6c4c6f73b7ed5582d62e51f8ed44a726fc381182
[ccan] / ccan / tdb2 / tdb1_transaction.c
1  /*
2    Unix SMB/CIFS implementation.
3
4    trivial database library
5
6    Copyright (C) Andrew Tridgell              2005
7
8      ** NOTE! The following LGPL license applies to the tdb
9      ** library. This does NOT imply that all of Samba is released
10      ** under the LGPL
11
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.
16
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.
21
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/>.
24 */
25
26 #include "tdb1_private.h"
27
28 /*
29   transaction design:
30
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
35
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
40
41   - dynamically allocated the transaction recover record, re-using it
42     for subsequent transactions. If a larger record is needed then
43     tdb1_free() the old record to place it on the normal tdb freelist
44     before allocating the new record
45
46   - during transactions, keep a linked list of writes all that have
47     been performed by intercepting all tdb1_write() calls. The hooked
48     transaction versions of tdb1_read() and tdb1_write() check this
49     linked list and try to use the elements of the list in preference
50     to the real database.
51
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)
55
56   - if the caller gains a lock during the transaction but doesn't
57     release it then fail the commit
58
59   - allow for nested calls to tdb1_transaction_start(), re-using the
60     existing transaction record. If the inner transaction is cancelled
61     then a subsequent commit will fail
62
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 tdb1_write
66
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
70
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.
77
78   - check for a valid recovery record on open of the tdb, while the
79     open 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
82     intervention.
83
84   - if TDB1_NOSYNC is passed to flags in tdb1_open then transactions are
85     still available, but no transaction recovery area is used and no
86     fsync/msync calls are made.
87
88   - if TDB1_ALLOW_NESTING is passed to flags in tdb open, or added using
89     tdb1_add_flags() transaction nesting is enabled.
90     It resets the TDB1_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.
93
94     Beware. when transactions are nested a transaction successfully
95     completed with tdb1_transaction_commit() can be silently unrolled later.
96
97   - if TDB1_DISALLOW_NESTING is passed to flags in tdb open, or added using
98     tdb1_add_flags() transaction nesting is disabled.
99     It resets the TDB1_ALLOW_NESTING flag, as both cannot be used together.
100     An attempt create a nested transaction will fail with TDB1_ERR_NESTING.
101     The default is that transaction nesting is allowed.
102     Note: this default may change in future versions of tdb.
103 */
104
105
106 /*
107   hold the context of any current transaction
108 */
109 struct tdb1_transaction {
110         /* we keep a mirrored copy of the tdb hash heads here so
111            tdb1_next_hash_chain() can operate efficiently */
112         uint32_t *hash_heads;
113
114         /* the original io methods - used to do IOs to the real db */
115         const struct tdb1_methods *io_methods;
116
117         /* the list of transaction blocks. When a block is first
118            written to, it gets created in this list */
119         uint8_t **blocks;
120         uint32_t num_blocks;
121         uint32_t block_size;      /* bytes in each block */
122         uint32_t last_block_size; /* number of valid bytes in the last block */
123
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;
128
129         /* when inside a transaction we need to keep track of any
130            nested tdb1_transaction_start() calls, as these are allowed,
131            but don't create a new transaction */
132         int nesting;
133
134         /* set when a prepare has already occurred */
135         bool prepared;
136         tdb1_off_t magic_offset;
137
138         /* old file size before transaction */
139         tdb1_len_t old_map_size;
140
141         /* did we expand in this transaction */
142         bool expanded;
143 };
144
145
146 /*
147   read while in a transaction. We need to check first if the data is in our list
148   of transaction elements, then if not do a real read
149 */
150 static int transaction1_read(struct tdb1_context *tdb, tdb1_off_t off, void *buf,
151                              tdb1_len_t len, int cv)
152 {
153         uint32_t blk;
154
155         /* break it down into block sized ops */
156         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
157                 tdb1_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
158                 if (transaction1_read(tdb, off, buf, len2, cv) != 0) {
159                         return -1;
160                 }
161                 len -= len2;
162                 off += len2;
163                 buf = (void *)(len2 + (char *)buf);
164         }
165
166         if (len == 0) {
167                 return 0;
168         }
169
170         blk = off / tdb->transaction->block_size;
171
172         /* see if we have it in the block list */
173         if (tdb->transaction->num_blocks <= blk ||
174             tdb->transaction->blocks[blk] == NULL) {
175                 /* nope, do a real read */
176                 if (tdb->transaction->io_methods->tdb1_read(tdb, off, buf, len, cv) != 0) {
177                         goto fail;
178                 }
179                 return 0;
180         }
181
182         /* it is in the block list. Now check for the last block */
183         if (blk == tdb->transaction->num_blocks-1) {
184                 if (len > tdb->transaction->last_block_size) {
185                         goto fail;
186                 }
187         }
188
189         /* now copy it out of this block */
190         memcpy(buf, tdb->transaction->blocks[blk] + (off % tdb->transaction->block_size), len);
191         if (cv) {
192                 tdb1_convert(buf, len);
193         }
194         return 0;
195
196 fail:
197         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "transaction_read: failed at off=%d len=%d\n", off, len));
198         tdb->ecode = TDB1_ERR_IO;
199         tdb->transaction->transaction_error = 1;
200         return -1;
201 }
202
203
204 /*
205   write while in a transaction
206 */
207 static int transaction1_write(struct tdb1_context *tdb, tdb1_off_t off,
208                              const void *buf, tdb1_len_t len)
209 {
210         uint32_t blk;
211
212         /* Only a commit is allowed on a prepared transaction */
213         if (tdb->transaction->prepared) {
214                 tdb->ecode = TDB1_ERR_EINVAL;
215                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "transaction_write: transaction already prepared, write not allowed\n"));
216                 tdb->transaction->transaction_error = 1;
217                 return -1;
218         }
219
220         /* if the write is to a hash head, then update the transaction
221            hash heads */
