check_type: fix incorrect documentation.
[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 /* If we were threaded, we could wait for unlock, but we're not, so fail. */
33 enum TDB_ERROR owner_conflict(struct tdb_context *tdb, const char *call)
34 {
35         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
36                           "%s: lock owned by another tdb in this process.",
37                           call);
38 }
39
40 /* If we fork, we no longer really own locks. */
41 bool check_lock_pid(struct tdb_context *tdb, const char *call, bool log)
42 {
43         /* No locks?  No problem! */
44         if (tdb->file->allrecord_lock.count == 0
45             && tdb->file->num_lockrecs == 0) {
46                 return true;
47         }
48
49         /* No fork?  No problem! */
50         if (tdb->file->locker == getpid()) {
51                 return true;
52         }
53
54         if (log) {
55                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
56                            "%s: fork() detected after lock acquisition!"
57                            " (%u vs %u)", call, tdb->file->locker, getpid());
58         }
59         return false;
60 }
61
62 int tdb_fcntl_lock(int fd, int rw, off_t off, off_t len, bool waitflag,
63                    void *unused)
64 {
65         struct flock fl;
66         int ret;
67
68         do {
69                 fl.l_type = rw;
70                 fl.l_whence = SEEK_SET;
71                 fl.l_start = off;
72                 fl.l_len = len;
73
74                 if (waitflag)
75                         ret = fcntl(fd, F_SETLKW, &fl);
76                 else
77                         ret = fcntl(fd, F_SETLK, &fl);
78         } while (ret != 0 && errno == EINTR);
79         return ret;
80 }
81
82 int tdb_fcntl_unlock(int fd, int rw, off_t off, off_t len, void *unused)
83 {
84         struct flock fl;
85         int ret;
86
87         do {
88                 fl.l_type = F_UNLCK;
89                 fl.l_whence = SEEK_SET;
90                 fl.l_start = off;
91                 fl.l_len = len;
92
93                 ret = fcntl(fd, F_SETLKW, &fl);
94         } while (ret != 0 && errno == EINTR);
95         return ret;
96 }
97
98 static int lock(struct tdb_context *tdb,
99                       int rw, off_t off, off_t len, bool waitflag)
100 {
101         int ret;
102         if (tdb->file->allrecord_lock.count == 0
103             && tdb->file->num_lockrecs == 0) {
104                 tdb->file->locker = getpid();
105         }
106
107         tdb->stats.lock_lowlevel++;
108         ret = tdb->lock_fn(tdb->file->fd, rw, off, len, waitflag,
109                            tdb->lock_data);
110         if (!waitflag) {
111                 tdb->stats.lock_nonblock++;
112                 if (ret != 0)
113                         tdb->stats.lock_nonblock_fail++;
114         }
115         return ret;
116 }
117
118 static int unlock(struct tdb_context *tdb, int rw, off_t off, off_t len)
119 {
120 #if 0 /* Check they matched up locks and unlocks correctly. */
121         char line[80];
122         FILE *locks;
123         bool found = false;
124
125         locks = fopen("/proc/locks", "r");
126
127         while (fgets(line, 80, locks)) {
128                 char *p;
129                 int type, start, l;
130
131                 /* eg. 1: FLOCK  ADVISORY  WRITE 2440 08:01:2180826 0 EOF */
132                 p = strchr(line, ':') + 1;
133                 if (strncmp(p, " POSIX  ADVISORY  ", strlen(" POSIX  ADVISORY  ")))
134                         continue;
135                 p += strlen(" FLOCK  ADVISORY  ");
136                 if (strncmp(p, "READ  ", strlen("READ  ")) == 0)
137                         type = F_RDLCK;
138                 else if (strncmp(p, "WRITE ", strlen("WRITE ")) == 0)
139                         type = F_WRLCK;
140                 else
141                         abort();
142                 p += 6;
143                 if (atoi(p) != getpid())
144                         continue;
145                 p = strchr(strchr(p, ' ') + 1, ' ') + 1;
146                 start = atoi(p);
147                 p = strchr(p, ' ') + 1;
148                 if (strncmp(p, "EOF", 3) == 0)
149                         l = 0;
150                 else
