Use -O not -O3: reduces ccan/tdb test time from 24 to 18 seconds.
[ccan] / ccan / tdb / 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 "tdb_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     tdb_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 tdb_write() calls. The hooked
48     transaction versions of tdb_read() and tdb_write() check this
49     linked list and try to use the elements of the list in preference
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 tdb_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 tdb_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     global lock is held. Automatically recover from the transaction
80     recovery area if needed, then continue with the open as
81     usual. This allows for smooth crash recovery with no administrator
82     intervention.
83
84   - if TDB_NOSYNC is passed to flags in tdb_open then transactions are
85     still available, but no transaction recovery area is used and no
86     fsync/msync calls are made.
87
88   - if TDB_ALLOW_NESTING is passed to flags in tdb open, or added using
89     tdb_add_flags() transaction is enabled.
90     The default is that transaction nesting is not allowed and an attempt
91     to create a nested transaction will fail with TDB_ERR_NESTING.
92
93     Beware. when transactions are nested a transaction successfully
94     completed with tdb_transaction_commit() can be silently unrolled later.
95 */
96
97
98 /*
99   hold the context of any current transaction
100 */
101 struct tdb_transaction {
102         /* we keep a mirrored copy of the tdb hash heads here so
103            tdb_next_hash_chain() can operate efficiently */
104         uint32_t *hash_heads;
105
106         /* the original io methods - used to do IOs to the real db */
107         const struct tdb_methods *io_methods;
108
109         /* the list of transaction blocks. When a block is first
110            written to, it gets created in this list */
111         uint8_t **blocks;
112         uint32_t num_blocks;
113         uint32_t block_size;      /* bytes in each block */
114         uint32_t last_block_size; /* number of valid bytes in the last block */
115
116         /* non-zero when an internal transaction error has
117            occurred. All write operations will then fail until the
118            transaction is ended */
119         int transaction_error;
120
121         /* when inside a transaction we need to keep track of any
122            nested tdb_transaction_start() calls, as these are allowed,
123            but don't create a new transaction */
124         int nesting;
125
126         /* set when a prepare has already occurred */
127         bool prepared;
128         tdb_off_t magic_offset;
129
130         /* old file size before transaction */
131         tdb_len_t old_map_size;
132
133         /* we should re-pack on commit */
134         bool need_repack;
135 };
136
137
138 /*
139   read while in a transaction. We need to check first if the data is in our list
140   of transaction elements, then if not do a real read
141 */
142 static int transaction_read(struct tdb_context *tdb, tdb_off_t off, void *buf, 
143                             tdb_len_t len, int cv)
144 {
145         uint32_t blk;
146
147         /* break it down into block sized ops */
148         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
149                 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
150                 if (transaction_read(tdb, off, buf, len2, cv) != 0) {
151                         return -1;
152                 }
153                 len -= len2;
154                 off += len2;
155                 buf = (void *)(len2 + (char *)buf);
156         }
157
158         if (len == 0) {
159                 return 0;
160         }
161
162         blk = off / tdb->transaction->block_size;
163
164         /* see if we have it in the block list */
165         if (tdb->transaction->num_blocks <= blk ||
166             tdb->transaction->blocks[blk] == NULL) {
167                 /* nope, do a real read */
168                 if (tdb->transaction->io_methods->tdb_read(tdb, off, buf, len, cv) != 0) {
169                         goto fail;
170                 }
171                 return 0;
172         }
173
174         /* it is in the block list. Now check for the last block */
175         if (blk == tdb->transaction->num_blocks-1) {
176                 if (len > tdb->transaction->last_block_size) {
177                         goto fail;
178                 }
179         }
180         
181         /* now copy it out of this block */
182         memcpy(buf, tdb->transaction->blocks[blk] + (off % tdb->transaction->block_size), len);
183         if (cv) {
184                 tdb_convert(buf, len);
185         }
186         return 0;
187
188 fail:
189         TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_read: failed at off=%d len=%d\n", off, len));
190         tdb->ecode = TDB_ERR_IO;
191         tdb->transaction->transaction_error = 1;
192         return -1;
193 }
194
195
196 /*
197   write while in a transaction
198 */
199 static int transaction_write(struct tdb_context *tdb, tdb_off_t off, 
200                              const void *buf, tdb_len_t len)
201 {
202         uint32_t blk;
203
204         /* Only a commit is allowed on a prepared transaction */
205         if (tdb->transaction->prepared) {
206                 tdb->ecode = TDB_ERR_EINVAL;
207                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_write: transaction already prepared, write not allowed\n"));
208                 tdb->transaction->transaction_error = 1;
209                 return -1;
210         }
211
212         /* if the write is to a hash head, then update the transaction
213            hash heads */
214         if (len == sizeof(tdb_off_t) && off >= FREELIST_TOP &&
215             off < FREELIST_TOP+TDB_HASHTABLE_SIZE(tdb)) {
216                 uint32_t chain = (off-FREELIST_TOP) / sizeof(tdb_off_t);
217                 memcpy(&tdb->transaction->hash_heads[chain], buf, len);
218         }
219
220         /* break it up into block sized chunks */
221         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
222                 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
223                 if (transaction_write(tdb, off, buf, len2) != 0) {
224                         return -1;
225                 }
226                 len -= len2;
227                 off += len2;
228                 if (buf != NULL) {
