99 It resets the TDB_ALLOW_NESTING flag, as both cannot be used together.
100 An attempt create a nested transaction will fail with TDB_ERR_NESTING.
101 The default is that transaction nesting is allowed.
102 Note: this default may change in future versions of tdb.
107 hold the context of any current transaction
109 struct tdb_transaction {
110 /* we keep a mirrored copy of the tdb hash heads here so
111 tdb_next_hash_chain() can operate efficiently */
112 uint32_t *hash_heads;
114 /* the original io methods - used to do IOs to the real db */
115 const struct tdb_methods *io_methods;
117 /* the list of transaction blocks. When a block is first
118 written to, it gets created in this list */
121 uint32_t block_size; /* bytes in each block */
122 uint32_t last_block_size; /* number of valid bytes in the last block */
124 /* non-zero when an internal transaction error has
125 occurred. All write operations will then fail until the
126 transaction is ended */
127 int transaction_error;
129 /* when inside a transaction we need to keep track of any
130 nested tdb_transaction_start() calls, as these are allowed,
131 but don't create a new transaction */
134 /* set when a prepare has already occurred */
136 tdb_off_t magic_offset;
138 /* set when the GLOBAL_LOCK has been taken */
139 bool global_lock_taken;
141 /* old file size before transaction */
142 tdb_len_t old_map_size;
144 /* we should re-pack on commit */
150 read while in a transaction. We need to check first if the data is in our list
151 of transaction elements, then if not do a real read
153 static int transaction_read(struct tdb_context *tdb, tdb_off_t off, void *buf,
154 tdb_len_t len, int cv)
158 /* break it down into block sized ops */
159 while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
160 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
161 if (transaction_read(tdb, off, buf, len2, cv) != 0) {
166 buf = (void *)(len2 + (char *)buf);
173 blk = off / tdb->transaction->block_size;
175 /* see if we have it in the block list */
176 if (tdb->transaction->num_blocks <= blk ||
177 tdb->transaction->blocks[blk] == NULL) {
178 /* nope, do a real read */
179 if (tdb->transaction->io_methods->tdb_read(tdb, off, buf, len, cv) != 0) {
185 /* it is in the block list. Now check for the last block */
186 if (blk == tdb->transaction->num_blocks-1) {
187 if (len > tdb->transaction->last_block_size) {
192 /* now copy it out of this block */
193 memcpy(buf, tdb->transaction->blocks[blk] + (off % tdb->transaction->block_size), len);
195 tdb_convert(buf, len);
200 TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_read: failed at off=%d len=%d\n", off, len));
201 tdb->ecode = TDB_ERR_IO;
202 tdb->transaction->transaction_error = 1;
208 write while in a transaction
210 static int transaction_write(struct tdb_context *tdb, tdb_off_t off,
211 const void *buf, tdb_len_t len)
215 /* Only a commit is allowed on a prepared transaction */
216 if (tdb->transaction->prepared) {
217 tdb->ecode = TDB_ERR_EINVAL;
218 TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_write: transaction already prepared, write not allowed\n"));
219 tdb->transaction->transaction_error = 1;
223 /* if the write is to a hash head, then update the transaction
225 if (len == sizeof(tdb_off_t) && off >= FREELIST_TOP &&
226 off < FREELIST_TOP+TDB_HASHTABLE_SIZE(tdb)) {
227 uint32_t chain = (off-FREELIST_TOP) / sizeof(tdb_off_t);
228 memcpy(&tdb->transaction->hash_heads[chain], buf, len);
231 /* break it up into block sized chunks */
232 while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
233 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
234 if (transaction_write(tdb, off, buf, len2) != 0) {
240 buf = (const void *)(len2 + (const char *)buf);
