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         if (waitflag)
  44                 return fcntl(tdb->fd, F_SETLKW, &fl);
  45         else
  46                 return fcntl(tdb->fd, F_SETLK, &fl);
  47 }
  48
  49 static int fcntl_unlock(struct tdb_context *tdb, int rw, off_t off, off_t len)
  50 {
  51         struct flock fl;
  52 #if 0 /* Check they matched up locks and unlocks correctly. */
  53         char line[80];
  54         FILE *locks;
  55         bool found = false;
  56
  57         locks = fopen("/proc/locks", "r");
  58
  59         while (fgets(line, 80, locks)) {
  60                 char *p;
  61                 int type, start, l;
  62
  63                 /* eg. 1: FLOCK  ADVISORY  WRITE 2440 08:01:2180826 0 EOF */
  64                 p = strchr(line, ':') + 1;
  65                 if (strncmp(p, " POSIX  ADVISORY  ", strlen(" POSIX  ADVISORY  ")))
  66                         continue;
  67                 p += strlen(" FLOCK  ADVISORY  ");
  68                 if (strncmp(p, "READ  ", strlen("READ  ")) == 0)
  69                         type = F_RDLCK;
  70                 else if (strncmp(p, "WRITE ", strlen("WRITE ")) == 0)
  71                         type = F_WRLCK;
  72                 else
  73                         abort();
  74                 p += 6;
  75                 if (atoi(p) != getpid())
  76                         continue;
  77                 p = strchr(strchr(p, ' ') + 1, ' ') + 1;
  78                 start = atoi(p);
  79                 p = strchr(p, ' ') + 1;
  80                 if (strncmp(p, "EOF", 3) == 0)
  81                         l = 0;
  82                 else
  83                         l = atoi(p) - start + 1;
  84
  85                 if (off == start) {
  86                         if (len != l) {
  87                                 fprintf(stderr, "Len %u should be %u: %s",
  88                                         (int)len, l, line);
  89                                 abort();
  90                         }
  91                         if (type != rw) {
  92                                 fprintf(stderr, "Type %s wrong: %s",
  93                                         rw == F_RDLCK ? "READ" : "WRITE", line);
  94                                 abort();
  95                         }
  96                         found = true;
  97                         break;
  98                 }
  99         }
 100
 101         if (!found) {
 102                 fprintf(stderr, "Unlock on %u@%u not found!\n",
 103                         (int)off, (int)len);
 104                 abort();
 105         }
 106
 107         fclose(locks);
 108 #endif
 109
 110         fl.l_type = F_UNLCK;
 111         fl.l_whence = SEEK_SET;
 112         fl.l_start = off;
 113         fl.l_len = len;
 114         fl.l_pid = 0;
 115
 116         return fcntl(tdb->fd, F_SETLKW, &fl);
 117 }
 118
 119 /* a byte range locking function - return 0 on success
 120    this functions locks/unlocks 1 byte at the specified offset.
 121
 122    note that a len of zero means lock to end of file
 123 */
 124 static int tdb_brlock(struct tdb_context *tdb,
 125                       int rw_type, tdb_off_t offset, tdb_off_t len,
 126                       enum tdb_lock_flags flags)
 127 {
 128         int ret;
 129
 130         if (tdb->flags & TDB_NOLOCK) {
 131                 return 0;
 132         }
 133
 134         if (rw_type == F_WRLCK && tdb->read_only) {
 135                 tdb->ecode = TDB_ERR_RDONLY;
 136                 return -1;
 137         }
 138
 139         /* A 32 bit system cannot open a 64-bit file, but it could have
 140          * expanded since then: check here. */
 141         if ((size_t)(offset + len) != offset + len) {
 142                 tdb->ecode = TDB_ERR_IO;
 143                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 144                          "tdb_brlock: lock on giant offset %llu\n",
 145                          (long long)(offset + len));
 146                 return -1;
 147         }
 148
 149         do {
 150                 ret = fcntl_lock(tdb, rw_type, offset, len,
