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_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         new_lck = (struct tdb_lock_type *)realloc(
 282                 tdb->lockrecs,
 283                 sizeof(*tdb->lockrecs) * (tdb->num_lockrecs+1));
 284         if (new_lck == NULL) {
 285                 tdb->ecode = TDB_ERR_OOM;
 286                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 287                          "tdb_lock: unable to allocate %llu lock structure",
 288                          (long long)(tdb->num_lockrecs + 1));
 289                 errno = ENOMEM;
 290                 return -1;
 291         }
 292         tdb->lockrecs = new_lck;
 293
 294         /* Since fcntl locks don't nest, we do a lock for the first one,
 295            and simply bump the count for future ones */
 296         if (tdb_brlock(tdb, ltype, offset, 1, flags)) {
 297                 return -1;
 298         }
 299
 300         tdb->lockrecs[tdb->num_lockrecs].off = offset;
 301         tdb->lockrecs[tdb->num_lockrecs].count = 1;
 302         tdb->lockrecs[tdb->num_lockrecs].ltype = ltype;
 303         tdb->num_lockrecs++;
 304
 305         return 0;
 306 }
 307
 308 static int tdb_lock_and_recover(struct tdb_context *tdb)
 309 {
 310 #if 0 /* FIXME */
 311
 312         int ret;
 313
 314         /* We need to match locking order in transaction commit. */
 315         if (tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT)) {
 316                 return -1;
 317         }
 318
 319         if (tdb_brlock(tdb, F_WRLCK, OPEN_LOCK, 1, TDB_LOCK_WAIT)) {
 320                 tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);
 321                 return -1;
 322         }
 323
 324         ret = tdb_transaction_recover(tdb);
 325
 326         tdb_brunlock(tdb, F_WRLCK, OPEN_LOCK, 1);
 327         tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0);
 328
 329         return ret;
 330 #else
 331         abort();
 332         return -1;
 333 #endif
 334 }
 335
 336 static bool tdb_needs_recovery(struct tdb_context *tdb)
 337 {
 338         /* FIXME */
 339         return false;
 340 }
 341
 342 static int tdb_nest_unlock(struct tdb_context *tdb, tdb_off_t off, int ltype)
 343 {
 344         int ret = -1;
 345         struct tdb_lock_type *lck;
 346
 347         if (tdb->flags & TDB_NOLOCK)
 348                 return 0;
 349
 350         lck = find_nestlock(tdb, off);
 351         if ((lck == NULL) || (lck->count == 0)) {
 352                 tdb->ecode = TDB_ERR_LOCK;
 353                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 354                          "tdb_unlock: no lock for %llu\n", (long long)off);
 355                 return -1;
 356         }
 357
 358         if (lck->count > 1) {
 359                 lck->count--;
 360                 return 0;
 361         }
 362
 363         /*
 364          * This lock has count==1 left, so we need to unlock it in the
 365          * kernel. We don't bother with decrementing the in-memory array
 366          * element, we're about to overwrite it with the last array element
 367          * anyway.
 368          */
 369         ret = tdb_brunlock(tdb, ltype, off, 1);
 370
 371         /*
 372          * Shrink the array by overwriting the element just unlocked with the
 373          * last array element.
 374          */
 375         *lck = tdb->lockrecs[--tdb->num_lockrecs];
 376
 377         return ret;
 378 }
 379
 380 #if 0
 381 /*
 382   get the transaction lock
 383  */
 384 int tdb_transaction_lock(struct tdb_context *tdb, int ltype,
 385                          enum tdb_lock_flags lockflags)
 386 {
 387         return tdb_nest_lock(tdb, TRANSACTION_LOCK, ltype, lockflags);
 388 }
 389
 390 /*
 391   release the transaction lock
 392  */
 393 int tdb_transaction_unlock(struct tdb_context *tdb, int ltype)
 394 {
 395         return tdb_nest_unlock(tdb, TRANSACTION_LOCK, ltype, false);
 396 }
 397 #endif
 398
 399 /* We only need to lock individual bytes, but Linux merges consecutive locks
 400  * so we lock in contiguous ranges. */
 401 static int tdb_lock_gradual(struct tdb_context *tdb,
 402                             int ltype, enum tdb_lock_flags flags,
 403                             tdb_off_t off, tdb_off_t len)
 404 {
 405         int ret;
 406         enum tdb_lock_flags nb_flags = (flags & ~TDB_LOCK_WAIT);
 407
 408         if (len <= 1) {
 409                 /* 0 would mean to end-of-file... */
 410                 assert(len != 0);
 411                 /* Single hash.  Just do blocking lock. */
 412                 return tdb_brlock(tdb, ltype, off, len, flags);
 413         }
 414
 415         /* First we try non-blocking. */
 416         ret = tdb_brlock(tdb, ltype, off, len, nb_flags);
 417         if (ret == 0) {
 418                 return 0;
 419         }
 420
 421         /* Try locking first half, then second. */
 422         ret = tdb_lock_gradual(tdb, ltype, flags, off, len / 2);
 423         if (ret == -1)
 424                 return -1;
 425
 426         ret = tdb_lock_gradual(tdb, ltype, flags,
 427                                     off + len / 2, len - len / 2);
 428         if (ret == -1) {
 429                 tdb_brunlock(tdb, ltype, off, len / 2);
 430                 return -1;
 431         }
 432         return 0;
 433 }
 434
 435 /* lock/unlock entire database.  It can only be upgradable if you have some
 436  * other way of guaranteeing exclusivity (ie. transaction write lock).