222         if (len == sizeof(tdb1_off_t) && off >= TDB1_FREELIST_TOP &&
223             off < TDB1_FREELIST_TOP+TDB1_HASHTABLE_SIZE(tdb)) {
224                 uint32_t chain = (off-TDB1_FREELIST_TOP) / sizeof(tdb1_off_t);
225                 memcpy(&tdb->transaction->hash_heads[chain], buf, len);
226         }
227
228         /* break it up into block sized chunks */
229         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
230                 tdb1_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
231                 if (transaction1_write(tdb, off, buf, len2) != 0) {
232                         return -1;
233                 }
234                 len -= len2;
235                 off += len2;
236                 if (buf != NULL) {
237                         buf = (const void *)(len2 + (const char *)buf);
238                 }
239         }
240
241         if (len == 0) {
242                 return 0;
243         }
244
245         blk = off / tdb->transaction->block_size;
246         off = off % tdb->transaction->block_size;
247
248         if (tdb->transaction->num_blocks <= blk) {
249                 uint8_t **new_blocks;
250                 /* expand the blocks array */
251                 if (tdb->transaction->blocks == NULL) {
252                         new_blocks = (uint8_t **)malloc(
253                                 (blk+1)*sizeof(uint8_t *));
254                 } else {
255                         new_blocks = (uint8_t **)realloc(
256                                 tdb->transaction->blocks,
257                                 (blk+1)*sizeof(uint8_t *));
258                 }
259                 if (new_blocks == NULL) {
260                         tdb->ecode = TDB1_ERR_OOM;
261                         goto fail;
262                 }
263                 memset(&new_blocks[tdb->transaction->num_blocks], 0,
264                        (1+(blk - tdb->transaction->num_blocks))*sizeof(uint8_t *));
265                 tdb->transaction->blocks = new_blocks;
266                 tdb->transaction->num_blocks = blk+1;
267                 tdb->transaction->last_block_size = 0;
268         }
269
270         /* allocate and fill a block? */
271         if (tdb->transaction->blocks[blk] == NULL) {
272                 tdb->transaction->blocks[blk] = (uint8_t *)calloc(tdb->transaction->block_size, 1);
273                 if (tdb->transaction->blocks[blk] == NULL) {
274                         tdb->ecode = TDB1_ERR_OOM;
275                         tdb->transaction->transaction_error = 1;
276                         return -1;
277                 }
278                 if (tdb->transaction->old_map_size > blk * tdb->transaction->block_size) {
279                         tdb1_len_t len2 = tdb->transaction->block_size;
280                         if (len2 + (blk * tdb->transaction->block_size) > tdb->transaction->old_map_size) {
281                                 len2 = tdb->transaction->old_map_size - (blk * tdb->transaction->block_size);
282                         }
283                         if (tdb->transaction->io_methods->tdb1_read(tdb, blk * tdb->transaction->block_size,
284                                                                    tdb->transaction->blocks[blk],
285                                                                    len2, 0) != 0) {
286                                 SAFE_FREE(tdb->transaction->blocks[blk]);
287                                 tdb->ecode = TDB1_ERR_IO;
288                                 goto fail;
289                         }
290                         if (blk == tdb->transaction->num_blocks-1) {
291                                 tdb->transaction->last_block_size = len2;
292                         }
293                 }
294         }
295
296         /* overwrite part of an existing block */
297         if (buf == NULL) {
298                 memset(tdb->transaction->blocks[blk] + off, 0, len);
299         } else {
300                 memcpy(tdb->transaction->blocks[blk] + off, buf, len);
301         }
302         if (blk == tdb->transaction->num_blocks-1) {
303                 if (len + off > tdb->transaction->last_block_size) {
304                         tdb->transaction->last_block_size = len + off;
305                 }
306         }
307
308         return 0;
309
310 fail:
311         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "transaction_write: failed at off=%d len=%d\n",
312                  (blk*tdb->transaction->block_size) + off, len));
313         tdb->transaction->transaction_error = 1;
314         return -1;
315 }
316
317
318 /*
319   write while in a transaction - this varient never expands the transaction blocks, it only
320   updates existing blocks. This means it cannot change the recovery size
321 */
322 static int transaction1_write_existing(struct tdb1_context *tdb, tdb1_off_t off,
323                                       const void *buf, tdb1_len_t len)
324 {
325         uint32_t blk;
326
327         /* break it up into block sized chunks */
328         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
329                 tdb1_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
330                 if (transaction1_write_existing(tdb, off, buf, len2) != 0) {
331                         return -1;
332                 }
333                 len -= len2;
334                 off += len2;
335                 if (buf != NULL) {
336                         buf = (const void *)(len2 + (const char *)buf);
337                 }
338         }
339
340         if (len == 0) {
341                 return 0;
342         }
343
344         blk = off / tdb->transaction->block_size;
345         off = off % tdb->transaction->block_size;
346
347         if (tdb->transaction->num_blocks <= blk ||
348             tdb->transaction->blocks[blk] == NULL) {
349                 return 0;
350         }
351
352         if (blk == tdb->transaction->num_blocks-1 &&
353             off + len > tdb->transaction->last_block_size) {
354                 if (off >= tdb->transaction->last_block_size) {
355                         return 0;
356                 }
357                 len = tdb->transaction->last_block_size - off;
358         }
359
360         /* overwrite part of an existing block */
361         memcpy(tdb->transaction->blocks[blk] + off, buf, len);
362
363         return 0;
364 }
365
366
367 /*
368   accelerated hash chain head search, using the cached hash heads
369 */
370 static void transaction1_next_hash_chain(struct tdb1_context *tdb, uint32_t *chain)
371 {
372         uint32_t h = *chain;
373         for (;h < tdb->header.hash_size;h++) {
374                 /* the +1 takes account of the freelist */
375                 if (0 != tdb->transaction->hash_heads[h+1]) {
376                         break;
377                 }
378         }
379         (*chain) = h;
380 }
381
382 /*
383   out of bounds check during a transaction
384 */
385 static int transaction1_oob(struct tdb1_context *tdb, tdb1_off_t len, int probe)
386 {
387         if (len <= tdb->map_size) {
388                 return 0;
389         }
390         tdb->ecode = TDB1_ERR_IO;
391         return -1;
392 }
393
394 /*
395   transaction version of tdb1_expand().