151                         l = atoi(p) - start + 1;
152
153                 if (off == start) {
154                         if (len != l) {
155                                 fprintf(stderr, "Len %u should be %u: %s",
156                                         (int)len, l, line);
157                                 abort();
158                         }
159                         if (type != rw) {
160                                 fprintf(stderr, "Type %s wrong: %s",
161                                         rw == F_RDLCK ? "READ" : "WRITE", line);
162                                 abort();
163                         }
164                         found = true;
165                         break;
166                 }
167         }
168
169         if (!found) {
170                 fprintf(stderr, "Unlock on %u@%u not found!",
171                         (int)off, (int)len);
172                 abort();
173         }
174
175         fclose(locks);
176 #endif
177
178         return tdb->unlock_fn(tdb->file->fd, rw, off, len, tdb->lock_data);
179 }
180
181 /* a byte range locking function - return 0 on success
182    this functions locks len bytes at the specified offset.
183
184    note that a len of zero means lock to end of file
185 */
186 enum TDB_ERROR tdb_brlock(struct tdb_context *tdb,
187                           int rw_type, tdb_off_t offset, tdb_off_t len,
188                           enum tdb_lock_flags flags)
189 {
190         int ret;
191
192         if (tdb->flags & TDB_NOLOCK) {
193                 return TDB_SUCCESS;
194         }
195
196         if (rw_type == F_WRLCK && (tdb->flags & TDB_RDONLY)) {
197                 return tdb_logerr(tdb, TDB_ERR_RDONLY, TDB_LOG_USE_ERROR,
198                                   "Write lock attempted on read-only database");
199         }
200
201         /* A 32 bit system cannot open a 64-bit file, but it could have
202          * expanded since then: check here. */
203         if ((size_t)(offset + len) != offset + len) {
204                 return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
205                                   "tdb_brlock: lock on giant offset %llu",
206                                   (long long)(offset + len));
207         }
208
209         ret = lock(tdb, rw_type, offset, len, flags & TDB_LOCK_WAIT);
210         if (ret != 0) {
211                 /* Generic lock error. errno set by fcntl.
212                  * EAGAIN is an expected return from non-blocking
213                  * locks. */
214                 if (!(flags & TDB_LOCK_PROBE)
215                     && (errno != EAGAIN && errno != EINTR)) {
216                         tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
217                                    "tdb_brlock failed (fd=%d) at"
218                                    " offset %zu rw_type=%d flags=%d len=%zu:"
219                                    " %s",
220                                    tdb->file->fd, (size_t)offset, rw_type,
221                                    flags, (size_t)len, strerror(errno));
222                 }
223                 return TDB_ERR_LOCK;
224         }
225         return TDB_SUCCESS;
226 }
227
228 enum TDB_ERROR tdb_brunlock(struct tdb_context *tdb,
229                             int rw_type, tdb_off_t offset, size_t len)
230 {
231         if (tdb->flags & TDB_NOLOCK) {
232                 return TDB_SUCCESS;
233         }
234
235         if (!check_lock_pid(tdb, "tdb_brunlock", true))
236                 return TDB_ERR_LOCK;
237
238         if (unlock(tdb, rw_type, offset, len) == -1) {
239                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
240                                   "tdb_brunlock failed (fd=%d) at offset %zu"
241                                   " rw_type=%d len=%zu: %s",
242                                   tdb->file->fd, (size_t)offset, rw_type,
243                                   (size_t)len, strerror(errno));
244         }
245         return TDB_SUCCESS;
246 }
247
248 /*
249   upgrade a read lock to a write lock. This needs to be handled in a
250   special way as some OSes (such as solaris) have too conservative
251   deadlock detection and claim a deadlock when progress can be
252   made. For those OSes we may loop for a while.