248 blk = off / tdb->transaction->block_size;
249 off = off % tdb->transaction->block_size;
251 if (tdb->transaction->num_blocks <= blk) {
252 uint8_t **new_blocks;
253 /* expand the blocks array */
254 if (tdb->transaction->blocks == NULL) {
255 new_blocks = (uint8_t **)malloc(
256 (blk+1)*sizeof(uint8_t *));
258 new_blocks = (uint8_t **)realloc(
259 tdb->transaction->blocks,
260 (blk+1)*sizeof(uint8_t *));
262 if (new_blocks == NULL) {
263 tdb->ecode = TDB_ERR_OOM;
266 memset(&new_blocks[tdb->transaction->num_blocks], 0,
267 (1+(blk - tdb->transaction->num_blocks))*sizeof(uint8_t *));
268 tdb->transaction->blocks = new_blocks;
269 tdb->transaction->num_blocks = blk+1;
270 tdb->transaction->last_block_size = 0;
273 /* allocate and fill a block? */
274 if (tdb->transaction->blocks[blk] == NULL) {
275 tdb->transaction->blocks[blk] = (uint8_t *)calloc(tdb->transaction->block_size, 1);
276 if (tdb->transaction->blocks[blk] == NULL) {
277 tdb->ecode = TDB_ERR_OOM;
278 tdb->transaction->transaction_error = 1;
281 if (tdb->transaction->old_map_size > blk * tdb->transaction->block_size) {
282 tdb_len_t len2 = tdb->transaction->block_size;
283 if (len2 + (blk * tdb->transaction->block_size) > tdb->transaction->old_map_size) {
284 len2 = tdb->transaction->old_map_size - (blk * tdb->transaction->block_size);
286 if (tdb->transaction->io_methods->tdb_read(tdb, blk * tdb->transaction->block_size,
287 tdb->transaction->blocks[blk],
289 SAFE_FREE(tdb->transaction->blocks[blk]);
290 tdb->ecode = TDB_ERR_IO;
293 if (blk == tdb->transaction->num_blocks-1) {
294 tdb->transaction->last_block_size = len2;
299 /* overwrite part of an existing block */
301 memset(tdb->transaction->blocks[blk] + off, 0, len);
303 memcpy(tdb->transaction->blocks[blk] + off, buf, len);
305 if (blk == tdb->transaction->num_blocks-1) {
306 if (len + off > tdb->transaction->last_block_size) {
307 tdb->transaction->last_block_size = len + off;
314 TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_write: failed at off=%d len=%d\n",
315 (blk*tdb->transaction->block_size) + off, len));
316 tdb->transaction->transaction_error = 1;
322 write while in a transaction - this varient never expands the transaction blocks, it only
323 updates existing blocks. This means it cannot change the recovery size
325 static int transaction_write_existing(struct tdb_context *tdb, tdb_off_t off,
326 const void *buf, tdb_len_t len)
330 /* break it up into block sized chunks */
331 while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
332 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
333 if (transaction_write_existing(tdb, off, buf, len2) != 0) {
339 buf = (const void *)(len2 + (const char *)buf);
347 blk = off / tdb->transaction->block_size;
348 off = off % tdb->transaction->block_size;
350 if (tdb->transaction->num_blocks <= blk ||
351 tdb->transaction->blocks[blk] == NULL) {
355 if (blk == tdb->transaction->num_blocks-1 &&
356 off + len > tdb->transaction->last_block_size) {
357 if (off >= tdb->transaction->last_block_size) {
360 len = tdb->transaction->last_block_size - off;
363 /* overwrite part of an existing block */
364 memcpy(tdb->transaction->blocks[blk] + off, buf, len);
371 accelerated hash chain head search, using the cached hash heads
373 static void transaction_next_hash_chain(struct tdb_context *tdb, uint32_t *chain)
376 for (;h < tdb->header.hash_size;h++) {
377 /* the +1 takes account of the freelist */
378 if (0 != tdb->transaction->hash_heads[h+1]) {
386 out of bounds check during a transaction
388 static int transaction_oob(struct tdb_context *tdb, tdb_off_t len, int probe)
390 if (len <= tdb->map_size) {
393 tdb->ecode = TDB_ERR_IO;
398 transaction version of tdb_expand().