396 */
397 static int transaction1_expand_file(struct tdb1_context *tdb, tdb1_off_t size,
398                                     tdb1_off_t addition)
399 {
400         /* add a write to the transaction elements, so subsequent
401            reads see the zero data */
402         if (transaction1_write(tdb, size, NULL, addition) != 0) {
403                 return -1;
404         }
405
406         tdb->transaction->expanded = true;
407
408         return 0;
409 }
410
411 static const struct tdb1_methods transaction1_methods = {
412         transaction1_read,
413         transaction1_write,
414         transaction1_next_hash_chain,
415         transaction1_oob,
416         transaction1_expand_file,
417 };
418
419
420 /*
421   start a tdb transaction. No token is returned, as only a single
422   transaction is allowed to be pending per tdb1_context
423 */
424 static int _tdb1_transaction_start(struct tdb1_context *tdb,
425                                   enum tdb1_lock_flags lockflags)
426 {
427         /* some sanity checks */
428         if (tdb->read_only || (tdb->flags & TDB1_INTERNAL) || tdb->traverse_read) {
429                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_start: cannot start a transaction on a read-only or internal db\n"));
430                 tdb->ecode = TDB1_ERR_EINVAL;
431                 return -1;
432         }
433
434         /* cope with nested tdb1_transaction_start() calls */
435         if (tdb->transaction != NULL) {
436                 if (!(tdb->flags & TDB1_ALLOW_NESTING)) {
437                         tdb->ecode = TDB1_ERR_NESTING;
438                         return -1;
439                 }
440                 tdb->transaction->nesting++;
441                 TDB1_LOG((tdb, TDB1_DEBUG_TRACE, "tdb1_transaction_start: nesting %d\n",
442                          tdb->transaction->nesting));
443                 return 0;
444         }
445
446         if (tdb1_have_extra_locks(tdb)) {
447                 /* the caller must not have any locks when starting a
448                    transaction as otherwise we'll be screwed by lack
449                    of nested locks in posix */
450                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_start: cannot start a transaction with locks held\n"));
451                 tdb->ecode = TDB1_ERR_LOCK;
452                 return -1;
453         }
454
455         if (tdb->travlocks.next != NULL) {
456                 /* you cannot use transactions inside a traverse (although you can use
457                    traverse inside a transaction) as otherwise you can end up with
458                    deadlock */
459                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_start: cannot start a transaction within a traverse\n"));
460                 tdb->ecode = TDB1_ERR_LOCK;
461                 return -1;
462         }
463
464         tdb->transaction = (struct tdb1_transaction *)
465                 calloc(sizeof(struct tdb1_transaction), 1);
466         if (tdb->transaction == NULL) {
467                 tdb->ecode = TDB1_ERR_OOM;
468                 return -1;
469         }
470
471         /* a page at a time seems like a reasonable compromise between compactness and efficiency */
472         tdb->transaction->block_size = tdb->page_size;
473
474         /* get the transaction write lock. This is a blocking lock. As
475            discussed with Volker, there are a number of ways we could
476            make this async, which we will probably do in the future */
477         if (tdb1_transaction_lock(tdb, F_WRLCK, lockflags) == -1) {
478                 SAFE_FREE(tdb->transaction->blocks);
479                 SAFE_FREE(tdb->transaction);
480                 if ((lockflags & TDB1_LOCK_WAIT) == 0) {
481                         tdb->ecode = TDB1_ERR_NOLOCK;
482                 }
483                 return -1;
484         }
485
486         /* get a read lock from the freelist to the end of file. This
487            is upgraded to a write lock during the commit */
488         if (tdb1_allrecord_lock(tdb, F_RDLCK, TDB1_LOCK_WAIT, true) == -1) {
489                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_start: failed to get hash locks\n"));
490                 goto fail_allrecord_lock;
491         }
492
493         /* setup a copy of the hash table heads so the hash scan in
494            traverse can be fast */
495         tdb->transaction->hash_heads = (uint32_t *)
496                 calloc(tdb->header.hash_size+1, sizeof(uint32_t));
497         if (tdb->transaction->hash_heads == NULL) {
498                 tdb->ecode = TDB1_ERR_OOM;
499                 goto fail;
500         }
501         if (tdb->methods->tdb1_read(tdb, TDB1_FREELIST_TOP, tdb->transaction->hash_heads,
502                                    TDB1_HASHTABLE_SIZE(tdb), 0) != 0) {
503                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_start: failed to read hash heads\n"));
504                 tdb->ecode = TDB1_ERR_IO;
505                 goto fail;
506         }
507
508         /* make sure we know about any file expansions already done by
509            anyone else */
510         tdb->methods->tdb1_oob(tdb, tdb->map_size + 1, 1);
511         tdb->transaction->old_map_size = tdb->map_size;
512
513         /* finally hook the io methods, replacing them with
514            transaction specific methods */
515         tdb->transaction->io_methods = tdb->methods;
516         tdb->methods = &transaction1_methods;
517
518         return 0;
519
520 fail:
521         tdb1_allrecord_unlock(tdb, F_RDLCK, false);
522 fail_allrecord_lock:
523         tdb1_transaction_unlock(tdb, F_WRLCK);
524         SAFE_FREE(tdb->transaction->blocks);
525         SAFE_FREE(tdb->transaction->hash_heads);
526         SAFE_FREE(tdb->transaction);
527         return -1;
528 }
529
530 _PUBLIC_ int tdb1_transaction_start(struct tdb1_context *tdb)
531 {
532         return _tdb1_transaction_start(tdb, TDB1_LOCK_WAIT);
533 }
534
