lib/tdb/common/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 "tdb_private.h"
  29
  30 void tdb_setalarm_sigptr(struct tdb_context *tdb, volatile sig_atomic_t *ptr)
  31 {
  32         tdb->interrupt_sig_ptr = ptr;
  33 }
  34
  35 static int fcntl_lock(struct tdb_context *tdb,
  36                       int rw, off_t off, off_t len, bool waitflag)
  37 {
  38         struct flock fl;
  39
  40         fl.l_type = rw;
  41         fl.l_whence = SEEK_SET;
  42         fl.l_start = off;
  43         fl.l_len = len;
  44         fl.l_pid = 0;
  45
  46         if (waitflag)
  47                 return fcntl(tdb->fd, F_SETLKW, &fl);
  48         else
  49                 return fcntl(tdb->fd, F_SETLK, &fl);
  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    On error, errno is also set so that errors are passed back properly
 126    through tdb_open().
 127
 128    note that a len of zero means lock to end of file
 129 */
 130 int tdb_brlock(struct tdb_context *tdb,
 131                int rw_type, tdb_off_t offset, size_t len,
 132                enum tdb_lock_flags flags)
 133 {
 134         int ret;
 135
 136         if (tdb->flags & TDB_NOLOCK) {
 137                 return 0;
 138         }
 139
 140         if (flags & TDB_LOCK_MARK_ONLY) {
 141                 return 0;
 142         }
 143
 144         if ((rw_type == F_WRLCK) && (tdb->read_only || tdb->traverse_read)) {
 145                 tdb->ecode = TDB_ERR_RDONLY;
 146                 return -1;
 147         }
 148
 149         do {
 150                 ret = fcntl_lock(tdb, rw_type, offset, len,
 151                                  flags & TDB_LOCK_WAIT);
 152                 /* Check for a sigalarm break. */
 153                 if (ret == -1 && errno == EINTR &&
 154                                 tdb->interrupt_sig_ptr &&
 155                                 *tdb->interrupt_sig_ptr) {
 156                         break;
 157                 }
 158         } while (ret == -1 && errno == EINTR);
 159
 160         if (ret == -1) {
 161                 tdb->ecode = TDB_ERR_LOCK;
 162                 /* Generic lock error. errno set by fcntl.
 163                  * EAGAIN is an expected return from non-blocking
 164                  * locks. */
 165                 if (!(flags & TDB_LOCK_PROBE) && errno != EAGAIN) {
 166                         TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock failed (fd=%d) at offset %d rw_type=%d flags=%d len=%d\n",
 167                                  tdb->fd, offset, rw_type, flags, (int)len));
 168                 }
 169                 return -1;
 170         }
 171         return 0;
 172 }
 173
 174 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_brunlock failed (fd=%d) at offset %d rw_type=%d len=%d\n",
 189                          tdb->fd, offset, rw_type, (int)len));
 190         }
 191         return ret;
 192 }
 193
 194 /*
 195   upgrade a read lock to a write lock. This needs to be handled in a
 196   special way as some OSes (such as solaris) have too conservative
 197   deadlock detection and claim a deadlock when progress can be
 198   made. For those OSes we may loop for a while.