 151                                  flags & TDB_LOCK_WAIT);
 152         } while (ret == -1 && errno == EINTR);
 153
 154         if (ret == -1) {
 155                 tdb->ecode = TDB_ERR_LOCK;
 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->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 161                                  "tdb_brlock failed (fd=%d) at"
 162                                  " offset %llu rw_type=%d flags=%d len=%llu\n",
 163                                  tdb->fd, (long long)offset, rw_type,
 164                                  flags, (long long)len);
 165                 }
 166                 return -1;
 167         }
 168         return 0;
 169 }
 170
 171 static int tdb_brunlock(struct tdb_context *tdb,
 172                         int rw_type, tdb_off_t offset, size_t len)
 173 {
 174         int ret;
 175
 176         if (tdb->flags & TDB_NOLOCK) {
 177                 return 0;
 178         }
 179
 180         do {
 181                 ret = fcntl_unlock(tdb, rw_type, offset, len);
 182         } while (ret == -1 && errno == EINTR);
 183
 184         if (ret == -1) {
 185                 tdb->log(tdb, TDB_DEBUG_TRACE, tdb->log_priv,
 186                          "tdb_brunlock failed (fd=%d) at offset %llu"
 187                          " rw_type=%d len=%llu\n",
 188                          tdb->fd, (long long)offset, rw_type, (long long)len);
 189         }
 190         return ret;
 191 }
 192
 193 #if 0
 194 /*
 195   upgrade a read lock to a write lock. This needs to be handled in a
 196   special way as some OSes (such as solaris) have too conservative
 197   deadlock detection and claim a deadlock when progress can be
 198   made. For those OSes we may loop for a while.
 199 */
 200 int tdb_allrecord_upgrade(struct tdb_context *tdb)
 201 {
 202         int count = 1000;
 203
 204         if (tdb->allrecord_lock.count != 1) {
 205                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 206                          "tdb_allrecord_upgrade failed: count %u too high\n",
 207                          tdb->allrecord_lock.count);
 208                 return -1;
 209         }
 210
 211         if (tdb->allrecord_lock.off != 1) {
 212                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 213                          "tdb_allrecord_upgrade failed: already upgraded?\n");
 214                 return -1;
 215         }
 216
 217         while (count--) {
 218                 struct timeval tv;
 219                 if (tdb_brlock(tdb, F_WRLCK,
 220                                TDB_HASH_LOCK_START
 221                                + (1ULL << tdb->header.v.hash_bits), 0,
 222                                TDB_LOCK_WAIT|TDB_LOCK_PROBE) == 0) {
 223                         tdb->allrecord_lock.ltype = F_WRLCK;
 224                         tdb->allrecord_lock.off = 0;
 225                         return 0;
 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         tdb->log(tdb, TDB_DEBUG_WARNING, tdb->log_priv,
 236                  "tdb_allrecord_upgrade failed\n");
 237         return -1;
 238 }
 239 #endif
 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 /* lock an offset in the database. */
 255 static int tdb_nest_lock(struct tdb_context *tdb, tdb_off_t offset, int ltype,
 256                          enum tdb_lock_flags flags)
 257 {
 258         struct tdb_lock_type *new_lck;
 259
 260         if (offset >= TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE + tdb->map_size / 8) {
 261                 tdb->ecode = TDB_ERR_LOCK;
 262                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 263                          "tdb_nest_lock: invalid offset %llu ltype=%d\n",
 264                          (long long)offset, ltype);
 265                 return -1;
 266         }
 267
 268         if (tdb->flags & TDB_NOLOCK)
 269                 return 0;
 270
 271         new_lck = find_nestlock(tdb, offset);
 272         if (new_lck) {
 273                 /*
 274                  * Just increment the in-memory struct, posix locks
 275                  * don't stack.
