git.ozlabs.org Git - ccan/blob - ccan/tdb/transaction.c

   1  /*
   2    Unix SMB/CIFS implementation.
   3
   4    trivial database library
   5
   6    Copyright (C) Andrew Tridgell              2005
   7
   8      ** NOTE! The following LGPL license applies to the tdb
   9      ** library. This does NOT imply that all of Samba is released
  10      ** under the LGPL
  11
  12    This library is free software; you can redistribute it and/or
  13    modify it under the terms of the GNU Lesser General Public
  14    License as published by the Free Software Foundation; either
  15    version 3 of the License, or (at your option) any later version.
  16
  17    This library is distributed in the hope that it will be useful,
  18    but WITHOUT ANY WARRANTY; without even the implied warranty of
  19    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20    Lesser General Public License for more details.
  21
  22    You should have received a copy of the GNU Lesser General Public
  23    License along with this library; if not, see <http://www.gnu.org/licenses/>.
  24 */
  25
  26 #include "tdb_private.h"
  27
  28 /*
  29   transaction design:
  30
  31   - only allow a single transaction at a time per database. This makes
  32     using the transaction API simpler, as otherwise the caller would
  33     have to cope with temporary failures in transactions that conflict
  34     with other current transactions
  35
  36   - keep the transaction recovery information in the same file as the
  37     database, using a special 'transaction recovery' record pointed at
  38     by the header. This removes the need for extra journal files as
  39     used by some other databases
  40
  41   - dynamically allocated the transaction recover record, re-using it
  42     for subsequent transactions. If a larger record is needed then
  43     tdb_free() the old record to place it on the normal tdb freelist
  44     before allocating the new record
  45
  46   - during transactions, keep a linked list of writes all that have
  47     been performed by intercepting all tdb_write() calls. The hooked
  48     transaction versions of tdb_read() and tdb_write() check this
  49     linked list and try to use the elements of the list in preference
  50     to the real database.
  51
  52   - don't allow any locks to be held when a transaction starts,
  53     otherwise we can end up with deadlock (plus lack of lock nesting
  54     in posix locks would mean the lock is lost)
  55
  56   - if the caller gains a lock during the transaction but doesn't
  57     release it then fail the commit
  58
  59   - allow for nested calls to tdb_transaction_start(), re-using the
  60     existing transaction record. If the inner transaction is cancelled
  61     then a subsequent commit will fail
  62
  63   - keep a mirrored copy of the tdb hash chain heads to allow for the
  64     fast hash heads scan on traverse, updating the mirrored copy in
  65     the transaction version of tdb_write
  66
  67   - allow callers to mix transaction and non-transaction use of tdb,
  68     although once a transaction is started then an exclusive lock is
  69     gained until the transaction is committed or cancelled
  70
  71   - the commit stategy involves first saving away all modified data
  72     into a linearised buffer in the transaction recovery area, then
  73     marking the transaction recovery area with a magic value to
  74     indicate a valid recovery record. In total 4 fsync/msync calls are
  75     needed per commit to prevent race conditions. It might be possible
  76     to reduce this to 3 or even 2 with some more work.
  77
  78   - check for a valid recovery record on open of the tdb, while the
  79     open lock is held. Automatically recover from the transaction
  80     recovery area if needed, then continue with the open as
  81     usual. This allows for smooth crash recovery with no administrator
  82     intervention.
  83
  84   - if TDB_NOSYNC is passed to flags in tdb_open then transactions are
  85     still available, but no transaction recovery area is used and no
  86     fsync/msync calls are made.
  87
  88   - if TDB_ALLOW_NESTING is passed to flags in tdb open, or added using
  89     tdb_add_flags() transaction nesting is enabled.
  90     It resets the TDB_DISALLOW_NESTING flag, as both cannot be used together.
  91     The default is that transaction nesting is allowed.
  92     Note: this default may change in future versions of tdb.
  93
  94     Beware. when transactions are nested a transaction successfully
  95     completed with tdb_transaction_commit() can be silently unrolled later.
  96
  97   - if TDB_DISALLOW_NESTING is passed to flags in tdb open, or added using
  98     tdb_add_flags() transaction nesting is disabled.