 437  * Note that we don't lock the free chains: currently noone can get those locks
 438  * without a hash chain lock first. */
 439 int tdb_allrecord_lock(struct tdb_context *tdb, int ltype,
 440                        enum tdb_lock_flags flags, bool upgradable)
 441 {
 442         /* FIXME: There are no locks on read-only dbs */
 443         if (tdb->read_only) {
 444                 tdb->ecode = TDB_ERR_LOCK;
 445                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 446                          "tdb_allrecord_lock: read-only\n");
 447                 return -1;
 448         }
 449
 450         if (tdb->allrecord_lock.count && tdb->allrecord_lock.ltype == ltype) {
 451                 tdb->allrecord_lock.count++;
 452                 return 0;
 453         }
 454
 455         if (tdb->allrecord_lock.count) {
 456                 /* a global lock of a different type exists */
 457                 tdb->ecode = TDB_ERR_LOCK;
 458                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 459                          "tdb_allrecord_lock: already have %s lock\n",
 460                          tdb->allrecord_lock.ltype == F_RDLCK
 461                          ? "read" : "write");
 462                 return -1;
 463         }
 464
 465         if (tdb_has_locks(tdb)) {
 466                 /* can't combine global and chain locks */
 467                 tdb->ecode = TDB_ERR_LOCK;
 468                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 469                          "tdb_allrecord_lock: already have chain lock\n");
 470                 return -1;
 471         }
 472
 473         if (upgradable && ltype != F_RDLCK) {
 474                 /* tdb error: you can't upgrade a write lock! */
 475                 tdb->ecode = TDB_ERR_LOCK;
 476                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 477                          "tdb_allrecord_lock: can't upgrade a write lock\n");
 478                 return -1;
 479         }
 480
 481 again:
 482         if (tdb_lock_gradual(tdb, ltype, flags, TDB_HASH_LOCK_START,
 483                              TDB_HASH_LOCK_RANGE)) {
 484                 if (!(flags & TDB_LOCK_PROBE)) {
 485                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 486                                  "tdb_lockall hashes failed (%s)\n",
 487                                  strerror(errno));
 488                 }
 489                 return -1;
 490         }
 491
 492         tdb->allrecord_lock.count = 1;
 493         /* If it's upgradable, it's actually exclusive so we can treat
 494          * it as a write lock. */
 495         tdb->allrecord_lock.ltype = upgradable ? F_WRLCK : ltype;
 496         tdb->allrecord_lock.off = upgradable;
 497
 498         /* Now check for needing recovery. */
 499         if (unlikely(tdb_needs_recovery(tdb))) {
 500                 tdb_allrecord_unlock(tdb, ltype);
 501                 if (tdb_lock_and_recover(tdb) == -1) {
 502                         return -1;
 503                 }
 504                 goto again;
 505         }
 506
 507         return 0;
 508 }
 509
 510 int tdb_lock_open(struct tdb_context *tdb)
 511 {
 512         return tdb_nest_lock(tdb, TDB_OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT);
 513 }
 514
 515 void tdb_unlock_open(struct tdb_context *tdb)
 516 {
 517         tdb_nest_unlock(tdb, TDB_OPEN_LOCK, F_WRLCK);
 518 }
 519
 520 int tdb_lock_expand(struct tdb_context *tdb, int ltype)
 521 {
 522         return tdb_nest_lock(tdb, TDB_EXPANSION_LOCK, ltype, TDB_LOCK_WAIT);
 523 }
 524
 525 void tdb_unlock_expand(struct tdb_context *tdb, int ltype)
 526 {
 527         tdb_nest_unlock(tdb, TDB_EXPANSION_LOCK, ltype);
 528 }
 529
 530 /* unlock entire db */
 531 int tdb_allrecord_unlock(struct tdb_context *tdb, int ltype)
 532 {
 533         /* FIXME: There are no locks on read-only dbs */
 534         if (tdb->read_only) {
 535                 tdb->ecode = TDB_ERR_LOCK;
 536                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 537                          "tdb_allrecord_unlock: read-only\n");
 538                 return -1;
 539         }
 540
 541         if (tdb->allrecord_lock.count == 0) {
 542                 tdb->ecode = TDB_ERR_LOCK;
 543                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 544                          "tdb_allrecord_unlock: not locked!\n");
 545                 return -1;
 546         }
 547
 548         /* Upgradable locks are marked as write locks. */