535 _PUBLIC_ int tdb1_transaction_start_nonblock(struct tdb1_context *tdb)
536 {
537         return _tdb1_transaction_start(tdb, TDB1_LOCK_NOWAIT|TDB1_LOCK_PROBE);
538 }
539
540 /*
541   sync to disk
542 */
543 static int transaction1_sync(struct tdb1_context *tdb, tdb1_off_t offset, tdb1_len_t length)
544 {
545         if (tdb->flags & TDB1_NOSYNC) {
546                 return 0;
547         }
548
549 #if HAVE_FDATASYNC
550         if (fdatasync(tdb->fd) != 0) {
551 #else
552         if (fsync(tdb->fd) != 0) {
553 #endif
554                 tdb->ecode = TDB1_ERR_IO;
555                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction: fsync failed\n"));
556                 return -1;
557         }
558 #if HAVE_MMAP
559         if (tdb->map_ptr) {
560                 tdb1_off_t moffset = offset & ~(tdb->page_size-1);
561                 if (msync(moffset + (char *)tdb->map_ptr,
562                           length + (offset - moffset), MS_SYNC) != 0) {
563                         tdb->ecode = TDB1_ERR_IO;
564                         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction: msync failed - %s\n",
565                                  strerror(errno)));
566                         return -1;
567                 }
568         }
569 #endif
570         return 0;
571 }
572
573
574 static int _tdb1_transaction_cancel(struct tdb1_context *tdb)
575 {
576         int i, ret = 0;
577
578         if (tdb->transaction == NULL) {
579                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_cancel: no transaction\n"));
580                 return -1;
581         }
582
583         if (tdb->transaction->nesting != 0) {
584                 tdb->transaction->transaction_error = 1;
585                 tdb->transaction->nesting--;
586                 return 0;
587         }
588
589         tdb->map_size = tdb->transaction->old_map_size;
590
591         /* free all the transaction blocks */
592         for (i=0;i<tdb->transaction->num_blocks;i++) {
593                 if (tdb->transaction->blocks[i] != NULL) {
594                         free(tdb->transaction->blocks[i]);
595                 }
596         }
597         SAFE_FREE(tdb->transaction->blocks);
598
599         if (tdb->transaction->magic_offset) {
600                 const struct tdb1_methods *methods = tdb->transaction->io_methods;
601                 const uint32_t invalid = TDB1_RECOVERY_INVALID_MAGIC;
602
603                 /* remove the recovery marker */
604                 if (methods->tdb1_write(tdb, tdb->transaction->magic_offset, &invalid, 4) == -1 ||
605                 transaction1_sync(tdb, tdb->transaction->magic_offset, 4) == -1) {
606                         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_cancel: failed to remove recovery magic\n"));
607                         ret = -1;
608                 }
609         }
610
611         /* This also removes the OPEN_LOCK, if we have it. */
612         tdb1_release_transaction_locks(tdb);
613
614         /* restore the normal io methods */
615         tdb->methods = tdb->transaction->io_methods;
616
617         SAFE_FREE(tdb->transaction->hash_heads);
618         SAFE_FREE(tdb->transaction);
619
620         return ret;
621 }
622
623 /*
624   cancel the current transaction
625 */
626 _PUBLIC_ int tdb1_transaction_cancel(struct tdb1_context *tdb)
627 {
628         return _tdb1_transaction_cancel(tdb);
629 }
630
631 /*
632   work out how much space the linearised recovery data will consume
633 */
634 static tdb1_len_t tdb1_recovery_size(struct tdb1_context *tdb)
635 {
636         tdb1_len_t recovery_size = 0;
637         int i;
638
639         recovery_size = sizeof(uint32_t);
640         for (i=0;i<tdb->transaction->num_blocks;i++) {
641                 if (i * tdb->transaction->block_size >= tdb->transaction->old_map_size) {
642                         break;
643                 }
644                 if (tdb->transaction->blocks[i] == NULL) {
645                         continue;
646                 }
647                 recovery_size += 2*sizeof(tdb1_off_t);
648                 if (i == tdb->transaction->num_blocks-1) {
649                         recovery_size += tdb->transaction->last_block_size;
650                 } else {
651                         recovery_size += tdb->transaction->block_size;
652                 }
653         }
654
655         return recovery_size;
656 }
657
658 int tdb1_recovery_area(struct tdb1_context *tdb,
659                       const struct tdb1_methods *methods,
660                       tdb1_off_t *recovery_offset,
661                       struct tdb1_record *rec)
662 {
663         if (tdb1_ofs_read(tdb, TDB1_RECOVERY_HEAD, recovery_offset) == -1) {
664                 return -1;
665         }
666
667         if (*recovery_offset == 0) {
668                 rec->rec_len = 0;
669                 return 0;
670         }
671
672         if (methods->tdb1_read(tdb, *recovery_offset, rec, sizeof(*rec),
673                               TDB1_DOCONV()) == -1) {
674                 return -1;
675         }
676
677         /* ignore invalid recovery regions: can happen in crash */
678         if (rec->magic != TDB1_RECOVERY_MAGIC &&
679             rec->magic != TDB1_RECOVERY_INVALID_MAGIC) {
680                 *recovery_offset = 0;
681                 rec->rec_len = 0;
682         }
683         return 0;
684 }
685
686 /*
687   allocate the recovery area, or use an existing recovery area if it is
688   large enough
689 */
690 static int tdb1_recovery_allocate(struct tdb1_context *tdb,
691                                  tdb1_len_t *recovery_size,
692                                  tdb1_off_t *recovery_offset,
693                                  tdb1_len_t *recovery_max_size)
694 {
695         struct tdb1_record rec;
696         const struct tdb1_methods *methods = tdb->transaction->io_methods;
697         tdb1_off_t recovery_head;
698
699         if (tdb1_recovery_area(tdb, methods, &recovery_head, &rec) == -1) {
