3e939c4b8ffe3c04e57a2bf67bdfbec51b3ddf90
[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!",
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 enum TDB_ERROR 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 TDB_SUCCESS;
135         }
136
137         if (rw_type == F_WRLCK && tdb->read_only) {
138                 return tdb_logerr(tdb, TDB_ERR_RDONLY, TDB_LOG_USE_ERROR,
139                                   "Write lock attempted on read-only database");
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                 return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
146                                   "tdb_brlock: lock on giant offset %llu",
147                                   (long long)(offset + len));
148         }
149
150         do {
151                 ret = fcntl_lock(tdb, rw_type, offset, len,
152                                  flags & TDB_LOCK_WAIT);
153         } while (ret == -1 && errno == EINTR);
154
155         if (ret == -1) {
156                 /* Generic lock error. errno set by fcntl.
157                  * EAGAIN is an expected return from non-blocking
158                  * locks. */
159                 if (!(flags & TDB_LOCK_PROBE) && errno != EAGAIN) {
160                         tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
161                                    "tdb_brlock failed (fd=%d) at"
162                                    " offset %zu rw_type=%d flags=%d len=%zu:"
163                                    " %s",
164                                    tdb->fd, (size_t)offset, rw_type,
165                                    flags, (size_t)len, strerror(errno));
166                 }
167                 return TDB_ERR_LOCK;
168         }
169         return TDB_SUCCESS;
170 }
171
172 static enum TDB_ERROR tdb_brunlock(struct tdb_context *tdb,
173                                    int rw_type, tdb_off_t offset, size_t len)
174 {
175         int ret;
176
177         if (tdb->flags & TDB_NOLOCK) {
178                 return TDB_SUCCESS;
179         }
180
181         do {
182                 ret = fcntl_unlock(tdb, rw_type, offset, len);
183         } while (ret == -1 && errno == EINTR);
184
185         if (ret == -1) {
186                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
187                                   "tdb_brunlock failed (fd=%d) at offset %zu"
188                                   " rw_type=%d len=%zu",
189                                   tdb->fd, (size_t)offset, rw_type,
190                                   (size_t)len);
191         }
192         return TDB_SUCCESS;
193 }
194
195 /*
196   upgrade a read lock to a write lock. This needs to be handled in a
197   special way as some OSes (such as solaris) have too conservative
198   deadlock detection and claim a deadlock when progress can be
199   made. For those OSes we may loop for a while.
200 */
201 enum TDB_ERROR tdb_allrecord_upgrade(struct tdb_context *tdb)
202 {
203         int count = 1000;
204
205         if (tdb->allrecord_lock.count != 1) {
206                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
207                                   "tdb_allrecord_upgrade failed:"
208                                   " count %u too high",
209                                   tdb->allrecord_lock.count);
210         }
211
212         if (tdb->allrecord_lock.off != 1) {
213                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
214                                   "tdb_allrecord_upgrade failed:"
215                                   " already upgraded?");
216         }
217
218         while (count--) {
219                 struct timeval tv;
220                 if (tdb_brlock(tdb, F_WRLCK,
221                                TDB_HASH_LOCK_START, 0,
222                                TDB_LOCK_WAIT|TDB_LOCK_PROBE) == TDB_SUCCESS) {
223                         tdb->allrecord_lock.ltype = F_WRLCK;
224                         tdb->allrecord_lock.off = 0;
225                         return TDB_SUCCESS;
226                 }
227                 if (errno != EDEADLK) {
228                         break;
229                 }
230                 /* sleep for as short a time as we can - more portable than usleep() */
231                 tv.tv_sec = 0;
232                 tv.tv_usec = 1;
233                 select(0, NULL, NULL, NULL, &tv);
234         }
235         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
236                           "tdb_allrecord_upgrade failed");
237 }
238
239 static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,
240                                            tdb_off_t offset)
241 {
242         unsigned int i;
243
244         for (i=0; i<tdb->num_lockrecs; i++) {
245                 if (tdb->lockrecs[i].off == offset) {
246                         return &tdb->lockrecs[i];
247                 }
248         }
249         return NULL;
250 }
251
252 enum TDB_ERROR tdb_lock_and_recover(struct tdb_context *tdb)
253 {
254         enum TDB_ERROR ecode;
255
256         ecode = tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK,
