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 /*
 194   upgrade a read lock to a write lock. This needs to be handled in a
 195   special way as some OSes (such as solaris) have too conservative
 196   deadlock detection and claim a deadlock when progress can be
 197   made. For those OSes we may loop for a while.
 198 */
 199 int tdb_allrecord_upgrade(struct tdb_context *tdb)
 200 {
 201         int count = 1000;
 202
 203         if (tdb->allrecord_lock.count != 1) {
 204                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 205                          "tdb_allrecord_upgrade failed: count %u too high\n",
 206                          tdb->allrecord_lock.count);
 207                 return -1;
 208         }
 209
 210         if (tdb->allrecord_lock.off != 1) {
 211                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 212                          "tdb_allrecord_upgrade failed: already upgraded?\n");
 213                 return -1;
 214         }
 215
 216         while (count--) {
 217                 struct timeval tv;
 218                 if (tdb_brlock(tdb, F_WRLCK,
 219                                TDB_HASH_LOCK_START, 0,
 220                                TDB_LOCK_WAIT|TDB_LOCK_PROBE) == 0) {
 221                         tdb->allrecord_lock.ltype = F_WRLCK;
 222                         tdb->allrecord_lock.off = 0;
 223                         return 0;
 224                 }
 225                 if (errno != EDEADLK) {
 226                         break;
 227                 }
 228                 /* sleep for as short a time as we can - more portable than usleep() */
 229                 tv.tv_sec = 0;
 230                 tv.tv_usec = 1;
 231                 select(0, NULL, NULL, NULL, &tv);
 232         }
 233         tdb->log(tdb, TDB_DEBUG_WARNING, tdb->log_priv,
 234                  "tdb_allrecord_upgrade failed\n");
 235         return -1;
 236 }
 237
 238 static struct tdb_lock_type *find_nestlock(struct tdb_context *tdb,
 239                                            tdb_off_t offset)
 240 {
 241         unsigned int i;
 242
 243         for (i=0; i<tdb->num_lockrecs; i++) {
 244                 if (tdb->lockrecs[i].off == offset) {
 245                         return &tdb->lockrecs[i];
 246                 }
 247         }
 248         return NULL;
 249 }
 250
 251 int tdb_lock_and_recover(struct tdb_context *tdb)
 252 {
 253         int ret;
 254
 255         if (tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK,
 256                                false) == -1) {
 257                 return -1;
 258         }
 259
 260         if (tdb_lock_open(tdb, TDB_LOCK_WAIT|TDB_LOCK_NOCHECK) == -1) {
 261                 tdb_allrecord_unlock(tdb, F_WRLCK);
 262                 return -1;
 263         }
 264         ret = tdb_transaction_recover(tdb);
 265
 266         tdb_unlock_open(tdb);
 267         tdb_allrecord_unlock(tdb, F_WRLCK);
 268
 269         return ret;
 270 }
 271
 272 /* lock an offset in the database. */
 273 static int tdb_nest_lock(struct tdb_context *tdb, tdb_off_t offset, int ltype,
 274                          enum tdb_lock_flags flags)
 275 {
 276         struct tdb_lock_type *new_lck;
 277
 278         if (offset > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE + tdb->map_size / 8) {
 279                 tdb->ecode = TDB_ERR_LOCK;
 280                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 281                          "tdb_nest_lock: invalid offset %llu ltype=%d\n",
 282                          (long long)offset, ltype);
 283                 return -1;
 284         }
 285
 286         if (tdb->flags & TDB_NOLOCK)
 287                 return 0;
 288
 289         new_lck = find_nestlock(tdb, offset);
 290         if (new_lck) {
 291                 if (new_lck->ltype == F_RDLCK && ltype == F_WRLCK) {
 292                         tdb->ecode = TDB_ERR_LOCK;
 293                         tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 294                                  "tdb_nest_lock: offset %llu has read lock\n",
 295                                  (long long)offset);
 296                         return -1;
 297                 }
 298                 /* Just increment the struct, posix locks don't stack. */
 299                 new_lck->count++;
 300                 return 0;
 301         }
 302
 303         if (tdb->num_lockrecs
 304             && offset >= TDB_HASH_LOCK_START
 305             && offset < TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE) {
 306                 tdb->ecode = TDB_ERR_LOCK;
 307                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 308                          "tdb_nest_lock: already have a hash lock?\n");
 309                 return -1;
 310         }
 311
 312         new_lck = (struct tdb_lock_type *)realloc(
