git.ozlabs.org Git - ccan/blob - ccan/tdb2/lock.c

   1  /*
   2    Unix SMB/CIFS implementation.
   3
   4    trivial database library
   5
   6    Copyright (C) Andrew Tridgell              1999-2005
   7    Copyright (C) Paul `Rusty' Russell              2000
   8    Copyright (C) Jeremy Allison                    2000-2003
   9
  10      ** NOTE! The following LGPL license applies to the tdb
  11      ** library. This does NOT imply that all of Samba is released
  12      ** under the LGPL
  13
  14    This library is free software; you can redistribute it and/or
  15    modify it under the terms of the GNU Lesser General Public
  16    License as published by the Free Software Foundation; either
  17    version 3 of the License, or (at your option) any later version.
  18
  19    This library is distributed in the hope that it will be useful,
  20    but WITHOUT ANY WARRANTY; without even the implied warranty of
  21    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  22    Lesser General Public License for more details.
  23
  24    You should have received a copy of the GNU Lesser General Public
  25    License along with this library; if not, see <http://www.gnu.org/licenses/>.
  26 */
  27
  28 #include "private.h"
  29 #include <assert.h>
  30 #include <ccan/build_assert/build_assert.h>
  31
  32 static int fcntl_lock(struct tdb_context *tdb,
  33                       int rw, off_t off, off_t len, bool waitflag)
  34 {
  35         struct flock fl;
  36
  37         fl.l_type = rw;
  38         fl.l_whence = SEEK_SET;
  39         fl.l_start = off;
  40         fl.l_len = len;
  41         fl.l_pid = 0;
  42
  43         add_stat(tdb, lock_lowlevel, 1);
  44         if (waitflag)
  45                 return fcntl(tdb->fd, F_SETLKW, &fl);
  46         else {
  47                 add_stat(tdb, lock_nonblock, 1);
  48                 return fcntl(tdb->fd, F_SETLK, &fl);
  49         }
  50 }
  51
  52 static int fcntl_unlock(struct tdb_context *tdb, int rw, off_t off, off_t len)
  53 {
  54         struct flock fl;
  55 #if 0 /* Check they matched up locks and unlocks correctly. */
  56         char line[80];
  57         FILE *locks;
  58         bool found = false;
  59
  60         locks = fopen("/proc/locks", "r");
  61
  62         while (fgets(line, 80, locks)) {
  63                 char *p;
  64                 int type, start, l;
  65
  66                 /* eg. 1: FLOCK  ADVISORY  WRITE 2440 08:01:2180826 0 EOF */
  67                 p = strchr(line, ':') + 1;
  68                 if (strncmp(p, " POSIX  ADVISORY  ", strlen(" POSIX  ADVISORY  ")))
  69                         continue;
  70                 p += strlen(" FLOCK  ADVISORY  ");
  71                 if (strncmp(p, "READ  ", strlen("READ  ")) == 0)
  72                         type = F_RDLCK;
  73                 else if (strncmp(p, "WRITE ", strlen("WRITE ")) == 0)
  74                         type = F_WRLCK;
  75                 else
  76                         abort();
  77                 p += 6;
  78                 if (atoi(p) != getpid())
  79                         continue;
  80                 p = strchr(strchr(p, ' ') + 1, ' ') + 1;
  81                 start = atoi(p);
  82                 p = strchr(p, ' ') + 1;
  83                 if (strncmp(p, "EOF", 3) == 0)
  84                         l = 0;
  85                 else
  86                         l = atoi(p) - start + 1;
  87
  88                 if (off == start) {
  89                         if (len != l) {
  90                                 fprintf(stderr, "Len %u should be %u: %s",
  91                                         (int)len, l, line);
  92                                 abort();
  93                         }
  94                         if (type != rw) {
  95                                 fprintf(stderr, "Type %s wrong: %s",
  96                                         rw == F_RDLCK ? "READ" : "WRITE", line);
  97                                 abort();
  98                         }
  99                         found = true;
 100                         break;
 101                 }
 102         }
 103
 104         if (!found) {
 105                 fprintf(stderr, "Unlock on %u@%u not found!",
 106                         (int)off, (int)len);
 107                 abort();
 108         }
 109
 110         fclose(locks);
 111 #endif
 112
 113         fl.l_type = F_UNLCK;
 114         fl.l_whence = SEEK_SET;
 115         fl.l_start = off;
 116         fl.l_len = len;
 117         fl.l_pid = 0;
 118
 119         return fcntl(tdb->fd, F_SETLKW, &fl);
 120 }
 121
 122 /* a byte range locking function - return 0 on success
 123    this functions locks/unlocks 1 byte at the specified offset.