 199 */
 200 int tdb_brlock_upgrade(struct tdb_context *tdb, tdb_off_t offset, size_t len)
 201 {
 202         int count = 1000;
 203         while (count--) {
 204                 struct timeval tv;
 205                 if (tdb_brlock(tdb, F_WRLCK, offset, len,
 206                                TDB_LOCK_WAIT|TDB_LOCK_PROBE) == 0) {
 207                         return 0;
 208                 }
 209                 if (errno != EDEADLK) {
 210                         break;
 211                 }
 212                 /* sleep for as short a time as we can - more portable than usleep() */
 213                 tv.tv_sec = 0;
 214                 tv.tv_usec = 1;
 215                 select(0, NULL, NULL, NULL, &tv);
 216         }
 217         TDB_LOG((tdb, TDB_DEBUG_TRACE,"tdb_brlock_upgrade failed at offset %d\n", offset));
 218         return -1;
 219 }
 220
 221 /* list -1 is the alloc list, otherwise a hash chain. */
 222 static tdb_off_t lock_offset(int list)
 223 {
 224         return FREELIST_TOP + 4*list;
 225 }
 226
 227 static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,
 228                                            tdb_off_t offset)
 229 {
 230         unsigned int i;
 231
 232         for (i=0; i<tdb->num_lockrecs; i++) {
 233                 if (tdb->lockrecs[i].off == offset) {
 234                         return &tdb->lockrecs[i];
 235                 }
 236         }
 237         return NULL;
 238 }
 239
 240 /* lock an offset in the database. */
 241 int tdb_nest_lock(struct tdb_context *tdb, uint32_t offset, int ltype,
 242                   enum tdb_lock_flags flags)
 243 {
 244         struct tdb_lock_type *new_lck;
 245
 246         if (offset >= lock_offset(tdb->header.hash_size)) {
 247                 tdb->ecode = TDB_ERR_LOCK;
 248                 TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_lock: invalid offset %u for ltype=%d\n",
 249                          offset, ltype));
 250                 return -1;
 251         }
 252         if (tdb->flags & TDB_NOLOCK)
 253                 return 0;
 254
 255         new_lck = find_nestlock(tdb, offset);
 256         if (new_lck) {
 257                 /*
 258                  * Just increment the in-memory struct, posix locks
 259                  * don't stack.
 260                  */
 261                 new_lck->count++;
 262                 return 0;
 263         }
 264
 265         new_lck = (struct tdb_lock_type *)realloc(
 266                 tdb->lockrecs,
 267                 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
 268         if (new_lck == NULL) {
 269                 errno = ENOMEM;
 270                 return -1;
 271         }
 272         tdb->lockrecs = new_lck;
 273
 274         /* Since fcntl locks don't nest, we do a lock for the first one,
 275            and simply bump the count for future ones */
 276         if (tdb->methods->brlock(tdb, ltype, offset, 1, flags)) {
 277                 return -1;
 278         }
 279
 280         tdb->num_locks++;
 281
 282         tdb->lockrecs[tdb->num_lockrecs].off = offset;
 283         tdb->lockrecs[tdb->num_lockrecs].count = 1;
 284         tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
 285         tdb->num_lockrecs += 1;
 286
 287         return 0;
 288 }
 289
 290 /* lock a list in the database. list -1 is the alloc list */
 291 int tdb_lock(struct tdb_context *tdb, int list, int ltype)
 292 {
 293         int ret;
 294
 295         /* a allrecord lock allows us to avoid per chain locks */
 296         if (tdb->allrecord_lock.count &&
 297             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
 298                 return 0;
 299         }
 300
 301         if (tdb->allrecord_lock.count) {
 302                 tdb->ecode = TDB_ERR_LOCK;
 303                 ret = -1;
 304         } else {
 305                 ret = tdb_nest_lock(tdb, lock_offset(list), ltype,
 306                                     TDB_LOCK_WAIT);
 307         }
 308         if (ret) {
 309                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lock failed on list %d "
 310                          "ltype=%d (%s)\n",  list, ltype, strerror(errno)));
 311         }
 312         return ret;
 313 }
 314
 315 /* lock a list in the database. list -1 is the alloc list. non-blocking lock */
 316 int tdb_lock_nonblock(struct tdb_context *tdb, int list, int ltype)
 317 {
 318         /* a allrecord lock allows us to avoid per chain locks */
 319         if (tdb->allrecord_lock.count &&
 320             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
 321                 return 0;
 322         }
 323
 324         if (tdb->allrecord_lock.count) {
 325                 tdb->ecode = TDB_ERR_LOCK;
 326                 return -1;
 327         }
 328
 329         return tdb_nest_lock(tdb, lock_offset(list), ltype, TDB_LOCK_NOWAIT);
 330 }
 331
 332
 333 int tdb_nest_unlock(struct tdb_context *tdb, uint32_t offset, int ltype,
 334                     bool mark_lock)
 335 {
 336         int ret = -1;
 337         struct tdb_lock_type *lck;
 338
 339         if (tdb->flags & TDB_NOLOCK)
 340                 return 0;
 341
 342         /* Sanity checks */
 343         if (offset >= lock_offset(tdb->header.hash_size)) {
 344                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: offset %u invalid (%d)\n", offset, tdb->header.hash_size));
 345                 return ret;
 346         }
 347
 348         lck = find_nestlock(tdb, offset);
 349         if ((lck == NULL) || (lck->count == 0)) {
 350                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: count is 0\n"));
 351                 return -1;
 352         }
 353
 354         if (lck->count > 1) {
 355                 lck->count--;
 356                 return 0;
 357         }
 358
 359         /*
 360          * This lock has count==1 left, so we need to unlock it in the
 361          * kernel. We don't bother with decrementing the in-memory array
 362          * element, we're about to overwrite it with the last array element
 363          * anyway.