700                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_recovery_allocate: failed to read recovery head\n"));
701                 return -1;
702         }
703
704         *recovery_size = tdb1_recovery_size(tdb);
705
706         if (recovery_head != 0 && *recovery_size <= rec.rec_len) {
707                 /* it fits in the existing area */
708                 *recovery_max_size = rec.rec_len;
709                 *recovery_offset = recovery_head;
710                 return 0;
711         }
712
713         /* we need to free up the old recovery area, then allocate a
714            new one at the end of the file. Note that we cannot use
715            tdb1_allocate() to allocate the new one as that might return
716            us an area that is being currently used (as of the start of
717            the transaction) */
718         if (recovery_head != 0) {
719                 if (tdb1_free(tdb, recovery_head, &rec) == -1) {
720                         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_recovery_allocate: failed to free previous recovery area\n"));
721                         return -1;
722                 }
723         }
724
725         /* the tdb1_free() call might have increased the recovery size */
726         *recovery_size = tdb1_recovery_size(tdb);
727
728         /* round up to a multiple of page size */
729         *recovery_max_size = TDB1_ALIGN(sizeof(rec) + *recovery_size, tdb->page_size) - sizeof(rec);
730         *recovery_offset = tdb->map_size;
731         recovery_head = *recovery_offset;
732
733         if (methods->tdb1_expand_file(tdb, tdb->transaction->old_map_size,
734                                      (tdb->map_size - tdb->transaction->old_map_size) +
735                                      sizeof(rec) + *recovery_max_size) == -1) {
736                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_recovery_allocate: failed to create recovery area\n"));
737                 return -1;
738         }
739
740         /* remap the file (if using mmap) */
741         methods->tdb1_oob(tdb, tdb->map_size + 1, 1);
742
743         /* we have to reset the old map size so that we don't try to expand the file
744            again in the transaction commit, which would destroy the recovery area */
745         tdb->transaction->old_map_size = tdb->map_size;
746
747         /* write the recovery header offset and sync - we can sync without a race here
748            as the magic ptr in the recovery record has not been set */
749         TDB1_CONV(recovery_head);
750         if (methods->tdb1_write(tdb, TDB1_RECOVERY_HEAD,
751                                &recovery_head, sizeof(tdb1_off_t)) == -1) {
752                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_recovery_allocate: failed to write recovery head\n"));
753                 return -1;
754         }
755         if (transaction1_write_existing(tdb, TDB1_RECOVERY_HEAD, &recovery_head, sizeof(tdb1_off_t)) == -1) {
756                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_recovery_allocate: failed to write recovery head\n"));
757                 return -1;
758         }
759
760         return 0;
761 }
762
763
764 /*
765   setup the recovery data that will be used on a crash during commit
766 */
767 static int transaction1_setup_recovery(struct tdb1_context *tdb,
768                                        tdb1_off_t *magic_offset)
769 {
770         tdb1_len_t recovery_size;
771         unsigned char *data, *p;
772         const struct tdb1_methods *methods = tdb->transaction->io_methods;
773         struct tdb1_record *rec;
774         tdb1_off_t recovery_offset, recovery_max_size;
775         tdb1_off_t old_map_size = tdb->transaction->old_map_size;
776         uint32_t magic, tailer;
777         int i;
778
779         /*
780           check that the recovery area has enough space
781         */
782         if (tdb1_recovery_allocate(tdb, &recovery_size,
783                                   &recovery_offset, &recovery_max_size) == -1) {
784                 return -1;
785         }
786
787         data = (unsigned char *)malloc(recovery_size + sizeof(*rec));
788         if (data == NULL) {
789                 tdb->ecode = TDB1_ERR_OOM;
790                 return -1;
791         }
792
793         rec = (struct tdb1_record *)data;
794         memset(rec, 0, sizeof(*rec));
795
796         rec->magic    = TDB1_RECOVERY_INVALID_MAGIC;
797         rec->data_len = recovery_size;
798         rec->rec_len  = recovery_max_size;
799         rec->key_len  = old_map_size;
800         TDB1_CONV(*rec);
801
802         /* build the recovery data into a single blob to allow us to do a single
803            large write, which should be more efficient */
804         p = data + sizeof(*rec);
805         for (i=0;i<tdb->transaction->num_blocks;i++) {
806                 tdb1_off_t offset;
807                 tdb1_len_t length;
808
809                 if (tdb->transaction->blocks[i] == NULL) {
810                         continue;
811                 }
812
813                 offset = i * tdb->transaction->block_size;
814                 length = tdb->transaction->block_size;
815                 if (i == tdb->transaction->num_blocks-1) {
816                         length = tdb->transaction->last_block_size;
817                 }
818
819                 if (offset >= old_map_size) {
820                         continue;
821                 }
822                 if (offset + length > tdb->transaction->old_map_size) {
823                         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_setup_recovery: transaction data over new region boundary\n"));
824                         free(data);
825                         tdb->ecode = TDB1_ERR_CORRUPT;
826                         return -1;
827                 }
828                 memcpy(p, &offset, 4);
829                 memcpy(p+4, &length, 4);
830                 if (TDB1_DOCONV()) {