 124
 125    note that a len of zero means lock to end of file
 126 */
 127 static 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_logerr(tdb, TDB_ERR_RDONLY, TDB_DEBUG_WARNING,
 139                            "Write lock attempted on read-only database");
 140                 return -1;
 141         }
 142
 143         /* A 32 bit system cannot open a 64-bit file, but it could have
 144          * expanded since then: check here. */
 145         if ((size_t)(offset + len) != offset + len) {
 146                 tdb_logerr(tdb, TDB_ERR_IO, TDB_DEBUG_ERROR,
 147                          "tdb_brlock: lock on giant offset %llu",
 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_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 164                                    "tdb_brlock failed (fd=%d) at"
 165                                    " offset %zu rw_type=%d flags=%d len=%zu:"
 166                                    " %s",
 167                                    tdb->fd, (size_t)offset, rw_type,
 168                                    flags, (size_t)len, strerror(errno));
 169                 }
 170                 return -1;
 171         }
 172         return 0;
 173 }
 174
 175 static int tdb_brunlock(struct tdb_context *tdb,
 176                         int rw_type, tdb_off_t offset, size_t len)
 177 {
 178         int ret;
 179
 180         if (tdb->flags & TDB_NOLOCK) {
 181                 return 0;
 182         }
 183
 184         do {
 185                 ret = fcntl_unlock(tdb, rw_type, offset, len);
 186         } while (ret == -1 && errno == EINTR);
 187
 188         if (ret == -1) {
 189                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 190                            "tdb_brunlock failed (fd=%d) at offset %zu"
 191                            " rw_type=%d len=%zu",
 192                            tdb->fd, (size_t)offset, rw_type, (size_t)len);
 193         }
 194         return ret;
 195 }
 196
 197 /*
 198   upgrade a read lock to a write lock. This needs to be handled in a
 199   special way as some OSes (such as solaris) have too conservative
 200   deadlock detection and claim a deadlock when progress can be
 201   made. For those OSes we may loop for a while.
 202 */
 203 int tdb_allrecord_upgrade(struct tdb_context *tdb)
 204 {
 205         int count = 1000;
 206
 207         if (tdb->allrecord_lock.count != 1) {
 208                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 209                            "tdb_allrecord_upgrade failed: count %u too high",
 210                            tdb->allrecord_lock.count);
 211                 return -1;
 212         }
 213
 214         if (tdb->allrecord_lock.off != 1) {
 215                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 216                            "tdb_allrecord_upgrade failed: already upgraded?");
 217                 return -1;
 218         }
 219
 220         while (count--) {
 221                 struct timeval tv;
 222                 if (tdb_brlock(tdb, F_WRLCK,
 223                                TDB_HASH_LOCK_START, 0,
 224                                TDB_LOCK_WAIT|TDB_LOCK_PROBE) == 0) {
 225                         tdb->allrecord_lock.ltype = F_WRLCK;
 226                         tdb->allrecord_lock.off = 0;
 227                         return 0;
 228                 }
 229                 if (errno != EDEADLK) {
 230                         break;
 231                 }
 232                 /* sleep for as short a time as we can - more portable than usleep() */
 233                 tv.tv_sec = 0;
 234                 tv.tv_usec = 1;
 235                 select(0, NULL, NULL, NULL, &tv);
 236         }
 237         tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 238                    "tdb_allrecord_upgrade failed");
 239         return -1;
 240 }
 241
 242 static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,
 243                                            tdb_off_t offset)
 244 {
 245         unsigned int i;
 246
 247         for (i=0; i<tdb->num_lockrecs; i++) {
 248                 if (tdb->lockrecs[i].off == offset) {
 249                         return &tdb->lockrecs[i];
 250                 }
 251         }
 252         return NULL;
 253 }
 254
 255 int tdb_lock_and_recover(struct tdb_context *tdb)
 256 {
 257         int ret;
 258
 259         if (tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK,