253 */
254 enum TDB_ERROR tdb_allrecord_upgrade(struct tdb_context *tdb, off_t start)
255 {
256         int count = 1000;
257
258         if (!check_lock_pid(tdb, "tdb_transaction_prepare_commit", true))
259                 return TDB_ERR_LOCK;
260
261         if (tdb->file->allrecord_lock.count != 1) {
262                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
263                                   "tdb_allrecord_upgrade failed:"
264                                   " count %u too high",
265                                   tdb->file->allrecord_lock.count);
266         }
267
268         if (tdb->file->allrecord_lock.off != 1) {
269                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
270                                   "tdb_allrecord_upgrade failed:"
271                                   " already upgraded?");
272         }
273
274         if (tdb->file->allrecord_lock.owner != tdb) {
275                 return owner_conflict(tdb, "tdb_allrecord_upgrade");
276         }
277
278         while (count--) {
279                 struct timeval tv;
280                 if (tdb_brlock(tdb, F_WRLCK, start, 0,
281                                TDB_LOCK_WAIT|TDB_LOCK_PROBE) == TDB_SUCCESS) {
282                         tdb->file->allrecord_lock.ltype = F_WRLCK;
283                         tdb->file->allrecord_lock.off = 0;
284                         return TDB_SUCCESS;
285                 }
286                 if (errno != EDEADLK) {
287                         break;
288                 }
289                 /* sleep for as short a time as we can - more portable than usleep() */
290                 tv.tv_sec = 0;
291                 tv.tv_usec = 1;
292                 select(0, NULL, NULL, NULL, &tv);
293         }
294
295         if (errno != EAGAIN && errno != EINTR)
296                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
297                            "tdb_allrecord_upgrade failed");
298         return TDB_ERR_LOCK;
299 }
300
301 static struct tdb_lock *find_nestlock(struct tdb_context *tdb, tdb_off_t offset,
302                                       const struct tdb_context *owner)
303 {
304         unsigned int i;
305
306         for (i=0; i<tdb->file->num_lockrecs; i++) {
307                 if (tdb->file->lockrecs[i].off == offset) {
308                         if (owner && tdb->file->lockrecs[i].owner != owner)
309                                 return NULL;
310                         return &tdb->file->lockrecs[i];
311                 }
312         }
313         return NULL;
314 }
315
316 enum TDB_ERROR tdb_lock_and_recover(struct tdb_context *tdb)
317 {
318         enum TDB_ERROR ecode;
319
320         if (!check_lock_pid(tdb, "tdb_transaction_prepare_commit", true))
321                 return TDB_ERR_LOCK;
322
323         ecode = tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK,
324                                    false);
325         if (ecode != TDB_SUCCESS) {
326                 return ecode;
327         }
328
329         ecode = tdb_lock_open(tdb, F_WRLCK, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK);
330         if (ecode != TDB_SUCCESS) {
331                 tdb_allrecord_unlock(tdb, F_WRLCK);
332                 return ecode;
333         }
334         ecode = tdb_transaction_recover(tdb);
335         tdb_unlock_open(tdb, F_WRLCK);
336         tdb_allrecord_unlock(tdb, F_WRLCK);
337
338         return ecode;
339 }
340
341 /* lock an offset in the database. */
342 enum TDB_ERROR tdb_nest_lock(struct tdb_context *tdb,
343                              tdb_off_t offset, int ltype,
344                              enum tdb_lock_flags flags)
345 {
346         struct tdb_lock *new_lck;
347         enum TDB_ERROR ecode;
348
349         if (!(tdb->flags & TDB_VERSION1)
350             && offset > (TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
351                          + tdb->file->map_size / 8)) {
352                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
353                                   "tdb_nest_lock: invalid offset %zu ltype=%d",
354                                   (size_t)offset, ltype);
355         }
356
357         if (tdb->flags & TDB_NOLOCK)
358                 return TDB_SUCCESS;
359
360         if (!check_lock_pid(tdb, "tdb_nest_lock", true)) {
