65e9dc25a6b743c1d5a50a75134d144104837011
[ccan] / ccan / tdb2 / lock.c
1  /* 
2    Unix SMB/CIFS implementation.
3
4    trivial database library
5
6    Copyright (C) Andrew Tridgell              1999-2005
7    Copyright (C) Paul `Rusty' Russell              2000
8    Copyright (C) Jeremy Allison                    2000-2003
9
10      ** NOTE! The following LGPL license applies to the tdb
11      ** library. This does NOT imply that all of Samba is released
12      ** under the LGPL
13
14    This library is free software; you can redistribute it and/or
15    modify it under the terms of the GNU Lesser General Public
16    License as published by the Free Software Foundation; either
17    version 3 of the License, or (at your option) any later version.
18
19    This library is distributed in the hope that it will be useful,
20    but WITHOUT ANY WARRANTY; without even the implied warranty of
21    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
22    Lesser General Public License for more details.
23
24    You should have received a copy of the GNU Lesser General Public
25    License along with this library; if not, see <http://www.gnu.org/licenses/>.
26 */
27
28 #include "private.h"
29 #include <assert.h>
30 #include <ccan/build_assert/build_assert.h>
31
32 static int fcntl_lock(struct tdb_context *tdb,
33                       int rw, off_t off, off_t len, bool waitflag)
34 {
35         struct flock fl;
36
37         fl.l_type = rw;
38         fl.l_whence = SEEK_SET;
39         fl.l_start = off;
40         fl.l_len = len;
41         fl.l_pid = 0;
42
43         add_stat(tdb, lock_lowlevel, 1);
44         if (waitflag)
45                 return fcntl(tdb->fd, F_SETLKW, &fl);
46         else {
47                 add_stat(tdb, lock_nonblock, 1);
48                 return fcntl(tdb->fd, F_SETLK, &fl);
49         }
50 }
51
52 static int fcntl_unlock(struct tdb_context *tdb, int rw, off_t off, off_t len)
53 {
54         struct flock fl;
55 #if 0 /* Check they matched up locks and unlocks correctly. */
56         char line[80];
57         FILE *locks;
58         bool found = false;
59
60         locks = fopen("/proc/locks", "r");
61
62         while (fgets(line, 80, locks)) {
63                 char *p;
64                 int type, start, l;
65
66                 /* eg. 1: FLOCK  ADVISORY  WRITE 2440 08:01:2180826 0 EOF */
67                 p = strchr(line, ':') + 1;
68                 if (strncmp(p, " POSIX  ADVISORY  ", strlen(" POSIX  ADVISORY  ")))
69                         continue;
70                 p += strlen(" FLOCK  ADVISORY  ");
71                 if (strncmp(p, "READ  ", strlen("READ  ")) == 0)
72                         type = F_RDLCK;
73                 else if (strncmp(p, "WRITE ", strlen("WRITE ")) == 0)
74                         type = F_WRLCK;
75                 else
76                         abort();
77                 p += 6;
78                 if (atoi(p) != getpid())
79                         continue;
80                 p = strchr(strchr(p, ' ') + 1, ' ') + 1;
81                 start = atoi(p);
82                 p = strchr(p, ' ') + 1;
83                 if (strncmp(p, "EOF", 3) == 0)
84                         l = 0;
85                 else
86                         l = atoi(p) - start + 1;
87
88                 if (off == start) {
89                         if (len != l) {
90                                 fprintf(stderr, "Len %u should be %u: %s",
91                                         (int)len, l, line);
92                                 abort();
93                         }
94                         if (type != rw) {
95                                 fprintf(stderr, "Type %s wrong: %s",
96                                         rw == F_RDLCK ? "READ" : "WRITE", line);
97                                 abort();
98                         }
99                         found = true;
100                         break;
101                 }
102         }
103
104         if (!found) {
105                 fprintf(stderr, "Unlock on %u@%u not found!\n",
106                         (int)off, (int)len);
107                 abort();
108         }
109
110         fclose(locks);
111 #endif
112
113         fl.l_type = F_UNLCK;
114         fl.l_whence = SEEK_SET;
115         fl.l_start = off;
116         fl.l_len = len;
117         fl.l_pid = 0;
118
119         return fcntl(tdb->fd, F_SETLKW, &fl);
120 }
121
122 /* a byte range locking function - return 0 on success
123    this functions locks/unlocks 1 byte at the specified offset.