 260                                false) == -1) {
 261                 return -1;
 262         }
 263
 264         if (tdb_lock_open(tdb, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK) == -1) {
 265                 tdb_allrecord_unlock(tdb, F_WRLCK);
 266                 return -1;
 267         }
 268         ret = tdb_transaction_recover(tdb);
 269
 270         tdb_unlock_open(tdb);
 271         tdb_allrecord_unlock(tdb, F_WRLCK);
 272
 273         return ret;
 274 }
 275
 276 /* lock an offset in the database. */
 277 static int tdb_nest_lock(struct tdb_context *tdb, tdb_off_t offset, int ltype,
 278                          enum tdb_lock_flags flags)
 279 {
 280         struct tdb_lock_type *new_lck;
 281
 282         if (offset > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE + tdb->map_size / 8) {
 283                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_FATAL,
 284                            "tdb_nest_lock: invalid offset %zu ltype=%d",
 285                            (size_t)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_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_FATAL,
 298                                    "tdb_nest_lock: offset %zu has read lock",
 299                                    (size_t)offset);
 300                         return -1;
 301                 }
 302                 /* Just increment the struct, posix locks don't stack. */
 303                 new_lck->count++;
 304                 return 0;
 305         }
 306
 307         if (tdb->num_lockrecs
 308             && offset >= TDB_HASH_LOCK_START
 309             && offset < TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE) {
 310                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_FATAL,
 311                            "tdb_nest_lock: already have a hash lock?");
 312                 return -1;
 313         }
 314
 315         new_lck = (struct tdb_lock_type *)realloc(
 316                 tdb->lockrecs,
 317                 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
 318         if (new_lck == NULL) {
 319                 tdb_logerr(tdb, TDB_ERR_OOM, TDB_DEBUG_ERROR,
 320                          "tdb_nest_lock: unable to allocate %zu lock struct",
 321                          tdb->num_lockrecs + 1);
 322                 errno = ENOMEM;
 323                 return -1;
 324         }
 325         tdb->lockrecs = new_lck;
 326
 327         /* Since fcntl locks don't nest, we do a lock for the first one,
 328            and simply bump the count for future ones */
 329         if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
 330                 return -1;
 331         }
 332
 333         /* First time we grab a lock, perhaps someone died in commit? */
 334         if (!(flags & TDB_LOCK_NOCHECK)
 335             && tdb->num_lockrecs == 0
 336             && unlikely(tdb_needs_recovery(tdb))) {
 337                 tdb_brunlock(tdb, ltype, offset, 1);
 338
 339                 if (tdb_lock_and_recover(tdb) == -1) {
 340                         return -1;
 341                 }
 342
 343                 if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
 344                         return -1;
 345                 }
 346         }
 347
 348         tdb->lockrecs[tdb->num_lockrecs].off = offset;
 349         tdb->lockrecs[tdb->num_lockrecs].count = 1;
 350         tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
 351         tdb->num_lockrecs++;
 352
 353         return 0;
 354 }
 355
 356 static int tdb_nest_unlock(struct tdb_context *tdb, tdb_off_t off, int ltype)
 357 {
 358         int ret = -1;
 359         struct tdb_lock_type *lck;
 360
 361         if (tdb->flags & TDB_NOLOCK)
 362                 return 0;
 363
 364         lck = find_nestlock(tdb, off);
 365         if ((lck == NULL) || (lck->count == 0)) {
 366                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 367                            "tdb_nest_unlock: no lock for %zu", (size_t)off);
 368                 return -1;
 369         }
 370
 371         if (lck->count > 1) {
 372                 lck->count--;
 373                 return 0;
 374         }
 375
 376         /*
 377          * This lock has count==1 left, so we need to unlock it in the
 378          * kernel. We don't bother with decrementing the in-memory array
 379          * element, we're about to overwrite it with the last array element
 380          * anyway.