831                         tdb1_convert(p, 8);
832                 }
833                 /* the recovery area contains the old data, not the
834                    new data, so we have to call the original tdb1_read
835                    method to get it */
836                 if (methods->tdb1_read(tdb, offset, p + 8, length, 0) != 0) {
837                         free(data);
838                         tdb->ecode = TDB1_ERR_IO;
839                         return -1;
840                 }
841                 p += 8 + length;
842         }
843
844         /* and the tailer */
845         tailer = sizeof(*rec) + recovery_max_size;
846         memcpy(p, &tailer, 4);
847         if (TDB1_DOCONV()) {
848                 tdb1_convert(p, 4);
849         }
850
851         /* write the recovery data to the recovery area */
852         if (methods->tdb1_write(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
853                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_setup_recovery: failed to write recovery data\n"));
854                 free(data);
855                 tdb->ecode = TDB1_ERR_IO;
856                 return -1;
857         }
858         if (transaction1_write_existing(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
859                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_setup_recovery: failed to write secondary recovery data\n"));
860                 free(data);
861                 tdb->ecode = TDB1_ERR_IO;
862                 return -1;
863         }
864
865         /* as we don't have ordered writes, we have to sync the recovery
866            data before we update the magic to indicate that the recovery
867            data is present */
868         if (transaction1_sync(tdb, recovery_offset, sizeof(*rec) + recovery_size) == -1) {
869                 free(data);
870                 return -1;
871         }
872
873         free(data);
874
875         magic = TDB1_RECOVERY_MAGIC;
876         TDB1_CONV(magic);
877
878         *magic_offset = recovery_offset + offsetof(struct tdb1_record, magic);
879
880         if (methods->tdb1_write(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
881                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_setup_recovery: failed to write recovery magic\n"));
882                 tdb->ecode = TDB1_ERR_IO;
883                 return -1;
884         }
885         if (transaction1_write_existing(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
886                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_setup_recovery: failed to write secondary recovery magic\n"));
887                 tdb->ecode = TDB1_ERR_IO;
888                 return -1;
889         }
890
891         /* ensure the recovery magic marker is on disk */
892         if (transaction1_sync(tdb, *magic_offset, sizeof(magic)) == -1) {
893                 return -1;
894         }
895
896         return 0;
897 }
898
899 static int _tdb1_transaction_prepare_commit(struct tdb1_context *tdb)
900 {
901         const struct tdb1_methods *methods;
902
903         if (tdb->transaction == NULL) {
904                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_prepare_commit: no transaction\n"));
905                 return -1;
906         }
907
908         if (tdb->transaction->prepared) {
909                 tdb->ecode = TDB1_ERR_EINVAL;
910                 _tdb1_transaction_cancel(tdb);
911                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_prepare_commit: transaction already prepared\n"));
912                 return -1;
913         }
914
915         if (tdb->transaction->transaction_error) {
916                 tdb->ecode = TDB1_ERR_IO;
917                 _tdb1_transaction_cancel(tdb);
918                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_prepare_commit: transaction error pending\n"));
919                 return -1;
920         }
921
922
923         if (tdb->transaction->nesting != 0) {
924                 return 0;
925         }
926
927         /* check for a null transaction */
928         if (tdb->transaction->blocks == NULL) {
929                 return 0;
930         }
931
932         methods = tdb->transaction->io_methods;
933
934         /* if there are any locks pending then the caller has not
935            nested their locks properly, so fail the transaction */
936         if (tdb1_have_extra_locks(tdb)) {
937                 tdb->ecode = TDB1_ERR_LOCK;
938                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_prepare_commit: locks pending on commit\n"));
939                 _tdb1_transaction_cancel(tdb);
940                 return -1;
941         }
942
943         /* upgrade the main transaction lock region to a write lock */
944         if (tdb1_allrecord_upgrade(tdb) == -1) {
945                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_prepare_commit: failed to upgrade hash locks\n"));
946                 _tdb1_transaction_cancel(tdb);
947                 return -1;
948         }
949
950         /* get the open lock - this prevents new users attaching to the database
951            during the commit */
952         if (tdb1_nest_lock(tdb, TDB1_OPEN_LOCK, F_WRLCK, TDB1_LOCK_WAIT) == -1) {
953                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_prepare_commit: failed to get open lock\n"));
954                 _tdb1_transaction_cancel(tdb);
955                 return -1;
956         }
957
958         if (!(tdb->flags & TDB1_NOSYNC)) {
959                 /* write the recovery data to the end of the file */
960                 if (transaction1_setup_recovery(tdb, &tdb->transaction->magic_offset) == -1) {
961                         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_prepare_commit: failed to setup recovery data\n"));
962                         _tdb1_transaction_cancel(tdb);
963                         return -1;
964                 }
965         }
966
967         tdb->transaction->prepared = true;
968