400 static int transaction_expand_file(struct tdb_context *tdb, tdb_off_t size,
403 /* add a write to the transaction elements, so subsequent
404 reads see the zero data */
405 if (transaction_write(tdb, size, NULL, addition) != 0) {
409 tdb->transaction->need_repack = true;
415 brlock during a transaction - ignore them
417 static int transaction_brlock(struct tdb_context *tdb,
418 int rw_type, tdb_off_t offset, size_t len,
419 enum tdb_lock_flags flags)
424 static int transaction_brunlock(struct tdb_context *tdb,
425 int rw_type, tdb_off_t offset, size_t len)
430 static const struct tdb_methods transaction_methods = {
433 transaction_next_hash_chain,
435 transaction_expand_file,
443 static int transaction_sync(struct tdb_context *tdb, tdb_off_t offset, tdb_len_t length)
445 if (tdb->flags & TDB_NOSYNC) {
449 if (fsync(tdb->fd) != 0) {
450 tdb->ecode = TDB_ERR_IO;
451 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: fsync failed\n"));
456 tdb_off_t moffset = offset & ~(tdb->page_size-1);
457 if (msync(moffset + (char *)tdb->map_ptr,
458 length + (offset - moffset), MS_SYNC) != 0) {
459 tdb->ecode = TDB_ERR_IO;
460 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: msync failed - %s\n",
469 /* ltype is F_WRLCK after prepare. */
470 int _tdb_transaction_cancel(struct tdb_context *tdb, int ltype)
474 if (tdb->transaction == NULL) {
475 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_cancel: no transaction\n"));
479 if (tdb->transaction->nesting != 0) {
480 tdb->transaction->transaction_error = 1;
481 tdb->transaction->nesting--;
485 tdb->map_size = tdb->transaction->old_map_size;
487 /* free all the transaction blocks */
488 for (i=0;i<tdb->transaction->num_blocks;i++) {
489 if (tdb->transaction->blocks[i] != NULL) {
490 free(tdb->transaction->blocks[i]);
493 SAFE_FREE(tdb->transaction->blocks);
495 if (tdb->transaction->magic_offset) {
496 const struct tdb_methods *methods = tdb->transaction->io_methods;
499 /* remove the recovery marker */
500 if (methods->tdb_write(tdb, tdb->transaction->magic_offset, &zero, 4) == -1 ||
501 transaction_sync(tdb, tdb->transaction->magic_offset, 4) == -1) {
502 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_cancel: failed to remove recovery magic\n"));
507 if (tdb->transaction->global_lock_taken) {
508 tdb_brunlock(tdb, F_WRLCK, GLOBAL_LOCK, 1);
509 tdb->transaction->global_lock_taken = false;
512 /* remove any global lock created during the transaction */
513 if (tdb->global_lock.count != 0) {
514 tdb_brunlock(tdb, tdb->global_lock.ltype,
515 FREELIST_TOP, 4*tdb->header.hash_size);
516 tdb->global_lock.count = 0;
519 /* remove any locks created during the transaction */
520 if (tdb->num_locks != 0) {
521 for (i=0;i<tdb->num_lockrecs;i++) {
522 tdb_brunlock(tdb, tdb->lockrecs[i].ltype,
523 FREELIST_TOP+4*tdb->lockrecs[i].list, 1);
526 tdb->num_lockrecs = 0;
527 SAFE_FREE(tdb->lockrecs);
530 /* restore the normal io methods */
531 tdb->methods = tdb->transaction->io_methods;
533 tdb_brunlock(tdb, ltype, FREELIST_TOP, 0);
534 tdb_transaction_unlock(tdb, F_WRLCK);
535 SAFE_FREE(tdb->transaction->hash_heads);
536 SAFE_FREE(tdb->transaction);
542 start a tdb transaction. No token is returned, as only a single
543 transaction is allowed to be pending per tdb_context
545 int tdb_transaction_start(struct tdb_context *tdb)
547 /* some sanity checks */
548 if (tdb->read_only || (tdb->flags & TDB_INTERNAL) || tdb->traverse_read) {
549 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction on a read-only or internal db\n"));
550 tdb->ecode = TDB_ERR_EINVAL;
554 /* cope with nested tdb_transaction_start() calls */
555 if (tdb->transaction != NULL) {
