git.ozlabs.org Git - ccan/blob - 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->file->fd, F_SETLKW, &fl);
  46         else {
  47                 add_stat(tdb, lock_nonblock, 1);
  48                 return fcntl(tdb->file->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->file->fd, F_SETLKW, &fl);
 120 }
 121
 122 /* a byte range locking function - return 0 on success
 123    this functions locks len bytes 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->file->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->file->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->file->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->file->allrecord_lock.count);
 210         }
 211
 212         if (tdb->file->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->file->allrecord_lock.ltype = F_WRLCK;
 224                         tdb->file->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->file->num_lockrecs; i++) {
 245                 if (tdb->file->lockrecs[i].off == offset) {
 246                         return &tdb->file->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         ecode = tdb_transaction_recover(tdb);
 268         tdb_unlock_open(tdb);
 269         tdb_allrecord_unlock(tdb, F_WRLCK);
 270
 271         return ecode;
 272 }
 273
 274 /* lock an offset in the database. */
 275 static enum TDB_ERROR tdb_nest_lock(struct tdb_context *tdb,
 276                                     tdb_off_t offset, int ltype,
 277                                     enum tdb_lock_flags flags)
 278 {
 279         struct tdb_lock_type *new_lck;
 280         enum TDB_ERROR ecode;
 281
 282         if (offset > (TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
 283                       + tdb->file->map_size / 8)) {
 284                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 285                                   "tdb_nest_lock: invalid offset %zu ltype=%d",
 286                                   (size_t)offset, ltype);
 287         }
 288
 289         if (tdb->flags & TDB_NOLOCK)
 290                 return TDB_SUCCESS;
 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                         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 298                                           "tdb_nest_lock:"
 299                                           " offset %zu has read lock",
 300                                           (size_t)offset);
 301                 }
 302                 /* Just increment the struct, posix locks don't stack. */
 303                 new_lck->count++;
 304                 return TDB_SUCCESS;
 305         }
 306
 307         if (tdb->file->num_lockrecs
 308             && offset >= TDB_HASH_LOCK_START
 309             && offset < TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE) {
 310                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 311                                   "tdb_nest_lock: already have a hash lock?");
 312         }
 313
 314         new_lck = (struct tdb_lock_type *)realloc(
 315                 tdb->file->lockrecs,
 316                 sizeof(*tdb->file->lockrecs) * (tdb->file->num_lockrecs+1));
 317         if (new_lck == NULL) {
 318                 return tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
 319                                   "tdb_nest_lock:"
 320                                   " unable to allocate %zu lock struct",
 321                                   tdb->file->num_lockrecs + 1);
 322         }
 323         tdb->file->lockrecs = new_lck;
 324
 325         /* Since fcntl locks don't nest, we do a lock for the first one,
 326            and simply bump the count for future ones */
 327         ecode = tdb_brlock(tdb, ltype, offset, 1, flags);
 328         if (ecode != TDB_SUCCESS) {
 329                 return ecode;
 330         }
 331
 332         /* First time we grab a lock, perhaps someone died in commit? */
 333         if (!(flags & TDB_LOCK_NOCHECK)
 334             && tdb->file->num_lockrecs == 0) {
 335                 tdb_bool_err berr = tdb_needs_recovery(tdb);
 336                 if (berr != false) {
 337                         tdb_brunlock(tdb, ltype, offset, 1);
 338
 339                         if (berr < 0)
 340                                 return berr;
 341                         ecode = tdb_lock_and_recover(tdb);
 342                         if (ecode == TDB_SUCCESS) {
 343                                 ecode = tdb_brlock(tdb, ltype, offset, 1,
 344                                                    flags);
 345                         }
 346                         if (ecode != TDB_SUCCESS) {
 347                                 return ecode;
 348                         }
 349                 }
 350         }
 351
 352         tdb->file->lockrecs[tdb->file->num_lockrecs].off = offset;
 353         tdb->file->lockrecs[tdb->file->num_lockrecs].count = 1;
 354         tdb->file->lockrecs[tdb->file->num_lockrecs].ltype = ltype;
 355         tdb->file->num_lockrecs++;
 356
 357         return TDB_SUCCESS;
 358 }
 359
 360 static enum TDB_ERROR tdb_nest_unlock(struct tdb_context *tdb,
 361                                       tdb_off_t off, int ltype)
 362 {
 363         struct tdb_lock_type *lck;
 364         enum TDB_ERROR ecode;
 365
 366         if (tdb->flags & TDB_NOLOCK)
 367                 return TDB_SUCCESS;
 368
 369         lck = find_nestlock(tdb, off);
 370         if ((lck == NULL) || (lck->count == 0)) {
 371                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 372                                   "tdb_nest_unlock: no lock for %zu",
 373                                   (size_t)off);
 374         }
 375
 376         if (lck->count > 1) {
 377                 lck->count--;
 378                 return TDB_SUCCESS;
 379         }
 380
 381         /*
 382          * This lock has count==1 left, so we need to unlock it in the
 383          * kernel. We don't bother with decrementing the in-memory array
 384          * element, we're about to overwrite it with the last array element
 385          * anyway.
