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->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         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 + tdb->map_size / 8) {
 283                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 284                                   "tdb_nest_lock: invalid offset %zu ltype=%d",
 285                                   (size_t)offset, ltype);
 286         }
 287
 288         if (tdb->flags & TDB_NOLOCK)
 289                 return TDB_SUCCESS;
 290
 291         add_stat(tdb, locks, 1);
 292
 293         new_lck = find_nestlock(tdb, offset);
 294         if (new_lck) {
 295                 if (new_lck->ltype == F_RDLCK && ltype == F_WRLCK) {
 296                         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 297                                           "tdb_nest_lock:"
 298                                           " offset %zu has read lock",
 299                                           (size_t)offset);
 300                 }
 301                 /* Just increment the struct, posix locks don't stack. */
 302                 new_lck->count++;
 303                 return TDB_SUCCESS;
 304         }
 305
 306         if (tdb->num_lockrecs
 307             && offset >= TDB_HASH_LOCK_START
 308             && offset < TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE) {
 309                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 310                                   "tdb_nest_lock: already have a hash lock?");
 311         }
 312
 313         new_lck = (struct tdb_lock_type *)realloc(
 314                 tdb->lockrecs,
 315                 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
 316         if (new_lck == NULL) {
 317                 return tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
 318                                   "tdb_nest_lock:"
 319                                   " unable to allocate %zu lock struct",
 320                                   tdb->num_lockrecs + 1);
 321         }
 322         tdb->lockrecs = new_lck;
 323
 324         /* Since fcntl locks don't nest, we do a lock for the first one,
 325            and simply bump the count for future ones */
 326         ecode = tdb_brlock(tdb, ltype, offset, 1, flags);
 327         if (ecode != TDB_SUCCESS) {
 328                 return ecode;
 329         }
 330
 331         /* First time we grab a lock, perhaps someone died in commit? */
 332         if (!(flags & TDB_LOCK_NOCHECK)
 333             && tdb->num_lockrecs == 0) {
 334                 tdb_bool_err berr = tdb_needs_recovery(tdb);
 335                 if (berr != false) {
 336                         tdb_brunlock(tdb, ltype, offset, 1);
 337
 338                         if (berr < 0)
 339                                 return berr;
 340                         ecode = tdb_lock_and_recover(tdb);
 341                         if (ecode == TDB_SUCCESS) {
 342                                 ecode = tdb_brlock(tdb, ltype, offset, 1,
 343                                                    flags);
 344                         }
 345                         if (ecode != TDB_SUCCESS) {
 346                                 return ecode;
 347                         }
 348                 }
 349         }
 350
 351         tdb->lockrecs[tdb->num_lockrecs].off = offset;
 352         tdb->lockrecs[tdb->num_lockrecs].count = 1;
 353         tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
 354         tdb->num_lockrecs++;
 355
 356         return TDB_SUCCESS;
 357 }
 358
 359 static enum TDB_ERROR tdb_nest_unlock(struct tdb_context *tdb,
 360                                       tdb_off_t off, int ltype)
 361 {
 362         struct tdb_lock_type *lck;
 363         enum TDB_ERROR ecode;
 364
 365         if (tdb->flags & TDB_NOLOCK)
 366                 return TDB_SUCCESS;
 367
 368         lck = find_nestlock(tdb, off);
 369         if ((lck == NULL) || (lck->count == 0)) {
 370                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 371                                   "tdb_nest_unlock: no lock for %zu",
 372                                   (size_t)off);
 373         }
 374
 375         if (lck->count > 1) {
 376                 lck->count--;
 377                 return TDB_SUCCESS;
 378         }
 379
 380         /*
 381          * This lock has count==1 left, so we need to unlock it in the
 382          * kernel. We don't bother with decrementing the in-memory array
 383          * element, we're about to overwrite it with the last array element
 384          * anyway.
 385          */
 386         ecode = tdb_brunlock(tdb, ltype, off, 1);
 387
 388         /*
 389          * Shrink the array by overwriting the element just unlocked with the
 390          * last array element.