257                                    false);
258         if (ecode != TDB_SUCCESS) {
259                 return ecode;
260         }
261
262         ecode = tdb_lock_open(tdb, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK);
263         if (ecode != TDB_SUCCESS) {
264                 tdb_allrecord_unlock(tdb, F_WRLCK);
265                 return ecode;
266         }
267         if (tdb_transaction_recover(tdb) == -1) {
268                 ecode = tdb->ecode;
269         }
270
271         tdb_unlock_open(tdb);
272         tdb_allrecord_unlock(tdb, F_WRLCK);
273
274         return ecode;
275 }
276
277 /* lock an offset in the database. */
278 static enum TDB_ERROR tdb_nest_lock(struct tdb_context *tdb,
279                                     tdb_off_t offset, int ltype,
280                                     enum tdb_lock_flags flags)
281 {
282         struct tdb_lock_type *new_lck;
283         enum TDB_ERROR ecode;
284
285         if (offset > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE + tdb->map_size / 8) {
286                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
287                                   "tdb_nest_lock: invalid offset %zu ltype=%d",
288                                   (size_t)offset, ltype);
289         }
290
291         if (tdb->flags & TDB_NOLOCK)
292                 return TDB_SUCCESS;
293
294         add_stat(tdb, locks, 1);
295
296         new_lck = find_nestlock(tdb, offset);
297         if (new_lck) {
298                 if (new_lck->ltype == F_RDLCK && ltype == F_WRLCK) {
299                         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
300                                           "tdb_nest_lock:"
301                                           " offset %zu has read lock",
302                                           (size_t)offset);
303                 }
304                 /* Just increment the struct, posix locks don't stack. */
305                 new_lck->count++;
306                 return TDB_SUCCESS;
307         }
308
309         if (tdb->num_lockrecs
310             && offset >= TDB_HASH_LOCK_START
311             && offset < TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE) {
312                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
313                                   "tdb_nest_lock: already have a hash lock?");
314         }
315
316         new_lck = (struct tdb_lock_type *)realloc(
317                 tdb->lockrecs,
318                 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
319         if (new_lck == NULL) {
320                 return tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
321                                   "tdb_nest_lock:"
322                                   " unable to allocate %zu lock struct",
323                                   tdb->num_lockrecs + 1);
324         }
325         tdb->lockrecs = new_lck;
326
327         /* Since fcntl locks don't nest, we do a lock for the first one,
328            and simply bump the count for future ones */
329         ecode = tdb_brlock(tdb, ltype, offset, 1, flags);
330         if (ecode != TDB_SUCCESS) {
331                 return ecode;
332         }
333
334         /* First time we grab a lock, perhaps someone died in commit? */
335         if (!(flags & TDB_LOCK_NOCHECK)
336             && tdb->num_lockrecs == 0
337             && unlikely(tdb_needs_recovery(tdb))) {
338                 tdb_brunlock(tdb, ltype, offset, 1);
339
340                 ecode = tdb_lock_and_recover(tdb);
341                 if (ecode == TDB_SUCCESS) {
342                         ecode = tdb_brlock(tdb, ltype, offset, 1, flags);
343                 }
344                 if (ecode != TDB_SUCCESS) {
345                         return ecode;
346                 }
347         }
348
349         tdb->lockrecs[tdb->num_lockrecs].off = offset;
350         tdb->lockrecs[tdb->num_lockrecs].count = 1;
351         tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
352         tdb->num_lockrecs++;
353
354         return TDB_SUCCESS;
355 }
356
357 static enum TDB_ERROR tdb_nest_unlock(struct tdb_context *tdb,
358                                       tdb_off_t off, int ltype)
359 {
360         struct tdb_lock_type *lck;
361         enum TDB_ERROR ecode;
362
363         if (tdb->flags & TDB_NOLOCK)
364                 return TDB_SUCCESS;
365
366         lck = find_nestlock(tdb, off);
367         if ((lck == NULL) || (lck->count == 0)) {
368                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
369                                   "tdb_nest_unlock: no lock for %zu",
370                                   (size_t)off);
371         }
372
373         if (lck->count > 1) {
374                 lck->count--;
375                 return TDB_SUCCESS;
376         }
377
378         /*
379          * This lock has count==1 left, so we need to unlock it in the
380          * kernel. We don't bother with decrementing the in-memory array
381          * element, we're about to overwrite it with the last array element
382          * anyway.