969         /* expand the file to the new size if needed */
970         if (tdb->map_size != tdb->transaction->old_map_size) {
971                 if (methods->tdb1_expand_file(tdb, tdb->transaction->old_map_size,
972                                              tdb->map_size -
973                                              tdb->transaction->old_map_size) == -1) {
974                         tdb->ecode = TDB1_ERR_IO;
975                         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_prepare_commit: expansion failed\n"));
976                         _tdb1_transaction_cancel(tdb);
977                         return -1;
978                 }
979                 tdb->map_size = tdb->transaction->old_map_size;
980                 methods->tdb1_oob(tdb, tdb->map_size + 1, 1);
981         }
982
983         /* Keep the open lock until the actual commit */
984
985         return 0;
986 }
987
988 /*
989    prepare to commit the current transaction
990 */
991 _PUBLIC_ int tdb1_transaction_prepare_commit(struct tdb1_context *tdb)
992 {
993         return _tdb1_transaction_prepare_commit(tdb);
994 }
995
996 /* A repack is worthwhile if the largest is less than half total free. */
997 static bool repack_worthwhile(struct tdb1_context *tdb)
998 {
999         tdb1_off_t ptr;
1000         struct tdb1_record rec;
1001         tdb1_len_t total = 0, largest = 0;
1002
1003         if (tdb1_ofs_read(tdb, TDB1_FREELIST_TOP, &ptr) == -1) {
1004                 return false;
1005         }
1006
1007         while (ptr != 0 && tdb1_rec_free_read(tdb, ptr, &rec) == 0) {
1008                 total += rec.rec_len;
1009                 if (rec.rec_len > largest) {
1010                         largest = rec.rec_len;
1011                 }
1012                 ptr = rec.next;
1013         }
1014
1015         return total > largest * 2;
1016 }
1017
1018 /*
1019   commit the current transaction
1020 */
1021 _PUBLIC_ int tdb1_transaction_commit(struct tdb1_context *tdb)
1022 {
1023         const struct tdb1_methods *methods;
1024         int i;
1025         bool need_repack = false;
1026
1027         if (tdb->transaction == NULL) {
1028                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_commit: no transaction\n"));
1029                 return -1;
1030         }
1031
1032         if (tdb->transaction->transaction_error) {
1033                 tdb->ecode = TDB1_ERR_IO;
1034                 _tdb1_transaction_cancel(tdb);
1035                 TDB1_LOG((tdb, TDB1_DEBUG_ERROR, "tdb1_transaction_commit: transaction error pending\n"));
1036                 return -1;
1037         }
1038
1039
1040         if (tdb->transaction->nesting != 0) {
1041                 tdb->transaction->nesting--;
1042                 return 0;
1043         }
1044
1045         /* check for a null transaction */
1046         if (tdb->transaction->blocks == NULL) {
1047                 _tdb1_transaction_cancel(tdb);
1048                 return 0;
1049         }
1050
1051         if (!tdb->transaction->prepared) {
1052                 int ret = _tdb1_transaction_prepare_commit(tdb);
1053                 if (ret)
1054                         return ret;
1055         }
1056
1057         methods = tdb->transaction->io_methods;
1058
1059         /* perform all the writes */
1060         for (i=0;i<tdb->transaction->num_blocks;i++) {
1061                 tdb1_off_t offset;
1062                 tdb1_len_t length;
1063
1064                 if (tdb->transaction->blocks[i] == NULL) {
1065                         continue;
1066                 }
1067
1068                 offset = i * tdb->transaction->block_size;
1069                 length = tdb->transaction->block_size;
1070                 if (i == tdb->transaction->num_blocks-1) {
1071                         length = tdb->transaction->last_block_size;
1072                 }
1073
1074                 if (methods->tdb1_write(tdb, offset, tdb->transaction->blocks[i], length) == -1) {
1075                         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_commit: write failed during commit\n"));
1076
1077                         /* we've overwritten part of the data and
1078                            possibly expanded the file, so we need to
1079                            run the crash recovery code */
1080                         tdb->methods = methods;
1081                         tdb1_transaction_recover(tdb);
1082
1083                         _tdb1_transaction_cancel(tdb);
1084
1085                         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_commit: write failed\n"));
1086                         return -1;
1087                 }
1088                 SAFE_FREE(tdb->transaction->blocks[i]);
1089         }
1090
1091         /* Do this before we drop lock or blocks. */
1092         if (tdb->transaction->expanded) {
1093                 need_repack = repack_worthwhile(tdb);
1094         }
1095
1096         SAFE_FREE(tdb->transaction->blocks);
1097         tdb->transaction->num_blocks = 0;
1098
1099         /* ensure the new data is on disk */
1100         if (transaction1_sync(tdb, 0, tdb->map_size) == -1) {
1101                 return -1;
1102         }
1103
1104         /*
1105           TODO: maybe write to some dummy hdr field, or write to magic
1106           offset without mmap, before the last sync, instead of the
1107           utime() call
1108         */
1109
1110         /* on some systems (like Linux 2.6.x) changes via mmap/msync
1111            don't change the mtime of the file, this means the file may
1112            not be backed up (as tdb rounding to block sizes means that
1113            file size changes are quite rare too). The following forces
1114            mtime changes when a transaction completes */
1115 #if HAVE_UTIME
1116         utime(tdb->name, NULL);
1117 #endif
1118
1119         /* use a transaction cancel to free memory and remove the
1120            transaction locks */
1121         _tdb1_transaction_cancel(tdb);
1122