556 if (!(tdb->flags & TDB_ALLOW_NESTING)) {
557 tdb->ecode = TDB_ERR_NESTING;
560 tdb_trace(tdb, "tdb_transaction_start");
561 tdb->transaction->nesting++;
562 TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_start: nesting %d\n",
563 tdb->transaction->nesting));
567 if (tdb->num_locks != 0 || tdb->global_lock.count) {
568 /* the caller must not have any locks when starting a
569 transaction as otherwise we'll be screwed by lack
570 of nested locks in posix */
571 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction with locks held\n"));
572 tdb->ecode = TDB_ERR_LOCK;
576 if (tdb->travlocks.next != NULL) {
577 /* you cannot use transactions inside a traverse (although you can use
578 traverse inside a transaction) as otherwise you can end up with
580 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction within a traverse\n"));
581 tdb->ecode = TDB_ERR_LOCK;
585 tdb->transaction = (struct tdb_transaction *)
586 calloc(sizeof(struct tdb_transaction), 1);
587 if (tdb->transaction == NULL) {
588 tdb->ecode = TDB_ERR_OOM;
592 /* a page at a time seems like a reasonable compromise between compactness and efficiency */
593 tdb->transaction->block_size = tdb->page_size;
595 /* get the transaction write lock. This is a blocking lock. As
596 discussed with Volker, there are a number of ways we could
597 make this async, which we will probably do in the future */
598 if (tdb_transaction_lock(tdb, F_WRLCK) == -1) {
599 SAFE_FREE(tdb->transaction->blocks);
600 SAFE_FREE(tdb->transaction);
604 /* get a read lock from the freelist to the end of file. This
605 is upgraded to a write lock during the commit */
606 if (tdb_brlock(tdb, F_RDLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT) == -1) {
607 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: failed to get hash locks\n"));
608 tdb->ecode = TDB_ERR_LOCK;
612 /* setup a copy of the hash table heads so the hash scan in
613 traverse can be fast */
614 tdb->transaction->hash_heads = (uint32_t *)
615 calloc(tdb->header.hash_size+1, sizeof(uint32_t));
616 if (tdb->transaction->hash_heads == NULL) {
617 tdb->ecode = TDB_ERR_OOM;
620 if (tdb->methods->tdb_read(tdb, FREELIST_TOP, tdb->transaction->hash_heads,
621 TDB_HASHTABLE_SIZE(tdb), 0) != 0) {
622 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_start: failed to read hash heads\n"));
623 tdb->ecode = TDB_ERR_IO;
627 /* make sure we know about any file expansions already done by
629 tdb->methods->tdb_oob(tdb, tdb->map_size + 1, 1);
630 tdb->transaction->old_map_size = tdb->map_size;
632 /* finally hook the io methods, replacing them with
633 transaction specific methods */
634 tdb->transaction->io_methods = tdb->methods;
635 tdb->methods = &transaction_methods;
637 /* Trace at the end, so we get sequence number correct. */
638 tdb_trace(tdb, "tdb_transaction_start");
642 tdb_brunlock(tdb, F_RDLCK, FREELIST_TOP, 0);
643 tdb_transaction_unlock(tdb, F_WRLCK);
644 SAFE_FREE(tdb->transaction->blocks);
645 SAFE_FREE(tdb->transaction->hash_heads);
646 SAFE_FREE(tdb->transaction);
652 cancel the current transaction
654 int tdb_transaction_cancel(struct tdb_context *tdb)
657 tdb_trace(tdb, "tdb_transaction_cancel");
658 if (tdb->transaction && tdb->transaction->prepared)
660 return _tdb_transaction_cancel(tdb, ltype);
664 work out how much space the linearised recovery data will consume
666 static tdb_len_t tdb_recovery_size(struct tdb_context *tdb)
668 tdb_len_t recovery_size = 0;
671 recovery_size = sizeof(uint32_t);
672 for (i=0;i<tdb->transaction->num_blocks;i++) {
673 if (i * tdb->transaction->block_size >= tdb->transaction->old_map_size) {