383          */
384         ecode = tdb_brunlock(tdb, ltype, off, 1);
385
386         /*
387          * Shrink the array by overwriting the element just unlocked with the
388          * last array element.
389          */
390         *lck = tdb->lockrecs[--tdb->num_lockrecs];
391
392         return ecode;
393 }
394
395 /*
396   get the transaction lock
397  */
398 enum TDB_ERROR tdb_transaction_lock(struct tdb_context *tdb, int ltype)
399 {
400         return tdb_nest_lock(tdb, TDB_TRANSACTION_LOCK, ltype, TDB_LOCK_WAIT);
401 }
402
403 /*
404   release the transaction lock
405  */
406 void tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
407 {
408         tdb_nest_unlock(tdb, TDB_TRANSACTION_LOCK, ltype);
409 }
410
411 /* We only need to lock individual bytes, but Linux merges consecutive locks
412  * so we lock in contiguous ranges. */
413 static enum TDB_ERROR tdb_lock_gradual(struct tdb_context *tdb,
414                                        int ltype, enum tdb_lock_flags flags,
415                                        tdb_off_t off, tdb_off_t len)
416 {
417         enum TDB_ERROR ecode;
418         enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);
419
420         if (len <= 1) {
421                 /* 0 would mean to end-of-file... */
422                 assert(len != 0);
423                 /* Single hash.  Just do blocking lock. */
424                 return tdb_brlock(tdb, ltype, off, len, flags);
425         }
426
427         /* First we try non-blocking. */
428         if (tdb_brlock(tdb, ltype, off, len, nb_flags) == TDB_SUCCESS) {
429                 return TDB_SUCCESS;
430         }
431
432         /* Try locking first half, then second. */
433         ecode = tdb_lock_gradual(tdb, ltype, flags, off, len / 2);
434         if (ecode != TDB_SUCCESS)
435                 return ecode;
436
437         ecode = tdb_lock_gradual(tdb, ltype, flags,
438                                  off + len / 2, len - len / 2);
439         if (ecode != TDB_SUCCESS) {
440                 tdb_brunlock(tdb, ltype, off, len / 2);
441         }
442         return ecode;
443 }
444
445 /* lock/unlock entire database.  It can only be upgradable if you have some
446  * other way of guaranteeing exclusivity (ie. transaction write lock). */
447 enum TDB_ERROR tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
448                                   enum tdb_lock_flags flags, bool upgradable)
449 {
450         enum TDB_ERROR ecode;
451
452         /* FIXME: There are no locks on read-only dbs */
453         if (tdb->read_only) {
454                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
455                                   "tdb_allrecord_lock: read-only");
456         }
457
458         if (tdb->allrecord_lock.count
459             && (ltype == F_RDLCK || tdb->allrecord_lock.ltype == F_WRLCK)) {
460                 tdb->allrecord_lock.count++;
461                 return TDB_SUCCESS;
462         }
463
464         if (tdb->allrecord_lock.count) {
465                 /* a global lock of a different type exists */
466                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
467                                   "tdb_allrecord_lock: already have %s lock",
468                                   tdb->allrecord_lock.ltype == F_RDLCK
469                                   ? "read" : "write");
470         }
471
472         if (tdb_has_hash_locks(tdb)) {
473                 /* can't combine global and chain locks */
474                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
475                                   "tdb_allrecord_lock:"
476                                   " already have chain lock");
477         }
478
479         if (upgradable && ltype != F_RDLCK) {
480                 /* tdb error: you can't upgrade a write lock! */
481                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
482                                   "tdb_allrecord_lock:"
483                                   " can't upgrade a write lock");
484         }
485
486         add_stat(tdb, locks, 1);
487 again:
488         /* Lock hashes, gradually. */
489         ecode = tdb_lock_gradual(tdb, ltype, flags, TDB_HASH_LOCK_START,
490                                  TDB_HASH_LOCK_RANGE);
491         if (ecode != TDB_SUCCESS) {
492                 if (!(flags & TDB_LOCK_PROBE)) {
493                         tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