 276                  */
 277                 new_lck->count++;
 278                 return 0;
 279         }
 280
 281         if (tdb->num_lockrecs
 282             && offset >= TDB_HASH_LOCK_START
 283             && offset < TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE) {
 284                 tdb->ecode = TDB_ERR_LOCK;
 285                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 286                          "tdb_nest_lock: already have a hash lock?\n");
 287                 return -1;
 288         }
 289
 290         new_lck = (struct tdb_lock_type *)realloc(
 291                 tdb->lockrecs,
 292                 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
 293         if (new_lck == NULL) {
 294                 tdb->ecode = TDB_ERR_OOM;
 295                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 296                          "tdb_nest_lock: unable to allocate %llu lock struct",
 297                          (long long)(tdb->num_lockrecs + 1));
 298                 errno = ENOMEM;
 299                 return -1;
 300         }
 301         tdb->lockrecs = new_lck;
 302
 303         /* Since fcntl locks don't nest, we do a lock for the first one,
 304            and simply bump the count for future ones */
 305         if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
 306                 return -1;
 307         }
 308
 309         tdb->lockrecs[tdb->num_lockrecs].off = offset;
 310         tdb->lockrecs[tdb->num_lockrecs].count = 1;
 311         tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
 312         tdb->num_lockrecs++;
 313
 314         return 0;
 315 }
 316
 317 static int tdb_lock_and_recover(struct tdb_context *tdb)
 318 {
 319 #if 0 /* FIXME */
 320
 321         int ret;
 322
 323         /* We need to match locking order in transaction commit. */
 324         if (tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT)) {
 325                 return -1;
 326         }
 327
 328         if (tdb_brlock(tdb, F_WRLCK, OPEN_LOCK, 1, TDB_LOCK_WAIT)) {
 329                 tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);
 330                 return -1;
 331         }
 332
 333         ret = tdb_transaction_recover(tdb);
 334
 335         tdb_brunlock(tdb, F_WRLCK, OPEN_LOCK, 1);
 336         tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);
 337
 338         return ret;
 339 #else
 340         abort();
 341         return -1;
 342 #endif
 343 }
 344
 345 static bool tdb_needs_recovery(struct tdb_context *tdb)
 346 {
 347         /* FIXME */
 348         return false;
 349 }
 350
 351 static int tdb_nest_unlock(struct tdb_context *tdb, tdb_off_t off, int ltype)
 352 {
 353         int ret = -1;
 354         struct tdb_lock_type *lck;
 355
 356         if (tdb->flags & TDB_NOLOCK)
 357                 return 0;
 358
 359         lck = find_nestlock(tdb, off);
 360         if ((lck == NULL) || (lck->count == 0)) {
 361                 tdb->ecode = TDB_ERR_LOCK;
 362                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 363                          "tdb_nest_unlock: no lock for %llu\n", (long long)off);
 364                 return -1;
 365         }
 366
 367         if (lck->count > 1) {
 368                 lck->count--;
 369                 return 0;
 370         }
 371
 372         /*
 373          * This lock has count==1 left, so we need to unlock it in the
 374          * kernel. We don't bother with decrementing the in-memory array
 375          * element, we're about to overwrite it with the last array element
 376          * anyway.
 377          */
 378         ret = tdb_brunlock(tdb, ltype, off, 1);
 379
 380         /*
 381          * Shrink the array by overwriting the element just unlocked with the
 382          * last array element.
 383          */
 384         *lck = tdb->lockrecs[--tdb->num_lockrecs];
 385
 386         return ret;
 387 }
 388
 389 #if 0
 390 /*
 391   get the transaction lock
 392  */
 393 int tdb_transaction_lock(struct tdb_context *tdb, int ltype,
 394                          enum tdb_lock_flags lockflags)
 395 {
 396         return tdb_nest_lock(tdb, TRANSACTION_LOCK, ltype, lockflags);
 397 }
 398
 399 /*
 400   release the transaction lock
 401  */
 402 int tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
 403 {
 404         return tdb_nest_unlock(tdb, TRANSACTION_LOCK, ltype, false);
 405 }
 406 #endif
 407
 408 /* We only need to lock individual bytes, but Linux merges consecutive locks
 409  * so we lock in contiguous ranges. */
 410 static int tdb_lock_gradual(struct tdb_context *tdb,
 411                             int ltype, enum tdb_lock_flags flags,
 412                             tdb_off_t off, tdb_off_t len)
 413 {
 414         int ret;
 415         enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);
 416
 417         if (len <= 1) {
 418                 /* 0 would mean to end-of-file... */