 549         if (tdb->allrecord_lock.ltype != ltype
 550             && (!tdb->allrecord_lock.off || ltype != F_RDLCK)) {
 551                 tdb->ecode = TDB_ERR_LOCK;
 552                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 553                          "tdb_allrecord_unlock: have %s lock\n",
 554                          tdb->allrecord_lock.ltype == F_RDLCK
 555                          ? "read" : "write");
 556                 return -1;
 557         }
 558
 559         if (tdb->allrecord_lock.count > 1) {
 560                 tdb->allrecord_lock.count--;
 561                 return 0;
 562         }
 563
 564         tdb->allrecord_lock.count = 0;
 565         tdb->allrecord_lock.ltype = 0;
 566
 567         return tdb_brunlock(tdb, ltype, TDB_HASH_LOCK_START,
 568                             TDB_HASH_LOCK_RANGE);
 569 }
 570
 571 bool tdb_has_expansion_lock(struct tdb_context *tdb)
 572 {
 573         return find_nestlock(tdb, TDB_EXPANSION_LOCK) != NULL
 574                 || (tdb->flags & TDB_NOLOCK);
 575 }
 576
 577 bool tdb_has_locks(struct tdb_context *tdb)
 578 {
 579         return tdb->allrecord_lock.count || tdb->num_lockrecs;
 580 }
 581
 582 #if 0
 583 /* lock entire database with write lock */
 584 int tdb_lockall(struct tdb_context *tdb)
 585 {
 586         tdb_trace(tdb, "tdb_lockall");
 587         return tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_WAIT, false);
 588 }
 589
 590 /* lock entire database with write lock - nonblocking varient */
 591 int tdb_lockall_nonblock(struct tdb_context *tdb)
 592 {
 593         int ret = tdb_allrecord_lock(tdb, F_WRLCK, TDB_LOCK_NOWAIT, false);
 594         tdb_trace_ret(tdb, "tdb_lockall_nonblock", ret);
 595         return ret;
 596 }
 597
 598 /* unlock entire database with write lock */
 599 int tdb_unlockall(struct tdb_context *tdb)
 600 {
 601         tdb_trace(tdb, "tdb_unlockall");
 602         return tdb_allrecord_unlock(tdb, F_WRLCK);
 603 }
 604
 605 /* lock entire database with read lock */
 606 int tdb_lockall_read(struct tdb_context *tdb)
 607 {
 608         tdb_trace(tdb, "tdb_lockall_read");
 609         return tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, false);
 610 }
 611
 612 /* lock entire database with read lock - nonblock varient */
 613 int tdb_lockall_read_nonblock(struct tdb_context *tdb)
 614 {
 615         int ret = tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_NOWAIT, false);
 616         tdb_trace_ret(tdb, "tdb_lockall_read_nonblock", ret);
 617         return ret;
 618 }
 619
 620 /* unlock entire database with read lock */
 621 int tdb_unlockall_read(struct tdb_context *tdb)
 622 {
 623         tdb_trace(tdb, "tdb_unlockall_read");
 624         return tdb_allrecord_unlock(tdb, F_RDLCK);
 625 }
 626 #endif
 627
 628 int tdb_lock_hashes(struct tdb_context *tdb,
 629                     tdb_off_t hash_lock,
 630                     tdb_len_t hash_range,
 631                     int ltype, enum tdb_lock_flags waitflag)
 632 {
 633         /* FIXME: Do this properly, using hlock_range */
 634         unsigned lock = TDB_HASH_LOCK_START
 635                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 636
 637         /* a allrecord lock allows us to avoid per chain locks */
 638         if (tdb->allrecord_lock.count &&
 639             (ltype == tdb->allrecord_lock.ltype || ltype == F_RDLCK)) {
 640                 return 0;
 641         }
 642
 643         if (tdb->allrecord_lock.count) {
 644                 tdb->ecode = TDB_ERR_LOCK;
 645                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 646                          "tdb_lock_list: have %s allrecordlock\n",
 647                          tdb->allrecord_lock.ltype == F_RDLCK
 648                          ? "read" : "write");
 649                 return -1;
 650         }
 651
 652         return tdb_nest_lock(tdb, lock, ltype, waitflag);
 653 }
 654
 655 int tdb_unlock_hashes(struct tdb_context *tdb,
 656                       tdb_off_t hash_lock,
 657                       tdb_len_t hash_range, int ltype)
 658 {
 659         unsigned lock = TDB_HASH_LOCK_START
 660                 + (hash_lock >> (64 - TDB_HASH_LOCK_RANGE_BITS));
 661
 662         /* a allrecord lock allows us to avoid per chain locks */
 663         if (tdb->allrecord_lock.count) {
 664                 if (tdb->allrecord_lock.ltype == F_RDLCK
 665                     && ltype == F_WRLCK) {