494                                    "tdb_allrecord_lock hashes failed");
495                 }
496                 return ecode;
497         }
498
499         /* Lock free tables: there to end of file. */
500         ecode = tdb_brlock(tdb, ltype,
501                            TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE,
502                            0, flags);
503         if (ecode != TDB_SUCCESS) {
504                 if (!(flags & TDB_LOCK_PROBE)) {
505                         tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
506                                  "tdb_allrecord_lock freetables failed");
507                 }
508                 tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START,
509                              TDB_HASH_LOCK_RANGE);
510                 return ecode;
511         }
512
513         tdb->allrecord_lock.count = 1;
514         /* If it's upgradable, it's actually exclusive so we can treat
515          * it as a write lock. */
516         tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
517         tdb->allrecord_lock.off = upgradable;
518
519         /* Now check for needing recovery. */
520         if (!(flags & TDB_LOCK_NOCHECK) && unlikely(tdb_needs_recovery(tdb))) {
521                 tdb_allrecord_unlock(tdb, ltype);
522                 ecode = tdb_lock_and_recover(tdb);
523                 if (ecode != TDB_SUCCESS) {
524                         return ecode;
525                 }
526                 goto again;
527         }
528
529         return TDB_SUCCESS;
530 }
531
532 enum TDB_ERROR tdb_lock_open(struct tdb_context *tdb, enum tdb_lock_flags flags)
533 {
534         return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, flags);
535 }
536
537 void tdb_unlock_open(struct tdb_context *tdb)
538 {
539         tdb_nest_unlock(tdb, TDB_OPEN_LOCK, F_WRLCK);
540 }
541
542 bool tdb_has_open_lock(struct tdb_context *tdb)
543 {
544         return find_nestlock(tdb, TDB_OPEN_LOCK) != NULL;
545 }
546
547 enum TDB_ERROR tdb_lock_expand(struct tdb_context *tdb, int ltype)
548 {
549         /* Lock doesn't protect data, so don't check (we recurse if we do!) */
550         return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype,
551                              TDB_LOCK_WAIT | TDB_LOCK_NOCHECK);
552 }
553
554 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
555 {
556         tdb_nest_unlock(tdb, TDB_EXPANSION_LOCK, ltype);
557 }
558
559 /* unlock entire db */
560 void tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
561 {
562         if (tdb->allrecord_lock.count == 0) {
563                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
564                            "tdb_allrecord_unlock: not locked!");
565                 return;
566         }
567
568         /* Upgradable locks are marked as write locks. */
569         if (tdb->allrecord_lock.ltype != ltype
570             && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) {
571                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
572                            "tdb_allrecord_unlock: have %s lock",
573                            tdb->allrecord_lock.ltype == F_RDLCK
574                            ? "read" : "write");
575                 return;
576         }
577
578         if (tdb->allrecord_lock.count > 1) {
579                 tdb->allrecord_lock.count--;
580                 return;
581         }
582
583         tdb->allrecord_lock.count = 0;
584         tdb->allrecord_lock.ltype = 0;
585
586         tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START, 0);
587 }
588
589 bool tdb_has_expansion_lock(struct tdb_context *tdb)
590 {
591         return find_nestlock(tdb, TDB_EXPANSION_LOCK) != NULL;
592 }
593
594 bool tdb_has_hash_locks(struct tdb_context *tdb)
595 {
596         unsigned int i;
597
598         for (i=0; i<tdb->num_lockrecs; i++) {
599                 if (tdb->lockrecs[i].off >= TDB_HASH_LOCK_START
600                     && tdb->lockrecs[i].off < (TDB_HASH_LOCK_START
601                                                + TDB_HASH_LOCK_RANGE))
602                         return true;
603         }
604         return false;
605 }
606
607 static bool tdb_has_free_lock(struct tdb_context *tdb)
608 {
609         unsigned int i;
610
611         for (i=0; i<tdb->num_lockrecs; i++) {
612                 if (tdb->lockrecs[i].off
613                     > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE)