361                 return TDB_ERR_LOCK;
362         }
363
364         tdb->stats.locks++;
365
366         new_lck = find_nestlock(tdb, offset, NULL);
367         if (new_lck) {
368                 if (new_lck->owner != tdb) {
369                         return owner_conflict(tdb, "tdb_nest_lock");
370                 }
371
372                 if (new_lck->ltype == F_RDLCK && ltype == F_WRLCK) {
373                         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
374                                           "tdb_nest_lock:"
375                                           " offset %zu has read lock",
376                                           (size_t)offset);
377                 }
378                 /* Just increment the struct, posix locks don't stack. */
379                 new_lck->count++;
380                 return TDB_SUCCESS;
381         }
382
383 #if 0
384         if (tdb->file->num_lockrecs
385             && offset >= TDB_HASH_LOCK_START
386             && offset < TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE) {
387                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
388                                   "tdb_nest_lock: already have a hash lock?");
389         }
390 #endif
391
392         new_lck = (struct tdb_lock *)realloc(
393                 tdb->file->lockrecs,
394                 sizeof(*tdb->file->lockrecs) * (tdb->file->num_lockrecs+1));
395         if (new_lck == NULL) {
396                 return tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
397                                   "tdb_nest_lock:"
398                                   " unable to allocate %zu lock struct",
399                                   tdb->file->num_lockrecs + 1);
400         }
401         tdb->file->lockrecs = new_lck;
402
403         /* Since fcntl locks don't nest, we do a lock for the first one,
404            and simply bump the count for future ones */
405         ecode = tdb_brlock(tdb, ltype, offset, 1, flags);
406         if (ecode != TDB_SUCCESS) {
407                 return ecode;
408         }
409
410         /* First time we grab a lock, perhaps someone died in commit? */
411         if (!(flags & TDB_LOCK_NOCHECK)
412             && tdb->file->num_lockrecs == 0) {
413                 tdb_bool_err berr = tdb_needs_recovery(tdb);
414                 if (berr != false) {
415                         tdb_brunlock(tdb, ltype, offset, 1);
416
417                         if (berr < 0)
418                                 return TDB_OFF_TO_ERR(berr);
419                         ecode = tdb_lock_and_recover(tdb);
420                         if (ecode == TDB_SUCCESS) {
421                                 ecode = tdb_brlock(tdb, ltype, offset, 1,
422                                                    flags);
423                         }
424                         if (ecode != TDB_SUCCESS) {
425                                 return ecode;
426                         }
427                 }
428         }
429
430         tdb->file->lockrecs[tdb->file->num_lockrecs].owner = tdb;
431         tdb->file->lockrecs[tdb->file->num_lockrecs].off = offset;
432         tdb->file->lockrecs[tdb->file->num_lockrecs].count = 1;
433         tdb->file->lockrecs[tdb->file->num_lockrecs].ltype = ltype;
434         tdb->file->num_lockrecs++;
435
436         return TDB_SUCCESS;
437 }
438
439 enum TDB_ERROR tdb_nest_unlock(struct tdb_context *tdb,
440                                tdb_off_t off, int ltype)
441 {
442         struct tdb_lock *lck;
443         enum TDB_ERROR ecode;
444
445         if (tdb->flags & TDB_NOLOCK)
446                 return TDB_SUCCESS;
447
448         lck = find_nestlock(tdb, off, tdb);
449         if ((lck == NULL) || (lck->count == 0)) {
450                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
451                                   "tdb_nest_unlock: no lock for %zu",
452                                   (size_t)off);
453         }
454
455         if (lck->count > 1) {
456                 lck->count--;
457                 return TDB_SUCCESS;
458         }
459
460         /*
461          * This lock has count==1 left, so we need to unlock it in the
462          * kernel. We don't bother with decrementing the in-memory array
463          * element, we're about to overwrite it with the last array element
464          * anyway.