 391          */
 392         *lck = tdb->lockrecs[--tdb->num_lockrecs];
 393
 394         return ecode;
 395 }
 396
 397 /*
 398   get the transaction lock
 399  */
 400 enum TDB_ERROR tdb_transaction_lock(struct tdb_context *tdb, int ltype)
 401 {
 402         return tdb_nest_lock(tdb, TDB_TRANSACTION_LOCK, ltype, TDB_LOCK_WAIT);
 403 }
 404
 405 /*
 406   release the transaction lock
 407  */
 408 void tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
 409 {
 410         tdb_nest_unlock(tdb, TDB_TRANSACTION_LOCK, ltype);
 411 }
 412
 413 /* We only need to lock individual bytes, but Linux merges consecutive locks
 414  * so we lock in contiguous ranges. */
 415 static enum TDB_ERROR tdb_lock_gradual(struct tdb_context *tdb,
 416                                        int ltype, enum tdb_lock_flags flags,
 417                                        tdb_off_t off, tdb_off_t len)
 418 {
 419         enum TDB_ERROR ecode;
 420         enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);
 421
 422         if (len <= 1) {
 423                 /* 0 would mean to end-of-file... */
 424                 assert(len != 0);
 425                 /* Single hash.  Just do blocking lock. */
 426                 return tdb_brlock(tdb, ltype, off, len, flags);
 427         }
 428
 429         /* First we try non-blocking. */
 430         if (tdb_brlock(tdb, ltype, off, len, nb_flags) == TDB_SUCCESS) {
 431                 return TDB_SUCCESS;
 432         }
 433
 434         /* Try locking first half, then second. */
 435         ecode = tdb_lock_gradual(tdb, ltype, flags, off, len / 2);
 436         if (ecode != TDB_SUCCESS)
 437                 return ecode;
 438
 439         ecode = tdb_lock_gradual(tdb, ltype, flags,
 440                                  off + len / 2, len - len / 2);
 441         if (ecode != TDB_SUCCESS) {
 442                 tdb_brunlock(tdb, ltype, off, len / 2);
 443         }
 444         return ecode;
 445 }
 446
 447 /* lock/unlock entire database.  It can only be upgradable if you have some
 448  * other way of guaranteeing exclusivity (ie. transaction write lock). */
 449 enum TDB_ERROR tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
 450                                   enum tdb_lock_flags flags, bool upgradable)
 451 {
 452         enum TDB_ERROR ecode;
 453         tdb_bool_err berr;
 454
 455         /* FIXME: There are no locks on read-only dbs */
 456         if (tdb->read_only) {
 457                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
 458                                   "tdb_allrecord_lock: read-only");
 459         }
 460
 461         if (tdb->allrecord_lock.count
 462             && (ltype == F_RDLCK || tdb->allrecord_lock.ltype == F_WRLCK)) {
 463                 tdb->allrecord_lock.count++;
 464                 return TDB_SUCCESS;
 465         }
 466
 467         if (tdb->allrecord_lock.count) {
 468                 /* a global lock of a different type exists */
 469                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
 470                                   "tdb_allrecord_lock: already have %s lock",
 471                                   tdb->allrecord_lock.ltype == F_RDLCK
 472                                   ? "read" : "write");
 473         }
 474
 475         if (tdb_has_hash_locks(tdb)) {
 476                 /* can't combine global and chain locks */
 477                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
 478                                   "tdb_allrecord_lock:"
 479                                   " already have chain lock");
 480         }
 481
 482         if (upgradable && ltype != F_RDLCK) {
 483                 /* tdb error: you can't upgrade a write lock! */
 484                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 485                                   "tdb_allrecord_lock:"
 486                                   " can't upgrade a write lock");
 487         }
 488
 489         add_stat(tdb, locks, 1);
 490 again:
 491         /* Lock hashes, gradually. */
 492         ecode = tdb_lock_gradual(tdb, ltype, flags, TDB_HASH_LOCK_START,
 493                                  TDB_HASH_LOCK_RANGE);
 494         if (ecode != TDB_SUCCESS) {
 495                 if (!(flags & TDB_LOCK_PROBE)) {
 496                         tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
 497                                    "tdb_allrecord_lock hashes failed");
 498                 }
 499                 return ecode;
 500         }
 501
 502         /* Lock free tables: there to end of file. */
 503         ecode = tdb_brlock(tdb, ltype,
 504                            TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE,
 505                            0, flags);
 506         if (ecode != TDB_SUCCESS) {
 507                 if (!(flags & TDB_LOCK_PROBE)) {
 508                         tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
 509                                  "tdb_allrecord_lock freetables failed");
 510                 }
 511                 tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START,
 512                              TDB_HASH_LOCK_RANGE);
 513                 return ecode;
 514         }
 515
 516         tdb->allrecord_lock.count = 1;
 517         /* If it's upgradable, it's actually exclusive so we can treat
 518          * it as a write lock. */
 519         tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
 520         tdb->allrecord_lock.off = upgradable;
 521
 522         /* Now check for needing recovery. */
 523         if (flags & TDB_LOCK_NOCHECK)
 524                 return TDB_SUCCESS;
 525
 526         berr = tdb_needs_recovery(tdb);
 527         if (likely(berr == false))
 528                 return TDB_SUCCESS;
 529
 530         tdb_allrecord_unlock(tdb, ltype);
 531         if (berr < 0)
 532                 return berr;