614                         return true;
615         }
616         return false;
617 }
618
619 enum TDB_ERROR tdb_lock_hashes(struct tdb_context *tdb,
620                                tdb_off_t hash_lock,
621                                tdb_len_t hash_range,
622                                int ltype, enum tdb_lock_flags waitflag)
623 {
624         /* FIXME: Do this properly, using hlock_range */
625         unsigned lock = TDB_HASH_LOCK_START
626                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
627
628         /* a allrecord lock allows us to avoid per chain locks */
629         if (tdb->allrecord_lock.count &&
630             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
631                 return TDB_SUCCESS;
632         }
633
634         if (tdb->allrecord_lock.count) {
635                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
636                                   "tdb_lock_hashes:"
637                                   " already have %s allrecordlock",
638                                   tdb->allrecord_lock.ltype == F_RDLCK
639                                   ? "read" : "write");
640         }
641
642         if (tdb_has_free_lock(tdb)) {
643                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
644                                   "tdb_lock_hashes: already have free lock");
645         }
646
647         if (tdb_has_expansion_lock(tdb)) {
648                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
649                                   "tdb_lock_hashes:"
650                                   " already have expansion lock");
651         }
652
653         return tdb_nest_lock(tdb, lock, ltype, waitflag);
654 }
655
656 enum TDB_ERROR tdb_unlock_hashes(struct tdb_context *tdb,
657                                  tdb_off_t hash_lock,
658                                  tdb_len_t hash_range, int ltype)
659 {
660         unsigned lock = TDB_HASH_LOCK_START
661                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
662
663         /* a allrecord lock allows us to avoid per chain locks */
664         if (tdb->allrecord_lock.count) {
665                 if (tdb->allrecord_lock.ltype == F_RDLCK
666                     && ltype == F_WRLCK) {
667                         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
668                                           "tdb_unlock_hashes RO allrecord!");
669                 }
670                 return TDB_SUCCESS;
671         }
672
673         return tdb_nest_unlock(tdb, lock, ltype);
674 }
675
676 /* Hash locks use TDB_HASH_LOCK_START + the next 30 bits.
677  * Then we begin; bucket offsets are sizeof(tdb_len_t) apart, so we divide.
678  * The result is that on 32 bit systems we don't use lock values > 2^31 on
679  * files that are less than 4GB.
680  */
681 static tdb_off_t free_lock_off(tdb_off_t b_off)
682 {
683         return TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
684                 + b_off / sizeof(tdb_off_t);
685 }
686
687 enum TDB_ERROR tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
688                                     enum tdb_lock_flags waitflag)
689 {
690         assert(b_off >= sizeof(struct tdb_header));
691
692         /* a allrecord lock allows us to avoid per chain locks */
693         if (tdb->allrecord_lock.count) {
694                 if (tdb->allrecord_lock.ltype == F_WRLCK)
695                         return 0;
696                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
697                                   "tdb_lock_free_bucket with"
698                                   " read-only allrecordlock!");
699         }
700
701 #if 0 /* FIXME */
702         if (tdb_has_expansion_lock(tdb)) {
703                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
704                                   "tdb_lock_free_bucket:"
705                                   " already have expansion lock");
706         }
707 #endif
708
709         return tdb_nest_lock(tdb, free_lock_off(b_off), F_WRLCK, waitflag);
710 }
711
712 void tdb_unlock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off)
713 {
714         if (tdb->allrecord_lock.count)
715                 return;
716
717         tdb_nest_unlock(tdb, free_lock_off(b_off), F_WRLCK);
718 }
719
720 void tdb_lock_init(struct tdb_context *tdb)
721 {
722         tdb->num_lockrecs = 0;
723         tdb->lockrecs = NULL;
724         tdb->allrecord_lock.count = 0;
725 }