 364          */
 365
 366         if (mark_lock) {
 367                 ret = 0;
 368         } else {
 369                 ret = tdb->methods->brunlock(tdb, ltype, offset, 1);
 370         }
 371         tdb->num_locks--;
 372
 373         /*
 374          * Shrink the array by overwriting the element just unlocked with the
 375          * last array element.
 376          */
 377
 378         if (tdb->num_lockrecs > 1) {
 379                 *lck = tdb->lockrecs[tdb->num_lockrecs-1];
 380         }
 381         tdb->num_lockrecs -= 1;
 382
 383         /*
 384          * We don't bother with realloc when the array shrinks, but if we have
 385          * a completely idle tdb we should get rid of the locked array.
 386          */
 387
 388         if (tdb->num_lockrecs == 0) {
 389                 SAFE_FREE(tdb->lockrecs);
 390         }
 391
 392         if (ret)
 393                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlock: An error occurred unlocking!\n"));
 394         return ret;
 395 }
 396
 397 int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
 398 {
 399         /* a global lock allows us to avoid per chain locks */
 400         if (tdb->allrecord_lock.count &&
 401             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
 402                 return 0;
 403         }
 404
 405         if (tdb->allrecord_lock.count) {
 406                 tdb->ecode = TDB_ERR_LOCK;
 407                 return -1;
 408         }
 409
 410         return tdb_nest_unlock(tdb, lock_offset(list), ltype, false);
 411 }
 412
 413 /*
 414   get the transaction lock
 415  */
 416 int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
 417 {
 418         return tdb_nest_lock(tdb, TRANSACTION_LOCK, ltype, TDB_LOCK_WAIT);
 419 }
 420
 421 /*
 422   release the transaction lock
 423  */
 424 int tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
 425 {
 426         return tdb_nest_unlock(tdb, TRANSACTION_LOCK, ltype, false);
 427 }
 428
 429
 430
 431
 432 /* lock/unlock entire database */
 433 static int _tdb_lockall(struct tdb_context *tdb, int ltype,
 434                         enum tdb_lock_flags flags)
 435 {
 436         /* There are no locks on read-only dbs */
 437         if (tdb->read_only || tdb->traverse_read) {
 438                 tdb->ecode = TDB_ERR_LOCK;
 439                 return -1;
 440         }
 441
 442         if (tdb->allrecord_lock.count && tdb->allrecord_lock.ltype == ltype) {
 443                 tdb->allrecord_lock.count++;
 444                 return 0;
 445         }
 446
 447         if (tdb->allrecord_lock.count) {
 448                 /* a global lock of a different type exists */
 449                 tdb->ecode = TDB_ERR_LOCK;
 450                 return -1;
 451         }
 452
 453         if (tdb_have_extra_locks(tdb)) {
 454                 /* can't combine global and chain locks */
 455                 tdb->ecode = TDB_ERR_LOCK;
 456                 return -1;
 457         }
 458
 459         if (tdb->methods->brlock(tdb, ltype,
 460                                  FREELIST_TOP, 4*tdb->header.hash_size,
 461                                  flags)) {
 462                 if (flags & TDB_LOCK_WAIT) {
 463                         TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_lockall failed (%s)\n", strerror(errno)));
 464                 }
 465                 return -1;
 466         }
 467
 468         tdb->allrecord_lock.count = 1;
 469         tdb->allrecord_lock.ltype = ltype;
 470
 471         return 0;
 472 }
 473
 474
 475
 476 /* unlock entire db */
 477 static int _tdb_unlockall(struct tdb_context *tdb, int ltype, bool mark_lock)
 478 {
 479         /* There are no locks on read-only dbs */
 480         if (tdb->read_only || tdb->traverse_read) {
 481                 tdb->ecode = TDB_ERR_LOCK;
 482                 return -1;
 483         }
 484
 485         if (tdb->allrecord_lock.ltype != ltype || tdb->allrecord_lock.count == 0) {
 486                 tdb->ecode = TDB_ERR_LOCK;
 487                 return -1;