676 if (tdb->transaction->blocks[i] == NULL) {
679 recovery_size += 2*sizeof(tdb_off_t);
680 if (i == tdb->transaction->num_blocks-1) {
681 recovery_size += tdb->transaction->last_block_size;
683 recovery_size += tdb->transaction->block_size;
687 return recovery_size;
691 allocate the recovery area, or use an existing recovery area if it is
694 static int tdb_recovery_allocate(struct tdb_context *tdb,
695 tdb_len_t *recovery_size,
696 tdb_off_t *recovery_offset,
697 tdb_len_t *recovery_max_size)
699 struct tdb_record rec;
700 const struct tdb_methods *methods = tdb->transaction->io_methods;
701 tdb_off_t recovery_head;
703 if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
704 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery head\n"));
710 if (recovery_head != 0 &&
711 methods->tdb_read(tdb, recovery_head, &rec, sizeof(rec), DOCONV()) == -1) {
712 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery record\n"));
716 *recovery_size = tdb_recovery_size(tdb);
718 if (recovery_head != 0 && *recovery_size <= rec.rec_len) {
719 /* it fits in the existing area */
720 *recovery_max_size = rec.rec_len;
721 *recovery_offset = recovery_head;
725 /* we need to free up the old recovery area, then allocate a
726 new one at the end of the file. Note that we cannot use
727 tdb_allocate() to allocate the new one as that might return
728 us an area that is being currently used (as of the start of
730 if (recovery_head != 0) {
731 if (tdb_free(tdb, recovery_head, &rec) == -1) {
732 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to free previous recovery area\n"));
737 /* the tdb_free() call might have increased the recovery size */
738 *recovery_size = tdb_recovery_size(tdb);
740 /* round up to a multiple of page size */
741 *recovery_max_size = TDB_ALIGN(sizeof(rec) + *recovery_size, tdb->page_size) - sizeof(rec);
742 *recovery_offset = tdb->map_size;
743 recovery_head = *recovery_offset;
745 if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
746 (tdb->map_size - tdb->transaction->old_map_size) +
747 sizeof(rec) + *recovery_max_size) == -1) {
748 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to create recovery area\n"));
752 /* remap the file (if using mmap) */
753 methods->tdb_oob(tdb, tdb->map_size + 1, 1);
755 /* we have to reset the old map size so that we don't try to expand the file
756 again in the transaction commit, which would destroy the recovery area */
757 tdb->transaction->old_map_size = tdb->map_size;
759 /* write the recovery header offset and sync - we can sync without a race here
760 as the magic ptr in the recovery record has not been set */
761 CONVERT(recovery_head);
762 if (methods->tdb_write(tdb, TDB_RECOVERY_HEAD,
763 &recovery_head, sizeof(tdb_off_t)) == -1) {
764 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
767 if (transaction_write_existing(tdb, TDB_RECOVERY_HEAD, &recovery_head, sizeof(tdb_off_t)) == -1) {
768 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
777 setup the recovery data that will be used on a crash during commit
779 static int transaction_setup_recovery(struct tdb_context *tdb,
780 tdb_off_t *magic_offset)
782 tdb_len_t recovery_size;
783 unsigned char *data, *p;
784 const struct tdb_methods *methods = tdb->transaction->io_methods;
785 struct tdb_record *rec;
786 tdb_off_t recovery_offset, recovery_max_size;
787 tdb_off_t old_map_size = tdb->transaction->old_map_size;
788 uint32_t magic, tailer;
792 check that the recovery area has enough space
794 if (tdb_recovery_allocate(tdb, &recovery_size,
795 &recovery_offset, &recovery_max_size) == -1) {
799 data = (unsigned char *)malloc(recovery_size + sizeof(*rec));
801 tdb->ecode = TDB_ERR_OOM;