124
125    note that a len of zero means lock to end of file
126 */
127 static int tdb_brlock(struct tdb_context *tdb,
128                       int rw_type, tdb_off_t offset, tdb_off_t len,
129                       enum tdb_lock_flags flags)
130 {
131         int ret;
132
133         if (tdb->flags & TDB_NOLOCK) {
134                 return 0;
135         }
136
137         if (rw_type == F_WRLCK && tdb->read_only) {
138                 tdb->ecode = TDB_ERR_RDONLY;
139                 return -1;
140         }
141
142         /* A 32 bit system cannot open a 64-bit file, but it could have
143          * expanded since then: check here. */
144         if ((size_t)(offset + len) != offset + len) {
145                 tdb->ecode = TDB_ERR_IO;
146                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
147                          "tdb_brlock: lock on giant offset %llu\n",
148                          (long long)(offset + len));
149                 return -1;
150         }
151
152         do {
153                 ret = fcntl_lock(tdb, rw_type, offset, len,
154                                  flags & TDB_LOCK_WAIT);
155         } while (ret == -1 && errno == EINTR);
156
157         if (ret == -1) {
158                 tdb->ecode = TDB_ERR_LOCK;
159                 /* Generic lock error. errno set by fcntl.
160                  * EAGAIN is an expected return from non-blocking
161                  * locks. */
162                 if (!(flags & TDB_LOCK_PROBE) && errno != EAGAIN) {
163                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
164                                  "tdb_brlock failed (fd=%d) at"
165                                  " offset %llu rw_type=%d flags=%d len=%llu\n",
166                                  tdb->fd, (long long)offset, rw_type,
167                                  flags, (long long)len);
168                 }
169                 return -1;
170         }
171         return 0;
172 }
173
174 static int tdb_brunlock(struct tdb_context *tdb,
175                         int rw_type, tdb_off_t offset, size_t len)
176 {
177         int ret;
178
179         if (tdb->flags & TDB_NOLOCK) {
180                 return 0;
181         }
182
183         do {
184                 ret = fcntl_unlock(tdb, rw_type, offset, len);
185         } while (ret == -1 && errno == EINTR);
186
187         if (ret == -1) {
188                 tdb->log(tdb, TDB_DEBUG_TRACE, tdb->log_priv,
189                          "tdb_brunlock failed (fd=%d) at offset %llu"
190                          " rw_type=%d len=%llu\n",
191                          tdb->fd, (long long)offset, rw_type, (long long)len);
192         }
193         return ret;
194 }
195
196 /*
197   upgrade a read lock to a write lock. This needs to be handled in a
198   special way as some OSes (such as solaris) have too conservative
199   deadlock detection and claim a deadlock when progress can be
200   made. For those OSes we may loop for a while.  
201 */
202 int tdb_allrecord_upgrade(struct tdb_context *tdb)
203 {
204         int count = 1000;
205
206         if (tdb->allrecord_lock.count != 1) {
207                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
208                          "tdb_allrecord_upgrade failed: count %u too high\n",
209                          tdb->allrecord_lock.count);
210                 return -1;
211         }
212
213         if (tdb->allrecord_lock.off != 1) {
214                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
215                          "tdb_allrecord_upgrade failed: already upgraded?\n");
216                 return -1;
217         }
218
219         while (count--) {
220                 struct timeval tv;
221                 if (tdb_brlock(tdb, F_WRLCK,
222                                TDB_HASH_LOCK_START, 0,
223                                TDB_LOCK_WAIT|TDB_LOCK_PROBE) == 0) {
224                         tdb->allrecord_lock.ltype = F_WRLCK;
225                         tdb->allrecord_lock.off = 0;
226                         return 0;
227                 }
228                 if (errno != EDEADLK) {
229                         break;
230                 }
231                 /* sleep for as short a time as we can - more portable than usleep() */
232                 tv.tv_sec = 0;
233                 tv.tv_usec = 1;
234                 select(0, NULL, NULL, NULL, &tv);
235         }
236         tdb->log(tdb, TDB_DEBUG_WARNING, tdb->log_priv,
237                  "tdb_allrecord_upgrade failed\n");
238         return -1;
239 }
240
241 static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,
242                                            tdb_off_t offset)
243 {
244         unsigned int i;
245
246         for (i=0; i<tdb->num_lockrecs; i++) {
247                 if (tdb->lockrecs[i].off == offset) {
248                         return &tdb->lockrecs[i];
249                 }
250         }
251         return NULL;
252 }
253
254 int tdb_lock_and_recover(struct tdb_context *tdb)