 381          */
 382         ret = tdb_brunlock(tdb, ltype, off, 1);
 383
 384         /*
 385          * Shrink the array by overwriting the element just unlocked with the
 386          * last array element.
 387          */
 388         *lck = tdb->lockrecs[--tdb->num_lockrecs];
 389
 390         return ret;
 391 }
 392
 393 /*
 394   get the transaction lock
 395  */
 396 int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
 397 {
 398         return tdb_nest_lock(tdb, TDB_TRANSACTION_LOCK, ltype, TDB_LOCK_WAIT);
 399 }
 400
 401 /*
 402   release the transaction lock
 403  */
 404 int tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
 405 {
 406         return tdb_nest_unlock(tdb, TDB_TRANSACTION_LOCK, ltype);
 407 }
 408
 409 /* We only need to lock individual bytes, but Linux merges consecutive locks
 410  * so we lock in contiguous ranges. */
 411 static int tdb_lock_gradual(struct tdb_context *tdb,
 412                             int ltype, enum tdb_lock_flags flags,
 413                             tdb_off_t off, tdb_off_t len)
 414 {
 415         int ret;
 416         enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);
 417
 418         if (len <= 1) {
 419                 /* 0 would mean to end-of-file... */
 420                 assert(len != 0);
 421                 /* Single hash.  Just do blocking lock. */
 422                 return tdb_brlock(tdb, ltype, off, len, flags);
 423         }
 424
 425         /* First we try non-blocking. */
 426         ret = tdb_brlock(tdb, ltype, off, len, nb_flags);
 427         if (ret == 0) {
 428                 return 0;
 429         }
 430
 431         /* Try locking first half, then second. */
 432         ret = tdb_lock_gradual(tdb, ltype, flags, off, len / 2);
 433         if (ret == -1)
 434                 return -1;
 435
 436         ret = tdb_lock_gradual(tdb, ltype, flags,
 437                                     off + len / 2, len - len / 2);
 438         if (ret == -1) {
 439                 tdb_brunlock(tdb, ltype, off, len / 2);
 440                 return -1;
 441         }
 442         return 0;
 443 }
 444
 445 /* lock/unlock entire database.  It can only be upgradable if you have some
 446  * other way of guaranteeing exclusivity (ie. transaction write lock). */
 447 int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
 448                        enum tdb_lock_flags flags, bool upgradable)
 449 {
 450         /* FIXME: There are no locks on read-only dbs */
 451         if (tdb->read_only) {
 452                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 453                            "tdb_allrecord_lock: read-only");
 454                 return -1;
 455         }
 456
 457         if (tdb->allrecord_lock.count
 458             && (ltype == F_RDLCK || tdb->allrecord_lock.ltype == F_WRLCK)) {
 459                 tdb->allrecord_lock.count++;
 460                 return 0;
 461         }
 462
 463         if (tdb->allrecord_lock.count) {
 464                 /* a global lock of a different type exists */
 465                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 466                            "tdb_allrecord_lock: already have %s lock",
 467                            tdb->allrecord_lock.ltype == F_RDLCK
 468                            ? "read" : "write");
 469                 return -1;
 470         }
 471
 472         if (tdb_has_hash_locks(tdb)) {
 473                 /* can't combine global and chain locks */
 474                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 475                          "tdb_allrecord_lock: already have chain lock");
 476                 return -1;
 477         }
 478
 479         if (upgradable && ltype != F_RDLCK) {
 480                 /* tdb error: you can't upgrade a write lock! */
 481                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 482                            "tdb_allrecord_lock: can't upgrade a write lock");
 483                 return -1;
 484         }
 485
 486         add_stat(tdb, locks, 1);
 487 again:
 488         /* Lock hashes, gradually. */
 489         if (tdb_lock_gradual(tdb, ltype, flags, TDB_HASH_LOCK_START,
 490                              TDB_HASH_LOCK_RANGE)) {
 491                 if (!(flags & TDB_LOCK_PROBE)) {
 492                         tdb_logerr(tdb, tdb->ecode, TDB_DEBUG_ERROR,
 493                                    "tdb_allrecord_lock hashes failed");
