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!\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    note that a len of zero means lock to end of file
 126 */
 127 static int 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 0;
 135         }
 136
 137         if (rw_type == F_WRLCK && tdb->read_only) {
 138                 tdb->ecode = TDB_ERR_RDONLY;
 139                 return -1;
 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                 tdb->ecode = TDB_ERR_IO;
 146                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 147                          "tdb_brlock: lock on giant offset %llu\n",
 148                          (long long)(offset + len));
 149                 return -1;
 150         }
 151
 152         do {
 153                 ret = fcntl_lock(tdb, rw_type, offset, len,
 154                                  flags & TDB_LOCK_WAIT);
 155         } while (ret == -1 && errno == EINTR);
 156
 157         if (ret == -1) {
 158                 tdb->ecode = TDB_ERR_LOCK;
 159                 /* Generic lock error. errno set by fcntl.
 160                  * EAGAIN is an expected return from non-blocking
 161                  * locks. */
 162                 if (!(flags & TDB_LOCK_PROBE) && errno != EAGAIN) {
 163                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 164                                  "tdb_brlock failed (fd=%d) at"
 165                                  " offset %llu rw_type=%d flags=%d len=%llu\n",
 166                                  tdb->fd, (long long)offset, rw_type,
 167                                  flags, (long long)len);
 168                 }
 169                 return -1;
 170         }
 171         return 0;
 172 }
 173
 174 static 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->log_priv,
 189                          "tdb_brunlock failed (fd=%d) at offset %llu"
 190                          " rw_type=%d len=%llu\n",
 191                          tdb->fd, (long long)offset, rw_type, (long long)len);
 192         }
 193         return ret;
 194 }
 195
 196 /*
 197   upgrade a read lock to a write lock. This needs to be handled in a
 198   special way as some OSes (such as solaris) have too conservative
 199   deadlock detection and claim a deadlock when progress can be
 200   made. For those OSes we may loop for a while.
 201 */
 202 int tdb_allrecord_upgrade(struct tdb_context *tdb)
 203 {
 204         int count = 1000;
 205
 206         if (tdb->allrecord_lock.count != 1) {
 207                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 208                          "tdb_allrecord_upgrade failed: count %u too high\n",
 209                          tdb->allrecord_lock.count);
 210                 return -1;
 211         }
 212
 213         if (tdb->allrecord_lock.off != 1) {
 214                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 215                          "tdb_allrecord_upgrade failed: already upgraded?\n");
 216                 return -1;
 217         }
 218
 219         while (count--) {
 220                 struct timeval tv;
 221                 if (tdb_brlock(tdb, F_WRLCK,
 222                                TDB_HASH_LOCK_START, 0,
 223                                TDB_LOCK_WAIT|TDB_LOCK_PROBE) == 0) {
 224                         tdb->allrecord_lock.ltype = F_WRLCK;
 225                         tdb->allrecord_lock.off = 0;
 226                         return 0;
 227                 }
 228                 if (errno != EDEADLK) {
 229                         break;
 230                 }
 231                 /* sleep for as short a time as we can - more portable than usleep() */
 232                 tv.tv_sec = 0;
 233                 tv.tv_usec = 1;
 234                 select(0, NULL, NULL, NULL, &tv);
 235         }
 236         tdb->log(tdb, TDB_DEBUG_WARNING, tdb->log_priv,
 237                  "tdb_allrecord_upgrade failed\n");
 238         return -1;
 239 }
 240
 241 static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,
 242                                            tdb_off_t offset)
 243 {
 244         unsigned int i;
 245
 246         for (i=0; i<tdb->num_lockrecs; i++) {
 247                 if (tdb->lockrecs[i].off == offset) {
 248                         return &tdb->lockrecs[i];
 249                 }
 250         }
 251         return NULL;
 252 }
 253
 254 int tdb_lock_and_recover(struct tdb_context *tdb)