255 {
256         int ret;
257
258         if (tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK,
259                                false) == -1) {
260                 return -1;
261         }
262
263         if (tdb_lock_open(tdb, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK) == -1) {
264                 tdb_allrecord_unlock(tdb, F_WRLCK);
265                 return -1;
266         }
267         ret = tdb_transaction_recover(tdb);
268
269         tdb_unlock_open(tdb);
270         tdb_allrecord_unlock(tdb, F_WRLCK);
271
272         return ret;
273 }
274
275 /* lock an offset in the database. */
276 static int tdb_nest_lock(struct tdb_context *tdb, tdb_off_t offset, int ltype,
277                          enum tdb_lock_flags flags)
278 {
279         struct tdb_lock_type *new_lck;
280
281         if (offset > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE + tdb->map_size / 8) {
282                 tdb->ecode = TDB_ERR_LOCK;
283                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
284                          "tdb_nest_lock: invalid offset %llu ltype=%d\n",
285                          (long long)offset, ltype);
286                 return -1;
287         }
288
289         if (tdb->flags & TDB_NOLOCK)
290                 return 0;
291
292         add_stat(tdb, locks, 1);
293
294         new_lck = find_nestlock(tdb, offset);
295         if (new_lck) {
296                 if (new_lck->ltype == F_RDLCK && ltype == F_WRLCK) {
297                         tdb->ecode = TDB_ERR_LOCK;
298                         tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
299                                  "tdb_nest_lock: offset %llu has read lock\n",
300                                  (long long)offset);
301                         return -1;
302                 }
303                 /* Just increment the struct, posix locks don't stack. */
304                 new_lck->count++;
305                 return 0;
306         }
307
308         if (tdb->num_lockrecs
309             && offset >= TDB_HASH_LOCK_START
310             && offset < TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE) {
311                 tdb->ecode = TDB_ERR_LOCK;
312                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
313                          "tdb_nest_lock: already have a hash lock?\n");
314                 return -1;
315         }
316
317         new_lck = (struct tdb_lock_type *)realloc(
318                 tdb->lockrecs,
319                 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
320         if (new_lck == NULL) {
321                 tdb->ecode = TDB_ERR_OOM;
322                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
323                          "tdb_nest_lock: unable to allocate %llu lock struct",
324                          (long long)(tdb->num_lockrecs + 1));
325                 errno = ENOMEM;
326                 return -1;
327         }
328         tdb->lockrecs = new_lck;
329
330         /* Since fcntl locks don't nest, we do a lock for the first one,
331            and simply bump the count for future ones */
332         if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
333                 return -1;
334         }
335
336         /* First time we grab a lock, perhaps someone died in commit? */
337         if (!(flags & TDB_LOCK_NOCHECK)
338             && tdb->num_lockrecs == 0
339             && unlikely(tdb_needs_recovery(tdb))) {
340                 tdb_brunlock(tdb, ltype, offset, 1);
341
342                 if (tdb_lock_and_recover(tdb) == -1) {
343                         return -1;
344                 }
345
346                 if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
347                         return -1;
348                 }
349         }
350
351         tdb->lockrecs[tdb->num_lockrecs].off = offset;
352         tdb->lockrecs[tdb->num_lockrecs].count = 1;
353         tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
354         tdb->num_lockrecs++;
355
356         return 0;
357 }
358
359 static int tdb_nest_unlock(struct tdb_context *tdb, tdb_off_t off, int ltype)
360 {
361         int ret = -1;
362         struct tdb_lock_type *lck;
363
364         if (tdb->flags & TDB_NOLOCK)
365                 return 0;
366
367         lck = find_nestlock(tdb, off);
368         if ((lck == NULL) || (lck->count == 0)) {
369                 tdb->ecode = TDB_ERR_LOCK;
370                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
371                          "tdb_nest_unlock: no lock for %llu\n", (long long)off);
372                 return -1;
373         }
374
375         if (lck->count > 1) {
376                 lck->count--;
377                 return 0;
378         }
379
380         /*
381          * This lock has count==1 left, so we need to unlock it in the
382          * kernel. We don't bother with decrementing the in-memory array
383          * element, we're about to overwrite it with the last array element
384          * anyway.