  99     It resets the TDB_ALLOW_NESTING flag, as both cannot be used together.
 100     An attempt create a nested transaction will fail with TDB_ERR_NESTING.
 101     The default is that transaction nesting is allowed.
 102     Note: this default may change in future versions of tdb.
 103 */
 104
 105
 106 /*
 107   hold the context of any current transaction
 108 */
 109 struct tdb_transaction {
 110         /* we keep a mirrored copy of the tdb hash heads here so
 111            tdb_next_hash_chain() can operate efficiently */
 112         uint32_t *hash_heads;
 113
 114         /* the original io methods - used to do IOs to the real db */
 115         const struct tdb_methods *io_methods;
 116
 117         /* the list of transaction blocks. When a block is first
 118            written to, it gets created in this list */
 119         uint8_t **blocks;
 120         uint32_t num_blocks;
 121         uint32_t block_size;      /* bytes in each block */
 122         uint32_t last_block_size; /* number of valid bytes in the last block */
 123
 124         /* non-zero when an internal transaction error has
 125            occurred. All write operations will then fail until the
 126            transaction is ended */
 127         int transaction_error;
 128
 129         /* when inside a transaction we need to keep track of any
 130            nested tdb_transaction_start() calls, as these are allowed,
 131            but don't create a new transaction */
 132         int nesting;
 133
 134         /* set when a prepare has already occurred */
 135         bool prepared;
 136         tdb_off_t magic_offset;
 137
 138         /* old file size before transaction */
 139         tdb_len_t old_map_size;
 140
 141         /* we should re-pack on commit */
 142         bool need_repack;
 143 };
 144
 145
 146 /*
 147   read while in a transaction. We need to check first if the data is in our list
 148   of transaction elements, then if not do a real read
 149 */
 150 static int transaction_read(struct tdb_context *tdb, tdb_off_t off, void *buf,
 151                             tdb_len_t len, int cv)
 152 {
 153         uint32_t blk;
 154
 155         /* break it down into block sized ops */
 156         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
 157                 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
 158                 if (transaction_read(tdb, off, buf, len2, cv) != 0) {
 159                         return -1;
 160                 }
 161                 len -= len2;
 162                 off += len2;
 163                 buf = (void *)(len2 + (char *)buf);
 164         }
 165
 166         if (len == 0) {
 167                 return 0;
 168         }
 169
 170         blk = off / tdb->transaction->block_size;
 171
 172         /* see if we have it in the block list */
 173         if (tdb->transaction->num_blocks <= blk ||
 174             tdb->transaction->blocks[blk] == NULL) {
 175                 /* nope, do a real read */
 176                 if (tdb->transaction->io_methods->tdb_read(tdb, off, buf, len, cv) != 0) {
 177                         goto fail;
 178                 }
 179                 return 0;
 180         }
 181
 182         /* it is in the block list. Now check for the last block */
 183         if (blk == tdb->transaction->num_blocks-1) {
 184                 if (len > tdb->transaction->last_block_size) {
 185                         goto fail;
 186                 }
 187         }
 188
 189         /* now copy it out of this block */
 190         memcpy(buf, tdb->transaction->blocks[blk] + (off % tdb->transaction->block_size), len);
 191         if (cv) {
 192                 tdb_convert(buf, len);
 193         }
 194         return 0;
 195
 196 fail:
 197         TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_read: failed at off=%d len=%d\n", off, len));
 198         tdb->ecode = TDB_ERR_IO;
 199         tdb->transaction->transaction_error = 1;
 200         return -1;
 201 }
 202
 203
 204 /*
 205   write while in a transaction
 206 */
 207 static int transaction_write(struct tdb_context *tdb, tdb_off_t off,
 208                              const void *buf, tdb_len_t len)
 209 {
 210         uint32_t blk;
 211
 212         /* Only a commit is allowed on a prepared transaction */
 213         if (tdb->transaction->prepared) {
 214                 tdb->ecode = TDB_ERR_EINVAL;
 215                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_write: transaction already prepared, write not allowed\n"));
 216                 tdb->transaction->transaction_error = 1;
 217                 return -1;
 218         }
 219
 220         /* if the write is to a hash head, then update the transaction
 221            hash heads */
 222         if (len == sizeof(tdb_off_t) && off >= FREELIST_TOP &&
 223             off < FREELIST_TOP+TDB_HASHTABLE_SIZE(tdb)) {
 224                 uint32_t chain = (off-FREELIST_TOP) / sizeof(tdb_off_t);
 225                 memcpy(&tdb->transaction->hash_heads[chain], buf, len);
 226         }
 227
 228         /* break it up into block sized chunks */
 229         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
 230                 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
 231                 if (transaction_write(tdb, off, buf, len2) != 0) {
 232                         return -1;
 233                 }
 234                 len -= len2;
 235                 off += len2;
 236                 if (buf != NULL) {
 237                         buf = (const void *)(len2 + (const char *)buf);
 238                 }
 239         }
 240
 241         if (len == 0) {
 242                 return 0;
 243         }
 244
 245         blk = off / tdb->transaction->block_size;
 246         off = off % tdb->transaction->block_size;
 247
 248         if (tdb->transaction->num_blocks <= blk) {
 249                 uint8_t **new_blocks;
 250                 /* expand the blocks array */
 251                 if (tdb->transaction->blocks == NULL) {
 252                         new_blocks = (uint8_t **)malloc(
 253                                 (blk+1)*sizeof(uint8_t *));
 254                 } else {
 255                         new_blocks = (uint8_t **)realloc(
 256                                 tdb->transaction->blocks,
 257                                 (blk+1)*sizeof(uint8_t *));
 258                 }
 259                 if (new_blocks == NULL) {
 260                         tdb->ecode = TDB_ERR_OOM;
 261                         goto fail;