229                         buf = (const void *)(len2 + (const char *)buf);
230                 }
231         }
232
233         if (len == 0) {
234                 return 0;
235         }
236
237         blk = off / tdb->transaction->block_size;
238         off = off % tdb->transaction->block_size;
239
240         if (tdb->transaction->num_blocks <= blk) {
241                 uint8_t **new_blocks;
242                 /* expand the blocks array */
243                 if (tdb->transaction->blocks == NULL) {
244                         new_blocks = (uint8_t **)malloc(
245                                 (blk+1)*sizeof(uint8_t *));
246                 } else {
247                         new_blocks = (uint8_t **)realloc(
248                                 tdb->transaction->blocks,
249                                 (blk+1)*sizeof(uint8_t *));
250                 }
251                 if (new_blocks == NULL) {
252                         tdb->ecode = TDB_ERR_OOM;
253                         goto fail;
254                 }
255                 memset(&new_blocks[tdb->transaction->num_blocks], 0, 
256                        (1+(blk - tdb->transaction->num_blocks))*sizeof(uint8_t *));
257                 tdb->transaction->blocks = new_blocks;
258                 tdb->transaction->num_blocks = blk+1;
259                 tdb->transaction->last_block_size = 0;
260         }
261
262         /* allocate and fill a block? */
263         if (tdb->transaction->blocks[blk] == NULL) {
264                 tdb->transaction->blocks[blk] = (uint8_t *)calloc(tdb->transaction->block_size, 1);
265                 if (tdb->transaction->blocks[blk] == NULL) {
266                         tdb->ecode = TDB_ERR_OOM;
267                         tdb->transaction->transaction_error = 1;
268                         return -1;                      
269                 }
270                 if (tdb->transaction->old_map_size > blk * tdb->transaction->block_size) {
271                         tdb_len_t len2 = tdb->transaction->block_size;
272                         if (len2 + (blk * tdb->transaction->block_size) > tdb->transaction->old_map_size) {
273                                 len2 = tdb->transaction->old_map_size - (blk * tdb->transaction->block_size);
274                         }
275                         if (tdb->transaction->io_methods->tdb_read(tdb, blk * tdb->transaction->block_size, 
276                                                                    tdb->transaction->blocks[blk], 
277                                                                    len2, 0) != 0) {
278                                 SAFE_FREE(tdb->transaction->blocks[blk]);                               
279                                 tdb->ecode = TDB_ERR_IO;
280                                 goto fail;
281                         }
282                         if (blk == tdb->transaction->num_blocks-1) {
283                                 tdb->transaction->last_block_size = len2;
284                         }                       
285                 }
286         }
287         
288         /* overwrite part of an existing block */
289         if (buf == NULL) {
290                 memset(tdb->transaction->blocks[blk] + off, 0, len);
291         } else {
292                 memcpy(tdb->transaction->blocks[blk] + off, buf, len);
293         }
294         if (blk == tdb->transaction->num_blocks-1) {
295                 if (len + off > tdb->transaction->last_block_size) {
296                         tdb->transaction->last_block_size = len + off;
297                 }
298         }
299
300         return 0;
301
302 fail:
303         TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_write: failed at off=%d len=%d\n", 
304                  (blk*tdb->transaction->block_size) + off, len));
305         tdb->transaction->transaction_error = 1;
306         return -1;
307 }
308
309
310 /*
311   write while in a transaction - this varient never expands the transaction blocks, it only
312   updates existing blocks. This means it cannot change the recovery size
313 */
314 static int transaction_write_existing(struct tdb_context *tdb, tdb_off_t off, 
315                                       const void *buf, tdb_len_t len)
316 {
317         uint32_t blk;
318
319         /* break it up into block sized chunks */
320         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
321                 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
322                 if (transaction_write_existing(tdb, off, buf, len2) != 0) {
323                         return -1;
324                 }
325                 len -= len2;
326                 off += len2;
327                 if (buf != NULL) {
328                         buf = (const void *)(len2 + (const char *)buf);
329                 }
330         }
331
332         if (len == 0) {
333                 return 0;
334         }
335
336         blk = off / tdb->transaction->block_size;
337         off = off % tdb->transaction->block_size;
338
339         if (tdb->transaction->num_blocks <= blk ||
340             tdb->transaction->blocks[blk] == NULL) {
341                 return 0;
342         }
343
344         if (blk == tdb->transaction->num_blocks-1 &&
345             off + len > tdb->transaction->last_block_size) {
346                 if (off >= tdb->transaction->last_block_size) {
347                         return 0;
348                 }
349                 len = tdb->transaction->last_block_size - off;
350         }
351
352         /* overwrite part of an existing block */
353         memcpy(tdb->transaction->blocks[blk] + off, buf, len);
354
355         return 0;
356 }
357
358
359 /*
360   accelerated hash chain head search, using the cached hash heads
361 */
362 static void transaction_next_hash_chain(struct tdb_context *tdb, uint32_t *chain)
363 {
364         uint32_t h = *chain;
365         for (;h < tdb->header.hash_size;h++) {
366                 /* the +1 takes account of the freelist */
367                 if (0 != tdb->transaction->hash_heads[h+1]) {
368                         break;
369                 }
370         }
371         (*chain) = h;
372 }
373
374 /*
375   out of bounds check during a transaction
376 */
377 static int transaction_oob(struct tdb_context *tdb, tdb_off_t len, int probe)
378 {
379         if (len <= tdb->map_size) {
380                 return 0;
381         }
382         tdb->ecode = TDB_ERR_IO;
383         return -1;
384 }
385
386 /*
387   transaction version of tdb_expand().