385          */
386         ret = tdb_brunlock(tdb, ltype, off, 1);
387
388         /*
389          * Shrink the array by overwriting the element just unlocked with the
390          * last array element.
391          */
392         *lck = tdb->lockrecs[--tdb->num_lockrecs];
393
394         return ret;
395 }
396
397 /*
398   get the transaction lock
399  */
400 int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
401 {
402         return tdb_nest_lock(tdb, TDB_TRANSACTION_LOCK, ltype, TDB_LOCK_WAIT);
403 }
404
405 /*
406   release the transaction lock
407  */
408 int tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
409 {
410         return tdb_nest_unlock(tdb, TDB_TRANSACTION_LOCK, ltype);
411 }
412
413 /* We only need to lock individual bytes, but Linux merges consecutive locks
414  * so we lock in contiguous ranges. */
415 static int tdb_lock_gradual(struct tdb_context *tdb,
416                             int ltype, enum tdb_lock_flags flags,
417                             tdb_off_t off, tdb_off_t len)
418 {
419         int ret;
420         enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);
421
422         if (len <= 1) {
423                 /* 0 would mean to end-of-file... */
424                 assert(len != 0);
425                 /* Single hash.  Just do blocking lock. */
426                 return tdb_brlock(tdb, ltype, off, len, flags);
427         }
428
429         /* First we try non-blocking. */
430         ret = tdb_brlock(tdb, ltype, off, len, nb_flags);
431         if (ret == 0) {
432                 return 0;
433         }
434
435         /* Try locking first half, then second. */
436         ret = tdb_lock_gradual(tdb, ltype, flags, off, len / 2);
437         if (ret == -1)
438                 return -1;
439
440         ret = tdb_lock_gradual(tdb, ltype, flags,
441                                     off + len / 2, len - len / 2);
442         if (ret == -1) {
443                 tdb_brunlock(tdb, ltype, off, len / 2);
444                 return -1;
445         }
446         return 0;
447 }
448
449 /* lock/unlock entire database.  It can only be upgradable if you have some
450  * other way of guaranteeing exclusivity (ie. transaction write lock). */
451 int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
452                        enum tdb_lock_flags flags, bool upgradable)
453 {
454         /* FIXME: There are no locks on read-only dbs */
455         if (tdb->read_only) {
456                 tdb->ecode = TDB_ERR_LOCK;
457                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
458                          "tdb_allrecord_lock: read-only\n");
459                 return -1;
460         }
461
462         if (tdb->allrecord_lock.count
463             && (ltype == F_RDLCK || tdb->allrecord_lock.ltype == F_WRLCK)) {
464                 tdb->allrecord_lock.count++;
465                 return 0;
466         }
467
468         if (tdb->allrecord_lock.count) {
469                 /* a global lock of a different type exists */
470                 tdb->ecode = TDB_ERR_LOCK;
471                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
472                          "tdb_allrecord_lock: already have %s lock\n",
473                          tdb->allrecord_lock.ltype == F_RDLCK
474                          ? "read" : "write");
475                 return -1;
476         }
477
478         if (tdb_has_hash_locks(tdb)) {
479                 /* can't combine global and chain locks */
480                 tdb->ecode = TDB_ERR_LOCK;
481                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
482                          "tdb_allrecord_lock: already have chain lock\n");
483                 return -1;
484         }
485
486         if (upgradable && ltype != F_RDLCK) {
487                 /* tdb error: you can't upgrade a write lock! */
488                 tdb->ecode = TDB_ERR_LOCK;
489                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
490                          "tdb_allrecord_lock: can't upgrade a write lock\n");
491                 return -1;
492         }
493
494         add_stat(tdb, locks, 1);
495 again:
496         /* Lock hashes, gradually. */
497         if (tdb_lock_gradual(tdb, ltype, flags, TDB_HASH_LOCK_START,
498                              TDB_HASH_LOCK_RANGE)) {
499                 if (!(flags & TDB_LOCK_PROBE)) {
500                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
501                                  "tdb_allrecord_lock hashes failed (%s)\n",
502                                  strerror(errno));
503                 }
504                 return -1;