 262                 }
 263                 memset(&new_blocks[tdb->transaction->num_blocks], 0,
 264                        (1+(blk - tdb->transaction->num_blocks))*sizeof(uint8_t *));
 265                 tdb->transaction->blocks = new_blocks;
 266                 tdb->transaction->num_blocks = blk+1;
 267                 tdb->transaction->last_block_size = 0;
 268         }
 269
 270         /* allocate and fill a block? */
 271         if (tdb->transaction->blocks[blk] == NULL) {
 272                 tdb->transaction->blocks[blk] = (uint8_t *)calloc(tdb->transaction->block_size, 1);
 273                 if (tdb->transaction->blocks[blk] == NULL) {
 274                         tdb->ecode = TDB_ERR_OOM;
 275                         tdb->transaction->transaction_error = 1;
 276                         return -1;
 277                 }
 278                 if (tdb->transaction->old_map_size > blk * tdb->transaction->block_size) {
 279                         tdb_len_t len2 = tdb->transaction->block_size;
 280                         if (len2 + (blk * tdb->transaction->block_size) > tdb->transaction->old_map_size) {
 281                                 len2 = tdb->transaction->old_map_size - (blk * tdb->transaction->block_size);
 282                         }
 283                         if (tdb->transaction->io_methods->tdb_read(tdb, blk * tdb->transaction->block_size,
 284                                                                    tdb->transaction->blocks[blk],
 285                                                                    len2, 0) != 0) {
 286                                 SAFE_FREE(tdb->transaction->blocks[blk]);
 287                                 tdb->ecode = TDB_ERR_IO;
 288                                 goto fail;
 289                         }
 290                         if (blk == tdb->transaction->num_blocks-1) {
 291                                 tdb->transaction->last_block_size = len2;
 292                         }
 293                 }
 294         }
 295
 296         /* overwrite part of an existing block */
 297         if (buf == NULL) {
 298                 memset(tdb->transaction->blocks[blk] + off, 0, len);
 299         } else {
 300                 memcpy(tdb->transaction->blocks[blk] + off, buf, len);
 301         }
 302         if (blk == tdb->transaction->num_blocks-1) {
 303                 if (len + off > tdb->transaction->last_block_size) {
 304                         tdb->transaction->last_block_size = len + off;
 305                 }
 306         }
 307
 308         return 0;
 309
 310 fail:
 311         TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_write: failed at off=%d len=%d\n",
 312                  (blk*tdb->transaction->block_size) + off, len));
 313         tdb->transaction->transaction_error = 1;
 314         return -1;
 315 }
 316
 317
 318 /*
 319   write while in a transaction - this varient never expands the transaction blocks, it only
 320   updates existing blocks. This means it cannot change the recovery size
 321 */
 322 static int transaction_write_existing(struct tdb_context *tdb, tdb_off_t off,
 323                                       const void *buf, tdb_len_t len)
 324 {
 325         uint32_t blk;
 326
 327         /* break it up into block sized chunks */
 328         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
 329                 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
 330                 if (transaction_write_existing(tdb, off, buf, len2) != 0) {
 331                         return -1;
 332                 }
 333                 len -= len2;
 334                 off += len2;
 335                 if (buf != NULL) {
 336                         buf = (const void *)(len2 + (const char *)buf);
 337                 }
 338         }
 339
 340         if (len == 0) {
 341                 return 0;
 342         }
 343
 344         blk = off / tdb->transaction->block_size;
 345         off = off % tdb->transaction->block_size;
 346
 347         if (tdb->transaction->num_blocks <= blk ||
 348             tdb->transaction->blocks[blk] == NULL) {
 349                 return 0;
 350         }
 351
 352         if (blk == tdb->transaction->num_blocks-1 &&
 353             off + len > tdb->transaction->last_block_size) {
 354                 if (off >= tdb->transaction->last_block_size) {
 355                         return 0;
 356                 }
 357                 len = tdb->transaction->last_block_size - off;
 358         }
 359
 360         /* overwrite part of an existing block */
 361         memcpy(tdb->transaction->blocks[blk] + off, buf, len);
 362
 363         return 0;
 364 }
 365
 366
 367 /*
 368   accelerated hash chain head search, using the cached hash heads
 369 */
 370 static void transaction_next_hash_chain(struct tdb_context *tdb, uint32_t *chain)
 371 {
 372         uint32_t h = *chain;
 373         for (;h < tdb->header.hash_size;h++) {
 374                 /* the +1 takes account of the freelist */
 375                 if (0 != tdb->transaction->hash_heads[h+1]) {
 376                         break;
 377                 }
 378         }
 379         (*chain) = h;
 380 }
 381
 382 /*
 383   out of bounds check during a transaction
 384 */
 385 static int transaction_oob(struct tdb_context *tdb, tdb_off_t len, int probe)
 386 {
 387         if (len <= tdb->map_size) {
 388                 return 0;
 389         }
 390         tdb->ecode = TDB_ERR_IO;
 391         return -1;
 392 }
 393
 394 /*
 395   transaction version of tdb_expand().
 396 */
 397 static int transaction_expand_file(struct tdb_context *tdb, tdb_off_t size,
 398                                    tdb_off_t addition)
 399 {
 400         /* add a write to the transaction elements, so subsequent
 401            reads see the zero data */
 402         if (transaction_write(tdb, size, NULL, addition) != 0) {
 403                 return -1;
 404         }
 405
 406         tdb->transaction->need_repack = true;
 407
 408         return 0;
 409 }
 410
 411 /*
 412   brlock during a transaction - ignore them
 413 */
 414 static int transaction_brlock(struct tdb_context *tdb,
 415                               int rw_type, tdb_off_t offset, size_t len,
 416                               enum tdb_lock_flags flags)
 417 {
 418         /* FIXME: We actually grab the open lock during a transaction. */
 419         if (offset == OPEN_LOCK)
 420                 return tdb_brlock(tdb, rw_type, offset, len, flags);
 421         return 0;
 422 }
 423