 255 {
 256         int ret;
 257
 258         if (tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK,
 259                                false) == -1) {
 260                 return -1;
 261         }
 262
 263         if (tdb_lock_open(tdb, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK) == -1) {
 264                 tdb_allrecord_unlock(tdb, F_WRLCK);
 265                 return -1;
 266         }
 267         ret = tdb_transaction_recover(tdb);
 268
 269         tdb_unlock_open(tdb);
 270         tdb_allrecord_unlock(tdb, F_WRLCK);
 271
 272         return ret;
 273 }
 274
 275 /* lock an offset in the database. */
 276 static int tdb_nest_lock(struct tdb_context *tdb, tdb_off_t offset, int ltype,
 277                          enum tdb_lock_flags flags)
 278 {
 279         struct tdb_lock_type *new_lck;
 280
 281         if (offset > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE + tdb->map_size / 8) {
 282                 tdb->ecode = TDB_ERR_LOCK;
 283                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 284                          "tdb_nest_lock: invalid offset %llu ltype=%d\n",
 285                          (long long)offset, ltype);
 286                 return -1;
 287         }
 288
 289         if (tdb->flags & TDB_NOLOCK)
 290                 return 0;
 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                         tdb->ecode = TDB_ERR_LOCK;
 298                         tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 299                                  "tdb_nest_lock: offset %llu has read lock\n",
 300                                  (long long)offset);
 301                         return -1;
 302                 }
 303                 /* Just increment the struct, posix locks don't stack. */
 304                 new_lck->count++;
 305                 return 0;
 306         }
 307
 308         if (tdb->num_lockrecs
 309             && offset >= TDB_HASH_LOCK_START
 310             && offset < TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE) {
 311                 tdb->ecode = TDB_ERR_LOCK;
 312                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 313                          "tdb_nest_lock: already have a hash lock?\n");
 314                 return -1;
 315         }
 316
 317         new_lck = (struct tdb_lock_type *)realloc(
 318                 tdb->lockrecs,
 319                 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
 320         if (new_lck == NULL) {
 321                 tdb->ecode = TDB_ERR_OOM;
 322                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 323                          "tdb_nest_lock: unable to allocate %llu lock struct",
 324                          (long long)(tdb->num_lockrecs + 1));
 325                 errno = ENOMEM;
 326                 return -1;
 327         }
 328         tdb->lockrecs = new_lck;
 329
 330         /* Since fcntl locks don't nest, we do a lock for the first one,
 331            and simply bump the count for future ones */
 332         if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
 333                 return -1;
 334         }
 335
 336         /* First time we grab a lock, perhaps someone died in commit? */
 337         if (!(flags & TDB_LOCK_NOCHECK)
 338             && tdb->num_lockrecs == 0
 339             && unlikely(tdb_needs_recovery(tdb))) {
 340                 tdb_brunlock(tdb, ltype, offset, 1);
 341
 342                 if (tdb_lock_and_recover(tdb) == -1) {
 343                         return -1;
 344                 }
 345
 346                 if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
 347                         return -1;
 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 0;
 357 }
 358
 359 static int tdb_nest_unlock(struct tdb_context *tdb, tdb_off_t off, int ltype)
 360 {
 361         int ret = -1;
 362         struct tdb_lock_type *lck;
 363
 364         if (tdb->flags & TDB_NOLOCK)
 365                 return 0;
 366
 367         lck = find_nestlock(tdb, off);
 368         if ((lck == NULL) || (lck->count == 0)) {
 369                 tdb->ecode = TDB_ERR_LOCK;
 370                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 371                          "tdb_nest_unlock: no lock for %llu\n", (long long)off);
 372                 return -1;
 373         }
 374
 375         if (lck->count > 1) {
 376                 lck->count--;