 386          */
 387         ecode = tdb_brunlock(tdb, ltype, off, 1);
 388
 389         /*
 390          * Shrink the array by overwriting the element just unlocked with the
 391          * last array element.
 392          */
 393         *lck = tdb->file->lockrecs[--tdb->file->num_lockrecs];
 394
 395         return ecode;
 396 }
 397
 398 /*
 399   get the transaction lock
 400  */
 401 enum TDB_ERROR tdb_transaction_lock(struct tdb_context *tdb, int ltype)
 402 {
 403         return tdb_nest_lock(tdb, TDB_TRANSACTION_LOCK, ltype, TDB_LOCK_WAIT);
 404 }
 405
 406 /*
 407   release the transaction lock
 408  */
 409 void tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
 410 {
 411         tdb_nest_unlock(tdb, TDB_TRANSACTION_LOCK, ltype);
 412 }
 413
 414 /* We only need to lock individual bytes, but Linux merges consecutive locks
 415  * so we lock in contiguous ranges. */
 416 static enum TDB_ERROR tdb_lock_gradual(struct tdb_context *tdb,
 417                                        int ltype, enum tdb_lock_flags flags,
 418                                        tdb_off_t off, tdb_off_t len)
 419 {
 420         enum TDB_ERROR ecode;
 421         enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);
 422
 423         if (len <= 1) {
 424                 /* 0 would mean to end-of-file... */
 425                 assert(len != 0);
 426                 /* Single hash.  Just do blocking lock. */
 427                 return tdb_brlock(tdb, ltype, off, len, flags);
 428         }
 429
 430         /* First we try non-blocking. */
 431         if (tdb_brlock(tdb, ltype, off, len, nb_flags) == TDB_SUCCESS) {
 432                 return TDB_SUCCESS;
 433         }
 434
 435         /* Try locking first half, then second. */
 436         ecode = tdb_lock_gradual(tdb, ltype, flags, off, len / 2);
 437         if (ecode != TDB_SUCCESS)
 438                 return ecode;
 439
 440         ecode = tdb_lock_gradual(tdb, ltype, flags,
 441                                  off + len / 2, len - len / 2);
 442         if (ecode != TDB_SUCCESS) {
 443                 tdb_brunlock(tdb, ltype, off, len / 2);
 444         }
 445         return ecode;
 446 }
 447
 448 /* lock/unlock entire database.  It can only be upgradable if you have some
 449  * other way of guaranteeing exclusivity (ie. transaction write lock). */
 450 enum TDB_ERROR tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
 451                                   enum tdb_lock_flags flags, bool upgradable)
 452 {
 453         enum TDB_ERROR ecode;
 454         tdb_bool_err berr;
 455
 456         if (tdb->file->allrecord_lock.count
 457             && (ltype == F_RDLCK
 458                 || tdb->file->allrecord_lock.ltype == F_WRLCK)) {
 459                 tdb->file->allrecord_lock.count++;
 460                 return TDB_SUCCESS;
 461         }
 462
 463         if (tdb->file->allrecord_lock.count) {
 464                 /* a global lock of a different type exists */
 465                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
 466                                   "tdb_allrecord_lock: already have %s lock",
 467                                   tdb->file->allrecord_lock.ltype == F_RDLCK
 468                                   ? "read" : "write");
 469         }
 470
 471         if (tdb_has_hash_locks(tdb)) {
 472                 /* can't combine global and chain locks */
 473                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
 474                                   "tdb_allrecord_lock:"
 475                                   " already have chain lock");
 476         }
 477
 478         if (upgradable && ltype != F_RDLCK) {
 479                 /* tdb error: you can't upgrade a write lock! */
 480                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 481                                   "tdb_allrecord_lock:"
 482                                   " can't upgrade a write lock");
 483         }
 484
 485         add_stat(tdb, locks, 1);
 486 again:
 487         /* Lock hashes, gradually. */
 488         ecode = tdb_lock_gradual(tdb, ltype, flags, TDB_HASH_LOCK_START,
 489                                  TDB_HASH_LOCK_RANGE);
 490         if (ecode != TDB_SUCCESS) {
 491                 if (!(flags & TDB_LOCK_PROBE)) {
 492                         tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
 493                                    "tdb_allrecord_lock hashes failed");
 494                 }
 495                 return ecode;
 496         }
 497
 498         /* Lock free tables: there to end of file. */
 499         ecode = tdb_brlock(tdb, ltype,