 488         }
 489
 490         if (tdb->allrecord_lock.count > 1) {
 491                 tdb->allrecord_lock.count--;
 492                 return 0;
 493         }
 494
 495         if (!mark_lock &&
 496             tdb->methods->brunlock(tdb, ltype,
 497                                    FREELIST_TOP, 4*tdb->header.hash_size)) {
 498                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_unlockall failed (%s)\n", strerror(errno)));
 499                 return -1;
 500         }
 501
 502         tdb->allrecord_lock.count = 0;
 503         tdb->allrecord_lock.ltype = 0;
 504
 505         return 0;
 506 }
 507
 508 /* lock entire database with write lock */
 509 int tdb_lockall(struct tdb_context *tdb)
 510 {
 511         tdb_trace(tdb, "tdb_lockall");
 512         return _tdb_lockall(tdb, F_WRLCK, TDB_LOCK_WAIT);
 513 }
 514
 515 /* lock entire database with write lock - mark only */
 516 int tdb_lockall_mark(struct tdb_context *tdb)
 517 {
 518         tdb_trace(tdb, "tdb_lockall_mark");
 519         return _tdb_lockall(tdb, F_WRLCK, TDB_LOCK_MARK_ONLY);
 520 }
 521
 522 /* unlock entire database with write lock - unmark only */
 523 int tdb_lockall_unmark(struct tdb_context *tdb)
 524 {
 525         tdb_trace(tdb, "tdb_lockall_unmark");
 526         return _tdb_unlockall(tdb, F_WRLCK, true);
 527 }
 528
 529 /* lock entire database with write lock - nonblocking varient */
 530 int tdb_lockall_nonblock(struct tdb_context *tdb)
 531 {
 532         int ret = _tdb_lockall(tdb, F_WRLCK, TDB_LOCK_NOWAIT);
 533         tdb_trace_ret(tdb, "tdb_lockall_nonblock", ret);
 534         return ret;
 535 }
 536
 537 /* unlock entire database with write lock */
 538 int tdb_unlockall(struct tdb_context *tdb)
 539 {
 540         tdb_trace(tdb, "tdb_unlockall");
 541         return _tdb_unlockall(tdb, F_WRLCK, false);
 542 }
 543
 544 /* lock entire database with read lock */
 545 int tdb_lockall_read(struct tdb_context *tdb)
 546 {
 547         tdb_trace(tdb, "tdb_lockall_read");
 548         return _tdb_lockall(tdb, F_RDLCK, TDB_LOCK_WAIT);
 549 }
 550
 551 /* lock entire database with read lock - nonblock varient */
 552 int tdb_lockall_read_nonblock(struct tdb_context *tdb)
 553 {
 554         int ret = _tdb_lockall(tdb, F_RDLCK, TDB_LOCK_NOWAIT);
 555         tdb_trace_ret(tdb, "tdb_lockall_read_nonblock", ret);
 556         return ret;
 557 }
 558
 559 /* unlock entire database with read lock */
 560 int tdb_unlockall_read(struct tdb_context *tdb)
 561 {
 562         tdb_trace(tdb, "tdb_unlockall_read");
 563         return _tdb_unlockall(tdb, F_RDLCK, false);
 564 }
 565
 566 /* lock/unlock one hash chain. This is meant to be used to reduce
 567    contention - it cannot guarantee how many records will be locked */
 568 int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
 569 {
 570         int ret = tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
 571         tdb_trace_1rec(tdb, "tdb_chainlock", key);
 572         return ret;
 573 }
 574
 575 /* lock/unlock one hash chain, non-blocking. This is meant to be used
 576    to reduce contention - it cannot guarantee how many records will be
 577    locked */
 578 int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)
 579 {
 580         int ret = tdb_lock_nonblock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
 581         tdb_trace_1rec_ret(tdb, "tdb_chainlock_nonblock", key, ret);
 582         return ret;
 583 }
 584
 585 /* mark a chain as locked without actually locking it. Warning! use with great caution! */
 586 int tdb_chainlock_mark(struct tdb_context *tdb, TDB_DATA key)
 587 {
 588         int ret = tdb_nest_lock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))),
 589                                 F_WRLCK, TDB_LOCK_MARK_ONLY);
 590         tdb_trace_1rec(tdb, "tdb_chainlock_mark", key);
 591         return ret;
 592 }
 593
 594 /* unmark a chain as locked without actually locking it. Warning! use with great caution! */
 595 int tdb_chainlock_unmark(struct tdb_context *tdb, TDB_DATA key)
 596 {