 313                 tdb->lockrecs,
 314                 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
 315         if (new_lck == NULL) {
 316                 tdb->ecode = TDB_ERR_OOM;
 317                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 318                          "tdb_nest_lock: unable to allocate %llu lock struct",
 319                          (long long)(tdb->num_lockrecs + 1));
 320                 errno = ENOMEM;
 321                 return -1;
 322         }
 323         tdb->lockrecs = new_lck;
 324
 325         /* Since fcntl locks don't nest, we do a lock for the first one,
 326            and simply bump the count for future ones */
 327         if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
 328                 return -1;
 329         }
 330
 331         /* First time we grab a lock, perhaps someone died in commit? */
 332         if (!(flags & TDB_LOCK_NOCHECK)
 333             && tdb->num_lockrecs == 0
 334             && unlikely(tdb_needs_recovery(tdb))) {
 335                 tdb_brunlock(tdb, ltype, offset, 1);
 336
 337                 if (tdb_lock_and_recover(tdb) == -1) {
 338                         return -1;
 339                 }
 340
 341                 if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
 342                         return -1;
 343                 }
 344         }
 345
 346         tdb->lockrecs[tdb->num_lockrecs].off = offset;
 347         tdb->lockrecs[tdb->num_lockrecs].count = 1;
 348         tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
 349         tdb->num_lockrecs++;
 350
 351         return 0;
 352 }
 353
 354 static int tdb_nest_unlock(struct tdb_context *tdb, tdb_off_t off, int ltype)
 355 {
 356         int ret = -1;
 357         struct tdb_lock_type *lck;
 358
 359         if (tdb->flags & TDB_NOLOCK)
 360                 return 0;
 361
 362         lck = find_nestlock(tdb, off);
 363         if ((lck == NULL) || (lck->count == 0)) {
 364                 tdb->ecode = TDB_ERR_LOCK;
 365                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 366                          "tdb_nest_unlock: no lock for %llu\n", (long long)off);
 367                 return -1;
 368         }
 369
 370         if (lck->count > 1) {
 371                 lck->count--;
 372                 return 0;
 373         }
 374
 375         /*
 376          * This lock has count==1 left, so we need to unlock it in the
 377          * kernel. We don't bother with decrementing the in-memory array
 378          * element, we're about to overwrite it with the last array element
 379          * anyway.
 380          */
 381         ret = tdb_brunlock(tdb, ltype, off, 1);
 382
 383         /*
 384          * Shrink the array by overwriting the element just unlocked with the
 385          * last array element.
 386          */
 387         *lck = tdb->lockrecs[--tdb->num_lockrecs];
 388
 389         return ret;
 390 }
 391
 392 /*
 393   get the transaction lock
 394  */
 395 int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
 396 {
 397         return tdb_nest_lock(tdb, TDB_TRANSACTION_LOCK, ltype, TDB_LOCK_WAIT);
 398 }
 399
 400 /*
 401   release the transaction lock
 402  */
 403 int tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
 404 {
 405         return tdb_nest_unlock(tdb, TDB_TRANSACTION_LOCK, ltype);
 406 }
 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
 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->ecode = TDB_ERR_LOCK;
 466                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 467                          "tdb_allrecord_lock: already have %s lock\n",
 468                          tdb->allrecord_lock.ltype == F_RDLCK
 469                          ? "read" : "write");
 470                 return -1;
 471         }
 472
 473         if (tdb_has_hash_locks(tdb)) {
 474                 /* can't combine global and chain locks */
 475                 tdb->ecode = TDB_ERR_LOCK;
 476                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 477                          "tdb_allrecord_lock: already have chain lock\n");
 478                 return -1;
 479         }
 480
 481         if (upgradable && ltype != F_RDLCK) {
 482                 /* tdb error: you can't upgrade a write lock! */
 483                 tdb->ecode = TDB_ERR_LOCK;
 484                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 485                          "tdb_allrecord_lock: can't upgrade a write lock\n");
 486                 return -1;
 487         }
 488
 489 again:
 490         /* Lock hashes, gradually. */
 491         if (tdb_lock_gradual(tdb, ltype, flags, TDB_HASH_LOCK_START,
 492                              TDB_HASH_LOCK_RANGE)) {
 493                 if (!(flags & TDB_LOCK_PROBE)) {