388 */
389 static int transaction_expand_file(struct tdb_context *tdb, tdb_off_t size, 
390                                    tdb_off_t addition)
391 {
392         /* add a write to the transaction elements, so subsequent
393            reads see the zero data */
394         if (transaction_write(tdb, size, NULL, addition) != 0) {
395                 return -1;
396         }
397
398         tdb->transaction->need_repack = true;
399
400         return 0;
401 }
402
403 /*
404   brlock during a transaction - ignore them
405 */
406 static int transaction_brlock(struct tdb_context *tdb,
407                               int rw_type, tdb_off_t offset, size_t len,
408                               enum tdb_lock_flags flags)
409 {
410         return 0;
411 }
412
413 static int transaction_brunlock(struct tdb_context *tdb,
414                                 int rw_type, tdb_off_t offset, size_t len)
415 {
416         return 0;
417 }
418
419 static const struct tdb_methods transaction_methods = {
420         transaction_read,
421         transaction_write,
422         transaction_next_hash_chain,
423         transaction_oob,
424         transaction_expand_file,
425         transaction_brlock,
426         transaction_brunlock
427 };
428
429 /*
430   sync to disk
431 */
432 static int transaction_sync(struct tdb_context *tdb, tdb_off_t offset, tdb_len_t length)
433 {       
434         if (tdb->flags & TDB_NOSYNC) {
435                 return 0;
436         }
437
438         if (fsync(tdb->fd) != 0) {
439                 tdb->ecode = TDB_ERR_IO;
440                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: fsync failed\n"));
441                 return -1;
442         }
443 #ifdef MS_SYNC
444         if (tdb->map_ptr) {
445                 tdb_off_t moffset = offset & ~(tdb->page_size-1);
446                 if (msync(moffset + (char *)tdb->map_ptr, 
447                           length + (offset - moffset), MS_SYNC) != 0) {
448                         tdb->ecode = TDB_ERR_IO;
449                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: msync failed - %s\n",
450                                  strerror(errno)));
451                         return -1;
452                 }
453         }
454 #endif
455         return 0;
456 }
457
458 /* ltype is F_WRLCK after prepare. */
459 int _tdb_transaction_cancel(struct tdb_context *tdb, int ltype)
460 {
461         int i, ret = 0;
462
463         if (tdb->transaction == NULL) {
464                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_cancel: no transaction\n"));
465                 return -1;
466         }
467
468         if (tdb->transaction->nesting != 0) {
469                 tdb->transaction->transaction_error = 1;
470                 tdb->transaction->nesting--;
471                 return 0;
472         }               
473
474         tdb->map_size = tdb->transaction->old_map_size;
475
476         /* free all the transaction blocks */
477         for (i=0;i<tdb->transaction->num_blocks;i++) {
478                 if (tdb->transaction->blocks[i] != NULL) {
479                         free(tdb->transaction->blocks[i]);
480                 }
481         }
482         SAFE_FREE(tdb->transaction->blocks);
483
484         if (tdb->transaction->magic_offset) {
485                 const struct tdb_methods *methods = tdb->transaction->io_methods;
486                 uint32_t zero = 0;
487
488                 /* remove the recovery marker */
489                 if (methods->tdb_write(tdb, tdb->transaction->magic_offset, &zero, 4) == -1 ||
490                 transaction_sync(tdb, tdb->transaction->magic_offset, 4) == -1) {
491                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_cancel: failed to remove recovery magic\n"));
492                         ret = -1;
493                 }
494         }
495
496         /* remove any global lock created during the transaction */
497         if (tdb->global_lock.count != 0) {
498                 tdb_brunlock(tdb, tdb->global_lock.ltype,
499                              FREELIST_TOP, 4*tdb->header.hash_size);
500                 tdb->global_lock.count = 0;
501         }
502
503         /* remove any locks created during the transaction */
504         if (tdb->num_locks != 0) {
505                 for (i=0;i<tdb->num_lockrecs;i++) {
506                         tdb_brunlock(tdb, tdb->lockrecs[i].ltype,
507                                      FREELIST_TOP+4*tdb->lockrecs[i].list, 1);
508                 }
509                 tdb->num_locks = 0;
510                 tdb->num_lockrecs = 0;
511                 SAFE_FREE(tdb->lockrecs);
512         }
513
514         /* restore the normal io methods */
515         tdb->methods = tdb->transaction->io_methods;
516
517         tdb_brunlock(tdb, ltype, FREELIST_TOP, 0);
518         tdb_transaction_unlock(tdb, F_WRLCK);
519         SAFE_FREE(tdb->transaction->hash_heads);
520         SAFE_FREE(tdb->transaction);
521         
522         return ret;
523 }
524
525 /*
526   start a tdb transaction. No token is returned, as only a single
527   transaction is allowed to be pending per tdb_context
528 */
529 int tdb_transaction_start(struct tdb_context *tdb)
530 {
531         /* some sanity checks */
532         if (tdb->read_only || (tdb->flags & TDB_INTERNAL) || tdb->traverse_read) {
533                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction on a read-only or internal db\n"));
534                 tdb->ecode = TDB_ERR_EINVAL;
535                 return -1;
536         }
537
538         /* cope with nested tdb_transaction_start() calls */
539         if (tdb->transaction != NULL) {
540                 if (!(tdb->flags & TDB_ALLOW_NESTING)) {
541                         tdb->ecode = TDB_ERR_NESTING;