 533         ecode = tdb_lock_and_recover(tdb);
 534         if (ecode != TDB_SUCCESS) {
 535                 return ecode;
 536         }
 537         goto again;
 538 }
 539
 540 enum TDB_ERROR tdb_lock_open(struct tdb_context *tdb, enum tdb_lock_flags flags)
 541 {
 542         return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, flags);
 543 }
 544
 545 void tdb_unlock_open(struct tdb_context *tdb)
 546 {
 547         tdb_nest_unlock(tdb, TDB_OPEN_LOCK, F_WRLCK);
 548 }
 549
 550 bool tdb_has_open_lock(struct tdb_context *tdb)
 551 {
 552         return find_nestlock(tdb, TDB_OPEN_LOCK) != NULL;
 553 }
 554
 555 enum TDB_ERROR tdb_lock_expand(struct tdb_context *tdb, int ltype)
 556 {
 557         /* Lock doesn't protect data, so don't check (we recurse if we do!) */
 558         return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype,
 559                              TDB_LOCK_WAIT | TDB_LOCK_NOCHECK);
 560 }
 561
 562 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
 563 {
 564         tdb_nest_unlock(tdb, TDB_EXPANSION_LOCK, ltype);
 565 }
 566
 567 /* unlock entire db */
 568 void tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
 569 {
 570         if (tdb->allrecord_lock.count == 0) {
 571                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_USE_ERROR,
 572                            "tdb_allrecord_unlock: not locked!");
 573                 return;
 574         }
 575
 576         /* Upgradable locks are marked as write locks. */
 577         if (tdb->allrecord_lock.ltype != ltype
 578             && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) {
 579                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 580                            "tdb_allrecord_unlock: have %s lock",
 581                            tdb->allrecord_lock.ltype == F_RDLCK
 582                            ? "read" : "write");
 583                 return;
 584         }
 585
 586         if (tdb->allrecord_lock.count > 1) {
 587                 tdb->allrecord_lock.count--;
 588                 return;
 589         }
 590
 591         tdb->allrecord_lock.count = 0;
 592         tdb->allrecord_lock.ltype = 0;
 593
 594         tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START, 0);
 595 }
 596
 597 bool tdb_has_expansion_lock(struct tdb_context *tdb)
 598 {
 599         return find_nestlock(tdb, TDB_EXPANSION_LOCK) != NULL;
 600 }
 601
 602 bool tdb_has_hash_locks(struct tdb_context *tdb)
 603 {
 604         unsigned int i;
 605
 606         for (i=0; i<tdb->num_lockrecs; i++) {
 607                 if (tdb->lockrecs[i].off >= TDB_HASH_LOCK_START
 608                     && tdb->lockrecs[i].off < (TDB_HASH_LOCK_START
 609                                                + TDB_HASH_LOCK_RANGE))
 610                         return true;
 611         }
 612         return false;
 613 }
 614
 615 static bool tdb_has_free_lock(struct tdb_context *tdb)
 616 {
 617         unsigned int i;
 618
 619         for (i=0; i<tdb->num_lockrecs; i++) {
 620                 if (tdb->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->allrecord_lock.count &&
 638             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
 639                 return TDB_SUCCESS;
 640         }
 641
 642         if (tdb->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->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         /* a allrecord lock allows us to avoid per chain locks */
 672         if (tdb->allrecord_lock.count) {
 673                 if (tdb->allrecord_lock.ltype == F_RDLCK
 674                     && ltype == F_WRLCK) {
 675                         return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 676                                           "tdb_unlock_hashes RO allrecord!");
 677                 }
 678                 return TDB_SUCCESS;
 679         }
 680
 681         return tdb_nest_unlock(tdb, lock, ltype);
 682 }
 683
 684 /* Hash locks use TDB_HASH_LOCK_START + the next 30 bits.
 685  * Then we begin; bucket offsets are sizeof(tdb_len_t) apart, so we divide.
 686  * The result is that on 32 bit systems we don't use lock values > 2^31 on
 687  * files that are less than 4GB.
 688  */
 689 static tdb_off_t free_lock_off(tdb_off_t b_off)
 690 {
 691         return TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
 692                 + b_off / sizeof(tdb_off_t);
 693 }
 694
 695 enum TDB_ERROR tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
 696                                     enum tdb_lock_flags waitflag)
 697 {
 698         assert(b_off >= sizeof(struct tdb_header));
 699
 700         /* a allrecord lock allows us to avoid per chain locks */
 701         if (tdb->allrecord_lock.count) {
 702                 if (tdb->allrecord_lock.ltype == F_WRLCK)
 703                         return 0;
 704                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 705                                   "tdb_lock_free_bucket with"
 706                                   " read-only allrecordlock!");
 707         }
 708
 709 #if 0 /* FIXME */
 710         if (tdb_has_expansion_lock(tdb)) {
 711                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 712                                   "tdb_lock_free_bucket:"
 713                                   " already have expansion lock");
 714         }
 715 #endif
 716
 717         return tdb_nest_lock(tdb, free_lock_off(b_off), F_WRLCK, waitflag);
 718 }
 719
 720 void tdb_unlock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off)
 721 {
 722         if (tdb->allrecord_lock.count)
 723                 return;
 724
 725         tdb_nest_unlock(tdb, free_lock_off(b_off), F_WRLCK);
 726 }
 727
 728 void tdb_lock_init(struct tdb_context *tdb)
 729 {
 730         tdb->num_lockrecs = 0;
 731         tdb->lockrecs = NULL;
 732         tdb->allrecord_lock.count = 0;
 733 }