 500                            TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE,
 501                            0, flags);
 502         if (ecode != TDB_SUCCESS) {
 503                 if (!(flags & TDB_LOCK_PROBE)) {
 504                         tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
 505                                  "tdb_allrecord_lock freetables failed");
 506                 }
 507                 tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START,
 508                              TDB_HASH_LOCK_RANGE);
 509                 return ecode;
 510         }
 511
 512         tdb->file->allrecord_lock.count = 1;
 513         /* If it's upgradable, it's actually exclusive so we can treat
 514          * it as a write lock. */
 515         tdb->file->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
 516         tdb->file->allrecord_lock.off = upgradable;
 517
 518         /* Now check for needing recovery. */
 519         if (flags & TDB_LOCK_NOCHECK)
 520                 return TDB_SUCCESS;
 521
 522         berr = tdb_needs_recovery(tdb);
 523         if (likely(berr == false))
 524                 return TDB_SUCCESS;
 525
 526         tdb_allrecord_unlock(tdb, ltype);
 527         if (berr < 0)
 528                 return berr;
 529         ecode = tdb_lock_and_recover(tdb);
 530         if (ecode != TDB_SUCCESS) {
 531                 return ecode;
 532         }
 533         goto again;
 534 }
 535
 536 enum TDB_ERROR tdb_lock_open(struct tdb_context *tdb, enum tdb_lock_flags flags)
 537 {
 538         return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, flags);
 539 }
 540
 541 void tdb_unlock_open(struct tdb_context *tdb)
 542 {
 543         tdb_nest_unlock(tdb, TDB_OPEN_LOCK, F_WRLCK);
 544 }
 545
 546 bool tdb_has_open_lock(struct tdb_context *tdb)
 547 {
 548         return !(tdb->flags & TDB_NOLOCK)
 549                 && find_nestlock(tdb, TDB_OPEN_LOCK) != NULL;
 550 }
 551
 552 enum TDB_ERROR tdb_lock_expand(struct tdb_context *tdb, int ltype)
 553 {
 554         /* Lock doesn't protect data, so don't check (we recurse if we do!) */
 555         return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype,
 556                              TDB_LOCK_WAIT | TDB_LOCK_NOCHECK);
 557 }
 558
 559 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
 560 {
 561         tdb_nest_unlock(tdb, TDB_EXPANSION_LOCK, ltype);
 562 }
 563
 564 /* unlock entire db */
 565 void tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
 566 {
 567         if (tdb->file->allrecord_lock.count == 0) {
 568                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
 569                            "tdb_allrecord_unlock: not locked!");
 570                 return;
 571         }
 572
 573         /* Upgradable locks are marked as write locks. */
 574         if (tdb->file->allrecord_lock.ltype != ltype
 575             && (!tdb->file->allrecord_lock.off || ltype != F_RDLCK)) {
 576                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 577                            "tdb_allrecord_unlock: have %s lock",
 578                            tdb->file->allrecord_lock.ltype == F_RDLCK
 579                            ? "read" : "write");
 580                 return;
 581         }
 582
 583         if (tdb->file->allrecord_lock.count > 1) {
 584                 tdb->file->allrecord_lock.count--;
 585                 return;
 586         }
 587
 588         tdb->file->allrecord_lock.count = 0;
 589         tdb->file->allrecord_lock.ltype = 0;
 590
 591         tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START, 0);
 592 }
 593
 594 bool tdb_has_expansion_lock(struct tdb_context *tdb)
 595 {
 596         return find_nestlock(tdb, TDB_EXPANSION_LOCK) != NULL;
 597 }
 598
 599 bool tdb_has_hash_locks(struct tdb_context *tdb)
 600 {
 601         unsigned int i;
 602
 603         for (i=0; i<tdb->file->num_lockrecs; i++) {
 604                 if (tdb->file->lockrecs[i].off >= TDB_HASH_LOCK_START
 605                     && tdb->file->lockrecs[i].off < (TDB_HASH_LOCK_START
 606                                                      + TDB_HASH_LOCK_RANGE))
 607                         return true;
 608         }
 609         return false;
 610 }
 611
 612 static bool tdb_has_free_lock(struct tdb_context *tdb)
 613 {
 614         unsigned int i;
 615
 616         if (tdb->flags & TDB_NOLOCK)
 617                 return false;
 618
 619         for (i=0; i<tdb->file->num_lockrecs; i++) {
 620                 if (tdb->file->lockrecs[i].off
 621                     > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE)