542                         return -1;
543                 }
544                 tdb_trace(tdb, "tdb_transaction_start");
545                 tdb->transaction->nesting++;
546                 TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_start: nesting %d\n", 
547                          tdb->transaction->nesting));
548                 return 0;
549         }
550
551         if (tdb->num_locks != 0 || tdb->global_lock.count) {
552                 /* the caller must not have any locks when starting a
553                    transaction as otherwise we'll be screwed by lack
554                    of nested locks in posix */
555                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction with locks held\n"));
556                 tdb->ecode = TDB_ERR_LOCK;
557                 return -1;
558         }
559
560         if (tdb->travlocks.next != NULL) {
561                 /* you cannot use transactions inside a traverse (although you can use
562                    traverse inside a transaction) as otherwise you can end up with
563                    deadlock */
564                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction within a traverse\n"));
565                 tdb->ecode = TDB_ERR_LOCK;
566                 return -1;
567         }
568
569         tdb->transaction = (struct tdb_transaction *)
570                 calloc(sizeof(struct tdb_transaction), 1);
571         if (tdb->transaction == NULL) {
572                 tdb->ecode = TDB_ERR_OOM;
573                 return -1;
574         }
575
576         /* a page at a time seems like a reasonable compromise between compactness and efficiency */
577         tdb->transaction->block_size = tdb->page_size;
578
579         /* get the transaction write lock. This is a blocking lock. As
580            discussed with Volker, there are a number of ways we could
581            make this async, which we will probably do in the future */
582         if (tdb_transaction_lock(tdb, F_WRLCK) == -1) {
583                 SAFE_FREE(tdb->transaction->blocks);
584                 SAFE_FREE(tdb->transaction);
585                 return -1;
586         }
587         
588         /* get a read lock from the freelist to the end of file. This
589            is upgraded to a write lock during the commit */
590         if (tdb_brlock(tdb, F_RDLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT) == -1) {
591                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: failed to get hash locks\n"));
592                 tdb->ecode = TDB_ERR_LOCK;
593                 goto fail;
594         }
595
596         /* setup a copy of the hash table heads so the hash scan in
597            traverse can be fast */
598         tdb->transaction->hash_heads = (uint32_t *)
599                 calloc(tdb->header.hash_size+1, sizeof(uint32_t));
600         if (tdb->transaction->hash_heads == NULL) {
601                 tdb->ecode = TDB_ERR_OOM;
602                 goto fail;
603         }
604         if (tdb->methods->tdb_read(tdb, FREELIST_TOP, tdb->transaction->hash_heads,
605                                    TDB_HASHTABLE_SIZE(tdb), 0) != 0) {
606                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_start: failed to read hash heads\n"));
607                 tdb->ecode = TDB_ERR_IO;
608                 goto fail;
609         }
610
611         /* make sure we know about any file expansions already done by
612            anyone else */
613         tdb->methods->tdb_oob(tdb, tdb->map_size + 1, 1);
614         tdb->transaction->old_map_size = tdb->map_size;
615
616         /* finally hook the io methods, replacing them with
617            transaction specific methods */
618         tdb->transaction->io_methods = tdb->methods;
619         tdb->methods = &transaction_methods;
620
621         /* Trace at the end, so we get sequence number correct. */
622         tdb_trace(tdb, "tdb_transaction_start");
623         return 0;
624         
625 fail:
626         tdb_brunlock(tdb, F_RDLCK, FREELIST_TOP, 0);
627         tdb_transaction_unlock(tdb, F_WRLCK);
628         SAFE_FREE(tdb->transaction->blocks);
629         SAFE_FREE(tdb->transaction->hash_heads);
630         SAFE_FREE(tdb->transaction);
631         return -1;
632 }
633
634
635 /*
636   cancel the current transaction
637 */
638 int tdb_transaction_cancel(struct tdb_context *tdb)
639 {
640         int ltype = F_RDLCK;
641         tdb_trace(tdb, "tdb_transaction_cancel");
642         if (tdb->transaction && tdb->transaction->prepared)
643                 ltype = F_WRLCK;
644         return _tdb_transaction_cancel(tdb, ltype);
645 }
646
647 /*
648   work out how much space the linearised recovery data will consume
649 */
650 static tdb_len_t tdb_recovery_size(struct tdb_context *tdb)
651 {
652         tdb_len_t recovery_size = 0;
653         int i;
654
655         recovery_size = sizeof(uint32_t);
656         for (i=0;i<tdb->transaction->num_blocks;i++) {
657                 if (i * tdb->transaction->block_size >= tdb->transaction->old_map_size) {
658                         break;
659                 }
660                 if (tdb->transaction->blocks[i] == NULL) {
661                         continue;
662                 }
663                 recovery_size += 2*sizeof(tdb_off_t);
664                 if (i == tdb->transaction->num_blocks-1) {
665                         recovery_size += tdb->transaction->last_block_size;
666                 } else {
667                         recovery_size += tdb->transaction->block_size;
668                 }
669         }       
670
671         return recovery_size;
672 }
673
674 /*
675   allocate the recovery area, or use an existing recovery area if it is
676   large enough
677 */
678 static int tdb_recovery_allocate(struct tdb_context *tdb, 