465          */
466         ecode = tdb_brunlock(tdb, ltype, off, 1);
467
468         /*
469          * Shrink the array by overwriting the element just unlocked with the
470          * last array element.
471          */
472         *lck = tdb->file->lockrecs[--tdb->file->num_lockrecs];
473
474         return ecode;
475 }
476
477 /*
478   get the transaction lock
479  */
480 enum TDB_ERROR tdb_transaction_lock(struct tdb_context *tdb, int ltype)
481 {
482         return tdb_nest_lock(tdb, TDB_TRANSACTION_LOCK, ltype, TDB_LOCK_WAIT);
483 }
484
485 /*
486   release the transaction lock
487  */
488 void tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
489 {
490         tdb_nest_unlock(tdb, TDB_TRANSACTION_LOCK, ltype);
491 }
492
493 /* We only need to lock individual bytes, but Linux merges consecutive locks
494  * so we lock in contiguous ranges. */
495 enum TDB_ERROR tdb_lock_gradual(struct tdb_context *tdb,
496                                 int ltype, enum tdb_lock_flags flags,
497                                 tdb_off_t off, tdb_off_t len)
498 {
499         enum TDB_ERROR ecode;
500         enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);
501
502         if (len <= 1) {
503                 /* 0 would mean to end-of-file... */
504                 assert(len != 0);
505                 /* Single hash.  Just do blocking lock. */
506                 return tdb_brlock(tdb, ltype, off, len, flags);
507         }
508
509         /* First we try non-blocking. */
510         ecode = tdb_brlock(tdb, ltype, off, len, nb_flags);
511         if (ecode != TDB_ERR_LOCK) {
512                 return ecode;
513         }
514
515         /* Try locking first half, then second. */
516         ecode = tdb_lock_gradual(tdb, ltype, flags, off, len / 2);
517         if (ecode != TDB_SUCCESS)
518                 return ecode;
519
520         ecode = tdb_lock_gradual(tdb, ltype, flags,
521                                  off + len / 2, len - len / 2);
522         if (ecode != TDB_SUCCESS) {
523                 tdb_brunlock(tdb, ltype, off, len / 2);
524         }
525         return ecode;
526 }
527
528 /* lock/unlock entire database.  It can only be upgradable if you have some
529  * other way of guaranteeing exclusivity (ie. transaction write lock). */
530 enum TDB_ERROR tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
531                                   enum tdb_lock_flags flags, bool upgradable)
532 {
533         enum TDB_ERROR ecode;
534         tdb_bool_err berr;
535
536         if (tdb->flags & TDB_VERSION1) {
537                 if (tdb1_allrecord_lock(tdb, ltype, flags, upgradable) == -1)
538                         return tdb->last_error;
539                 return TDB_SUCCESS;
540         }
541
542         if (tdb->flags & TDB_NOLOCK)
543                 return TDB_SUCCESS;
544
545         if (!check_lock_pid(tdb, "tdb_allrecord_lock", true)) {
546                 return TDB_ERR_LOCK;
547         }
548
549         if (tdb->file->allrecord_lock.count) {
550                 if (tdb->file->allrecord_lock.owner != tdb) {
551                         return owner_conflict(tdb, "tdb_allrecord_lock");
552                 }
553
554                 if (ltype == F_RDLCK
555                     || tdb->file->allrecord_lock.ltype == F_WRLCK) {
556                         tdb->file->allrecord_lock.count++;
557                         return TDB_SUCCESS;
558                 }
559
560                 /* a global lock of a different type exists */
561                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
562                                   "tdb_allrecord_lock: already have %s lock",
563                                   tdb->file->allrecord_lock.ltype == F_RDLCK
564                                   ? "read" : "write");
565         }
566
567         if (tdb_has_hash_locks(tdb)) {
568                 /* can't combine global and chain locks */
569                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
570                                   "tdb_allrecord_lock:"
571                                   " already have chain lock");
572         }
573
574         if (upgradable && ltype != F_RDLCK) {
575                 /* tdb error: you can't upgrade a write lock! */
576                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
