tdb2: change API to return the error value.
[ccan] / ccan / tdb2 / transaction.c
1  /*
2    Unix SMB/CIFS implementation.
3
4    trivial database library
5
6    Copyright (C) Andrew Tridgell              2005
7    Copyright (C) Rusty Russell                2010
8
9      ** NOTE! The following LGPL license applies to the tdb
10      ** library. This does NOT imply that all of Samba is released
11      ** under the LGPL
12
13    This library is free software; you can redistribute it and/or
14    modify it under the terms of the GNU Lesser General Public
15    License as published by the Free Software Foundation; either
16    version 3 of the License, or (at your option) any later version.
17
18    This library is distributed in the hope that it will be useful,
19    but WITHOUT ANY WARRANTY; without even the implied warranty of
20    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
21    Lesser General Public License for more details.
22
23    You should have received a copy of the GNU Lesser General Public
24    License along with this library; if not, see <http://www.gnu.org/licenses/>.
25 */
26
27 #include "private.h"
28 #define SAFE_FREE(x) do { if ((x) != NULL) {free(x); (x)=NULL;} } while(0)
29
30 /*
31   transaction design:
32
33   - only allow a single transaction at a time per database. This makes
34     using the transaction API simpler, as otherwise the caller would
35     have to cope with temporary failures in transactions that conflict
36     with other current transactions
37
38   - keep the transaction recovery information in the same file as the
39     database, using a special 'transaction recovery' record pointed at
40     by the header. This removes the need for extra journal files as
41     used by some other databases
42
43   - dynamically allocated the transaction recover record, re-using it
44     for subsequent transactions. If a larger record is needed then
45     tdb_free() the old record to place it on the normal tdb freelist
46     before allocating the new record
47
48   - during transactions, keep a linked list of writes all that have
49     been performed by intercepting all tdb_write() calls. The hooked
50     transaction versions of tdb_read() and tdb_write() check this
51     linked list and try to use the elements of the list in preference
52     to the real database.
53
54   - don't allow any locks to be held when a transaction starts,
55     otherwise we can end up with deadlock (plus lack of lock nesting
56     in posix locks would mean the lock is lost)
57
58   - if the caller gains a lock during the transaction but doesn't
59     release it then fail the commit
60
61   - allow for nested calls to tdb_transaction_start(), re-using the
62     existing transaction record. If the inner transaction is cancelled
63     then a subsequent commit will fail
64
65   - keep a mirrored copy of the tdb hash chain heads to allow for the
66     fast hash heads scan on traverse, updating the mirrored copy in
67     the transaction version of tdb_write
68
69   - allow callers to mix transaction and non-transaction use of tdb,
70     although once a transaction is started then an exclusive lock is
71     gained until the transaction is committed or cancelled
72
73   - the commit stategy involves first saving away all modified data
74     into a linearised buffer in the transaction recovery area, then
75     marking the transaction recovery area with a magic value to
76     indicate a valid recovery record. In total 4 fsync/msync calls are
77     needed per commit to prevent race conditions. It might be possible
78     to reduce this to 3 or even 2 with some more work.
79
80   - check for a valid recovery record on open of the tdb, while the
81     open lock is held. Automatically recover from the transaction
82     recovery area if needed, then continue with the open as
83     usual. This allows for smooth crash recovery with no administrator
84     intervention.
85
86   - if TDB_NOSYNC is passed to flags in tdb_open then transactions are
87     still available, but no transaction recovery area is used and no
88     fsync/msync calls are made.
89 */
90
91
92 /*
93   hold the context of any current transaction
94 */
95 struct tdb_transaction {
96         /* the original io methods - used to do IOs to the real db */
97         const struct tdb_methods *io_methods;
98
99         /* the list of transaction blocks. When a block is first
100            written to, it gets created in this list */
101         uint8_t **blocks;
102         size_t num_blocks;
103         size_t last_block_size; /* number of valid bytes in the last block */
104
105         /* non-zero when an internal transaction error has
106            occurred. All write operations will then fail until the
107            transaction is ended */
108         int transaction_error;
109
110         /* when inside a transaction we need to keep track of any
111            nested tdb_transaction_start() calls, as these are allowed,
112            but don't create a new transaction */
113         int nesting;
114
115         /* set when a prepare has already occurred */
116         bool prepared;
117         tdb_off_t magic_offset;
118
119         /* old file size before transaction */
120         tdb_len_t old_map_size;
121 };
122
123
124 /*
125   read while in a transaction. We need to check first if the data is in our list
126   of transaction elements, then if not do a real read
127 */
128 static enum TDB_ERROR transaction_read(struct tdb_context *tdb, tdb_off_t off,
129                                        void *buf, tdb_len_t len)
130 {
131         size_t blk;
132         enum TDB_ERROR ecode;
133
134         /* break it down into block sized ops */
135         while (len + (off % getpagesize()) > getpagesize()) {
136                 tdb_len_t len2 = getpagesize() - (off % getpagesize());
137                 ecode = transaction_read(tdb, off, buf, len2);
138                 if (ecode != TDB_SUCCESS) {
139                         return ecode;
140                 }
141                 len -= len2;
142                 off += len2;
143                 buf = (void *)(len2 + (char *)buf);
144         }
145
146         if (len == 0) {
147                 return TDB_SUCCESS;
148         }
149
150         blk = off / getpagesize();
151
152         /* see if we have it in the block list */
153         if (tdb->transaction->num_blocks <= blk ||
154             tdb->transaction->blocks[blk] == NULL) {
155                 /* nope, do a real read */