679                                  tdb_len_t *recovery_size,
680                                  tdb_off_t *recovery_offset,
681                                  tdb_len_t *recovery_max_size)
682 {
683         struct list_struct rec;
684         const struct tdb_methods *methods = tdb->transaction->io_methods;
685         tdb_off_t recovery_head;
686
687         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
688                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery head\n"));
689                 return -1;
690         }
691
692         rec.rec_len = 0;
693
694         if (recovery_head != 0 && 
695             methods->tdb_read(tdb, recovery_head, &rec, sizeof(rec), DOCONV()) == -1) {
696                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery record\n"));
697                 return -1;
698         }
699
700         *recovery_size = tdb_recovery_size(tdb);
701
702         if (recovery_head != 0 && *recovery_size <= rec.rec_len) {
703                 /* it fits in the existing area */
704                 *recovery_max_size = rec.rec_len;
705                 *recovery_offset = recovery_head;
706                 return 0;
707         }
708
709         /* we need to free up the old recovery area, then allocate a
710            new one at the end of the file. Note that we cannot use
711            tdb_allocate() to allocate the new one as that might return
712            us an area that is being currently used (as of the start of
713            the transaction) */
714         if (recovery_head != 0) {
715                 if (tdb_free(tdb, recovery_head, &rec) == -1) {
716                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to free previous recovery area\n"));
717                         return -1;
718                 }
719         }
720
721         /* the tdb_free() call might have increased the recovery size */
722         *recovery_size = tdb_recovery_size(tdb);
723
724         /* round up to a multiple of page size */
725         *recovery_max_size = TDB_ALIGN(sizeof(rec) + *recovery_size, tdb->page_size) - sizeof(rec);
726         *recovery_offset = tdb->map_size;
727         recovery_head = *recovery_offset;
728
729         if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size, 
730                                      (tdb->map_size - tdb->transaction->old_map_size) +
731                                      sizeof(rec) + *recovery_max_size) == -1) {
732                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to create recovery area\n"));
733                 return -1;
734         }
735
736         /* remap the file (if using mmap) */
737         methods->tdb_oob(tdb, tdb->map_size + 1, 1);
738
739         /* we have to reset the old map size so that we don't try to expand the file
740            again in the transaction commit, which would destroy the recovery area */
741         tdb->transaction->old_map_size = tdb->map_size;
742
743         /* write the recovery header offset and sync - we can sync without a race here
744            as the magic ptr in the recovery record has not been set */
745         CONVERT(recovery_head);
746         if (methods->tdb_write(tdb, TDB_RECOVERY_HEAD, 
747                                &recovery_head, sizeof(tdb_off_t)) == -1) {
748                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
749                 return -1;
750         }
751         if (transaction_write_existing(tdb, TDB_RECOVERY_HEAD, &recovery_head, sizeof(tdb_off_t)) == -1) {
752                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
753                 return -1;
754         }
755
756         return 0;
757 }
758
759
760 /*
761   setup the recovery data that will be used on a crash during commit
762 */
763 static int transaction_setup_recovery(struct tdb_context *tdb, 
764                                       tdb_off_t *magic_offset)
765 {
766         tdb_len_t recovery_size;
767         unsigned char *data, *p;
768         const struct tdb_methods *methods = tdb->transaction->io_methods;
769         struct list_struct *rec;
770         tdb_off_t recovery_offset, recovery_max_size;
771         tdb_off_t old_map_size = tdb->transaction->old_map_size;
772         uint32_t magic, tailer;
773         int i;
774
775         /*
776           check that the recovery area has enough space
777         */
778         if (tdb_recovery_allocate(tdb, &recovery_size, 
779                                   &recovery_offset, &recovery_max_size) == -1) {
780                 return -1;
781         }
782
783         data = (unsigned char *)malloc(recovery_size + sizeof(*rec));
784         if (data == NULL) {
785                 tdb->ecode = TDB_ERR_OOM;
786                 return -1;
787         }
788
789         rec = (struct list_struct *)data;
790         memset(rec, 0, sizeof(*rec));
791
792         rec->magic    = 0;
793         rec->data_len = recovery_size;
794         rec->rec_len  = recovery_max_size;
795         rec->key_len  = old_map_size;
796         CONVERT(rec);
797
798         /* build the recovery data into a single blob to allow us to do a single
799            large write, which should be more efficient */
800         p = data + sizeof(*rec);
801         for (i=0;i<tdb->transaction->num_blocks;i++) {
802                 tdb_off_t offset;
803                 tdb_len_t length;
804
805                 if (tdb->transaction->blocks[i] == NULL) {
806                         continue;
807                 }
808
809                 offset = i * tdb->transaction->block_size;
810                 length = tdb->transaction->block_size;
811                 if (i == tdb->transaction->num_blocks-1) {
812                         length = tdb->transaction->last_block_size;