 377                 return 0;
 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         ret = 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 ret;
 395 }
 396
 397 /*
 398   get the transaction lock
 399  */
 400 int 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 int tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
 409 {
 410         return 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 int 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         int ret;
 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         ret = tdb_brlock(tdb, ltype, off, len, nb_flags);
 431         if (ret == 0) {
 432                 return 0;
 433         }
 434
 435         /* Try locking first half, then second. */
 436         ret = tdb_lock_gradual(tdb, ltype, flags, off, len / 2);
 437         if (ret == -1)
 438                 return -1;
 439
 440         ret = tdb_lock_gradual(tdb, ltype, flags,
 441                                     off + len / 2, len - len / 2);
 442         if (ret == -1) {
 443                 tdb_brunlock(tdb, ltype, off, len / 2);
 444                 return -1;
 445         }
 446         return 0;
 447 }
 448
 449 /* lock/unlock entire database.  It can only be upgradable if you have some
 450  * other way of guaranteeing exclusivity (ie. transaction write lock). */
 451 int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
 452                        enum tdb_lock_flags flags, bool upgradable)
 453 {
 454         /* FIXME: There are no locks on read-only dbs */
 455         if (tdb->read_only) {
 456                 tdb->ecode = TDB_ERR_LOCK;
 457                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 458                          "tdb_allrecord_lock: read-only\n");
 459                 return -1;
 460         }
 461
 462         if (tdb->allrecord_lock.count
 463             && (ltype == F_RDLCK || tdb->allrecord_lock.ltype == F_WRLCK)) {
 464                 tdb->allrecord_lock.count++;
 465                 return 0;
 466         }
 467
 468         if (tdb->allrecord_lock.count) {
 469                 /* a global lock of a different type exists */
 470                 tdb->ecode = TDB_ERR_LOCK;
 471                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 472                          "tdb_allrecord_lock: already have %s lock\n",
 473                          tdb->allrecord_lock.ltype == F_RDLCK
 474                          ? "read" : "write");
 475                 return -1;
 476         }
 477
 478         if (tdb_has_hash_locks(tdb)) {
 479                 /* can't combine global and chain locks */
 480                 tdb->ecode = TDB_ERR_LOCK;
 481                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 482                          "tdb_allrecord_lock: already have chain lock\n");
 483                 return -1;
 484         }
 485
 486         if (upgradable && ltype != F_RDLCK) {
 487                 /* tdb error: you can't upgrade a write lock! */
 488                 tdb->ecode = TDB_ERR_LOCK;
 489                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 490                          "tdb_allrecord_lock: can't upgrade a write lock\n");
 491                 return -1;
 492         }
 493
 494         add_stat(tdb, locks, 1);
 495 again:
 496         /* Lock hashes, gradually. */
 497         if (tdb_lock_gradual(tdb, ltype, flags, TDB_HASH_LOCK_START,
 498                              TDB_HASH_LOCK_RANGE)) {
 499                 if (!(flags & TDB_LOCK_PROBE)) {
 500                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 501                                  "tdb_allrecord_lock hashes failed (%s)\n",
 502                                  strerror(errno));
 503                 }
 504                 return -1;
 505         }
 506
 507         /* Lock free lists: there to end of file. */
 508         if (tdb_brlock(tdb, ltype, TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE,
 509                        0, flags)) {
 510                 if (!(flags & TDB_LOCK_PROBE)) {
 511                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 512                                  "tdb_allrecord_lock freelist failed (%s)\n",
 513                                  strerror(errno));
 514                 }
 515                 tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START,
 516                              TDB_HASH_LOCK_RANGE);