156                 ecode = tdb->transaction->io_methods->tread(tdb, off, buf, len);
157                 if (ecode != TDB_SUCCESS) {
158                         goto fail;
159                 }
160                 return 0;
161         }
162
163         /* it is in the block list. Now check for the last block */
164         if (blk == tdb->transaction->num_blocks-1) {
165                 if (len > tdb->transaction->last_block_size) {
166                         ecode = TDB_ERR_IO;
167                         goto fail;
168                 }
169         }
170
171         /* now copy it out of this block */
172         memcpy(buf, tdb->transaction->blocks[blk] + (off % getpagesize()), len);
173         return TDB_SUCCESS;
174
175 fail:
176         tdb->transaction->transaction_error = 1;
177         return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
178                           "transaction_read: failed at off=%zu len=%zu",
179                           (size_t)off, (size_t)len);
180 }
181
182
183 /*
184   write while in a transaction
185 */
186 static enum TDB_ERROR transaction_write(struct tdb_context *tdb, tdb_off_t off,
187                                         const void *buf, tdb_len_t len)
188 {
189         size_t blk;
190         enum TDB_ERROR ecode;
191
192         /* Only a commit is allowed on a prepared transaction */
193         if (tdb->transaction->prepared) {
194                 ecode = tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_ERROR,
195                                    "transaction_write: transaction already"
196                                    " prepared, write not allowed");
197                 goto fail;
198         }
199
200         /* break it up into block sized chunks */
201         while (len + (off % getpagesize()) > getpagesize()) {
202                 tdb_len_t len2 = getpagesize() - (off % getpagesize());
203                 ecode = transaction_write(tdb, off, buf, len2);
204                 if (ecode != TDB_SUCCESS) {
205                         return -1;
206                 }
207                 len -= len2;
208                 off += len2;
209                 if (buf != NULL) {
210                         buf = (const void *)(len2 + (const char *)buf);
211                 }
212         }
213
214         if (len == 0) {
215                 return TDB_SUCCESS;
216         }
217
218         blk = off / getpagesize();
219         off = off % getpagesize();
220
221         if (tdb->transaction->num_blocks <= blk) {
222                 uint8_t **new_blocks;
223                 /* expand the blocks array */
224                 if (tdb->transaction->blocks == NULL) {
225                         new_blocks = (uint8_t **)malloc(
226                                 (blk+1)*sizeof(uint8_t *));
227                 } else {
228                         new_blocks = (uint8_t **)realloc(
229                                 tdb->transaction->blocks,
230                                 (blk+1)*sizeof(uint8_t *));
231                 }
232                 if (new_blocks == NULL) {
233                         ecode = tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
234                                            "transaction_write:"
235                                            " failed to allocate");
236                         goto fail;
237                 }
238                 memset(&new_blocks[tdb->transaction->num_blocks], 0,
239                        (1+(blk - tdb->transaction->num_blocks))*sizeof(uint8_t *));
240                 tdb->transaction->blocks = new_blocks;
241                 tdb->transaction->num_blocks = blk+1;
242                 tdb->transaction->last_block_size = 0;
243         }
244
245         /* allocate and fill a block? */
246         if (tdb->transaction->blocks[blk] == NULL) {
247                 tdb->transaction->blocks[blk] = (uint8_t *)calloc(getpagesize(), 1);
248                 if (tdb->transaction->blocks[blk] == NULL) {
249                         ecode = tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
250                                            "transaction_write:"
251                                            " failed to allocate");
252                         goto fail;
253                 }
254                 if (tdb->transaction->old_map_size > blk * getpagesize()) {
255                         tdb_len_t len2 = getpagesize();
256                         if (len2 + (blk * getpagesize()) > tdb->transaction->old_map_size) {
257                                 len2 = tdb->transaction->old_map_size - (blk * getpagesize());
258                         }
259                         ecode = tdb->transaction->io_methods->tread(tdb,
260                                         blk * getpagesize(),
261                                         tdb->transaction->blocks[blk],
262                                         len2);
263                         if (ecode != TDB_SUCCESS) {
264                                 ecode = tdb_logerr(tdb, ecode,
265                                                    TDB_LOG_ERROR,
266                                                    "transaction_write:"
267                                                    " failed to"
268                                                    " read old block: %s",
269                                                    strerror(errno));
270                                 SAFE_FREE(tdb->transaction->blocks[blk]);
271                                 goto fail;
272                         }
273                         if (blk == tdb->transaction->num_blocks-1) {
274                                 tdb->transaction->last_block_size = len2;
275                         }
276                 }
277         }
278
279         /* overwrite part of an existing block */
280         if (buf == NULL) {
281                 memset(tdb->transaction->blocks[blk] + off, 0, len);
282         } else {
283                 memcpy(tdb->transaction->blocks[blk] + off, buf, len);
284         }
285         if (blk == tdb->transaction->num_blocks-1) {
286                 if (len + off > tdb->transaction->last_block_size) {
287                         tdb->transaction->last_block_size = len + off;
288                 }
289         }
290
291         return TDB_SUCCESS;
292
293 fail:
294         tdb->transaction->transaction_error = 1;
295         return ecode;
296 }
297
298
299 /*
300   write while in a transaction - this varient never expands the transaction blocks, it only