813                 }
814                 
815                 if (offset >= old_map_size) {
816                         continue;
817                 }
818                 if (offset + length > tdb->transaction->old_map_size) {
819                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: transaction data over new region boundary\n"));
820                         free(data);
821                         tdb->ecode = TDB_ERR_CORRUPT;
822                         return -1;
823                 }
824                 memcpy(p, &offset, 4);
825                 memcpy(p+4, &length, 4);
826                 if (DOCONV()) {
827                         tdb_convert(p, 8);
828                 }
829                 /* the recovery area contains the old data, not the
830                    new data, so we have to call the original tdb_read
831                    method to get it */
832                 if (methods->tdb_read(tdb, offset, p + 8, length, 0) != 0) {
833                         free(data);
834                         tdb->ecode = TDB_ERR_IO;
835                         return -1;
836                 }
837                 p += 8 + length;
838         }
839
840         /* and the tailer */
841         tailer = sizeof(*rec) + recovery_max_size;
842         memcpy(p, &tailer, 4);
843         CONVERT(p);
844
845         /* write the recovery data to the recovery area */
846         if (methods->tdb_write(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
847                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery data\n"));
848                 free(data);
849                 tdb->ecode = TDB_ERR_IO;
850                 return -1;
851         }
852         if (transaction_write_existing(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
853                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery data\n"));
854                 free(data);
855                 tdb->ecode = TDB_ERR_IO;
856                 return -1;
857         }
858
859         /* as we don't have ordered writes, we have to sync the recovery
860            data before we update the magic to indicate that the recovery
861            data is present */
862         if (transaction_sync(tdb, recovery_offset, sizeof(*rec) + recovery_size) == -1) {
863                 free(data);
864                 return -1;
865         }
866
867         free(data);
868
869         magic = TDB_RECOVERY_MAGIC;
870         CONVERT(magic);
871
872         *magic_offset = recovery_offset + offsetof(struct list_struct, magic);
873
874         if (methods->tdb_write(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
875                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery magic\n"));
876                 tdb->ecode = TDB_ERR_IO;
877                 return -1;
878         }
879         if (transaction_write_existing(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
880                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery magic\n"));
881                 tdb->ecode = TDB_ERR_IO;
882                 return -1;
883         }
884
885         /* ensure the recovery magic marker is on disk */
886         if (transaction_sync(tdb, *magic_offset, sizeof(magic)) == -1) {
887                 return -1;
888         }
889
890         return 0;
891 }
892
893 static int _tdb_transaction_prepare_commit(struct tdb_context *tdb)
894 {       
895         const struct tdb_methods *methods;
896
897         if (tdb->transaction == NULL) {
898                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: no transaction\n"));
899                 return -1;
900         }
901
902         if (tdb->transaction->prepared) {
903                 tdb->ecode = TDB_ERR_EINVAL;
904                 _tdb_transaction_cancel(tdb, F_WRLCK);
905                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction already prepared\n"));
906                 return -1;
907         }
908
909         if (tdb->transaction->transaction_error) {
910                 tdb->ecode = TDB_ERR_IO;
911                 _tdb_transaction_cancel(tdb, F_RDLCK);
912                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction error pending\n"));
913                 return -1;
914         }
915
916
917         if (tdb->transaction->nesting != 0) {
918                 tdb->transaction->nesting--;
919                 return 0;
920         }               
921
922         /* check for a null transaction */
923         if (tdb->transaction->blocks == NULL) {
924                 return 0;
925         }
926
927         methods = tdb->transaction->io_methods;
928         
929         /* if there are any locks pending then the caller has not
930            nested their locks properly, so fail the transaction */
931         if (tdb->num_locks || tdb->global_lock.count) {
932                 tdb->ecode = TDB_ERR_LOCK;
933                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: locks pending on commit\n"));
934                 _tdb_transaction_cancel(tdb, F_RDLCK);
935                 return -1;
936         }
937
938         /* upgrade the main transaction lock region to a write lock */
939         if (tdb_brlock_upgrade(tdb, FREELIST_TOP, 0) == -1) {
940                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to upgrade hash locks\n"));
941                 tdb->ecode = TDB_ERR_LOCK;
942                 _tdb_transaction_cancel(tdb, F_RDLCK);
943                 return -1;
944         }
945
946         /* get the global lock - this prevents new users attaching to the database
947            during the commit */
948         if (tdb_brlock(tdb, F_WRLCK, GLOBAL_LOCK, 1, TDB_LOCK_WAIT) == -1) {
949                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to get global lock\n"));