 424 static int transaction_brunlock(struct tdb_context *tdb,
 425                                 int rw_type, tdb_off_t offset, size_t len)
 426 {
 427         return 0;
 428 }
 429
 430 static const struct tdb_methods transaction_methods = {
 431         transaction_read,
 432         transaction_write,
 433         transaction_next_hash_chain,
 434         transaction_oob,
 435         transaction_expand_file,
 436         transaction_brlock,
 437         transaction_brunlock
 438 };
 439
 440 /*
 441   sync to disk
 442 */
 443 static int transaction_sync(struct tdb_context *tdb, tdb_off_t offset, tdb_len_t length)
 444 {
 445         if (tdb->flags & TDB_NOSYNC) {
 446                 return 0;
 447         }
 448
 449         if (fsync(tdb->fd) != 0) {
 450                 tdb->ecode = TDB_ERR_IO;
 451                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: fsync failed\n"));
 452                 return -1;
 453         }
 454 #ifdef MS_SYNC
 455         if (tdb->map_ptr) {
 456                 tdb_off_t moffset = offset & ~(tdb->page_size-1);
 457                 if (msync(moffset + (char *)tdb->map_ptr,
 458                           length + (offset - moffset), MS_SYNC) != 0) {
 459                         tdb->ecode = TDB_ERR_IO;
 460                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: msync failed - %s\n",
 461                                  strerror(errno)));
 462                         return -1;
 463                 }
 464         }
 465 #endif
 466         return 0;
 467 }
 468
 469
 470 static int _tdb_transaction_cancel(struct tdb_context *tdb)
 471 {
 472         int i, ret = 0;
 473
 474         if (tdb->transaction == NULL) {
 475                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_cancel: no transaction\n"));
 476                 return -1;
 477         }
 478
 479         if (tdb->transaction->nesting != 0) {
 480                 tdb->transaction->transaction_error = 1;
 481                 tdb->transaction->nesting--;
 482                 return 0;
 483         }
 484
 485         tdb->map_size = tdb->transaction->old_map_size;
 486
 487         /* free all the transaction blocks */
 488         for (i=0;i<tdb->transaction->num_blocks;i++) {
 489                 if (tdb->transaction->blocks[i] != NULL) {
 490                         free(tdb->transaction->blocks[i]);
 491                 }
 492         }
 493         SAFE_FREE(tdb->transaction->blocks);
 494
 495         if (tdb->transaction->magic_offset) {
 496                 const struct tdb_methods *methods = tdb->transaction->io_methods;
 497                 uint32_t invalid = TDB_RECOVERY_INVALID_MAGIC;
 498
 499                 /* remove the recovery marker */
 500                 if (methods->tdb_write(tdb, tdb->transaction->magic_offset, &invalid, 4) == -1 ||
 501                 transaction_sync(tdb, tdb->transaction->magic_offset, 4) == -1) {
 502                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_cancel: failed to remove recovery magic\n"));
 503                         ret = -1;
 504                 }
 505         }
 506
 507         /* This also removes the OPEN_LOCK, if we have it. */
 508         tdb_release_extra_locks(tdb);
 509
 510         /* restore the normal io methods */
 511         tdb->methods = tdb->transaction->io_methods;
 512
 513         tdb_transaction_unlock(tdb, F_WRLCK);
 514         SAFE_FREE(tdb->transaction->hash_heads);
 515         SAFE_FREE(tdb->transaction);
 516
 517         return ret;
 518 }
 519
 520 /*
 521   start a tdb transaction. No token is returned, as only a single
 522   transaction is allowed to be pending per tdb_context
 523 */
 524 int tdb_transaction_start(struct tdb_context *tdb)
 525 {
 526         /* some sanity checks */
 527         if (tdb->read_only || (tdb->flags & TDB_INTERNAL) || tdb->traverse_read) {
 528                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction on a read-only or internal db\n"));
 529                 tdb->ecode = TDB_ERR_EINVAL;
 530                 return -1;
 531         }
 532
 533         /* cope with nested tdb_transaction_start() calls */
 534         if (tdb->transaction != NULL) {
 535                 if (!(tdb->flags & TDB_ALLOW_NESTING)) {
 536                         tdb->ecode = TDB_ERR_NESTING;
 537                         return -1;
 538                 }
 539                 tdb_trace(tdb, "tdb_transaction_start");
 540                 tdb->transaction->nesting++;
 541                 TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_start: nesting %d\n",
 542                          tdb->transaction->nesting));
 543                 return 0;
 544         }
 545
 546         if (tdb_have_extra_locks(tdb)) {
 547                 /* the caller must not have any locks when starting a
 548                    transaction as otherwise we'll be screwed by lack
 549                    of nested locks in posix */
 550                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction with locks held\n"));
 551                 tdb->ecode = TDB_ERR_LOCK;
 552                 return -1;
 553         }
 554
 555         if (tdb->travlocks.next != NULL) {
 556                 /* you cannot use transactions inside a traverse (although you can use
 557                    traverse inside a transaction) as otherwise you can end up with
 558                    deadlock */
 559                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction within a traverse\n"));
 560                 tdb->ecode = TDB_ERR_LOCK;
 561                 return -1;
 562         }
 563
 564         tdb->transaction = (struct tdb_transaction *)
 565                 calloc(sizeof(struct tdb_transaction), 1);
 566         if (tdb->transaction == NULL) {
 567                 tdb->ecode = TDB_ERR_OOM;
 568                 return -1;
 569         }
 570
 571         /* a page at a time seems like a reasonable compromise between compactness and efficiency */
 572         tdb->transaction->block_size = tdb->page_size;
 573
 574         /* get the transaction write lock. This is a blocking lock. As
 575            discussed with Volker, there are a number of ways we could
 576            make this async, which we will probably do in the future */
 577         if (tdb_transaction_lock(tdb, F_WRLCK) == -1) {
 578                 SAFE_FREE(tdb->transaction->blocks);
 579                 SAFE_FREE(tdb->transaction);
 580                 return -1;
 581         }
 582
 583         /* get a read lock from the freelist to the end of file. This