301   updates existing blocks. This means it cannot change the recovery size
302 */
303 static void transaction_write_existing(struct tdb_context *tdb, tdb_off_t off,
304                                        const void *buf, tdb_len_t len)
305 {
306         size_t blk;
307
308         /* break it up into block sized chunks */
309         while (len + (off % getpagesize()) > getpagesize()) {
310                 tdb_len_t len2 = getpagesize() - (off % getpagesize());
311                 transaction_write_existing(tdb, off, buf, len2);
312                 len -= len2;
313                 off += len2;
314                 if (buf != NULL) {
315                         buf = (const void *)(len2 + (const char *)buf);
316                 }
317         }
318
319         if (len == 0) {
320                 return;
321         }
322
323         blk = off / getpagesize();
324         off = off % getpagesize();
325
326         if (tdb->transaction->num_blocks <= blk ||
327             tdb->transaction->blocks[blk] == NULL) {
328                 return;
329         }
330
331         if (blk == tdb->transaction->num_blocks-1 &&
332             off + len > tdb->transaction->last_block_size) {
333                 if (off >= tdb->transaction->last_block_size) {
334                         return;
335                 }
336                 len = tdb->transaction->last_block_size - off;
337         }
338
339         /* overwrite part of an existing block */
340         memcpy(tdb->transaction->blocks[blk] + off, buf, len);
341 }
342
343
344 /*
345   out of bounds check during a transaction
346 */
347 static enum TDB_ERROR transaction_oob(struct tdb_context *tdb, tdb_off_t len,
348                                       bool probe)
349 {
350         if (len <= tdb->map_size) {
351                 return TDB_SUCCESS;
352         }
353         if (!probe) {
354                 tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
355                            "tdb_oob len %lld beyond transaction size %lld",
356                            (long long)len,
357                            (long long)tdb->map_size);
358         }
359         return TDB_ERR_IO;
360 }
361
362 /*
363   transaction version of tdb_expand().
364 */
365 static enum TDB_ERROR transaction_expand_file(struct tdb_context *tdb,
366                                               tdb_off_t addition)
367 {
368         enum TDB_ERROR ecode;
369
370         /* add a write to the transaction elements, so subsequent
371            reads see the zero data */
372         ecode = transaction_write(tdb, tdb->map_size, NULL, addition);
373         if (ecode == TDB_SUCCESS) {
374                 tdb->map_size += addition;
375         }
376         return ecode;
377 }
378
379 static void *transaction_direct(struct tdb_context *tdb, tdb_off_t off,
380                                 size_t len, bool write_mode)
381 {
382         size_t blk = off / getpagesize(), end_blk;
383
384         /* This is wrong for zero-length blocks, but will fail gracefully */
385         end_blk = (off + len - 1) / getpagesize();
386
387         /* Can only do direct if in single block and we've already copied. */
388         if (write_mode) {
389                 if (blk != end_blk)
390                         return NULL;
391                 if (blk >= tdb->transaction->num_blocks)
392                         return NULL;
393                 if (tdb->transaction->blocks[blk] == NULL)
394                         return NULL;
395                 return tdb->transaction->blocks[blk] + off % getpagesize();
396         }
397
398         /* Single which we have copied? */
399         if (blk == end_blk
400             && blk < tdb->transaction->num_blocks
401             && tdb->transaction->blocks[blk])
402                 return tdb->transaction->blocks[blk] + off % getpagesize();
403
404         /* Otherwise must be all not copied. */
405         while (blk < end_blk) {
406                 if (blk >= tdb->transaction->num_blocks)
407                         break;
408                 if (tdb->transaction->blocks[blk])
409                         return NULL;
410                 blk++;
411         }
412         return tdb->transaction->io_methods->direct(tdb, off, len, false);
413 }
414
415 static const struct tdb_methods transaction_methods = {
416         transaction_read,
417         transaction_write,
418         transaction_oob,
419         transaction_expand_file,
420         transaction_direct,
421 };
422
423 /*
424   sync to disk
425 */
426 static enum TDB_ERROR transaction_sync(struct tdb_context *tdb,
427                                        tdb_off_t offset, tdb_len_t length)
428 {
429         if (tdb->flags & TDB_NOSYNC) {
430                 return TDB_SUCCESS;
431         }
432
433         if (fsync(tdb->fd) != 0) {
434                 return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
435                                   "tdb_transaction: fsync failed: %s",
436                                   strerror(errno));
437         }
438 #ifdef MS_SYNC
439         if (tdb->map_ptr) {
440                 tdb_off_t moffset = offset & ~(getpagesize()-1);
441                 if (msync(moffset + (char *)tdb->map_ptr,
442                           length + (offset - moffset), MS_SYNC) != 0) {
443                         return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
444                                           "tdb_transaction: msync failed: %s",
445                                           strerror(errno));
446                 }
447         }
448 #endif
449         return TDB_SUCCESS;
450 }
451
452
453 static void _tdb_transaction_cancel(struct tdb_context *tdb)
454 {
455         int i;
456         enum TDB_ERROR ecode;
457
458         if (tdb->transaction == NULL) {
459                 tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
460                            "tdb_transaction_cancel: no transaction");
461                 return;
462         }
463
464         if (tdb->transaction->nesting != 0) {
465                 tdb->transaction->transaction_error = 1;
466                 tdb->transaction->nesting--;
467                 return;
468         }
469
470         tdb->map_size = tdb->transaction->old_map_size;
471
472         /* free all the transaction blocks */
473         for (i=0;i<tdb->transaction->num_blocks;i++) {
474                 if (tdb->transaction->blocks[i] != NULL) {
475                         free(tdb->transaction->blocks[i]);
476                 }
477         }
478         SAFE_FREE(tdb->transaction->blocks);