 622                         return true;
 623         }
 624         return false;
 625 }
 626
 627 enum TDB_ERROR tdb_lock_hashes(struct tdb_context *tdb,
 628                                tdb_off_t hash_lock,
 629                                tdb_len_t hash_range,
 630                                int ltype, enum tdb_lock_flags waitflag)
 631 {
 632         /* FIXME: Do this properly, using hlock_range */
 633         unsigned lock = TDB_HASH_LOCK_START
 634                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 635
 636         /* a allrecord lock allows us to avoid per chain locks */
 637         if (tdb->file->allrecord_lock.count &&
 638             (ltype == tdb->file->allrecord_lock.ltype || ltype == F_RDLCK)) {
 639                 return TDB_SUCCESS;
 640         }
 641
 642         if (tdb->file->allrecord_lock.count) {
 643                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
 644                                   "tdb_lock_hashes:"
 645                                   " already have %s allrecordlock",
 646                                   tdb->file->allrecord_lock.ltype == F_RDLCK
 647                                   ? "read" : "write");
 648         }
 649
 650         if (tdb_has_free_lock(tdb)) {
 651                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 652                                   "tdb_lock_hashes: already have free lock");
 653         }
 654
 655         if (tdb_has_expansion_lock(tdb)) {
 656                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 657                                   "tdb_lock_hashes:"
 658                                   " already have expansion lock");
 659         }
 660
 661         return tdb_nest_lock(tdb, lock, ltype, waitflag);
 662 }
 663
 664 enum TDB_ERROR tdb_unlock_hashes(struct tdb_context *tdb,
 665                                  tdb_off_t hash_lock,
 666                                  tdb_len_t hash_range, int ltype)
 667 {
 668         unsigned lock = TDB_HASH_LOCK_START
 669                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 670
 671         if (tdb->flags & TDB_NOLOCK)
 672                 return 0;
 673
 674         /* a allrecord lock allows us to avoid per chain locks */
 675         if (tdb->file->allrecord_lock.count) {
 676                 if (tdb->file->allrecord_lock.ltype == F_RDLCK
 677                     && ltype == F_WRLCK) {
 678                         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 679                                           "tdb_unlock_hashes RO allrecord!");
 680                 }
 681                 return TDB_SUCCESS;
 682         }
 683
 684         return tdb_nest_unlock(tdb, lock, ltype);
 685 }
 686
 687 /* Hash locks use TDB_HASH_LOCK_START + the next 30 bits.
 688  * Then we begin; bucket offsets are sizeof(tdb_len_t) apart, so we divide.
 689  * The result is that on 32 bit systems we don't use lock values > 2^31 on
 690  * files that are less than 4GB.
 691  */
 692 static tdb_off_t free_lock_off(tdb_off_t b_off)
 693 {
 694         return TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
 695                 + b_off / sizeof(tdb_off_t);
 696 }
 697
 698 enum TDB_ERROR tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
 699                                     enum tdb_lock_flags waitflag)
 700 {
 701         assert(b_off >= sizeof(struct tdb_header));
 702
 703         if (tdb->flags & TDB_NOLOCK)
 704                 return 0;
 705
 706         /* a allrecord lock allows us to avoid per chain locks */
 707         if (tdb->file->allrecord_lock.count) {
 708                 if (tdb->file->allrecord_lock.ltype == F_WRLCK)
 709                         return 0;
 710                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 711                                   "tdb_lock_free_bucket with"
 712                                   " read-only allrecordlock!");
 713         }
 714
 715 #if 0 /* FIXME */
 716         if (tdb_has_expansion_lock(tdb)) {
 717                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 718                                   "tdb_lock_free_bucket:"
 719                                   " already have expansion lock");
 720         }
 721 #endif
 722
 723         return tdb_nest_lock(tdb, free_lock_off(b_off), F_WRLCK, waitflag);
 724 }
 725
 726 void tdb_unlock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off)
 727 {
 728         if (tdb->file->allrecord_lock.count)
 729                 return;
 730
 731         tdb_nest_unlock(tdb, free_lock_off(b_off), F_WRLCK);
 732 }