 584            is upgraded to a write lock during the commit */
 585         if (tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, true) == -1) {
 586                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: failed to get hash locks\n"));
 587                 goto fail_allrecord_lock;
 588         }
 589
 590         /* setup a copy of the hash table heads so the hash scan in
 591            traverse can be fast */
 592         tdb->transaction->hash_heads = (uint32_t *)
 593                 calloc(tdb->header.hash_size+1, sizeof(uint32_t));
 594         if (tdb->transaction->hash_heads == NULL) {
 595                 tdb->ecode = TDB_ERR_OOM;
 596                 goto fail;
 597         }
 598         if (tdb->methods->tdb_read(tdb, FREELIST_TOP, tdb->transaction->hash_heads,
 599                                    TDB_HASHTABLE_SIZE(tdb), 0) != 0) {
 600                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_start: failed to read hash heads\n"));
 601                 tdb->ecode = TDB_ERR_IO;
 602                 goto fail;
 603         }
 604
 605         /* make sure we know about any file expansions already done by
 606            anyone else */
 607         tdb->methods->tdb_oob(tdb, tdb->map_size + 1, 1);
 608         tdb->transaction->old_map_size = tdb->map_size;
 609
 610         /* finally hook the io methods, replacing them with
 611            transaction specific methods */
 612         tdb->transaction->io_methods = tdb->methods;
 613         tdb->methods = &transaction_methods;
 614
 615         /* Trace at the end, so we get sequence number correct. */
 616         tdb_trace(tdb, "tdb_transaction_start");
 617         return 0;
 618
 619 fail:
 620         tdb_allrecord_unlock(tdb, F_RDLCK, false);
 621 fail_allrecord_lock:
 622         tdb_transaction_unlock(tdb, F_WRLCK);
 623         SAFE_FREE(tdb->transaction->blocks);
 624         SAFE_FREE(tdb->transaction->hash_heads);
 625         SAFE_FREE(tdb->transaction);
 626         return -1;
 627 }
 628
 629
 630 /*
 631   cancel the current transaction
 632 */
 633 int tdb_transaction_cancel(struct tdb_context *tdb)
 634 {
 635         tdb_trace(tdb, "tdb_transaction_cancel");
 636         return _tdb_transaction_cancel(tdb);
 637 }
 638
 639 /*
 640   work out how much space the linearised recovery data will consume
 641 */
 642 static tdb_len_t tdb_recovery_size(struct tdb_context *tdb)
 643 {
 644         tdb_len_t recovery_size = 0;
 645         int i;
 646
 647         recovery_size = sizeof(uint32_t);
 648         for (i=0;i<tdb->transaction->num_blocks;i++) {
 649                 if (i * tdb->transaction->block_size >= tdb->transaction->old_map_size) {
 650                         break;
 651                 }
 652                 if (tdb->transaction->blocks[i] == NULL) {
 653                         continue;
 654                 }
 655                 recovery_size += 2*sizeof(tdb_off_t);
 656                 if (i == tdb->transaction->num_blocks-1) {
 657                         recovery_size += tdb->transaction->last_block_size;
 658                 } else {
 659                         recovery_size += tdb->transaction->block_size;
 660                 }
 661         }
 662
 663         return recovery_size;
 664 }
 665
 666 /*
 667   allocate the recovery area, or use an existing recovery area if it is
 668   large enough
 669 */
 670 static int tdb_recovery_allocate(struct tdb_context *tdb,
 671                                  tdb_len_t *recovery_size,
 672                                  tdb_off_t *recovery_offset,
 673                                  tdb_len_t *recovery_max_size)
 674 {
 675         struct tdb_record rec;
 676         const struct tdb_methods *methods = tdb->transaction->io_methods;
 677         tdb_off_t recovery_head;
 678
 679         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
 680                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery head\n"));
 681                 return -1;
 682         }
 683
 684         rec.rec_len = 0;
 685
 686         if (recovery_head != 0 &&
 687             methods->tdb_read(tdb, recovery_head, &rec, sizeof(rec), DOCONV()) == -1) {
 688                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery record\n"));
 689                 return -1;
 690         }
 691
 692         *recovery_size = tdb_recovery_size(tdb);
 693
 694         if (recovery_head != 0 && *recovery_size <= rec.rec_len) {
 695                 /* it fits in the existing area */
 696                 *recovery_max_size = rec.rec_len;
 697                 *recovery_offset = recovery_head;
 698                 return 0;
 699         }
 700
 701         /* we need to free up the old recovery area, then allocate a
 702            new one at the end of the file. Note that we cannot use
 703            tdb_allocate() to allocate the new one as that might return
 704            us an area that is being currently used (as of the start of
 705            the transaction) */
 706         if (recovery_head != 0) {
 707                 if (tdb_free(tdb, recovery_head, &rec) == -1) {
 708                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to free previous recovery area\n"));
 709                         return -1;
 710                 }
 711         }
 712
 713         /* the tdb_free() call might have increased the recovery size */
 714         *recovery_size = tdb_recovery_size(tdb);
 715
 716         /* round up to a multiple of page size */
 717         *recovery_max_size = TDB_ALIGN(sizeof(rec) + *recovery_size, tdb->page_size) - sizeof(rec);
 718         *recovery_offset = tdb->map_size;
 719         recovery_head = *recovery_offset;
 720
 721         if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
 722                                      (tdb->map_size - tdb->transaction->old_map_size) +
 723                                      sizeof(rec) + *recovery_max_size) == -1) {
 724                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to create recovery area\n"));
 725                 return -1;
 726         }
 727
 728         /* remap the file (if using mmap) */
 729         methods->tdb_oob(tdb, tdb->map_size + 1, 1);
 730
 731         /* we have to reset the old map size so that we don't try to expand the file
 732            again in the transaction commit, which would destroy the recovery area */
 733         tdb->transaction->old_map_size = tdb->map_size;
 734
 735         /* write the recovery header offset and sync - we can sync without a race here