479
480         if (tdb->transaction->magic_offset) {
481                 const struct tdb_methods *methods = tdb->transaction->io_methods;
482                 uint64_t invalid = TDB_RECOVERY_INVALID_MAGIC;
483
484                 /* remove the recovery marker */
485                 ecode = methods->twrite(tdb, tdb->transaction->magic_offset,
486                                         &invalid, sizeof(invalid));
487                 if (ecode == TDB_SUCCESS)
488                         ecode = transaction_sync(tdb,
489                                                  tdb->transaction->magic_offset,
490                                                  sizeof(invalid));
491                 if (ecode != TDB_SUCCESS) {
492                         tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
493                                    "tdb_transaction_cancel: failed to remove"
494                                    " recovery magic");
495                 }
496         }
497
498         if (tdb->allrecord_lock.count)
499                 tdb_allrecord_unlock(tdb, tdb->allrecord_lock.ltype);
500
501         /* restore the normal io methods */
502         tdb->methods = tdb->transaction->io_methods;
503
504         tdb_transaction_unlock(tdb, F_WRLCK);
505
506         if (tdb_has_open_lock(tdb))
507                 tdb_unlock_open(tdb);
508
509         SAFE_FREE(tdb->transaction);
510 }
511
512 /*
513   start a tdb transaction. No token is returned, as only a single
514   transaction is allowed to be pending per tdb_context
515 */
516 enum TDB_ERROR tdb_transaction_start(struct tdb_context *tdb)
517 {
518         enum TDB_ERROR ecode;
519
520         /* some sanity checks */
521         if (tdb->read_only || (tdb->flags & TDB_INTERNAL)) {
522                 return tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
523                                   "tdb_transaction_start: cannot start a"
524                                   " transaction on a read-only or internal db");
525         }
526
527         /* cope with nested tdb_transaction_start() calls */
528         if (tdb->transaction != NULL) {
529                 return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_USE_ERROR,
530                                   "tdb_transaction_start:"
531                                   " already inside transaction");
532         }
533
534         if (tdb_has_hash_locks(tdb)) {
535                 /* the caller must not have any locks when starting a
536                    transaction as otherwise we'll be screwed by lack
537                    of nested locks in posix */
538                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
539                                   "tdb_transaction_start: cannot start a"
540                                   " transaction with locks held");
541         }
542
543         tdb->transaction = (struct tdb_transaction *)
544                 calloc(sizeof(struct tdb_transaction), 1);
545         if (tdb->transaction == NULL) {
546                 return tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
547                                   "tdb_transaction_start: cannot allocate");
548         }
549
550         /* get the transaction write lock. This is a blocking lock. As
551            discussed with Volker, there are a number of ways we could
552            make this async, which we will probably do in the future */
553         ecode = tdb_transaction_lock(tdb, F_WRLCK);
554         if (ecode != TDB_SUCCESS) {
555                 SAFE_FREE(tdb->transaction->blocks);
556                 SAFE_FREE(tdb->transaction);
557                 return ecode;
558         }
559
560         /* get a read lock over entire file. This is upgraded to a write
561            lock during the commit */
562         ecode = tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, true);
563         if (ecode != TDB_SUCCESS) {
564                 goto fail_allrecord_lock;
565         }
566
567         /* make sure we know about any file expansions already done by
568            anyone else */
569         tdb->methods->oob(tdb, tdb->map_size + 1, true);
570         tdb->transaction->old_map_size = tdb->map_size;
571
572         /* finally hook the io methods, replacing them with
573            transaction specific methods */
574         tdb->transaction->io_methods = tdb->methods;
575         tdb->methods = &transaction_methods;
576         return TDB_SUCCESS;
577
578 fail_allrecord_lock:
579         tdb_transaction_unlock(tdb, F_WRLCK);
580         SAFE_FREE(tdb->transaction->blocks);
581         SAFE_FREE(tdb->transaction);
582         return ecode;
583 }
584
585
586 /*
587   cancel the current transaction
588 */
589 void tdb_transaction_cancel(struct tdb_context *tdb)
590 {
591         _tdb_transaction_cancel(tdb);
592 }
593
594 /*
595   work out how much space the linearised recovery data will consume
596 */
597 static tdb_len_t tdb_recovery_size(struct tdb_context *tdb)
598 {
599         tdb_len_t recovery_size = 0;
600         int i;
601
602         recovery_size = sizeof(tdb_len_t);
603         for (i=0;i<tdb->transaction->num_blocks;i++) {
604                 if (i * getpagesize() >= tdb->transaction->old_map_size) {
605                         break;
606                 }
607                 if (tdb->transaction->blocks[i] == NULL) {
608                         continue;
609                 }
610                 recovery_size += 2*sizeof(tdb_off_t);
611                 if (i == tdb->transaction->num_blocks-1) {
612                         recovery_size += tdb->transaction->last_block_size;
613                 } else {
614                         recovery_size += getpagesize();
615                 }
616         }
617
618         return recovery_size;
619 }
620
621 /*
622   allocate the recovery area, or use an existing recovery area if it is
623   large enough
624 */
625 static enum TDB_ERROR tdb_recovery_allocate(struct tdb_context *tdb,
626                                             tdb_len_t *recovery_size,
627                                             tdb_off_t *recovery_offset,
628                                             tdb_len_t *recovery_max_size)
629 {
630         struct tdb_recovery_record rec;
631         const struct tdb_methods *methods = tdb->transaction->io_methods;
632         tdb_off_t recovery_head;
633         size_t addition;
634         enum TDB_ERROR ecode;
635
636         recovery_head = tdb_read_off(tdb, offsetof(struct tdb_header,recovery));