505         }
506
507         /* Lock free lists: there to end of file. */
508         if (tdb_brlock(tdb, ltype, TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE,
509                        0, flags)) {
510                 if (!(flags & TDB_LOCK_PROBE)) {
511                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
512                                  "tdb_allrecord_lock freelist failed (%s)\n",
513                                  strerror(errno));
514                 }
515                 tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START, 
516                              TDB_HASH_LOCK_RANGE);
517                 return -1;
518         }
519
520         tdb->allrecord_lock.count = 1;
521         /* If it's upgradable, it's actually exclusive so we can treat
522          * it as a write lock. */
523         tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
524         tdb->allrecord_lock.off = upgradable;
525
526         /* Now check for needing recovery. */
527         if (!(flags & TDB_LOCK_NOCHECK) && unlikely(tdb_needs_recovery(tdb))) {
528                 tdb_allrecord_unlock(tdb, ltype);
529                 if (tdb_lock_and_recover(tdb) == -1) {
530                         return -1;
531                 }               
532                 goto again;
533         }
534
535         return 0;
536 }
537
538 int tdb_lock_open(struct tdb_context *tdb, enum tdb_lock_flags flags)
539 {
540         return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, flags);
541 }
542
543 void tdb_unlock_open(struct tdb_context *tdb)
544 {
545         tdb_nest_unlock(tdb, TDB_OPEN_LOCK, F_WRLCK);
546 }
547
548 bool tdb_has_open_lock(struct tdb_context *tdb)
549 {
550         return find_nestlock(tdb, TDB_OPEN_LOCK) != NULL;
551 }
552
553 int tdb_lock_expand(struct tdb_context *tdb, int ltype)
554 {
555         /* Lock doesn't protect data, so don't check (we recurse if we do!) */
556         return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype,
557                              TDB_LOCK_WAIT | TDB_LOCK_NOCHECK);
558 }
559
560 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
561 {
562         tdb_nest_unlock(tdb, TDB_EXPANSION_LOCK, ltype);
563 }
564
565 /* unlock entire db */
566 int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
567 {
568         /* FIXME: There are no locks on read-only dbs */
569         if (tdb->read_only) {
570                 tdb->ecode = TDB_ERR_LOCK;
571                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
572                          "tdb_allrecord_unlock: read-only\n");
573                 return -1;
574         }
575
576         if (tdb->allrecord_lock.count == 0) {
577                 tdb->ecode = TDB_ERR_LOCK;
578                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
579                          "tdb_allrecord_unlock: not locked!\n");
580                 return -1;
581         }
582
583         /* Upgradable locks are marked as write locks. */
584         if (tdb->allrecord_lock.ltype != ltype
585             && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) {
586                 tdb->ecode = TDB_ERR_LOCK;
587                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
588                          "tdb_allrecord_unlock: have %s lock\n",
589                          tdb->allrecord_lock.ltype == F_RDLCK
590                          ? "read" : "write");
591                 return -1;
592         }
593
594         if (tdb->allrecord_lock.count > 1) {
595                 tdb->allrecord_lock.count--;
596                 return 0;
597         }
598
599         tdb->allrecord_lock.count = 0;
600         tdb->allrecord_lock.ltype = 0;
601
602         return tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START, 0);
603 }
604
605 bool tdb_has_expansion_lock(struct tdb_context *tdb)
606 {
607         return find_nestlock(tdb, TDB_EXPANSION_LOCK) != NULL;
608 }
609
610 bool tdb_has_hash_locks(struct tdb_context *tdb)
611 {
612         unsigned int i;
613
614         for (i=0; i<tdb->num_lockrecs; i++) {
615                 if (tdb->lockrecs[i].off >= TDB_HASH_LOCK_START
616                     && tdb->lockrecs[i].off < (TDB_HASH_LOCK_START
617                                                + TDB_HASH_LOCK_RANGE))
618                         return true;
619         }
620         return false;
621 }
622
623 static bool tdb_has_free_lock(struct tdb_context *tdb)
624 {
625         unsigned int i;
626
627         for (i=0; i<tdb->num_lockrecs; i++) {
628                 if (tdb->lockrecs[i].off
629                     > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE)
