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