 736            as the magic ptr in the recovery record has not been set */
 737         CONVERT(recovery_head);
 738         if (methods->tdb_write(tdb, TDB_RECOVERY_HEAD,
 739                                &recovery_head, sizeof(tdb_off_t)) == -1) {
 740                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
 741                 return -1;
 742         }
 743         if (transaction_write_existing(tdb, TDB_RECOVERY_HEAD, &recovery_head, sizeof(tdb_off_t)) == -1) {
 744                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
 745                 return -1;
 746         }
 747
 748         return 0;
 749 }
 750
 751
 752 /*
 753   setup the recovery data that will be used on a crash during commit
 754 */
 755 static int transaction_setup_recovery(struct tdb_context *tdb,
 756                                       tdb_off_t *magic_offset)
 757 {
 758         tdb_len_t recovery_size;
 759         unsigned char *data, *p;
 760         const struct tdb_methods *methods = tdb->transaction->io_methods;
 761         struct tdb_record *rec;
 762         tdb_off_t recovery_offset, recovery_max_size;
 763         tdb_off_t old_map_size = tdb->transaction->old_map_size;
 764         uint32_t magic, tailer;
 765         int i;
 766
 767         /*
 768           check that the recovery area has enough space
 769         */
 770         if (tdb_recovery_allocate(tdb, &recovery_size,
 771                                   &recovery_offset, &recovery_max_size) == -1) {
 772                 return -1;
 773         }
 774
 775         data = (unsigned char *)malloc(recovery_size + sizeof(*rec));
 776         if (data == NULL) {
 777                 tdb->ecode = TDB_ERR_OOM;
 778                 return -1;
 779         }
 780
 781         rec = (struct tdb_record *)data;
 782         memset(rec, 0, sizeof(*rec));
 783
 784         rec->magic    = TDB_RECOVERY_INVALID_MAGIC;
 785         rec->data_len = recovery_size;
 786         rec->rec_len  = recovery_max_size;
 787         rec->key_len  = old_map_size;
 788         CONVERT(rec);
 789
 790         /* build the recovery data into a single blob to allow us to do a single
 791            large write, which should be more efficient */
 792         p = data + sizeof(*rec);
 793         for (i=0;i<tdb->transaction->num_blocks;i++) {
 794                 tdb_off_t offset;
 795                 tdb_len_t length;
 796
 797                 if (tdb->transaction->blocks[i] == NULL) {
 798                         continue;
 799                 }
 800
 801                 offset = i * tdb->transaction->block_size;
 802                 length = tdb->transaction->block_size;
 803                 if (i == tdb->transaction->num_blocks-1) {
 804                         length = tdb->transaction->last_block_size;
 805                 }
 806
 807                 if (offset >= old_map_size) {
 808                         continue;
 809                 }
 810                 if (offset + length > tdb->transaction->old_map_size) {
 811                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: transaction data over new region boundary\n"));
 812                         free(data);
 813                         tdb->ecode = TDB_ERR_CORRUPT;
 814                         return -1;
 815                 }
 816                 memcpy(p, &offset, 4);
 817                 memcpy(p+4, &length, 4);
 818                 if (DOCONV()) {
 819                         tdb_convert(p, 8);
 820                 }
 821                 /* the recovery area contains the old data, not the
 822                    new data, so we have to call the original tdb_read
 823                    method to get it */
 824                 if (methods->tdb_read(tdb, offset, p + 8, length, 0) != 0) {
 825                         free(data);
 826                         tdb->ecode = TDB_ERR_IO;
 827                         return -1;
 828                 }
 829                 p += 8 + length;
 830         }
 831
 832         /* and the tailer */
 833         tailer = sizeof(*rec) + recovery_max_size;
 834         memcpy(p, &tailer, 4);
 835         CONVERT(p);
 836
 837         /* write the recovery data to the recovery area */
 838         if (methods->tdb_write(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
 839                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery data\n"));
 840                 free(data);
 841                 tdb->ecode = TDB_ERR_IO;
 842                 return -1;
 843         }
 844         if (transaction_write_existing(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
 845                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery data\n"));
 846                 free(data);
 847                 tdb->ecode = TDB_ERR_IO;
 848                 return -1;
 849         }
 850
 851         /* as we don't have ordered writes, we have to sync the recovery
 852            data before we update the magic to indicate that the recovery
 853            data is present */
 854         if (transaction_sync(tdb, recovery_offset, sizeof(*rec) + recovery_size) == -1) {
 855                 free(data);
 856                 return -1;
 857         }
 858
 859         free(data);
 860
 861         magic = TDB_RECOVERY_MAGIC;
 862         CONVERT(magic);
 863
 864         *magic_offset = recovery_offset + offsetof(struct tdb_record, magic);
 865
 866         if (methods->tdb_write(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
 867                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery magic\n"));
 868                 tdb->ecode = TDB_ERR_IO;
 869                 return -1;
 870         }
 871         if (transaction_write_existing(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
 872                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery magic\n"));
 873                 tdb->ecode = TDB_ERR_IO;
 874                 return -1;
 875         }
 876
 877         /* ensure the recovery magic marker is on disk */
 878         if (transaction_sync(tdb, *magic_offset, sizeof(magic)) == -1) {
 879                 return -1;
 880         }
 881
 882         return 0;
 883 }
 884
 885 static int _tdb_transaction_prepare_commit(struct tdb_context *tdb)
 886 {
 887         const struct tdb_methods *methods;
 888
 889         if (tdb->transaction == NULL) {
 890                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: no transaction\n"));
 891                 return -1;
 892         }
 893