 597         tdb_trace_1rec(tdb, "tdb_chainlock_unmark", key);
 598         return tdb_nest_unlock(tdb, lock_offset(BUCKET(tdb->hash_fn(&key))),
 599                                F_WRLCK, true);
 600 }
 601
 602 int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
 603 {
 604         tdb_trace_1rec(tdb, "tdb_chainunlock", key);
 605         return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
 606 }
 607
 608 int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
 609 {
 610         int ret;
 611         ret = tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
 612         tdb_trace_1rec(tdb, "tdb_chainlock_read", key);
 613         return ret;
 614 }
 615
 616 int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
 617 {
 618         tdb_trace_1rec(tdb, "tdb_chainunlock_read", key);
 619         return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
 620 }
 621
 622
 623
 624 /* record lock stops delete underneath */
 625 int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
 626 {
 627         if (tdb->allrecord_lock.count) {
 628                 return 0;
 629         }
 630         return off ? tdb->methods->brlock(tdb, F_RDLCK, off, 1, TDB_LOCK_WAIT) : 0;
 631 }
 632
 633 /*
 634   Write locks override our own fcntl readlocks, so check it here.
 635   Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
 636   an error to fail to get the lock here.
 637 */
 638 int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
 639 {
 640         struct tdb_traverse_lock *i;
 641         for (i = &tdb->travlocks; i; i = i->next)
 642                 if (i->off == off)
 643                         return -1;
 644         return tdb->methods->brlock(tdb, F_WRLCK, off, 1, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE);
 645 }
 646
 647 int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
 648 {
 649         return tdb->methods->brunlock(tdb, F_WRLCK, off, 1);
 650 }
 651
 652 /* fcntl locks don't stack: avoid unlocking someone else's */
 653 int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
 654 {
 655         struct tdb_traverse_lock *i;
 656         uint32_t count = 0;
 657
 658         if (tdb->allrecord_lock.count) {
 659                 return 0;
 660         }
 661
 662         if (off == 0)
 663                 return 0;
 664         for (i = &tdb->travlocks; i; i = i->next)
 665                 if (i->off == off)
 666                         count++;
 667         return (count == 1 ? tdb->methods->brunlock(tdb, F_RDLCK, off, 1) : 0);
 668 }
 669
 670 bool tdb_have_extra_locks(struct tdb_context *tdb)
 671 {
 672         unsigned int extra = tdb->num_lockrecs;
 673
 674         if (tdb->allrecord_lock.count) {
 675                 return true;
 676         }
 677
 678         /* In a transaction, we expect to hold the transaction lock */
 679         if (tdb->transaction && find_nestlock(tdb, TRANSACTION_LOCK)) {
 680                 extra--;
 681         }
 682
 683         return extra;
 684 }
 685
 686 /* The transaction code uses this to remove all locks.  Note that this
 687    may include OPEN_LOCK. */
 688 void tdb_release_extra_locks(struct tdb_context *tdb)
 689 {
 690         unsigned int i, extra = 0;
 691
 692         if (tdb->allrecord_lock.count != 0) {
 693                 tdb_brunlock(tdb, tdb->allrecord_lock.ltype,
 694                              FREELIST_TOP, 4*tdb->header.hash_size);
 695                 tdb->allrecord_lock.count = 0;
 696         }
 697
 698         for (i=0;i<tdb->num_lockrecs;i++) {
 699                 struct tdb_lock_type *lck = &tdb->lockrecs[i];
 700
 701                 if (tdb->transaction && lck->off == TRANSACTION_LOCK) {
 702                         tdb->lockrecs[extra++] = *lck;
 703                 } else {
 704                         tdb_brunlock(tdb, lck->ltype, lck->off, 1);
 705                 }
 706         }
 707         tdb->num_locks = extra;
 708         tdb->num_lockrecs = extra;
 709         if (tdb->num_lockrecs == 0) {
 710                 SAFE_FREE(tdb->lockrecs);
 711         }
 712 }