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