 894         if (tdb->transaction->prepared) {
 895                 tdb->ecode = TDB_ERR_EINVAL;
 896                 _tdb_transaction_cancel(tdb);
 897                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction already prepared\n"));
 898                 return -1;
 899         }
 900
 901         if (tdb->transaction->transaction_error) {
 902                 tdb->ecode = TDB_ERR_IO;
 903                 _tdb_transaction_cancel(tdb);
 904                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction error pending\n"));
 905                 return -1;
 906         }
 907
 908
 909         if (tdb->transaction->nesting != 0) {
 910                 tdb->transaction->nesting--;
 911                 return 0;
 912         }
 913
 914         /* check for a null transaction */
 915         if (tdb->transaction->blocks == NULL) {
 916                 return 0;
 917         }
 918
 919         methods = tdb->transaction->io_methods;
 920
 921         /* if there are any locks pending then the caller has not
 922            nested their locks properly, so fail the transaction */
 923         if (tdb_have_extra_locks(tdb)) {
 924                 tdb->ecode = TDB_ERR_LOCK;
 925                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: locks pending on commit\n"));
 926                 _tdb_transaction_cancel(tdb);
 927                 return -1;
 928         }
 929
 930         /* upgrade the main transaction lock region to a write lock */
 931         if (tdb_allrecord_upgrade(tdb) == -1) {
 932                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to upgrade hash locks\n"));
 933                 _tdb_transaction_cancel(tdb);
 934                 return -1;
 935         }
 936
 937         /* get the open lock - this prevents new users attaching to the database
 938            during the commit */
 939         if (tdb_nest_lock(tdb, OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT) == -1) {
 940                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to get open lock\n"));
 941                 _tdb_transaction_cancel(tdb);
 942                 return -1;
 943         }
 944
 945         if (!(tdb->flags & TDB_NOSYNC)) {
 946                 /* write the recovery data to the end of the file */
 947                 if (transaction_setup_recovery(tdb, &tdb->transaction->magic_offset) == -1) {
 948                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: failed to setup recovery data\n"));
 949                         _tdb_transaction_cancel(tdb);
 950                         return -1;
 951                 }
 952         }
 953
 954         tdb->transaction->prepared = true;
 955
 956         /* expand the file to the new size if needed */
 957         if (tdb->map_size != tdb->transaction->old_map_size) {
 958                 if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
 959                                              tdb->map_size -
 960                                              tdb->transaction->old_map_size) == -1) {
 961                         tdb->ecode = TDB_ERR_IO;
 962                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: expansion failed\n"));
 963                         _tdb_transaction_cancel(tdb);
 964                         return -1;
 965                 }
 966                 tdb->map_size = tdb->transaction->old_map_size;
 967                 methods->tdb_oob(tdb, tdb->map_size + 1, 1);
 968         }
 969
 970         /* Keep the open lock until the actual commit */
 971
 972         return 0;
 973 }
 974
 975 /*
 976    prepare to commit the current transaction
 977 */
 978 int tdb_transaction_prepare_commit(struct tdb_context *tdb)
 979 {
 980         tdb_trace(tdb, "tdb_transaction_prepare_commit");
 981         return _tdb_transaction_prepare_commit(tdb);
 982 }
 983
 984 /*
 985   commit the current transaction
 986 */
 987 int tdb_transaction_commit(struct tdb_context *tdb)
 988 {
 989         const struct tdb_methods *methods;
 990         int i;
 991         bool need_repack;
 992
 993         if (tdb->transaction == NULL) {
 994                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: no transaction\n"));
 995                 return -1;
 996         }
 997
 998         tdb_trace(tdb, "tdb_transaction_commit");
 999
1000         if (tdb->transaction->transaction_error) {
1001                 tdb->ecode = TDB_ERR_IO;
1002                 tdb_transaction_cancel(tdb);
1003                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: transaction error pending\n"));
1004                 return -1;
1005         }
1006
1007
1008         if (tdb->transaction->nesting != 0) {
1009                 tdb->transaction->nesting--;
1010                 return 0;
1011         }
1012
1013         /* check for a null transaction */
1014         if (tdb->transaction->blocks == NULL) {
1015                 _tdb_transaction_cancel(tdb);
1016                 return 0;
1017         }
1018
1019         if (!tdb->transaction->prepared) {
1020                 int ret = _tdb_transaction_prepare_commit(tdb);
1021                 if (ret)
1022                         return ret;
1023         }
1024
1025         methods = tdb->transaction->io_methods;
1026
1027         /* perform all the writes */
1028         for (i=0;i<tdb->transaction->num_blocks;i++) {
1029                 tdb_off_t offset;
1030                 tdb_len_t length;
1031
1032                 if (tdb->transaction->blocks[i] == NULL) {
1033                         continue;
1034                 }
1035
1036                 offset = i * tdb->transaction->block_size;
1037                 length = tdb->transaction->block_size;
1038                 if (i == tdb->transaction->num_blocks-1) {
1039                         length = tdb->transaction->last_block_size;
1040                 }
1041
1042                 if (methods->tdb_write(tdb, offset, tdb->transaction->blocks[i], length) == -1) {
1043                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed during commit\n"));
1044
1045                         /* we've overwritten part of the data and
1046                            possibly expanded the file, so we need to
1047                            run the crash recovery code */
1048                         tdb->methods = methods;
1049                         tdb_transaction_recover(tdb);
1050
1051                         _tdb_transaction_cancel(tdb);
1052
1053                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed\n"));