805 rec = (struct tdb_record *)data;
806 memset(rec, 0, sizeof(*rec));
809 rec->data_len = recovery_size;
810 rec->rec_len = recovery_max_size;
811 rec->key_len = old_map_size;
814 /* build the recovery data into a single blob to allow us to do a single
815 large write, which should be more efficient */
816 p = data + sizeof(*rec);
817 for (i=0;i<tdb->transaction->num_blocks;i++) {
821 if (tdb->transaction->blocks[i] == NULL) {
825 offset = i * tdb->transaction->block_size;
826 length = tdb->transaction->block_size;
827 if (i == tdb->transaction->num_blocks-1) {
828 length = tdb->transaction->last_block_size;
831 if (offset >= old_map_size) {
834 if (offset + length > tdb->transaction->old_map_size) {
835 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: transaction data over new region boundary\n"));
837 tdb->ecode = TDB_ERR_CORRUPT;
840 memcpy(p, &offset, 4);
841 memcpy(p+4, &length, 4);
845 /* the recovery area contains the old data, not the
846 new data, so we have to call the original tdb_read
848 if (methods->tdb_read(tdb, offset, p + 8, length, 0) != 0) {
850 tdb->ecode = TDB_ERR_IO;
857 tailer = sizeof(*rec) + recovery_max_size;
858 memcpy(p, &tailer, 4);
861 /* write the recovery data to the recovery area */
862 if (methods->tdb_write(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
863 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery data\n"));
865 tdb->ecode = TDB_ERR_IO;
868 if (transaction_write_existing(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
869 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery data\n"));
871 tdb->ecode = TDB_ERR_IO;
875 /* as we don't have ordered writes, we have to sync the recovery
876 data before we update the magic to indicate that the recovery
878 if (transaction_sync(tdb, recovery_offset, sizeof(*rec) + recovery_size) == -1) {
885 magic = TDB_RECOVERY_MAGIC;
888 *magic_offset = recovery_offset + offsetof(struct tdb_record, magic);
890 if (methods->tdb_write(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
891 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery magic\n"));
892 tdb->ecode = TDB_ERR_IO;
895 if (transaction_write_existing(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
896 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery magic\n"));
897 tdb->ecode = TDB_ERR_IO;
901 /* ensure the recovery magic marker is on disk */
902 if (transaction_sync(tdb, *magic_offset, sizeof(magic)) == -1) {
909 static int _tdb_transaction_prepare_commit(struct tdb_context *tdb)
911 const struct tdb_methods *methods;
913 if (tdb->transaction == NULL) {
914 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: no transaction\n"));
918 if (tdb->transaction->prepared) {
919 tdb->ecode = TDB_ERR_EINVAL;
920 _tdb_transaction_cancel(tdb, F_WRLCK);
921 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction already prepared\n"));
925 if (tdb->transaction->transaction_error) {
926 tdb->ecode = TDB_ERR_IO;
927 _tdb_transaction_cancel(tdb, F_RDLCK);
928 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction error pending\n"));
933 if (tdb->transaction->nesting != 0) {
934 tdb->transaction->nesting--;
938 /* check for a null transaction */
939 if (tdb->transaction->blocks == NULL) {
943 methods = tdb->transaction->io_methods;
945 /* if there are any locks pending then the caller has not
946 nested their locks properly, so fail the transaction */
947 if (tdb->num_locks || tdb->global_lock.count) {
948 tdb->ecode = TDB_ERR_LOCK;
949 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: locks pending on commit\n"));
950 _tdb_transaction_cancel(tdb, F_RDLCK);
954 /* upgrade the main transaction lock region to a write lock */