637         if (TDB_OFF_IS_ERR(recovery_head)) {
638                 return tdb_logerr(tdb, recovery_head, TDB_LOG_ERROR,
639                                   "tdb_recovery_allocate:"
640                                   " failed to read recovery head");
641         }
642
643         if (recovery_head != 0) {
644                 ecode = methods->tread(tdb, recovery_head, &rec, sizeof(rec));
645                 if (ecode != TDB_SUCCESS) {
646                         return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
647                                           "tdb_recovery_allocate:"
648                                           " failed to read recovery record");
649                 }
650                 tdb_convert(tdb, &rec, sizeof(rec));
651                 /* ignore invalid recovery regions: can happen in crash */
652                 if (rec.magic != TDB_RECOVERY_MAGIC &&
653                     rec.magic != TDB_RECOVERY_INVALID_MAGIC) {
654                         recovery_head = 0;
655                 }
656         }
657
658         *recovery_size = tdb_recovery_size(tdb);
659
660         if (recovery_head != 0 && *recovery_size <= rec.max_len) {
661                 /* it fits in the existing area */
662                 *recovery_max_size = rec.max_len;
663                 *recovery_offset = recovery_head;
664                 return TDB_SUCCESS;
665         }
666
667         /* we need to free up the old recovery area, then allocate a
668            new one at the end of the file. Note that we cannot use
669            normal allocation to allocate the new one as that might return
670            us an area that is being currently used (as of the start of
671            the transaction) */
672         if (recovery_head != 0) {
673                 add_stat(tdb, frees, 1);
674                 ecode = add_free_record(tdb, recovery_head,
675                                         sizeof(rec) + rec.max_len);
676                 if (ecode != TDB_SUCCESS) {
677                         return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
678                                           "tdb_recovery_allocate:"
679                                           " failed to free previous"
680                                           " recovery area");
681                 }
682         }
683
684         /* the tdb_free() call might have increased the recovery size */
685         *recovery_size = tdb_recovery_size(tdb);
686
687         /* round up to a multiple of page size */
688         *recovery_max_size
689                 = (((sizeof(rec) + *recovery_size) + getpagesize()-1)
690                    & ~(getpagesize()-1))
691                 - sizeof(rec);
692         *recovery_offset = tdb->map_size;
693         recovery_head = *recovery_offset;
694
695         /* Restore ->map_size before calling underlying expand_file.
696            Also so that we don't try to expand the file again in the
697            transaction commit, which would destroy the recovery
698            area */
699         addition = (tdb->map_size - tdb->transaction->old_map_size) +
700                 sizeof(rec) + *recovery_max_size;
701         tdb->map_size = tdb->transaction->old_map_size;
702         ecode = methods->expand_file(tdb, addition);
703         if (ecode != TDB_SUCCESS) {
704                 return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
705                                   "tdb_recovery_allocate:"
706                                   " failed to create recovery area");
707         }
708
709         /* we have to reset the old map size so that we don't try to
710            expand the file again in the transaction commit, which
711            would destroy the recovery area */
712         tdb->transaction->old_map_size = tdb->map_size;
713
714         /* write the recovery header offset and sync - we can sync without a race here
715            as the magic ptr in the recovery record has not been set */
716         tdb_convert(tdb, &recovery_head, sizeof(recovery_head));
717         ecode = methods->twrite(tdb, offsetof(struct tdb_header, recovery),
718                                 &recovery_head, sizeof(tdb_off_t));
719         if (ecode != TDB_SUCCESS) {
720                 return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
721                                   "tdb_recovery_allocate:"
722                                   " failed to write recovery head");
723         }
724         transaction_write_existing(tdb, offsetof(struct tdb_header, recovery),
725                                    &recovery_head,
726                                    sizeof(tdb_off_t));
727         return TDB_SUCCESS;
728 }
729
730 /* Set up header for the recovery record. */
731 static void set_recovery_header(struct tdb_recovery_record *rec,
732                                 uint64_t magic,
733                                 uint64_t datalen, uint64_t actuallen,
734                                 uint64_t oldsize)
735 {
736         rec->magic = magic;
737         rec->max_len = actuallen;
738         rec->len = datalen;
739         rec->eof = oldsize;
740 }
741
742 /*
743   setup the recovery data that will be used on a crash during commit
744 */
745 static enum TDB_ERROR transaction_setup_recovery(struct tdb_context *tdb,
746                                                  tdb_off_t *magic_offset)
747 {
748         tdb_len_t recovery_size;
749         unsigned char *data, *p;
750         const struct tdb_methods *methods = tdb->transaction->io_methods;
751         struct tdb_recovery_record *rec;
752         tdb_off_t recovery_offset, recovery_max_size;
753         tdb_off_t old_map_size = tdb->transaction->old_map_size;
754         uint64_t magic, tailer;
755         int i;
756         enum TDB_ERROR ecode;
757
758         /*
759           check that the recovery area has enough space
760         */
761         ecode = tdb_recovery_allocate(tdb, &recovery_size,
762                                       &recovery_offset, &recovery_max_size);
763         if (ecode != TDB_SUCCESS) {
764                 return ecode;
765         }
766
767         data = (unsigned char *)malloc(recovery_size + sizeof(*rec));
768         if (data == NULL) {
769                 return tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
770                                   "transaction_setup_recovery:"
771                                   " cannot allocate");
772         }
773
774         rec = (struct tdb_recovery_record *)data;