 517                 return -1;
 518         }
 519
 520         tdb->allrecord_lock.count = 1;
 521         /* If it's upgradable, it's actually exclusive so we can treat
 522          * it as a write lock. */
 523         tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
 524         tdb->allrecord_lock.off = upgradable;
 525
 526         /* Now check for needing recovery. */
 527         if (!(flags & TDB_LOCK_NOCHECK) && unlikely(tdb_needs_recovery(tdb))) {
 528                 tdb_allrecord_unlock(tdb, ltype);
 529                 if (tdb_lock_and_recover(tdb) == -1) {
 530                         return -1;
 531                 }
 532                 goto again;
 533         }
 534
 535         return 0;
 536 }
 537
 538 int tdb_lock_open(struct tdb_context *tdb, enum tdb_lock_flags flags)
 539 {
 540         return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, flags);
 541 }
 542
 543 void tdb_unlock_open(struct tdb_context *tdb)
 544 {
 545         tdb_nest_unlock(tdb, TDB_OPEN_LOCK, F_WRLCK);
 546 }
 547
 548 bool tdb_has_open_lock(struct tdb_context *tdb)
 549 {
 550         return find_nestlock(tdb, TDB_OPEN_LOCK) != NULL;
 551 }
 552
 553 int tdb_lock_expand(struct tdb_context *tdb, int ltype)
 554 {
 555         /* Lock doesn't protect data, so don't check (we recurse if we do!) */
 556         return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype,
 557                              TDB_LOCK_WAIT | TDB_LOCK_NOCHECK);
 558 }
 559
 560 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
 561 {
 562         tdb_nest_unlock(tdb, TDB_EXPANSION_LOCK, ltype);
 563 }
 564
 565 /* unlock entire db */
 566 int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
 567 {
 568         /* FIXME: There are no locks on read-only dbs */
 569         if (tdb->read_only) {
 570                 tdb->ecode = TDB_ERR_LOCK;
 571                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 572                          "tdb_allrecord_unlock: read-only\n");
 573                 return -1;
 574         }
 575
 576         if (tdb->allrecord_lock.count == 0) {
 577                 tdb->ecode = TDB_ERR_LOCK;
 578                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 579                          "tdb_allrecord_unlock: not locked!\n");
 580                 return -1;
 581         }
 582
 583         /* Upgradable locks are marked as write locks. */
 584         if (tdb->allrecord_lock.ltype != ltype
 585             && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) {
 586                 tdb->ecode = TDB_ERR_LOCK;
 587                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 588                          "tdb_allrecord_unlock: have %s lock\n",
 589                          tdb->allrecord_lock.ltype == F_RDLCK
 590                          ? "read" : "write");
 591                 return -1;
 592         }
 593
 594         if (tdb->allrecord_lock.count > 1) {
 595                 tdb->allrecord_lock.count--;
 596                 return 0;
 597         }
 598
 599         tdb->allrecord_lock.count = 0;
 600         tdb->allrecord_lock.ltype = 0;
 601
 602         return tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START, 0);
 603 }
 604
 605 bool tdb_has_expansion_lock(struct tdb_context *tdb)
 606 {
 607         return find_nestlock(tdb, TDB_EXPANSION_LOCK) != NULL;
 608 }
 609
 610 bool tdb_has_hash_locks(struct tdb_context *tdb)
 611 {
 612         unsigned int i;
 613
 614         for (i=0; i<tdb->num_lockrecs; i++) {
 615                 if (tdb->lockrecs[i].off >= TDB_HASH_LOCK_START
 616                     && tdb->lockrecs[i].off < (TDB_HASH_LOCK_START
 617                                                + TDB_HASH_LOCK_RANGE))
 618                         return true;
 619         }
 620         return false;
 621 }
 622
 623 static bool tdb_has_free_lock(struct tdb_context *tdb)
 624 {
 625         unsigned int i;
 626
 627         for (i=0; i<tdb->num_lockrecs; i++) {
 628                 if (tdb->lockrecs[i].off
 629                     > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE)
 630                         return true;
 631         }
 632         return false;
 633 }
 634
 635 int tdb_lock_hashes(struct tdb_context *tdb,
 636                     tdb_off_t hash_lock,
 637                     tdb_len_t hash_range,
 638                     int ltype, enum tdb_lock_flags waitflag)