1123         if (need_repack) {
1124                 return tdb1_repack(tdb);
1125         }
1126
1127         return 0;
1128 }
1129
1130
1131 /*
1132   recover from an aborted transaction. Must be called with exclusive
1133   database write access already established (including the open
1134   lock to prevent new processes attaching)
1135 */
1136 int tdb1_transaction_recover(struct tdb1_context *tdb)
1137 {
1138         tdb1_off_t recovery_head, recovery_eof;
1139         unsigned char *data, *p;
1140         uint32_t zero = 0;
1141         struct tdb1_record rec;
1142
1143         /* find the recovery area */
1144         if (tdb1_ofs_read(tdb, TDB1_RECOVERY_HEAD, &recovery_head) == -1) {
1145                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_recover: failed to read recovery head\n"));
1146                 tdb->ecode = TDB1_ERR_IO;
1147                 return -1;
1148         }
1149
1150         if (recovery_head == 0) {
1151                 /* we have never allocated a recovery record */
1152                 return 0;
1153         }
1154
1155         /* read the recovery record */
1156         if (tdb->methods->tdb1_read(tdb, recovery_head, &rec,
1157                                    sizeof(rec), TDB1_DOCONV()) == -1) {
1158                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_recover: failed to read recovery record\n"));
1159                 tdb->ecode = TDB1_ERR_IO;
1160                 return -1;
1161         }
1162
1163         if (rec.magic != TDB1_RECOVERY_MAGIC) {
1164                 /* there is no valid recovery data */
1165                 return 0;
1166         }
1167
1168         if (tdb->read_only) {
1169                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_recover: attempt to recover read only database\n"));
1170                 tdb->ecode = TDB1_ERR_CORRUPT;
1171                 return -1;
1172         }
1173
1174         recovery_eof = rec.key_len;
1175
1176         data = (unsigned char *)malloc(rec.data_len);
1177         if (data == NULL) {
1178                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_recover: failed to allocate recovery data\n"));
1179                 tdb->ecode = TDB1_ERR_OOM;
1180                 return -1;
1181         }
1182
1183         /* read the full recovery data */
1184         if (tdb->methods->tdb1_read(tdb, recovery_head + sizeof(rec), data,
1185                                    rec.data_len, 0) == -1) {
1186                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_recover: failed to read recovery data\n"));
1187                 tdb->ecode = TDB1_ERR_IO;
1188                 return -1;
1189         }
1190
1191         /* recover the file data */
1192         p = data;
1193         while (p+8 < data + rec.data_len) {
1194                 uint32_t ofs, len;
1195                 if (TDB1_DOCONV()) {
1196                         tdb1_convert(p, 8);
1197                 }
1198                 memcpy(&ofs, p, 4);
1199                 memcpy(&len, p+4, 4);
1200
1201                 if (tdb->methods->tdb1_write(tdb, ofs, p+8, len) == -1) {
1202                         free(data);
1203                         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_recover: failed to recover %d bytes at offset %d\n", len, ofs));
1204                         tdb->ecode = TDB1_ERR_IO;
1205                         return -1;
1206                 }
1207                 p += 8 + len;
1208         }
1209
1210         free(data);
1211
1212         if (transaction1_sync(tdb, 0, tdb->map_size) == -1) {
1213                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_recover: failed to sync recovery\n"));
1214                 tdb->ecode = TDB1_ERR_IO;
1215                 return -1;
1216         }
1217
1218         /* if the recovery area is after the recovered eof then remove it */
1219         if (recovery_eof <= recovery_head) {
1220                 if (tdb1_ofs_write(tdb, TDB1_RECOVERY_HEAD, &zero) == -1) {
1221                         TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_recover: failed to remove recovery head\n"));
1222                         tdb->ecode = TDB1_ERR_IO;
1223                         return -1;
1224                 }
1225         }
1226
1227         /* remove the recovery magic */
1228         if (tdb1_ofs_write(tdb, recovery_head + offsetof(struct tdb1_record, magic),
1229                           &zero) == -1) {
1230                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_recover: failed to remove recovery magic\n"));
1231                 tdb->ecode = TDB1_ERR_IO;
1232                 return -1;
1233         }
1234
1235         if (transaction1_sync(tdb, 0, recovery_eof) == -1) {
1236                 TDB1_LOG((tdb, TDB1_DEBUG_FATAL, "tdb1_transaction_recover: failed to sync2 recovery\n"));
1237                 tdb->ecode = TDB1_ERR_IO;
1238                 return -1;
1239         }
1240
1241         TDB1_LOG((tdb, TDB1_DEBUG_TRACE, "tdb1_transaction_recover: recovered %d byte database\n",
1242                  recovery_eof));
1243
1244         /* all done */
1245         return 0;
1246 }
1247
1248 /* Any I/O failures we say "needs recovery". */
1249 bool tdb1_needs_recovery(struct tdb1_context *tdb)
1250 {
1251         tdb1_off_t recovery_head;
1252         struct tdb1_record rec;
1253
1254         /* find the recovery area */
1255         if (tdb1_ofs_read(tdb, TDB1_RECOVERY_HEAD, &recovery_head) == -1) {
1256                 return true;
1257         }
1258
1259         if (recovery_head == 0) {
1260                 /* we have never allocated a recovery record */
1261                 return false;
1262         }
1263
1264         /* read the recovery record */
1265         if (tdb->methods->tdb1_read(tdb, recovery_head, &rec,
1266                                    sizeof(rec), TDB1_DOCONV()) == -1) {
1267                 return true;
1268         }
1269
1270         return (rec.magic == TDB1_RECOVERY_MAGIC);
1271 }