775         set_recovery_header(rec, TDB_RECOVERY_INVALID_MAGIC,
776                             recovery_size, recovery_max_size, old_map_size);
777         tdb_convert(tdb, rec, sizeof(*rec));
778
779         /* build the recovery data into a single blob to allow us to do a single
780            large write, which should be more efficient */
781         p = data + sizeof(*rec);
782         for (i=0;i<tdb->transaction->num_blocks;i++) {
783                 tdb_off_t offset;
784                 tdb_len_t length;
785
786                 if (tdb->transaction->blocks[i] == NULL) {
787                         continue;
788                 }
789
790                 offset = i * getpagesize();
791                 length = getpagesize();
792                 if (i == tdb->transaction->num_blocks-1) {
793                         length = tdb->transaction->last_block_size;
794                 }
795
796                 if (offset >= old_map_size) {
797                         continue;
798                 }
799                 if (offset + length > tdb->map_size) {
800                         free(data);
801                         return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
802                                           "tdb_transaction_setup_recovery:"
803                                           " transaction data over new region"
804                                           " boundary");
805                 }
806                 memcpy(p, &offset, sizeof(offset));
807                 memcpy(p + sizeof(offset), &length, sizeof(length));
808                 tdb_convert(tdb, p, sizeof(offset) + sizeof(length));
809
810                 /* the recovery area contains the old data, not the
811                    new data, so we have to call the original tdb_read
812                    method to get it */
813                 ecode = methods->tread(tdb, offset,
814                                        p + sizeof(offset) + sizeof(length),
815                                        length);
816                 if (ecode != TDB_SUCCESS) {
817                         free(data);
818                         return ecode;
819                 }
820                 p += sizeof(offset) + sizeof(length) + length;
821         }
822
823         /* and the tailer */
824         tailer = sizeof(*rec) + recovery_max_size;
825         memcpy(p, &tailer, sizeof(tailer));
826         tdb_convert(tdb, p, sizeof(tailer));
827
828         /* write the recovery data to the recovery area */
829         ecode = methods->twrite(tdb, recovery_offset, data,
830                                 sizeof(*rec) + recovery_size);
831         if (ecode != TDB_SUCCESS) {
832                 free(data);
833                 return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
834                                   "tdb_transaction_setup_recovery:"
835                                   " failed to write recovery data");
836         }
837         transaction_write_existing(tdb, recovery_offset, data,
838                                    sizeof(*rec) + recovery_size);
839
840         /* as we don't have ordered writes, we have to sync the recovery
841            data before we update the magic to indicate that the recovery
842            data is present */
843         ecode = transaction_sync(tdb, recovery_offset,
844                                  sizeof(*rec) + recovery_size);
845         if (ecode != TDB_SUCCESS) {
846                 free(data);
847                 return ecode;
848         }
849
850         free(data);
851
852         magic = TDB_RECOVERY_MAGIC;
853         tdb_convert(tdb, &magic, sizeof(magic));
854
855         *magic_offset = recovery_offset + offsetof(struct tdb_recovery_record,
856                                                    magic);
857
858         ecode = methods->twrite(tdb, *magic_offset, &magic, sizeof(magic));
859         if (ecode != TDB_SUCCESS) {
860                 return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
861                                   "tdb_transaction_setup_recovery:"
862                                   " failed to write recovery magic");
863         }
864         transaction_write_existing(tdb, *magic_offset, &magic, sizeof(magic));
865
866         /* ensure the recovery magic marker is on disk */
867         return transaction_sync(tdb, *magic_offset, sizeof(magic));
868 }
869
870 static enum TDB_ERROR _tdb_transaction_prepare_commit(struct tdb_context *tdb)
871 {
872         const struct tdb_methods *methods;
873         enum TDB_ERROR ecode;
874
875         if (tdb->transaction == NULL) {
876                 return tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
877                                   "tdb_transaction_prepare_commit:"
878                                   " no transaction");
879         }
880
881         if (tdb->transaction->prepared) {
882                 _tdb_transaction_cancel(tdb);
883                 return tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
884                                   "tdb_transaction_prepare_commit:"
885                                   " transaction already prepared");
886         }
887
888         if (tdb->transaction->transaction_error) {
889                 _tdb_transaction_cancel(tdb);
890                 return tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_ERROR,
891                                   "tdb_transaction_prepare_commit:"
892                                   " transaction error pending");
893         }
894
895
896         if (tdb->transaction->nesting != 0) {
897                 tdb->transaction->nesting--;
898                 return TDB_SUCCESS;
899         }
900
901         /* check for a null transaction */
902         if (tdb->transaction->blocks == NULL) {
903                 return TDB_SUCCESS;
904         }
905
906         methods = tdb->transaction->io_methods;
907
908         /* upgrade the main transaction lock region to a write lock */
909         ecode = tdb_allrecord_upgrade(tdb);
910         if (ecode != TDB_SUCCESS) {
911                 tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
912                          "tdb_transaction_prepare_commit:"
913                          " failed to upgrade hash locks");
914                 _tdb_transaction_cancel(tdb);
915                 return ecode;
916         }
917
918         /* get the open lock - this prevents new users attaching to the database
919            during the commit */
920         ecode = tdb_lock_open(tdb, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK);