577                                   "tdb_allrecord_lock:"
578                                   " can't upgrade a write lock");
579         }
580
581         tdb->stats.locks++;
582 again:
583         /* Lock hashes, gradually. */
584         ecode = tdb_lock_gradual(tdb, ltype, flags, TDB_HASH_LOCK_START,
585                                  TDB_HASH_LOCK_RANGE);
586         if (ecode != TDB_SUCCESS)
587                 return ecode;
588
589         /* Lock free tables: there to end of file. */
590         ecode = tdb_brlock(tdb, ltype,
591                            TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE,
592                            0, flags);
593         if (ecode != TDB_SUCCESS) {
594                 tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START,
595                              TDB_HASH_LOCK_RANGE);
596                 return ecode;
597         }
598
599         tdb->file->allrecord_lock.owner = tdb;
600         tdb->file->allrecord_lock.count = 1;
601         /* If it's upgradable, it's actually exclusive so we can treat
602          * it as a write lock. */
603         tdb->file->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
604         tdb->file->allrecord_lock.off = upgradable;
605
606         /* Now check for needing recovery. */
607         if (flags & TDB_LOCK_NOCHECK)
608                 return TDB_SUCCESS;
609
610         berr = tdb_needs_recovery(tdb);
611         if (likely(berr == false))
612                 return TDB_SUCCESS;
613
614         tdb_allrecord_unlock(tdb, ltype);
615         if (berr < 0)
616                 return TDB_OFF_TO_ERR(berr);
617         ecode = tdb_lock_and_recover(tdb);
618         if (ecode != TDB_SUCCESS) {
619                 return ecode;
620         }
621         goto again;
622 }
623
624 enum TDB_ERROR tdb_lock_open(struct tdb_context *tdb,
625                              int ltype, enum tdb_lock_flags flags)
626 {
627         return tdb_nest_lock(tdb, TDB_OPEN_LOCK, ltype, flags);
628 }
629
630 void tdb_unlock_open(struct tdb_context *tdb, int ltype)
631 {
632         tdb_nest_unlock(tdb, TDB_OPEN_LOCK, ltype);
633 }
634
635 bool tdb_has_open_lock(struct tdb_context *tdb)
636 {
637         return !(tdb->flags & TDB_NOLOCK)
638                 && find_nestlock(tdb, TDB_OPEN_LOCK, tdb) != NULL;
639 }
640
641 enum TDB_ERROR tdb_lock_expand(struct tdb_context *tdb, int ltype)
642 {
643         /* Lock doesn't protect data, so don't check (we recurse if we do!) */
644         return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype,
645                              TDB_LOCK_WAIT | TDB_LOCK_NOCHECK);
646 }
647
648 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
649 {
650         tdb_nest_unlock(tdb, TDB_EXPANSION_LOCK, ltype);
651 }
652
653 /* unlock entire db */
654 void tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
655 {
656         if (tdb->flags & TDB_VERSION1) {
657                 tdb1_allrecord_unlock(tdb, ltype);
658                 return;
659         }
660
661         if (tdb->flags & TDB_NOLOCK)
662                 return;
663
664         if (tdb->file->allrecord_lock.count == 0) {
665                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
666                            "tdb_allrecord_unlock: not locked!");
667                 return;
668         }
669
670         if (tdb->file->allrecord_lock.owner != tdb) {
671                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
672                            "tdb_allrecord_unlock: not locked by us!");
673                 return;
674         }
675
676         /* Upgradable locks are marked as write locks. */
677         if (tdb->file->allrecord_lock.ltype != ltype
678             && (!tdb->file->allrecord_lock.off || ltype != F_RDLCK)) {
679                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
680                            "tdb_allrecord_unlock: have %s lock",
681                            tdb->file->allrecord_lock.ltype == F_RDLCK
682                            ? "read" : "write");
683                 return;
684         }
685
686         if (tdb->file->allrecord_lock.count > 1) {
687                 tdb->file->allrecord_lock.count--;
688                 return;
689         }
690
691         tdb->file->allrecord_lock.count = 0;
692         tdb->file->allrecord_lock.ltype = 0;
693