 419                 assert(len != 0);
 420                 /* Single hash.  Just do blocking lock. */
 421                 return tdb_brlock(tdb, ltype, off, len, flags);
 422         }
 423
 424         /* First we try non-blocking. */
 425         ret = tdb_brlock(tdb, ltype, off, len, nb_flags);
 426         if (ret == 0) {
 427                 return 0;
 428         }
 429
 430         /* Try locking first half, then second. */
 431         ret = tdb_lock_gradual(tdb, ltype, flags, off, len / 2);
 432         if (ret == -1)
 433                 return -1;
 434
 435         ret = tdb_lock_gradual(tdb, ltype, flags,
 436                                     off + len / 2, len - len / 2);
 437         if (ret == -1) {
 438                 tdb_brunlock(tdb, ltype, off, len / 2);
 439                 return -1;
 440         }
 441         return 0;
 442 }
 443
 444 /* lock/unlock entire database.  It can only be upgradable if you have some
 445  * other way of guaranteeing exclusivity (ie. transaction write lock). */
 446 int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
 447                        enum tdb_lock_flags flags, bool upgradable)
 448 {
 449         /* FIXME: There are no locks on read-only dbs */
 450         if (tdb->read_only) {
 451                 tdb->ecode = TDB_ERR_LOCK;
 452                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 453                          "tdb_allrecord_lock: read-only\n");
 454                 return -1;
 455         }
 456
 457         if (tdb->allrecord_lock.count && tdb->allrecord_lock.ltype == ltype) {
 458                 tdb->allrecord_lock.count++;
 459                 return 0;
 460         }
 461
 462         if (tdb->allrecord_lock.count) {
 463                 /* a global lock of a different type exists */
 464                 tdb->ecode = TDB_ERR_LOCK;
 465                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 466                          "tdb_allrecord_lock: already have %s lock\n",
 467                          tdb->allrecord_lock.ltype == F_RDLCK
 468                          ? "read" : "write");
 469                 return -1;
 470         }
 471
 472         if (tdb_has_locks(tdb)) {
 473                 /* can't combine global and chain locks */
 474                 tdb->ecode = TDB_ERR_LOCK;
 475                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 476                          "tdb_allrecord_lock: already have chain lock\n");
 477                 return -1;
 478         }
 479
 480         if (upgradable && ltype != F_RDLCK) {
 481                 /* tdb error: you can't upgrade a write lock! */
 482                 tdb->ecode = TDB_ERR_LOCK;
 483                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 484                          "tdb_allrecord_lock: can't upgrade a write lock\n");
 485                 return -1;
 486         }
 487
 488 again:
 489         /* Lock hashes, gradually. */
 490         if (tdb_lock_gradual(tdb, ltype, flags, TDB_HASH_LOCK_START,
 491                              TDB_HASH_LOCK_RANGE)) {
 492                 if (!(flags & TDB_LOCK_PROBE)) {
 493                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 494                                  "tdb_allrecord_lock hashes failed (%s)\n",
 495                                  strerror(errno));
 496                 }
 497                 return -1;
 498         }
 499
 500         /* Lock free lists: there to end of file. */
 501         if (tdb_brlock(tdb, ltype, TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE,
 502                        0, flags)) {
 503                 if (!(flags & TDB_LOCK_PROBE)) {
 504                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 505                                  "tdb_allrecord_lock freelist failed (%s)\n",
 506                                  strerror(errno));
 507                 }
 508                 tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START,
 509                              TDB_HASH_LOCK_RANGE);
 510                 return -1;
 511         }
 512
 513         tdb->allrecord_lock.count = 1;
 514         /* If it's upgradable, it's actually exclusive so we can treat
 515          * it as a write lock. */
 516         tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
 517         tdb->allrecord_lock.off = upgradable;
 518
 519         /* Now check for needing recovery. */
 520         if (unlikely(tdb_needs_recovery(tdb))) {
 521                 tdb_allrecord_unlock(tdb, ltype);
 522                 if (tdb_lock_and_recover(tdb) == -1) {
 523                         return -1;
 524                 }
 525                 goto again;
 526         }
 527
 528         return 0;
 529 }
 530
 531 int tdb_lock_open(struct tdb_context *tdb)
 532 {
 533         return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT);
 534 }
 535
 536 void tdb_unlock_open(struct tdb_context *tdb)
 537 {