 494                 }
 495                 return -1;
 496         }
 497
 498         /* Lock free tables: there to end of file. */
 499         if (tdb_brlock(tdb, ltype, TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE,
 500                        0, flags)) {
 501                 if (!(flags & TDB_LOCK_PROBE)) {
 502                         tdb_logerr(tdb, tdb->ecode, TDB_DEBUG_ERROR,
 503                                  "tdb_allrecord_lock freetables failed");
 504                 }
 505                 tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START,
 506                              TDB_HASH_LOCK_RANGE);
 507                 return -1;
 508         }
 509
 510         tdb->allrecord_lock.count = 1;
 511         /* If it's upgradable, it's actually exclusive so we can treat
 512          * it as a write lock. */
 513         tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
 514         tdb->allrecord_lock.off = upgradable;
 515
 516         /* Now check for needing recovery. */
 517         if (!(flags & TDB_LOCK_NOCHECK) && unlikely(tdb_needs_recovery(tdb))) {
 518                 tdb_allrecord_unlock(tdb, ltype);
 519                 if (tdb_lock_and_recover(tdb) == -1) {
 520                         return -1;
 521                 }
 522                 goto again;
 523         }
 524
 525         return 0;
 526 }
 527
 528 int tdb_lock_open(struct tdb_context *tdb, enum tdb_lock_flags flags)
 529 {
 530         return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, flags);
 531 }
 532
 533 void tdb_unlock_open(struct tdb_context *tdb)
 534 {
 535         tdb_nest_unlock(tdb, TDB_OPEN_LOCK, F_WRLCK);
 536 }
 537
 538 bool tdb_has_open_lock(struct tdb_context *tdb)
 539 {
 540         return find_nestlock(tdb, TDB_OPEN_LOCK) != NULL;
 541 }
 542
 543 int tdb_lock_expand(struct tdb_context *tdb, int ltype)
 544 {
 545         /* Lock doesn't protect data, so don't check (we recurse if we do!) */
 546         return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype,
 547                              TDB_LOCK_WAIT | TDB_LOCK_NOCHECK);
 548 }
 549
 550 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
 551 {
 552         tdb_nest_unlock(tdb, TDB_EXPANSION_LOCK, ltype);
 553 }
 554
 555 /* unlock entire db */
 556 int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
 557 {
 558         if (tdb->allrecord_lock.count == 0) {
 559                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 560                            "tdb_allrecord_unlock: not locked!");
 561                 return -1;
 562         }
 563
 564         /* Upgradable locks are marked as write locks. */
 565         if (tdb->allrecord_lock.ltype != ltype
 566             && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) {
 567                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 568                          "tdb_allrecord_unlock: have %s lock",
 569                            tdb->allrecord_lock.ltype == F_RDLCK
 570                            ? "read" : "write");
 571                 return -1;
 572         }
 573
 574         if (tdb->allrecord_lock.count > 1) {
 575                 tdb->allrecord_lock.count--;
 576                 return 0;
 577         }
 578
 579         tdb->allrecord_lock.count = 0;
 580         tdb->allrecord_lock.ltype = 0;
 581
 582         return tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START, 0);
 583 }
 584
 585 bool tdb_has_expansion_lock(struct tdb_context *tdb)
 586 {
 587         return find_nestlock(tdb, TDB_EXPANSION_LOCK) != NULL;
 588 }
 589
 590 bool tdb_has_hash_locks(struct tdb_context *tdb)
 591 {
 592         unsigned int i;
 593
 594         for (i=0; i<tdb->num_lockrecs; i++) {
 595                 if (tdb->lockrecs[i].off >= TDB_HASH_LOCK_START
 596                     && tdb->lockrecs[i].off < (TDB_HASH_LOCK_START
 597                                                + TDB_HASH_LOCK_RANGE))
 598                         return true;
 599         }
 600         return false;
 601 }
 602
 603 static bool tdb_has_free_lock(struct tdb_context *tdb)
 604 {
 605         unsigned int i;
 606
 607         for (i=0; i<tdb->num_lockrecs; i++) {
 608                 if (tdb->lockrecs[i].off
 609                     > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE)
 610                         return true;