694         tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START, 0);
695 }
696
697 bool tdb_has_expansion_lock(struct tdb_context *tdb)
698 {
699         return find_nestlock(tdb, TDB_EXPANSION_LOCK, tdb) != NULL;
700 }
701
702 bool tdb_has_hash_locks(struct tdb_context *tdb)
703 {
704         unsigned int i;
705
706         for (i=0; i<tdb->file->num_lockrecs; i++) {
707                 if (tdb->file->lockrecs[i].off >= TDB_HASH_LOCK_START
708                     && tdb->file->lockrecs[i].off < (TDB_HASH_LOCK_START
709                                                      + TDB_HASH_LOCK_RANGE))
710                         return true;
711         }
712         return false;
713 }
714
715 static bool tdb_has_free_lock(struct tdb_context *tdb)
716 {
717         unsigned int i;
718
719         if (tdb->flags & TDB_NOLOCK)
720                 return false;
721
722         for (i=0; i<tdb->file->num_lockrecs; i++) {
723                 if (tdb->file->lockrecs[i].off
724                     > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE)
725                         return true;
726         }
727         return false;
728 }
729
730 enum TDB_ERROR tdb_lock_hashes(struct tdb_context *tdb,
731                                tdb_off_t hash_lock,
732                                tdb_len_t hash_range,
733                                int ltype, enum tdb_lock_flags waitflag)
734 {
735         /* FIXME: Do this properly, using hlock_range */
736         unsigned l = TDB_HASH_LOCK_START
737                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
738
739         /* a allrecord lock allows us to avoid per chain locks */
740         if (tdb->file->allrecord_lock.count) {
741                 if (!check_lock_pid(tdb, "tdb_lock_hashes", true))
742                         return TDB_ERR_LOCK;
743
744                 if (tdb->file->allrecord_lock.owner != tdb)
745                         return owner_conflict(tdb, "tdb_lock_hashes");
746                 if (ltype == tdb->file->allrecord_lock.ltype
747                     || ltype == F_RDLCK) {
748                         return TDB_SUCCESS;
749                 }
750
751                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
752                                   "tdb_lock_hashes:"
753                                   " already have %s allrecordlock",
754                                   tdb->file->allrecord_lock.ltype == F_RDLCK
755                                   ? "read" : "write");
756         }
757
758         if (tdb_has_free_lock(tdb)) {
759                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
760                                   "tdb_lock_hashes: already have free lock");
761         }
762
763         if (tdb_has_expansion_lock(tdb)) {
764                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
765                                   "tdb_lock_hashes:"
766                                   " already have expansion lock");
767         }
768
769         return tdb_nest_lock(tdb, l, ltype, waitflag);
770 }
771
772 enum TDB_ERROR tdb_unlock_hashes(struct tdb_context *tdb,
773                                  tdb_off_t hash_lock,
774                                  tdb_len_t hash_range, int ltype)
775 {
776         unsigned l = TDB_HASH_LOCK_START
777                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
778
779         if (tdb->flags & TDB_NOLOCK)
780                 return 0;
781
782         /* a allrecord lock allows us to avoid per chain locks */
783         if (tdb->file->allrecord_lock.count) {
784                 if (tdb->file->allrecord_lock.ltype == F_RDLCK
785                     && ltype == F_WRLCK) {
786                         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
787                                           "tdb_unlock_hashes RO allrecord!");
788                 }
789                 if (tdb->file->allrecord_lock.owner != tdb) {
790                         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
791                                           "tdb_unlock_hashes:"
792                                           " not locked by us!");
793                 }
794                 return TDB_SUCCESS;
795         }
796
797         return tdb_nest_unlock(tdb, l, ltype);
798 }
799
800 /* Hash locks use TDB_HASH_LOCK_START + the next 30 bits.