 494                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 495                                  "tdb_allrecord_lock hashes failed (%s)\n",
 496                                  strerror(errno));
 497                 }
 498                 return -1;
 499         }
 500
 501         /* Lock free lists: there to end of file. */
 502         if (tdb_brlock(tdb, ltype, TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE,
 503                        0, flags)) {
 504                 if (!(flags & TDB_LOCK_PROBE)) {
 505                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 506                                  "tdb_allrecord_lock freelist failed (%s)\n",
 507                                  strerror(errno));
 508                 }
 509                 tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START,
 510                              TDB_HASH_LOCK_RANGE);
 511                 return -1;
 512         }
 513
 514         tdb->allrecord_lock.count = 1;
 515         /* If it's upgradable, it's actually exclusive so we can treat
 516          * it as a write lock. */
 517         tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
 518         tdb->allrecord_lock.off = upgradable;
 519
 520         /* Now check for needing recovery. */
 521         if (!(flags & TDB_LOCK_NOCHECK) && unlikely(tdb_needs_recovery(tdb))) {
 522                 tdb_allrecord_unlock(tdb, ltype);
 523                 if (tdb_lock_and_recover(tdb) == -1) {
 524                         return -1;
 525                 }
 526                 goto again;
 527         }
 528
 529         return 0;
 530 }
 531
 532 int tdb_lock_open(struct tdb_context *tdb, enum tdb_lock_flags flags)
 533 {
 534         return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, flags);
 535 }
 536
 537 void tdb_unlock_open(struct tdb_context *tdb)
 538 {
 539         tdb_nest_unlock(tdb, TDB_OPEN_LOCK, F_WRLCK);
 540 }
 541
 542 bool tdb_has_open_lock(struct tdb_context *tdb)
 543 {
 544         return find_nestlock(tdb, TDB_OPEN_LOCK) != NULL;
 545 }
 546
 547 int tdb_lock_expand(struct tdb_context *tdb, int ltype)
 548 {
 549         /* Lock doesn't protect data, so don't check (we recurse if we do!) */
 550         return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype,
 551                              TDB_LOCK_WAIT | TDB_LOCK_NOCHECK);
 552 }
 553
 554 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
 555 {
 556         tdb_nest_unlock(tdb, TDB_EXPANSION_LOCK, ltype);
 557 }
 558
 559 /* unlock entire db */
 560 int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
 561 {
 562         /* FIXME: There are no locks on read-only dbs */
 563         if (tdb->read_only) {
 564                 tdb->ecode = TDB_ERR_LOCK;
 565                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 566                          "tdb_allrecord_unlock: read-only\n");
 567                 return -1;
 568         }
 569
 570         if (tdb->allrecord_lock.count == 0) {
 571                 tdb->ecode = TDB_ERR_LOCK;
 572                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 573                          "tdb_allrecord_unlock: not locked!\n");
 574                 return -1;
 575         }
 576
 577         /* Upgradable locks are marked as write locks. */
 578         if (tdb->allrecord_lock.ltype != ltype
 579             && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) {
 580                 tdb->ecode = TDB_ERR_LOCK;
 581                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 582                          "tdb_allrecord_unlock: have %s lock\n",
 583                          tdb->allrecord_lock.ltype == F_RDLCK
 584                          ? "read" : "write");
 585                 return -1;
 586         }
 587
 588         if (tdb->allrecord_lock.count > 1) {
 589                 tdb->allrecord_lock.count--;
 590                 return 0;
 591         }
 592
 593         tdb->allrecord_lock.count = 0;
 594         tdb->allrecord_lock.ltype = 0;
 595
 596         return tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START, 0);
 597 }
 598
 599 bool tdb_has_expansion_lock(struct tdb_context *tdb)
 600 {
 601         return find_nestlock(tdb, TDB_EXPANSION_LOCK) != NULL;
 602 }
 603
 604 bool tdb_has_hash_locks(struct tdb_context *tdb)
 605 {
 606         unsigned int i;
 607
 608         for (i=0; i<tdb->num_lockrecs; i++) {
 609                 if (tdb->lockrecs[i].off >= TDB_HASH_LOCK_START
 610                     && tdb->lockrecs[i].off < (TDB_HASH_LOCK_START
 611                                                + TDB_HASH_LOCK_RANGE))
 612                         return true;
 613         }
 614         return false;
 615 }
 616
 617 static bool tdb_has_free_lock(struct tdb_context *tdb)
 618 {
 619         unsigned int i;
 620
 621         for (i=0; i<tdb->num_lockrecs; i++) {