 611         }
 612         return false;
 613 }
 614
 615 int tdb_lock_hashes(struct tdb_context *tdb,
 616                     tdb_off_t hash_lock,
 617                     tdb_len_t hash_range,
 618                     int ltype, enum tdb_lock_flags waitflag)
 619 {
 620         /* FIXME: Do this properly, using hlock_range */
 621         unsigned lock = TDB_HASH_LOCK_START
 622                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 623
 624         /* a allrecord lock allows us to avoid per chain locks */
 625         if (tdb->allrecord_lock.count &&
 626             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
 627                 return 0;
 628         }
 629
 630         if (tdb->allrecord_lock.count) {
 631                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 632                            "tdb_lock_hashes: already have %s allrecordlock",
 633                            tdb->allrecord_lock.ltype == F_RDLCK
 634                            ? "read" : "write");
 635                 return -1;
 636         }
 637
 638         if (tdb_has_free_lock(tdb)) {
 639                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 640                            "tdb_lock_hashes: already have free lock");
 641                 return -1;
 642         }
 643
 644         if (tdb_has_expansion_lock(tdb)) {
 645                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 646                            "tdb_lock_hashes: already have expansion lock");
 647                 return -1;
 648         }
 649
 650         return tdb_nest_lock(tdb, lock, ltype, waitflag);
 651 }
 652
 653 int tdb_unlock_hashes(struct tdb_context *tdb,
 654                       tdb_off_t hash_lock,
 655                       tdb_len_t hash_range, int ltype)
 656 {
 657         unsigned lock = TDB_HASH_LOCK_START
 658                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 659
 660         /* a allrecord lock allows us to avoid per chain locks */
 661         if (tdb->allrecord_lock.count) {
 662                 if (tdb->allrecord_lock.ltype == F_RDLCK
 663                     && ltype == F_WRLCK) {
 664                         tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_FATAL,
 665                                    "tdb_unlock_hashes RO allrecord!");
 666                         return -1;
 667                 }
 668                 return 0;
 669         }
 670
 671         return tdb_nest_unlock(tdb, lock, ltype);
 672 }
 673
 674 /* Hash locks use TDB_HASH_LOCK_START + the next 30 bits.
 675  * Then we begin; bucket offsets are sizeof(tdb_len_t) apart, so we divide.
 676  * The result is that on 32 bit systems we don't use lock values > 2^31 on
 677  * files that are less than 4GB.
 678  */
 679 static tdb_off_t free_lock_off(tdb_off_t b_off)
 680 {
 681         return TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
 682                 + b_off / sizeof(tdb_off_t);
 683 }
 684
 685 int tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
 686                          enum tdb_lock_flags waitflag)
 687 {
 688         assert(b_off >= sizeof(struct tdb_header));
 689
 690         /* a allrecord lock allows us to avoid per chain locks */
 691         if (tdb->allrecord_lock.count) {
 692                 if (tdb->allrecord_lock.ltype == F_WRLCK)
 693                         return 0;
 694                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_FATAL,
 695                          "tdb_lock_free_bucket with RO allrecordlock!");
 696                 return -1;
 697         }
 698
 699 #if 0 /* FIXME */
 700         if (tdb_has_expansion_lock(tdb)) {
 701                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_DEBUG_ERROR,
 702                            "tdb_lock_free_bucket: already have expansion lock");
 703                 return -1;
 704         }
 705 #endif
 706
 707         return tdb_nest_lock(tdb, free_lock_off(b_off), F_WRLCK, waitflag);
 708 }
 709
 710 void tdb_unlock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off)
 711 {
 712         if (tdb->allrecord_lock.count)
 713                 return;
 714
 715         tdb_nest_unlock(tdb, free_lock_off(b_off), F_WRLCK);
 716 }
 717
 718 void tdb_lock_init(struct tdb_context *tdb)
 719 {
 720         tdb->num_lockrecs = 0;
 721         tdb->lockrecs = NULL;
 722         tdb->allrecord_lock.count = 0;
 723 }