801  * Then we begin; bucket offsets are sizeof(tdb_len_t) apart, so we divide.
802  * The result is that on 32 bit systems we don't use lock values > 2^31 on
803  * files that are less than 4GB.
804  */
805 static tdb_off_t free_lock_off(tdb_off_t b_off)
806 {
807         return TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
808                 + b_off / sizeof(tdb_off_t);
809 }
810
811 enum TDB_ERROR tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
812                                     enum tdb_lock_flags waitflag)
813 {
814         assert(b_off >= sizeof(struct tdb_header));
815
816         if (tdb->flags & TDB_NOLOCK)
817                 return 0;
818
819         /* a allrecord lock allows us to avoid per chain locks */
820         if (tdb->file->allrecord_lock.count) {
821                 if (!check_lock_pid(tdb, "tdb_lock_free_bucket", true))
822                         return TDB_ERR_LOCK;
823
824                 if (tdb->file->allrecord_lock.owner != tdb) {
825                         return owner_conflict(tdb, "tdb_lock_free_bucket");
826                 }
827
828                 if (tdb->file->allrecord_lock.ltype == F_WRLCK)
829                         return 0;
830                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
831                                   "tdb_lock_free_bucket with"
832                                   " read-only allrecordlock!");
833         }
834
835 #if 0 /* FIXME */
836         if (tdb_has_expansion_lock(tdb)) {
837                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
838                                   "tdb_lock_free_bucket:"
839                                   " already have expansion lock");
840         }
841 #endif
842
843         return tdb_nest_lock(tdb, free_lock_off(b_off), F_WRLCK, waitflag);
844 }
845
846 void tdb_unlock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off)
847 {
848         if (tdb->file->allrecord_lock.count)
849                 return;
850
851         tdb_nest_unlock(tdb, free_lock_off(b_off), F_WRLCK);
852 }
853
854 enum TDB_ERROR tdb_lockall(struct tdb_context *tdb)
855 {
856         return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT, false);
857 }
858
859 void tdb_unlockall(struct tdb_context *tdb)
860 {
861         tdb_allrecord_unlock(tdb, F_WRLCK);
862 }
863
864 enum TDB_ERROR tdb_lockall_read(struct tdb_context *tdb)
865 {
866         return tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, false);
867 }
868
869 void tdb_unlockall_read(struct tdb_context *tdb)
870 {
871         tdb_allrecord_unlock(tdb, F_RDLCK);
872 }
873
874 void tdb_lock_cleanup(struct tdb_context *tdb)
875 {
876         unsigned int i;
877
878         /* We don't want to warn: they're allowed to close tdb after fork. */
879         if (!check_lock_pid(tdb, "tdb_close", false))
880                 return;
881
882         while (tdb->file->allrecord_lock.count
883                && tdb->file->allrecord_lock.owner == tdb) {
884                 tdb_allrecord_unlock(tdb, tdb->file->allrecord_lock.ltype);
885         }
886
887         for (i=0; i<tdb->file->num_lockrecs; i++) {
888                 if (tdb->file->lockrecs[i].owner == tdb) {
889                         tdb_nest_unlock(tdb,
890                                         tdb->file->lockrecs[i].off,
891                                         tdb->file->lockrecs[i].ltype);
892                         i--;
893                 }
894         }
895 }