630                         return true;
631         }
632         return false;
633 }
634
635 int tdb_lock_hashes(struct tdb_context *tdb,
636                     tdb_off_t hash_lock,
637                     tdb_len_t hash_range,
638                     int ltype, enum tdb_lock_flags waitflag)
639 {
640         /* FIXME: Do this properly, using hlock_range */
641         unsigned lock = TDB_HASH_LOCK_START
642                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
643
644         /* a allrecord lock allows us to avoid per chain locks */
645         if (tdb->allrecord_lock.count &&
646             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
647                 return 0;
648         }
649
650         if (tdb->allrecord_lock.count) {
651                 tdb->ecode = TDB_ERR_LOCK;
652                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
653                          "tdb_lock_hashes: have %s allrecordlock\n",
654                          tdb->allrecord_lock.ltype == F_RDLCK
655                          ? "read" : "write");
656                 return -1;
657         }
658
659         if (tdb_has_free_lock(tdb)) {
660                 tdb->ecode = TDB_ERR_LOCK;
661                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
662                          "tdb_lock_hashes: have free lock already\n");
663                 return -1;
664         }
665
666         if (tdb_has_expansion_lock(tdb)) {
667                 tdb->ecode = TDB_ERR_LOCK;
668                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
669                          "tdb_lock_hashes: have expansion lock already\n");
670                 return -1;
671         }
672
673         return tdb_nest_lock(tdb, lock, ltype, waitflag);
674 }
675
676 int tdb_unlock_hashes(struct tdb_context *tdb,
677                       tdb_off_t hash_lock,
678                       tdb_len_t hash_range, int ltype)
679 {
680         unsigned lock = TDB_HASH_LOCK_START
681                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
682
683         /* a allrecord lock allows us to avoid per chain locks */
684         if (tdb->allrecord_lock.count) {
685                 if (tdb->allrecord_lock.ltype == F_RDLCK
686                     && ltype == F_WRLCK) {
687                         tdb->ecode = TDB_ERR_LOCK;
688                         tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
689                                  "tdb_unlock_hashes RO allrecord!\n");
690                         return -1;
691                 }
692                 return 0;
693         }
694
695         return tdb_nest_unlock(tdb, lock, ltype);
696 }
697
698 /* Hash locks use TDB_HASH_LOCK_START + the next 30 bits.
699  * Then we begin; bucket offsets are sizeof(tdb_len_t) apart, so we divide.
700  * The result is that on 32 bit systems we don't use lock values > 2^31 on
701  * files that are less than 4GB.
702  */
703 static tdb_off_t free_lock_off(tdb_off_t b_off)
704 {
705         return TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
706                 + b_off / sizeof(tdb_off_t);
707 }
708
709 int tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
710                          enum tdb_lock_flags waitflag)
711 {
712         assert(b_off >= sizeof(struct tdb_header));
713
714         /* a allrecord lock allows us to avoid per chain locks */
715         if (tdb->allrecord_lock.count) {
716                 if (tdb->allrecord_lock.ltype == F_WRLCK)
717                         return 0;
718                 tdb->ecode = TDB_ERR_LOCK;
719                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
720                          "tdb_lock_free_bucket with RO allrecordlock!\n");
721                 return -1;
722         }
723
724 #if 0 /* FIXME */
725         if (tdb_has_expansion_lock(tdb)) {
726                 tdb->ecode = TDB_ERR_LOCK;
727                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
728                          "tdb_lock_free_bucket: have expansion lock already\n");
729                 return -1;
730         }
731 #endif
732
733         return tdb_nest_lock(tdb, free_lock_off(b_off), F_WRLCK, waitflag);
734 }
735
736 void tdb_unlock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off)
737 {
738         if (tdb->allrecord_lock.count)
739                 return;
740
741         tdb_nest_unlock(tdb, free_lock_off(b_off), F_WRLCK);
742 }
743
744 void tdb_lock_init(struct tdb_context *tdb)
745 {
746         tdb->num_lockrecs = 0;
747         tdb->lockrecs = NULL;
748         tdb->allrecord_lock.count = 0;
749 }