1054                         return -1;
1055                 }
1056                 SAFE_FREE(tdb->transaction->blocks[i]);
1057         }
1058
1059         SAFE_FREE(tdb->transaction->blocks);
1060         tdb->transaction->num_blocks = 0;
1061
1062         /* ensure the new data is on disk */
1063         if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1064                 return -1;
1065         }
1066
1067         /*
1068           TODO: maybe write to some dummy hdr field, or write to magic
1069           offset without mmap, before the last sync, instead of the
1070           utime() call
1071         */
1072
1073         /* on some systems (like Linux 2.6.x) changes via mmap/msync
1074            don't change the mtime of the file, this means the file may
1075            not be backed up (as tdb rounding to block sizes means that
1076            file size changes are quite rare too). The following forces
1077            mtime changes when a transaction completes */
1078 #if HAVE_UTIME
1079         utime(tdb->name, NULL);
1080 #endif
1081
1082         need_repack = tdb->transaction->need_repack;
1083
1084         /* use a transaction cancel to free memory and remove the
1085            transaction locks */
1086         _tdb_transaction_cancel(tdb);
1087
1088         if (need_repack) {
1089                 return tdb_repack(tdb);
1090         }
1091
1092         return 0;
1093 }
1094
1095
1096 /*
1097   recover from an aborted transaction. Must be called with exclusive
1098   database write access already established (including the open
1099   lock to prevent new processes attaching)
1100 */
1101 int tdb_transaction_recover(struct tdb_context *tdb)
1102 {
1103         tdb_off_t recovery_head, recovery_eof;
1104         unsigned char *data, *p;
1105         uint32_t zero = 0;
1106         struct tdb_record rec;
1107
1108         /* find the recovery area */
1109         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
1110                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery head\n"));
1111                 tdb->ecode = TDB_ERR_IO;
1112                 return -1;
1113         }
1114
1115         if (recovery_head == 0) {
1116                 /* we have never allocated a recovery record */
1117                 return 0;
1118         }
1119
1120         /* read the recovery record */
1121         if (tdb->methods->tdb_read(tdb, recovery_head, &rec,
1122                                    sizeof(rec), DOCONV()) == -1) {
1123                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery record\n"));
1124                 tdb->ecode = TDB_ERR_IO;
1125                 return -1;
1126         }
1127
1128         if (rec.magic != TDB_RECOVERY_MAGIC) {
1129                 /* there is no valid recovery data */
1130                 return 0;
1131         }
1132
1133         if (tdb->read_only) {
1134                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: attempt to recover read only database\n"));
1135                 tdb->ecode = TDB_ERR_CORRUPT;
1136                 return -1;
1137         }
1138
1139         recovery_eof = rec.key_len;
1140
1141         data = (unsigned char *)malloc(rec.data_len);
1142         if (data == NULL) {
1143                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to allocate recovery data\n"));
1144                 tdb->ecode = TDB_ERR_OOM;
1145                 return -1;
1146         }
1147
1148         /* read the full recovery data */
1149         if (tdb->methods->tdb_read(tdb, recovery_head + sizeof(rec), data,
1150                                    rec.data_len, 0) == -1) {
1151                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery data\n"));
1152                 tdb->ecode = TDB_ERR_IO;
1153                 return -1;
1154         }
1155
1156         /* recover the file data */
1157         p = data;
1158         while (p+8 < data + rec.data_len) {
1159                 uint32_t ofs, len;
1160                 if (DOCONV()) {
1161                         tdb_convert(p, 8);
1162                 }
1163                 memcpy(&ofs, p, 4);
1164                 memcpy(&len, p+4, 4);
1165
1166                 if (tdb->methods->tdb_write(tdb, ofs, p+8, len) == -1) {
1167                         free(data);
1168                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to recover %d bytes at offset %d\n", len, ofs));
1169                         tdb->ecode = TDB_ERR_IO;
1170                         return -1;
1171                 }
1172                 p += 8 + len;
1173         }
1174
1175         free(data);
1176
1177         if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1178                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync recovery\n"));
1179                 tdb->ecode = TDB_ERR_IO;
1180                 return -1;
1181         }
1182
1183         /* if the recovery area is after the recovered eof then remove it */
1184         if (recovery_eof <= recovery_head) {
1185                 if (tdb_ofs_write(tdb, TDB_RECOVERY_HEAD, &zero) == -1) {
1186                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery head\n"));
1187                         tdb->ecode = TDB_ERR_IO;
1188                         return -1;
1189                 }
1190         }
1191
1192         /* remove the recovery magic */
1193         if (tdb_ofs_write(tdb, recovery_head + offsetof(struct tdb_record, magic),
1194                           &zero) == -1) {
1195                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery magic\n"));
1196                 tdb->ecode = TDB_ERR_IO;
1197                 return -1;
1198         }
1199
1200         /* reduce the file size to the old size */
1201         tdb_munmap(tdb);
1202         if (ftruncate(tdb->fd, recovery_eof) != 0) {
1203                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to reduce to recovery size\n"));
1204                 tdb->ecode = TDB_ERR_IO;
1205                 return -1;
1206         }
1207         tdb->map_size = recovery_eof;
1208         tdb_mmap(tdb);
1209
1210         if (transaction_sync(tdb, 0, recovery_eof) == -1) {
1211                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync2 recovery\n"));
1212                 tdb->ecode = TDB_ERR_IO;
1213                 return -1;
1214         }
1215
1216         TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_recover: recovered %d byte database\n",
1217                  recovery_eof));
1218
1219         /* all done */
1220         return 0;
1221 }