955 if (tdb_brlock_upgrade(tdb, FREELIST_TOP, 0) == -1) {
956 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to upgrade hash locks\n"));
957 tdb->ecode = TDB_ERR_LOCK;
958 _tdb_transaction_cancel(tdb, F_RDLCK);
962 /* get the global lock - this prevents new users attaching to the database
964 if (tdb_brlock(tdb, F_WRLCK, GLOBAL_LOCK, 1, TDB_LOCK_WAIT) == -1) {
965 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to get global lock\n"));
966 tdb->ecode = TDB_ERR_LOCK;
967 _tdb_transaction_cancel(tdb, F_WRLCK);
971 tdb->transaction->global_lock_taken = true;
973 if (!(tdb->flags & TDB_NOSYNC)) {
974 /* write the recovery data to the end of the file */
975 if (transaction_setup_recovery(tdb, &tdb->transaction->magic_offset) == -1) {
976 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: failed to setup recovery data\n"));
977 _tdb_transaction_cancel(tdb, F_WRLCK);
982 tdb->transaction->prepared = true;
984 /* expand the file to the new size if needed */
985 if (tdb->map_size != tdb->transaction->old_map_size) {
986 if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
988 tdb->transaction->old_map_size) == -1) {
989 tdb->ecode = TDB_ERR_IO;
990 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: expansion failed\n"));
991 _tdb_transaction_cancel(tdb, F_WRLCK);
994 tdb->map_size = tdb->transaction->old_map_size;
995 methods->tdb_oob(tdb, tdb->map_size + 1, 1);
998 /* Keep the global lock until the actual commit */
1004 prepare to commit the current transaction
1006 int tdb_transaction_prepare_commit(struct tdb_context *tdb)
1008 tdb_trace(tdb, "tdb_transaction_prepare_commit");
1009 return _tdb_transaction_prepare_commit(tdb);
1013 commit the current transaction
1015 int tdb_transaction_commit(struct tdb_context *tdb)
1017 const struct tdb_methods *methods;
1021 if (tdb->transaction == NULL) {
1022 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: no transaction\n"));
1026 tdb_trace(tdb, "tdb_transaction_commit");
1028 if (tdb->transaction->transaction_error) {
1029 tdb->ecode = TDB_ERR_IO;
1030 tdb_transaction_cancel(tdb);
1031 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: transaction error pending\n"));
1036 if (tdb->transaction->nesting != 0) {
1037 tdb->transaction->nesting--;
1041 /* check for a null transaction */
1042 if (tdb->transaction->blocks == NULL) {
1043 _tdb_transaction_cancel(tdb, F_RDLCK);
1047 if (!tdb->transaction->prepared) {
1048 int ret = _tdb_transaction_prepare_commit(tdb);
1053 methods = tdb->transaction->io_methods;
1055 /* perform all the writes */
1056 for (i=0;i<tdb->transaction->num_blocks;i++) {
1060 if (tdb->transaction->blocks[i] == NULL) {
1064 offset = i * tdb->transaction->block_size;
1065 length = tdb->transaction->block_size;
1066 if (i == tdb->transaction->num_blocks-1) {
1067 length = tdb->transaction->last_block_size;
1070 if (methods->tdb_write(tdb, offset, tdb->transaction->blocks[i], length) == -1) {
1071 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed during commit\n"));
1073 /* we've overwritten part of the data and
1074 possibly expanded the file, so we need to
1075 run the crash recovery code */
1076 tdb->methods = methods;
1077 tdb_transaction_recover(tdb);
1079 _tdb_transaction_cancel(tdb, F_WRLCK);
1081 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed\n"));
1084 SAFE_FREE(tdb->transaction->blocks[i]);
1087 SAFE_FREE(tdb->transaction->blocks);
1088 tdb->transaction->num_blocks = 0;
1090 /* ensure the new data is on disk */
1091 if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1096 TODO: maybe write to some dummy hdr field, or write to magic