 666                         tdb->ecode = TDB_ERR_LOCK;
 667                         tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 668                                  "tdb_unlock_list RO allrecord!\n");
 669                         return -1;
 670                 }
 671                 return 0;
 672         }
 673
 674         return tdb_nest_unlock(tdb, lock, ltype);
 675 }
 676
 677 /* Hash locks use TDB_HASH_LOCK_START + the next 30 bits.
 678  * Then we begin; bucket offsets are sizeof(tdb_len_t) apart, so we divide.
 679  * The result is that on 32 bit systems we don't use lock values > 2^31 on
 680  * files that are less than 4GB.
 681  */
 682 static tdb_off_t free_lock_off(tdb_off_t b_off)
 683 {
 684         return TDB_HASH_LOCK_START + TDB_HASH_LOCK_RANGE + b_off / sizeof(tdb_off_t);
 685 }
 686
 687 int tdb_lock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off,
 688                          enum tdb_lock_flags waitflag)
 689 {
 690         assert(b_off >= sizeof(struct tdb_header));
 691
 692         /* You're supposed to have a hash lock first! */
 693         if (!(tdb->flags & TDB_NOLOCK) && !tdb_has_locks(tdb)) {
 694                 tdb->ecode = TDB_ERR_LOCK;
 695                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 696                          "tdb_lock_free_list without lock!\n");
 697                 return -1;
 698         }
 699
 700         /* a allrecord lock allows us to avoid per chain locks */
 701         if (tdb->allrecord_lock.count) {
 702                 if (tdb->allrecord_lock.ltype == F_WRLCK)
 703                         return 0;
 704                 tdb->ecode = TDB_ERR_LOCK;
 705                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 706                          "tdb_lock_free_list with RO allrecordlock!\n");
 707                 return -1;
 708         }
 709
 710         return tdb_nest_lock(tdb, free_lock_off(b_off), F_WRLCK, waitflag);
 711 }
 712
 713 void tdb_unlock_free_bucket(struct tdb_context *tdb, tdb_off_t b_off)
 714 {
 715         if (tdb->allrecord_lock.count)
 716                 return;
 717
 718         tdb_nest_unlock(tdb, free_lock_off(b_off), F_WRLCK);
 719 }
 720
 721 /* Even if the entry isn't in this hash bucket, you'd have to lock this
 722  * bucket to find it. */
 723 static int chainlock(struct tdb_context *tdb, const TDB_DATA *key,
 724                      int ltype, enum tdb_lock_flags waitflag,
 725                      const char *func)
 726 {
 727         int ret;
 728         uint64_t h = tdb_hash(tdb, key->dptr, key->dsize);
 729
 730         ret = tdb_lock_hashes(tdb, h, 1, ltype, waitflag);
 731         tdb_trace_1rec(tdb, func, *key);
 732         return ret;
 733 }
 734
 735 /* lock/unlock one hash chain. This is meant to be used to reduce
 736    contention - it cannot guarantee how many records will be locked */
 737 int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
 738 {
 739         return chainlock(tdb, &key, F_WRLCK, TDB_LOCK_WAIT, "tdb_chainlock");
 740 }
 741
 742 int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
 743 {
 744         uint64_t h = tdb_hash(tdb, key.dptr, key.dsize);
 745         tdb_trace_1rec(tdb, "tdb_chainunlock", key);
 746         return tdb_unlock_hashes(tdb, h, 1, F_WRLCK);
 747 }
 748
 749 #if 0
 750 /* lock/unlock one hash chain, non-blocking. This is meant to be used
 751    to reduce contention - it cannot guarantee how many records will be
 752    locked */
 753 int tdb_chainlock_nonblock(struct tdb_context *tdb, TDB_DATA key)
 754 {
 755         return chainlock(tdb, &key, F_WRLCK, TDB_LOCK_NOWAIT,
 756                          "tdb_chainlock_nonblock");
 757 }
 758
 759 int tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
 760 {
 761         return chainlock(tdb, &key, F_RDLCK, TDB_LOCK_WAIT,
 762                          "tdb_chainlock_read");
 763 }
 764
 765 int tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
 766 {
 767         uint64_t h = tdb_hash(tdb, key.dptr, key.dsize);
 768         tdb_trace_1rec(tdb, "tdb_chainunlock_read", key);
 769         return tdb_unlock_list(tdb, h & ((1ULL << tdb->header.v.hash_bits)-1),
 770                                F_RDLCK);
 771 }
 772
 773 /* record lock stops delete underneath */
 774 int tdb_lock_record(struct tdb_context *tdb, tdb_off_t off)
 775 {
 776         if (tdb->allrecord_lock.count) {
 777                 return 0;
 778         }
 779         return off ? tdb_brlock(tdb, F_RDLCK, off, 1, TDB_LOCK_WAIT) : 0;