 538         tdb_nest_unlock(tdb, TDB_OPEN_LOCK, F_WRLCK);
 539 }
 540
 541 int tdb_lock_expand(struct tdb_context *tdb, int ltype)
 542 {
 543         return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype, TDB_LOCK_WAIT);
 544 }
 545
 546 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
 547 {
 548         tdb_nest_unlock(tdb, TDB_EXPANSION_LOCK, ltype);
 549 }
 550
 551 /* unlock entire db */
 552 int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
 553 {
 554         /* FIXME: There are no locks on read-only dbs */
 555         if (tdb->read_only) {
 556                 tdb->ecode = TDB_ERR_LOCK;
 557                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 558                          "tdb_allrecord_unlock: read-only\n");
 559                 return -1;
 560         }
 561
 562         if (tdb->allrecord_lock.count == 0) {
 563                 tdb->ecode = TDB_ERR_LOCK;
 564                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 565                          "tdb_allrecord_unlock: not locked!\n");
 566                 return -1;
 567         }
 568
 569         /* Upgradable locks are marked as write locks. */
 570         if (tdb->allrecord_lock.ltype != ltype
 571             && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) {
 572                 tdb->ecode = TDB_ERR_LOCK;
 573                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 574                          "tdb_allrecord_unlock: have %s lock\n",
 575                          tdb->allrecord_lock.ltype == F_RDLCK
 576                          ? "read" : "write");
 577                 return -1;
 578         }
 579
 580         if (tdb->allrecord_lock.count > 1) {
 581                 tdb->allrecord_lock.count--;
 582                 return 0;
 583         }
 584
 585         tdb->allrecord_lock.count = 0;
 586         tdb->allrecord_lock.ltype = 0;
 587
 588         return tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START, 0);
 589 }
 590
 591 bool tdb_has_expansion_lock(struct tdb_context *tdb)
 592 {
 593         return find_nestlock(tdb, TDB_EXPANSION_LOCK) != NULL;
 594 }
 595
 596 bool tdb_has_locks(struct tdb_context *tdb)
 597 {
 598         return tdb->allrecord_lock.count || tdb->num_lockrecs;
 599 }
 600
 601 #if 0
 602 /* lock entire database with write lock */
 603 int tdb_lockall(struct tdb_context *tdb)
 604 {
 605         tdb_trace(tdb, "tdb_lockall");
 606         return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT, false);
 607 }
 608
 609 /* lock entire database with write lock - nonblocking varient */
 610 int tdb_lockall_nonblock(struct tdb_context *tdb)
 611 {
 612         int ret = tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_NOWAIT, false);
 613         tdb_trace_ret(tdb, "tdb_lockall_nonblock", ret);
 614         return ret;
 615 }
 616
 617 /* unlock entire database with write lock */
 618 int tdb_unlockall(struct tdb_context *tdb)
 619 {
 620         tdb_trace(tdb, "tdb_unlockall");
 621         return tdb_allrecord_unlock(tdb, F_WRLCK);
 622 }
 623
 624 /* lock entire database with read lock */
 625 int tdb_lockall_read(struct tdb_context *tdb)
 626 {
 627         tdb_trace(tdb, "tdb_lockall_read");
 628         return tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, false);
 629 }
 630
 631 /* lock entire database with read lock - nonblock varient */
 632 int tdb_lockall_read_nonblock(struct tdb_context *tdb)
 633 {
 634         int ret = tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_NOWAIT, false);
 635         tdb_trace_ret(tdb, "tdb_lockall_read_nonblock", ret);
 636         return ret;
 637 }
 638
 639 /* unlock entire database with read lock */
 640 int tdb_unlockall_read(struct tdb_context *tdb)
 641 {
 642         tdb_trace(tdb, "tdb_unlockall_read");
 643         return tdb_allrecord_unlock(tdb, F_RDLCK);
 644 }
 645 #endif
 646
 647 static bool tdb_has_free_lock(struct tdb_context *tdb)
 648 {
 649         unsigned int i;
 650
 651         for (i=0; i<tdb->num_lockrecs; i++) {
 652                 if (tdb->lockrecs[i].off
 653                     > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE)
 654                         return true;
 655         }
 656         return false;
 657 }
 658
 659 int tdb_lock_hashes(struct tdb_context *tdb,
 660                     tdb_off_t hash_lock,
 661                     tdb_len_t hash_range,
 662                     int ltype, enum tdb_lock_flags waitflag)
 663 {
 664         /* FIXME: Do this properly, using hlock_range */
 665         unsigned lock = TDB_HASH_LOCK_START
 666                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 667
 668         /* a allrecord lock allows us to avoid per chain locks */
 669         if (tdb->allrecord_lock.count &&
 670             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
 671                 return 0;
 672         }
 673
 674         if (tdb->allrecord_lock.count) {