1097 offset without mmap, before the last sync, instead of the
1101 /* on some systems (like Linux 2.6.x) changes via mmap/msync
1102 don't change the mtime of the file, this means the file may
1103 not be backed up (as tdb rounding to block sizes means that
1104 file size changes are quite rare too). The following forces
1105 mtime changes when a transaction completes */
1107 utime(tdb->name, NULL);
1110 need_repack = tdb->transaction->need_repack;
1112 /* use a transaction cancel to free memory and remove the
1113 transaction locks */
1114 _tdb_transaction_cancel(tdb, F_WRLCK);
1117 return tdb_repack(tdb);
1125 recover from an aborted transaction. Must be called with exclusive
1126 database write access already established (including the global
1127 lock to prevent new processes attaching)
1129 int tdb_transaction_recover(struct tdb_context *tdb)
1131 tdb_off_t recovery_head, recovery_eof;
1132 unsigned char *data, *p;
1134 struct tdb_record rec;
1136 /* find the recovery area */
1137 if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
1138 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery head\n"));
1139 tdb->ecode = TDB_ERR_IO;
1143 if (recovery_head == 0) {
1144 /* we have never allocated a recovery record */
1148 /* read the recovery record */
1149 if (tdb->methods->tdb_read(tdb, recovery_head, &rec,
1150 sizeof(rec), DOCONV()) == -1) {
1151 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery record\n"));
1152 tdb->ecode = TDB_ERR_IO;
1156 if (rec.magic != TDB_RECOVERY_MAGIC) {
1157 /* there is no valid recovery data */
1161 if (tdb->read_only) {
1162 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: attempt to recover read only database\n"));
1163 tdb->ecode = TDB_ERR_CORRUPT;
1167 recovery_eof = rec.key_len;
1169 data = (unsigned char *)malloc(rec.data_len);
1171 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to allocate recovery data\n"));
1172 tdb->ecode = TDB_ERR_OOM;
1176 /* read the full recovery data */
1177 if (tdb->methods->tdb_read(tdb, recovery_head + sizeof(rec), data,
1178 rec.data_len, 0) == -1) {
1179 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery data\n"));
1180 tdb->ecode = TDB_ERR_IO;
1184 /* recover the file data */
1186 while (p+8 < data + rec.data_len) {
1192 memcpy(&len, p+4, 4);
1194 if (tdb->methods->tdb_write(tdb, ofs, p+8, len) == -1) {
1196 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to recover %d bytes at offset %d\n", len, ofs));
1197 tdb->ecode = TDB_ERR_IO;
1205 if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1206 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync recovery\n"));
1207 tdb->ecode = TDB_ERR_IO;
1211 /* if the recovery area is after the recovered eof then remove it */
1212 if (recovery_eof <= recovery_head) {
1213 if (tdb_ofs_write(tdb, TDB_RECOVERY_HEAD, &zero) == -1) {
1214 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery head\n"));
1215 tdb->ecode = TDB_ERR_IO;
1220 /* remove the recovery magic */
1221 if (tdb_ofs_write(tdb, recovery_head + offsetof(struct tdb_record, magic),
1223 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery magic\n"));
1224 tdb->ecode = TDB_ERR_IO;
1228 /* reduce the file size to the old size */
1230 if (ftruncate(tdb->fd, recovery_eof) != 0) {
1231 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to reduce to recovery size\n"));
1232 tdb->ecode = TDB_ERR_IO;
1235 tdb->map_size = recovery_eof;
1238 if (transaction_sync(tdb, 0, recovery_eof) == -1) {
1239 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync2 recovery\n"));
1240 tdb->ecode = TDB_ERR_IO;
1244 TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_recover: recovered %d byte database\n",