 622                 if (tdb->lockrecs[i].off
 623                     > TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE)
 624                         return true;
 625         }
 626         return false;
 627 }
 628
 629 int tdb_lock_hashes(struct tdb_context *tdb,
 630                     tdb_off_t hash_lock,
 631                     tdb_len_t hash_range,
 632                     int ltype, enum tdb_lock_flags waitflag)
 633 {
 634         /* FIXME: Do this properly, using hlock_range */
 635         unsigned lock = TDB_HASH_LOCK_START
 636                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 637
 638         /* a allrecord lock allows us to avoid per chain locks */
 639         if (tdb->allrecord_lock.count &&
 640             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
 641                 return 0;
 642         }
 643
 644         if (tdb->allrecord_lock.count) {
 645                 tdb->ecode = TDB_ERR_LOCK;
 646                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 647                          "tdb_lock_hashes: have %s allrecordlock\n",
 648                          tdb->allrecord_lock.ltype == F_RDLCK
 649                          ? "read" : "write");
 650                 return -1;
 651         }
 652
 653         if (tdb_has_free_lock(tdb)) {
 654                 tdb->ecode = TDB_ERR_LOCK;
 655                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 656                          "tdb_lock_hashes: have free lock already\n");
 657                 return -1;
 658         }
 659
 660         if (tdb_has_expansion_lock(tdb)) {
 661                 tdb->ecode = TDB_ERR_LOCK;
 662                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 663                          "tdb_lock_hashes: have expansion lock already\n");
 664                 return -1;
 665         }
 666
 667         return tdb_nest_lock(tdb, lock, ltype, waitflag);
 668 }
 669
 670 int tdb_unlock_hashes(struct tdb_context *tdb,
 671                       tdb_off_t hash_lock,
 672                       tdb_len_t hash_range, int ltype)
 673 {
 674         unsigned lock = TDB_HASH_LOCK_START
 675                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 676
 677         /* a allrecord lock allows us to avoid per chain locks */
 678         if (tdb->allrecord_lock.count) {
 679                 if (tdb->allrecord_lock.ltype == F_RDLCK
 680                     && ltype == F_WRLCK) {
 681                         tdb->ecode = TDB_ERR_LOCK;
 682                         tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 683                                  "tdb_unlock_hashes RO allrecord!\n");
 684                         return -1;
 685                 }
 686                 return 0;
 687         }
 688
 689         return tdb_nest_unlock(tdb, lock, ltype);
 690 }
 691
 692 /* Hash locks use TDB_HASH_LOCK_START + the next 30 bits.
 693  * Then we begin; bucket offsets are sizeof(tdb_len_t) apart, so we divide.
 694  * The result is that on 32 bit systems we don't use lock values > 2^31 on
 695  * files that are less than 4GB.
 696  */
 697 static tdb_off_t free_lock_off(tdb_off_t b_off)
 698 {
 699         return TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE
 700                 + b_off / sizeof(tdb_off_t);
 701 }
 702
 703 int tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
 704                          enum tdb_lock_flags waitflag)
 705 {
 706         assert(b_off >= sizeof(struct tdb_header));
 707
 708         /* a allrecord lock allows us to avoid per chain locks */
 709         if (tdb->allrecord_lock.count) {
 710                 if (tdb->allrecord_lock.ltype == F_WRLCK)
 711                         return 0;
 712                 tdb->ecode = TDB_ERR_LOCK;
 713                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 714                          "tdb_lock_free_bucket with RO allrecordlock!\n");
 715                 return -1;
 716         }
 717
 718 #if 0 /* FIXME */
 719         if (tdb_has_expansion_lock(tdb)) {
 720                 tdb->ecode = TDB_ERR_LOCK;
 721                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 722                          "tdb_lock_free_bucket: have expansion lock already\n");
 723                 return -1;
 724         }
 725 #endif
 726
 727         return tdb_nest_lock(tdb, free_lock_off(b_off), F_WRLCK, waitflag);
 728 }
 729
 730 void tdb_unlock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off)
 731 {
 732         if (tdb->allrecord_lock.count)
 733                 return;
 734
 735         tdb_nest_unlock(tdb, free_lock_off(b_off), F_WRLCK);
 736 }
 737
 738 void tdb_lock_init(struct tdb_context *tdb)
 739 {
 740         tdb->num_lockrecs = 0;
 741         tdb->lockrecs = NULL;
 742         tdb->allrecord_lock.count = 0;
 743 }