950                 tdb->ecode = TDB_ERR_LOCK;
951                 _tdb_transaction_cancel(tdb, F_WRLCK);
952                 return -1;
953         }
954
955         if (!(tdb->flags & TDB_NOSYNC)) {
956                 /* write the recovery data to the end of the file */
957                 if (transaction_setup_recovery(tdb, &tdb->transaction->magic_offset) == -1) {
958                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: failed to setup recovery data\n"));
959                         tdb_brunlock(tdb, F_WRLCK, GLOBAL_LOCK, 1);
960                         _tdb_transaction_cancel(tdb, F_WRLCK);
961                         return -1;
962                 }
963         }
964
965         tdb->transaction->prepared = true;
966
967         /* expand the file to the new size if needed */
968         if (tdb->map_size != tdb->transaction->old_map_size) {
969                 if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size, 
970                                              tdb->map_size - 
971                                              tdb->transaction->old_map_size) == -1) {
972                         tdb->ecode = TDB_ERR_IO;
973                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: expansion failed\n"));
974                         tdb_brunlock(tdb, F_WRLCK, GLOBAL_LOCK, 1);
975                         _tdb_transaction_cancel(tdb, F_WRLCK);
976                         return -1;
977                 }
978                 tdb->map_size = tdb->transaction->old_map_size;
979                 methods->tdb_oob(tdb, tdb->map_size + 1, 1);
980         }
981
982         /* Keep the global lock until the actual commit */
983
984         return 0;
985 }
986
987 /*
988    prepare to commit the current transaction
989 */
990 int tdb_transaction_prepare_commit(struct tdb_context *tdb)
991 {       
992         tdb_trace(tdb, "tdb_transaction_prepare_commit");
993         return _tdb_transaction_prepare_commit(tdb);
994 }
995
996 /*
997   commit the current transaction
998 */
999 int tdb_transaction_commit(struct tdb_context *tdb)
1000 {       
1001         const struct tdb_methods *methods;
1002         int i;
1003         bool need_repack;
1004
1005         if (tdb->transaction == NULL) {
1006                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: no transaction\n"));
1007                 return -1;
1008         }
1009
1010         tdb_trace(tdb, "tdb_transaction_commit");
1011
1012         if (tdb->transaction->transaction_error) {
1013                 tdb->ecode = TDB_ERR_IO;
1014                 tdb_transaction_cancel(tdb);
1015                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: transaction error pending\n"));
1016                 return -1;
1017         }
1018
1019
1020         if (tdb->transaction->nesting != 0) {
1021                 tdb->transaction->nesting--;
1022                 return 0;
1023         }
1024
1025         /* check for a null transaction */
1026         if (tdb->transaction->blocks == NULL) {
1027                 _tdb_transaction_cancel(tdb, F_RDLCK);
1028                 return 0;
1029         }
1030
1031         if (!tdb->transaction->prepared) {
1032                 int ret = _tdb_transaction_prepare_commit(tdb);
1033                 if (ret)
1034                         return ret;
1035         }
1036
1037         methods = tdb->transaction->io_methods;
1038
1039         /* perform all the writes */
1040         for (i=0;i<tdb->transaction->num_blocks;i++) {
1041                 tdb_off_t offset;
1042                 tdb_len_t length;
1043
1044                 if (tdb->transaction->blocks[i] == NULL) {
1045                         continue;
1046                 }
1047
1048                 offset = i * tdb->transaction->block_size;
1049                 length = tdb->transaction->block_size;
1050                 if (i == tdb->transaction->num_blocks-1) {
1051                         length = tdb->transaction->last_block_size;
1052                 }
1053
1054                 if (methods->tdb_write(tdb, offset, tdb->transaction->blocks[i], length) == -1) {
1055                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed during commit\n"));
1056                         
1057                         /* we've overwritten part of the data and
1058                            possibly expanded the file, so we need to
1059                            run the crash recovery code */
1060                         tdb->methods = methods;
1061                         tdb_transaction_recover(tdb); 
1062
1063                         _tdb_transaction_cancel(tdb, F_WRLCK);
1064                         tdb_brunlock(tdb, F_WRLCK, GLOBAL_LOCK, 1);
1065
1066                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed\n"));
1067                         return -1;
1068                 }
1069                 SAFE_FREE(tdb->transaction->blocks[i]);
1070         } 
1071
1072         SAFE_FREE(tdb->transaction->blocks);
1073         tdb->transaction->num_blocks = 0;
1074
1075         /* ensure the new data is on disk */
1076         if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1077                 return -1;
1078         }
1079
1080         tdb_brunlock(tdb, F_WRLCK, GLOBAL_LOCK, 1);
1081
1082         /*
1083           TODO: maybe write to some dummy hdr field, or write to magic
1084           offset without mmap, before the last sync, instead of the
1085           utime() call
1086         */
1087
1088         /* on some systems (like Linux 2.6.x) changes via mmap/msync
1089            don't change the mtime of the file, this means the file may
1090            not be backed up (as tdb rounding to block sizes means that
1091            file size changes are quite rare too). The following forces