 675                 tdb->ecode = TDB_ERR_LOCK;
 676                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 677                          "tdb_lock_hashes: have %s allrecordlock\n",
 678                          tdb->allrecord_lock.ltype == F_RDLCK
 679                          ? "read" : "write");
 680                 return -1;
 681         }
 682
 683         if (tdb_has_free_lock(tdb)) {
 684                 tdb->ecode = TDB_ERR_LOCK;
 685                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 686                          "tdb_lock_hashes: have free lock already\n");
 687                 return -1;
 688         }
 689
 690         if (tdb_has_expansion_lock(tdb)) {
 691                 tdb->ecode = TDB_ERR_LOCK;
 692                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 693                          "tdb_lock_hashes: have expansion lock already\n");
 694                 return -1;
 695         }
 696
 697         return tdb_nest_lock(tdb, lock, ltype, waitflag);
 698 }
 699
 700 int tdb_unlock_hashes(struct tdb_context *tdb,
 701                       tdb_off_t hash_lock,
 702                       tdb_len_t hash_range, int ltype)
 703 {
 704         unsigned lock = TDB_HASH_LOCK_START
 705                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 706
 707         /* a allrecord lock allows us to avoid per chain locks */
 708         if (tdb->allrecord_lock.count) {
 709                 if (tdb->allrecord_lock.ltype == F_RDLCK
 710                     && ltype == F_WRLCK) {
 711                         tdb->ecode = TDB_ERR_LOCK;
 712                         tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 713                                  "tdb_unlock_hashes RO allrecord!\n");
 714                         return -1;
 715                 }
 716                 return 0;
 717         }
 718
 719         return tdb_nest_unlock(tdb, lock, ltype);
 720 }
 721
 722 /* Hash locks use TDB_HASH_LOCK_START + the next 30 bits.
 723  * Then we begin; bucket offsets are sizeof(tdb_len_t) apart, so we divide.
 724  * The result is that on 32 bit systems we don't use lock values > 2^31 on
 725  * files that are less than 4GB.
 726  */
 727 static tdb_off_t free_lock_off(tdb_off_t b_off)
 728 {
 729         return TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
 730                 + b_off / sizeof(tdb_off_t);
 731 }
 732
 733 int tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
 734                          enum tdb_lock_flags waitflag)
 735 {
 736         assert(b_off >= sizeof(struct tdb_header));
 737
 738         /* a allrecord lock allows us to avoid per chain locks */
 739         if (tdb->allrecord_lock.count) {
 740                 if (tdb->allrecord_lock.ltype == F_WRLCK)
 741                         return 0;
 742                 tdb->ecode = TDB_ERR_LOCK;
 743                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 744                          "tdb_lock_free_bucket with RO allrecordlock!\n");
 745                 return -1;
 746         }
 747
 748 #if 0 /* FIXME */
 749         if (tdb_has_expansion_lock(tdb)) {
 750                 tdb->ecode = TDB_ERR_LOCK;
 751                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 752                          "tdb_lock_free_bucket: have expansion lock already\n");
 753                 return -1;
 754         }
 755 #endif
 756
 757         return tdb_nest_lock(tdb, free_lock_off(b_off), F_WRLCK, waitflag);
 758 }
 759
 760 void tdb_unlock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off)
 761 {
 762         if (tdb->allrecord_lock.count)
 763                 return;
 764
 765         tdb_nest_unlock(tdb, free_lock_off(b_off), F_WRLCK);
 766 }
 767
 768 #if 0
 769 /* lock/unlock one hash chain, non-blocking. This is meant to be used
 770    to reduce contention - it cannot guarantee how many records will be
 771    locked */
 772 int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)
 773 {
 774         return chainlock(tdb, &key, F_WRLCK, TDB_LOCK_NOWAIT,
 775                          "tdb_chainlock_nonblock");
 776 }
 777
 778 int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
 779 {
 780         return chainlock(tdb, &key, F_RDLCK, TDB_LOCK_WAIT,
 781                          "tdb_chainlock_read");
 782 }
 783
 784 int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
 785 {
 786         uint64_t h = tdb_hash(tdb, key.dptr, key.dsize);
 787         tdb_trace_1rec(tdb, "tdb_chainunlock_read", key);
 788         return tdb_unlock_list(tdb, h & ((1ULL << tdb->header.v.hash_bits)-1),
 789                                F_RDLCK);
 790 }
 791
 792 /* record lock stops delete underneath */
 793 int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
 794 {
 795         if (tdb->allrecord_lock.count) {
 796                 return 0;
 797         }
 798         return off ? tdb_brlock(tdb, F_RDLCK, off, 1, TDB_LOCK_WAIT) : 0;