 639 {
 640         /* FIXME: Do this properly, using hlock_range */
 641         unsigned lock = TDB_HASH_LOCK_START
 642                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 643
 644         /* a allrecord lock allows us to avoid per chain locks */
 645         if (tdb->allrecord_lock.count &&
 646             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
 647                 return 0;
 648         }
 649
 650         if (tdb->allrecord_lock.count) {
 651                 tdb->ecode = TDB_ERR_LOCK;
 652                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 653                          "tdb_lock_hashes: have %s allrecordlock\n",
 654                          tdb->allrecord_lock.ltype == F_RDLCK
 655                          ? "read" : "write");
 656                 return -1;
 657         }
 658
 659         if (tdb_has_free_lock(tdb)) {
 660                 tdb->ecode = TDB_ERR_LOCK;
 661                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 662                          "tdb_lock_hashes: have free lock already\n");
 663                 return -1;
 664         }
 665
 666         if (tdb_has_expansion_lock(tdb)) {
 667                 tdb->ecode = TDB_ERR_LOCK;
 668                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 669                          "tdb_lock_hashes: have expansion lock already\n");
 670                 return -1;
 671         }
 672
 673         return tdb_nest_lock(tdb, lock, ltype, waitflag);
 674 }
 675
 676 int tdb_unlock_hashes(struct tdb_context *tdb,
 677                       tdb_off_t hash_lock,
 678                       tdb_len_t hash_range, int ltype)
 679 {
 680         unsigned lock = TDB_HASH_LOCK_START
 681                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 682
 683         /* a allrecord lock allows us to avoid per chain locks */
 684         if (tdb->allrecord_lock.count) {
 685                 if (tdb->allrecord_lock.ltype == F_RDLCK
 686                     && ltype == F_WRLCK) {
 687                         tdb->ecode = TDB_ERR_LOCK;
 688                         tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 689                                  "tdb_unlock_hashes RO allrecord!\n");
 690                         return -1;
 691                 }
 692                 return 0;
 693         }
 694
 695         return tdb_nest_unlock(tdb, lock, ltype);
 696 }
 697
 698 /* Hash locks use TDB_HASH_LOCK_START + the next 30 bits.
 699  * Then we begin; bucket offsets are sizeof(tdb_len_t) apart, so we divide.
 700  * The result is that on 32 bit systems we don't use lock values > 2^31 on
 701  * files that are less than 4GB.
 702  */
 703 static tdb_off_t free_lock_off(tdb_off_t b_off)
 704 {
 705         return TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
 706                 + b_off / sizeof(tdb_off_t);
 707 }
 708
 709 int tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
 710                          enum tdb_lock_flags waitflag)
 711 {
 712         assert(b_off >= sizeof(struct tdb_header));
 713
 714         /* a allrecord lock allows us to avoid per chain locks */
 715         if (tdb->allrecord_lock.count) {
 716                 if (tdb->allrecord_lock.ltype == F_WRLCK)
 717                         return 0;
 718                 tdb->ecode = TDB_ERR_LOCK;
 719                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 720                          "tdb_lock_free_bucket with RO allrecordlock!\n");
 721                 return -1;
 722         }
 723
 724 #if 0 /* FIXME */
 725         if (tdb_has_expansion_lock(tdb)) {
 726                 tdb->ecode = TDB_ERR_LOCK;
 727                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 728                          "tdb_lock_free_bucket: have expansion lock already\n");
 729                 return -1;
 730         }
 731 #endif
 732
 733         return tdb_nest_lock(tdb, free_lock_off(b_off), F_WRLCK, waitflag);
 734 }
 735
 736 void tdb_unlock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off)
 737 {
 738         if (tdb->allrecord_lock.count)
 739                 return;
 740
 741         tdb_nest_unlock(tdb, free_lock_off(b_off), F_WRLCK);
 742 }
 743
 744 void tdb_lock_init(struct tdb_context *tdb)
 745 {
 746         tdb->num_lockrecs = 0;
 747         tdb->lockrecs = NULL;
 748         tdb->allrecord_lock.count = 0;
 749 }