1092            mtime changes when a transaction completes */
1093 #if HAVE_UTIME
1094         utime(tdb->name, NULL);
1095 #endif
1096
1097         need_repack = tdb->transaction->need_repack;
1098
1099         /* use a transaction cancel to free memory and remove the
1100            transaction locks */
1101         _tdb_transaction_cancel(tdb, F_WRLCK);
1102
1103         if (need_repack) {
1104                 return tdb_repack(tdb);
1105         }
1106
1107         return 0;
1108 }
1109
1110
1111 /*
1112   recover from an aborted transaction. Must be called with exclusive
1113   database write access already established (including the global
1114   lock to prevent new processes attaching)
1115 */
1116 int tdb_transaction_recover(struct tdb_context *tdb)
1117 {
1118         tdb_off_t recovery_head, recovery_eof;
1119         unsigned char *data, *p;
1120         uint32_t zero = 0;
1121         struct list_struct rec;
1122
1123         /* find the recovery area */
1124         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
1125                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery head\n"));
1126                 tdb->ecode = TDB_ERR_IO;
1127                 return -1;
1128         }
1129
1130         if (recovery_head == 0) {
1131                 /* we have never allocated a recovery record */
1132                 return 0;
1133         }
1134
1135         /* read the recovery record */
1136         if (tdb->methods->tdb_read(tdb, recovery_head, &rec, 
1137                                    sizeof(rec), DOCONV()) == -1) {
1138                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery record\n"));           
1139                 tdb->ecode = TDB_ERR_IO;
1140                 return -1;
1141         }
1142
1143         if (rec.magic != TDB_RECOVERY_MAGIC) {
1144                 /* there is no valid recovery data */
1145                 return 0;
1146         }
1147
1148         if (tdb->read_only) {
1149                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: attempt to recover read only database\n"));
1150                 tdb->ecode = TDB_ERR_CORRUPT;
1151                 return -1;
1152         }
1153
1154         recovery_eof = rec.key_len;
1155
1156         data = (unsigned char *)malloc(rec.data_len);
1157         if (data == NULL) {
1158                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to allocate recovery data\n"));         
1159                 tdb->ecode = TDB_ERR_OOM;
1160                 return -1;
1161         }
1162
1163         /* read the full recovery data */
1164         if (tdb->methods->tdb_read(tdb, recovery_head + sizeof(rec), data,
1165                                    rec.data_len, 0) == -1) {
1166                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery data\n"));             
1167                 tdb->ecode = TDB_ERR_IO;
1168                 return -1;
1169         }
1170
1171         /* recover the file data */
1172         p = data;
1173         while (p+8 < data + rec.data_len) {
1174                 uint32_t ofs, len;
1175                 if (DOCONV()) {
1176                         tdb_convert(p, 8);
1177                 }
1178                 memcpy(&ofs, p, 4);
1179                 memcpy(&len, p+4, 4);
1180
1181                 if (tdb->methods->tdb_write(tdb, ofs, p+8, len) == -1) {
1182                         free(data);
1183                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to recover %d bytes at offset %d\n", len, ofs));
1184                         tdb->ecode = TDB_ERR_IO;
1185                         return -1;
1186                 }
1187                 p += 8 + len;
1188         }
1189
1190         free(data);
1191
1192         if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1193                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync recovery\n"));
1194                 tdb->ecode = TDB_ERR_IO;
1195                 return -1;
1196         }
1197
1198         /* if the recovery area is after the recovered eof then remove it */
1199         if (recovery_eof <= recovery_head) {
1200                 if (tdb_ofs_write(tdb, TDB_RECOVERY_HEAD, &zero) == -1) {
1201                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery head\n"));
1202                         tdb->ecode = TDB_ERR_IO;
1203                         return -1;                      
1204                 }
1205         }
1206
1207         /* remove the recovery magic */
1208         if (tdb_ofs_write(tdb, recovery_head + offsetof(struct list_struct, magic), 
1209                           &zero) == -1) {
1210                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery magic\n"));
1211                 tdb->ecode = TDB_ERR_IO;
1212                 return -1;                      
1213         }
1214         
1215         /* reduce the file size to the old size */
1216         tdb_munmap(tdb);
1217         if (ftruncate(tdb->fd, recovery_eof) != 0) {
1218                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to reduce to recovery size\n"));
1219                 tdb->ecode = TDB_ERR_IO;
1220                 return -1;                      
1221         }
1222         tdb->map_size = recovery_eof;
1223         tdb_mmap(tdb);
1224
1225         if (transaction_sync(tdb, 0, recovery_eof) == -1) {
1226                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync2 recovery\n"));
1227                 tdb->ecode = TDB_ERR_IO;
1228                 return -1;
1229         }
1230
1231         TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_recover: recovered %d byte database\n", 
1232                  recovery_eof));
1233
1234         /* all done */
1235         return 0;
1236 }