921         if (ecode != TDB_SUCCESS) {
922                 tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
923                            "tdb_transaction_prepare_commit:"
924                            " failed to get open lock");
925                 _tdb_transaction_cancel(tdb);
926                 return ecode;
927         }
928
929         /* Since we have whole db locked, we don't need the expansion lock. */
930         if (!(tdb->flags & TDB_NOSYNC)) {
931                 /* write the recovery data to the end of the file */
932                 ecode = transaction_setup_recovery(tdb,
933                                                    &tdb->transaction
934                                                    ->magic_offset);
935                 if (ecode != TDB_SUCCESS) {
936                         tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
937                                  "tdb_transaction_prepare_commit:"
938                                  " failed to setup recovery data");
939                         _tdb_transaction_cancel(tdb);
940                         return ecode;
941                 }
942         }
943
944         tdb->transaction->prepared = true;
945
946         /* expand the file to the new size if needed */
947         if (tdb->map_size != tdb->transaction->old_map_size) {
948                 tdb_len_t add = tdb->map_size - tdb->transaction->old_map_size;
949                 /* Restore original map size for tdb_expand_file */
950                 tdb->map_size = tdb->transaction->old_map_size;
951                 ecode = methods->expand_file(tdb, add);
952                 if (ecode != TDB_SUCCESS) {
953                         tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
954                                  "tdb_transaction_prepare_commit:"
955                                  " expansion failed");
956                         _tdb_transaction_cancel(tdb);
957                         return ecode;
958                 }
959         }
960
961         /* Keep the open lock until the actual commit */
962         return TDB_SUCCESS;
963 }
964
965 /*
966    prepare to commit the current transaction
967 */
968 enum TDB_ERROR tdb_transaction_prepare_commit(struct tdb_context *tdb)
969 {
970         return _tdb_transaction_prepare_commit(tdb);
971 }
972
973 /*
974   commit the current transaction
975 */
976 enum TDB_ERROR tdb_transaction_commit(struct tdb_context *tdb)
977 {
978         const struct tdb_methods *methods;
979         int i;
980         enum TDB_ERROR ecode;
981
982         if (tdb->transaction == NULL) {
983                 return tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
984                                   "tdb_transaction_commit: no transaction");
985         }
986
987         tdb_trace(tdb, "tdb_transaction_commit");
988
989         if (tdb->transaction->nesting != 0) {
990                 tdb->transaction->nesting--;
991                 return TDB_SUCCESS;
992         }
993
994         /* check for a null transaction */
995         if (tdb->transaction->blocks == NULL) {
996                 _tdb_transaction_cancel(tdb);
997                 return TDB_SUCCESS;
998         }
999
1000         if (!tdb->transaction->prepared) {
1001                 ecode = _tdb_transaction_prepare_commit(tdb);
1002                 if (ecode != TDB_SUCCESS)
1003                         return ecode;
1004         }
1005
1006         methods = tdb->transaction->io_methods;
1007
1008         /* perform all the writes */
1009         for (i=0;i<tdb->transaction->num_blocks;i++) {
1010                 tdb_off_t offset;
1011                 tdb_len_t length;
1012
1013                 if (tdb->transaction->blocks[i] == NULL) {
1014                         continue;
1015                 }
1016
1017                 offset = i * getpagesize();
1018                 length = getpagesize();
1019                 if (i == tdb->transaction->num_blocks-1) {
1020                         length = tdb->transaction->last_block_size;
1021                 }
1022
1023                 ecode = methods->twrite(tdb, offset,
1024                                         tdb->transaction->blocks[i], length);
1025                 if (ecode != TDB_SUCCESS) {
1026                         tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
1027                                    "tdb_transaction_commit:"
1028                                    " write failed during commit");
1029
1030                         /* we've overwritten part of the data and
1031                            possibly expanded the file, so we need to
1032                            run the crash recovery code */
1033                         tdb->methods = methods;
1034                         tdb_transaction_recover(tdb);
1035
1036                         _tdb_transaction_cancel(tdb);
1037
1038                         return ecode;
1039                 }
1040                 SAFE_FREE(tdb->transaction->blocks[i]);
1041         }
1042
1043         SAFE_FREE(tdb->transaction->blocks);
1044         tdb->transaction->num_blocks = 0;
1045
1046         /* ensure the new data is on disk */
1047         ecode = transaction_sync(tdb, 0, tdb->map_size);
1048         if (ecode != TDB_SUCCESS) {
1049                 return ecode;
1050         }
1051
1052         /*
1053           TODO: maybe write to some dummy hdr field, or write to magic
1054           offset without mmap, before the last sync, instead of the
1055           utime() call
1056         */
1057
1058         /* on some systems (like Linux 2.6.x) changes via mmap/msync
1059            don't change the mtime of the file, this means the file may
1060            not be backed up (as tdb rounding to block sizes means that
1061            file size changes are quite rare too). The following forces
1062            mtime changes when a transaction completes */
1063 #if HAVE_UTIME
1064         utime(tdb->name, NULL);
1065 #endif
1066
1067         /* use a transaction cancel to free memory and remove the
1068            transaction locks */
1069         _tdb_transaction_cancel(tdb);
1070
1071         return TDB_SUCCESS;
1072 }
1073
1074
1075 /*
1076   recover from an aborted transaction. Must be called with exclusive
1077   database write access already established (including the open
1078   lock to prevent new processes attaching)
1079 */
1080 enum TDB_ERROR tdb_transaction_recover(struct tdb_context *tdb)
1081 {
1082         tdb_off_t recovery_head, recovery_eof;