 799 }
 800
 801 /*
 802   Write locks override our own fcntl readlocks, so check it here.
 803   Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
 804   an error to fail to get the lock here.
 805 */
 806 int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
 807 {
 808         struct tdb_traverse_lock *i;
 809         for (i = &tdb->travlocks; i; i = i->next)
 810                 if (i->off == off)
 811                         return -1;
 812         if (tdb->allrecord_lock.count) {
 813                 if (tdb->allrecord_lock.ltype == F_WRLCK) {
 814                         return 0;
 815                 }
 816                 return -1;
 817         }
 818         return tdb_brlock(tdb, F_WRLCK, off, 1, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE);
 819 }
 820
 821 int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
 822 {
 823         if (tdb->allrecord_lock.count) {
 824                 return 0;
 825         }
 826         return tdb_brunlock(tdb, F_WRLCK, off, 1);
 827 }
 828
 829 /* fcntl locks don't stack: avoid unlocking someone else's */
 830 int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
 831 {
 832         struct tdb_traverse_lock *i;
 833         uint32_t count = 0;
 834
 835         if (tdb->allrecord_lock.count) {
 836                 return 0;
 837         }
 838
 839         if (off == 0)
 840                 return 0;
 841         for (i = &tdb->travlocks; i; i = i->next)
 842                 if (i->off == off)
 843                         count++;
 844         return (count == 1 ? tdb_brunlock(tdb, F_RDLCK, off, 1) : 0);
 845 }
 846
 847 /* The transaction code uses this to remove all locks. */
 848 void tdb_release_transaction_locks(struct tdb_context *tdb)
 849 {
 850         unsigned int i;
 851
 852         if (tdb->allrecord_lock.count != 0) {
 853                 tdb_off_t hash_size, free_size;
 854
 855                 hash_size = (1ULL << tdb->header.v.hash_bits)
 856                         * sizeof(tdb_off_t);
 857                 free_size = tdb->header.v.free_zones
 858                         * (tdb->header.v.free_buckets + 1) * sizeof(tdb_off_t);
 859
 860                 tdb_brunlock(tdb, tdb->allrecord_lock.ltype,
 861                              tdb->header.v.hash_off, hash_size);
 862                 tdb_brunlock(tdb, tdb->allrecord_lock.ltype,
 863                              tdb->header.v.free_off, free_size);
 864                 tdb->allrecord_lock.count = 0;
 865                 tdb->allrecord_lock.ltype = 0;
 866         }
 867
 868         for (i = 0; i<tdb->num_lockrecs; i++) {
 869                 struct tdb_lock_type *lck = &tdb->lockrecs[i];
 870
 871                 tdb_brunlock(tdb, lck->ltype, lck->off, 1);
 872         }
 873         tdb->num_lockrecs = 0;
 874         SAFE_FREE(tdb->lockrecs);
 875         tdb->header_uptodate = false;
 876 }
 877 #endif
 878
 879 void tdb_lock_init(struct tdb_context *tdb)
 880 {
 881         tdb->num_lockrecs = 0;
 882         tdb->lockrecs = NULL;
 883         tdb->allrecord_lock.count = 0;
 884 }