 780 }
 781
 782 /*
 783   Write locks override our own fcntl readlocks, so check it here.
 784   Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
 785   an error to fail to get the lock here.
 786 */
 787 int tdb_write_lock_record(struct tdb_context *tdb, tdb_off_t off)
 788 {
 789         struct tdb_traverse_lock *i;
 790         for (i = &tdb->travlocks; i; i = i->next)
 791                 if (i->off == off)
 792                         return -1;
 793         if (tdb->allrecord_lock.count) {
 794                 if (tdb->allrecord_lock.ltype == F_WRLCK) {
 795                         return 0;
 796                 }
 797                 return -1;
 798         }
 799         return tdb_brlock(tdb, F_WRLCK, off, 1, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE);
 800 }
 801
 802 int tdb_write_unlock_record(struct tdb_context *tdb, tdb_off_t off)
 803 {
 804         if (tdb->allrecord_lock.count) {
 805                 return 0;
 806         }
 807         return tdb_brunlock(tdb, F_WRLCK, off, 1);
 808 }
 809
 810 /* fcntl locks don't stack: avoid unlocking someone else's */
 811 int tdb_unlock_record(struct tdb_context *tdb, tdb_off_t off)
 812 {
 813         struct tdb_traverse_lock *i;
 814         uint32_t count = 0;
 815
 816         if (tdb->allrecord_lock.count) {
 817                 return 0;
 818         }
 819
 820         if (off == 0)
 821                 return 0;
 822         for (i = &tdb->travlocks; i; i = i->next)
 823                 if (i->off == off)
 824                         count++;
 825         return (count == 1 ? tdb_brunlock(tdb, F_RDLCK, off, 1) : 0);
 826 }
 827
 828 /* The transaction code uses this to remove all locks. */
 829 void tdb_release_transaction_locks(struct tdb_context *tdb)
 830 {
 831         unsigned int i;
 832
 833         if (tdb->allrecord_lock.count != 0) {
 834                 tdb_off_t hash_size, free_size;
 835
 836                 hash_size = (1ULL << tdb->header.v.hash_bits)
 837                         * sizeof(tdb_off_t);
 838                 free_size = tdb->header.v.free_zones
 839                         * (tdb->header.v.free_buckets + 1) * sizeof(tdb_off_t);
 840
 841                 tdb_brunlock(tdb, tdb->allrecord_lock.ltype,
 842                              tdb->header.v.hash_off, hash_size);
 843                 tdb_brunlock(tdb, tdb->allrecord_lock.ltype,
 844                              tdb->header.v.free_off, free_size);
 845                 tdb->allrecord_lock.count = 0;
 846                 tdb->allrecord_lock.ltype = 0;
 847         }
 848
 849         for (i = 0; i<tdb->num_lockrecs; i++) {
 850                 struct tdb_lock_type *lck = &tdb->lockrecs[i];
 851
 852                 tdb_brunlock(tdb, lck->ltype, lck->off, 1);
 853         }
 854         tdb->num_lockrecs = 0;
 855         SAFE_FREE(tdb->lockrecs);
 856         tdb->header_uptodate = false;
 857 }
 858 #endif
 859
 860 void tdb_lock_init(struct tdb_context *tdb)
 861 {
 862         tdb->num_lockrecs = 0;
 863         tdb->lockrecs = NULL;
 864         tdb->allrecord_lock.count = 0;
 865 }