1083         unsigned char *data, *p;
1084         struct tdb_recovery_record rec;
1085         enum TDB_ERROR ecode;
1086
1087         /* find the recovery area */
1088         recovery_head = tdb_read_off(tdb, offsetof(struct tdb_header,recovery));
1089         if (TDB_OFF_IS_ERR(recovery_head)) {
1090                 return tdb_logerr(tdb, recovery_head, TDB_LOG_ERROR,
1091                                   "tdb_transaction_recover:"
1092                                   " failed to read recovery head");
1093         }
1094
1095         if (recovery_head == 0) {
1096                 /* we have never allocated a recovery record */
1097                 return TDB_SUCCESS;
1098         }
1099
1100         /* read the recovery record */
1101         ecode = tdb_read_convert(tdb, recovery_head, &rec, sizeof(rec));
1102         if (ecode != TDB_SUCCESS) {
1103                 return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
1104                                   "tdb_transaction_recover:"
1105                                   " failed to read recovery record");
1106         }
1107
1108         if (rec.magic != TDB_RECOVERY_MAGIC) {
1109                 /* there is no valid recovery data */
1110                 return TDB_SUCCESS;
1111         }
1112
1113         if (tdb->read_only) {
1114                 return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
1115                                   "tdb_transaction_recover:"
1116                                   " attempt to recover read only database");
1117         }
1118
1119         recovery_eof = rec.eof;
1120
1121         data = (unsigned char *)malloc(rec.len);
1122         if (data == NULL) {
1123                 return tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
1124                                   "tdb_transaction_recover:"
1125                                   " failed to allocate recovery data");
1126         }
1127
1128         /* read the full recovery data */
1129         ecode = tdb->methods->tread(tdb, recovery_head + sizeof(rec), data,
1130                                     rec.len);
1131         if (ecode != TDB_SUCCESS) {
1132                 return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
1133                                   "tdb_transaction_recover:"
1134                                   " failed to read recovery data");
1135         }
1136
1137         /* recover the file data */
1138         p = data;
1139         while (p+sizeof(tdb_off_t)+sizeof(tdb_len_t) < data + rec.len) {
1140                 tdb_off_t ofs;
1141                 tdb_len_t len;
1142                 tdb_convert(tdb, p, sizeof(ofs) + sizeof(len));
1143                 memcpy(&ofs, p, sizeof(ofs));
1144                 memcpy(&len, p + sizeof(ofs), sizeof(len));
1145                 p += sizeof(ofs) + sizeof(len);
1146
1147                 ecode = tdb->methods->twrite(tdb, ofs, p, len);
1148                 if (ecode != TDB_SUCCESS) {
1149                         free(data);
1150                         return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
1151                                           "tdb_transaction_recover:"
1152                                           " failed to recover %zu bytes"
1153                                           " at offset %zu",
1154                                           (size_t)len, (size_t)ofs);
1155                 }
1156                 p += len;
1157         }
1158
1159         free(data);
1160
1161         ecode = transaction_sync(tdb, 0, tdb->map_size);
1162         if (ecode != TDB_SUCCESS) {
1163                 return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
1164                                   "tdb_transaction_recover:"
1165                                   " failed to sync recovery");
1166         }
1167
1168         /* if the recovery area is after the recovered eof then remove it */
1169         if (recovery_eof <= recovery_head) {
1170                 ecode = tdb_write_off(tdb, offsetof(struct tdb_header,
1171                                                     recovery),
1172                                       0);
1173                 if (ecode != TDB_SUCCESS) {
1174                         return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
1175                                           "tdb_transaction_recover:"
1176                                           " failed to remove recovery head");
1177                 }
1178         }
1179
1180         /* remove the recovery magic */
1181         ecode = tdb_write_off(tdb,
1182                               recovery_head
1183                               + offsetof(struct tdb_recovery_record, magic),
1184                               TDB_RECOVERY_INVALID_MAGIC);
1185         if (ecode != TDB_SUCCESS) {
1186                 return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
1187                                   "tdb_transaction_recover:"
1188                                   " failed to remove recovery magic");
1189         }
1190
1191         ecode = transaction_sync(tdb, 0, recovery_eof);
1192         if (ecode != TDB_SUCCESS) {
1193                 return tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
1194                                   "tdb_transaction_recover:"
1195                                   " failed to sync2 recovery");
1196         }
1197
1198         tdb_logerr(tdb, TDB_SUCCESS, TDB_LOG_WARNING,
1199                    "tdb_transaction_recover: recovered %zu byte database",
1200                    (size_t)recovery_eof);
1201
1202         /* all done */
1203         return TDB_SUCCESS;
1204 }
1205
1206 tdb_bool_err tdb_needs_recovery(struct tdb_context *tdb)
1207 {
1208         tdb_off_t recovery_head;
1209         struct tdb_recovery_record rec;
1210         enum TDB_ERROR ecode;
1211
1212         /* find the recovery area */
1213         recovery_head = tdb_read_off(tdb, offsetof(struct tdb_header,recovery));
1214         if (TDB_OFF_IS_ERR(recovery_head)) {
1215                 return recovery_head;
1216         }
1217
1218         if (recovery_head == 0) {
1219                 /* we have never allocated a recovery record */
1220                 return false;
1221         }
1222
1223         /* read the recovery record */
1224         ecode = tdb_read_convert(tdb, recovery_head, &rec, sizeof(rec));
1225         if (ecode != TDB_SUCCESS) {
1226                 return ecode;
1227         }
1228
1229         return (rec.magic == TDB_RECOVERY_MAGIC);
1230 }