lib/tdb/common/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 fsync/msync calls are made.  This means we
  86     are still proof against a process dying during transaction commit,
  87     but not against machine reboot.
  88
  89   - if TDB_ALLOW_NESTING is passed to flags in tdb open, or added using
  90     tdb_add_flags() transaction nesting is enabled.
  91     It resets the TDB_DISALLOW_NESTING flag, as both cannot be used together.
  92     The default is that transaction nesting is allowed.
  93     Note: this default may change in future versions of tdb.
  94
  95     Beware. when transactions are nested a transaction successfully
  96     completed with tdb_transaction_commit() can be silently unrolled later.
  97
  98   - if TDB_DISALLOW_NESTING is passed to flags in tdb open, or added using
  99     tdb_add_flags() transaction nesting is disabled.
 100     It resets the TDB_ALLOW_NESTING flag, as both cannot be used together.
 101     An attempt create a nested transaction will fail with TDB_ERR_NESTING.
 102     The default is that transaction nesting is allowed.
 103     Note: this default may change in future versions of tdb.
 104 */
 105
 106
 107 /*
 108   hold the context of any current transaction
 109 */
 110 struct tdb_transaction {
 111         /* we keep a mirrored copy of the tdb hash heads here so
 112            tdb_next_hash_chain() can operate efficiently */
 113         uint32_t *hash_heads;
 114
 115         /* the original io methods - used to do IOs to the real db */
 116         const struct tdb_methods *io_methods;
 117
 118         /* the list of transaction blocks. When a block is first
 119            written to, it gets created in this list */
 120         uint8_t **blocks;
 121         uint32_t num_blocks;
 122         uint32_t block_size;      /* bytes in each block */
 123         uint32_t last_block_size; /* number of valid bytes in the last block */
 124
 125         /* non-zero when an internal transaction error has
 126            occurred. All write operations will then fail until the
 127            transaction is ended */
 128         int transaction_error;
 129
 130         /* when inside a transaction we need to keep track of any
 131            nested tdb_transaction_start() calls, as these are allowed,
 132            but don't create a new transaction */
 133         int nesting;
 134
 135         /* set when a prepare has already occurred */
 136         bool prepared;
 137         tdb_off_t magic_offset;
 138
 139         /* old file size before transaction */
 140         tdb_len_t old_map_size;
 141
 142         /* did we expand in this transaction */
 143         bool expanded;
 144 };
 145
 146
 147 /*
 148   read while in a transaction. We need to check first if the data is in our list
 149   of transaction elements, then if not do a real read
 150 */
 151 static int transaction_read(struct tdb_context *tdb, tdb_off_t off, void *buf,
 152                             tdb_len_t len, int cv)
 153 {
 154         uint32_t blk;
 155
 156         /* break it down into block sized ops */
 157         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
 158                 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
 159                 if (transaction_read(tdb, off, buf, len2, cv) != 0) {
 160                         return -1;
 161                 }
 162                 len -= len2;
 163                 off += len2;
 164                 buf = (void *)(len2 + (char *)buf);
 165         }
 166
 167         if (len == 0) {
 168                 return 0;
 169         }
 170
 171         blk = off / tdb->transaction->block_size;
 172
 173         /* see if we have it in the block list */
 174         if (tdb->transaction->num_blocks <= blk ||
 175             tdb->transaction->blocks[blk] == NULL) {
 176                 /* nope, do a real read */
 177                 if (tdb->transaction->io_methods->tdb_read(tdb, off, buf, len, cv) != 0) {
 178                         goto fail;
 179                 }
 180                 return 0;
 181         }
 182
 183         /* it is in the block list. Now check for the last block */
 184         if (blk == tdb->transaction->num_blocks-1) {
 185                 if (len > tdb->transaction->last_block_size) {
 186                         goto fail;
 187                 }
 188         }
 189
 190         /* now copy it out of this block */
 191         memcpy(buf, tdb->transaction->blocks[blk] + (off % tdb->transaction->block_size), len);
 192         if (cv) {
 193                 tdb_convert(buf, len);
 194         }
 195         return 0;
 196
 197 fail:
 198         TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_read: failed at off=%d len=%d\n", off, len));
 199         tdb->ecode = TDB_ERR_IO;
 200         tdb->transaction->transaction_error = 1;
 201         return -1;
 202 }
 203
 204
 205 /*
 206   write while in a transaction
 207 */
 208 static int transaction_write(struct tdb_context *tdb, tdb_off_t off,
 209                              const void *buf, tdb_len_t len)
 210 {
 211         uint32_t blk;
 212
 213         /* Only a commit is allowed on a prepared transaction */
 214         if (tdb->transaction->prepared) {
 215                 tdb->ecode = TDB_ERR_EINVAL;
 216                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_write: transaction already prepared, write not allowed\n"));
 217                 tdb->transaction->transaction_error = 1;
 218                 return -1;
 219         }
 220
 221         /* if the write is to a hash head, then update the transaction
 222            hash heads */
 223         if (len == sizeof(tdb_off_t) && off >= FREELIST_TOP &&
 224             off < FREELIST_TOP+TDB_HASHTABLE_SIZE(tdb)) {
 225                 uint32_t chain = (off-FREELIST_TOP) / sizeof(tdb_off_t);
 226                 memcpy(&tdb->transaction->hash_heads[chain], buf, len);
 227         }
 228
 229         /* break it up into block sized chunks */
 230         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
 231                 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
 232                 if (transaction_write(tdb, off, buf, len2) != 0) {
 233                         return -1;
 234                 }
 235                 len -= len2;
 236                 off += len2;
 237                 if (buf != NULL) {
 238                         buf = (const void *)(len2 + (const char *)buf);
 239                 }
 240         }
 241
 242         if (len == 0) {
 243                 return 0;
 244         }
 245
 246         blk = off / tdb->transaction->block_size;
 247         off = off % tdb->transaction->block_size;
 248
 249         if (tdb->transaction->num_blocks <= blk) {
 250                 uint8_t **new_blocks;
 251                 /* expand the blocks array */
 252                 new_blocks = (uint8_t **)realloc(tdb->transaction->blocks,
 253                                                  (blk+1)*sizeof(uint8_t *));
 254                 if (new_blocks == NULL) {
 255                         tdb->ecode = TDB_ERR_OOM;
 256                         goto fail;
 257                 }
 258                 memset(&new_blocks[tdb->transaction->num_blocks], 0,
 259                        (1+(blk - tdb->transaction->num_blocks))*sizeof(uint8_t *));
 260                 tdb->transaction->blocks = new_blocks;
 261                 tdb->transaction->num_blocks = blk+1;
 262                 tdb->transaction->last_block_size = 0;
 263         }
 264
 265         /* allocate and fill a block? */
 266         if (tdb->transaction->blocks[blk] == NULL) {
 267                 tdb->transaction->blocks[blk] = (uint8_t *)calloc(tdb->transaction->block_size, 1);
 268                 if (tdb->transaction->blocks[blk] == NULL) {
 269                         tdb->ecode = TDB_ERR_OOM;
 270                         tdb->transaction->transaction_error = 1;
 271                         return -1;
 272                 }
 273                 if (tdb->transaction->old_map_size > blk * tdb->transaction->block_size) {
 274                         tdb_len_t len2 = tdb->transaction->block_size;
 275                         if (len2 + (blk * tdb->transaction->block_size) > tdb->transaction->old_map_size) {
 276                                 len2 = tdb->transaction->old_map_size - (blk * tdb->transaction->block_size);
 277                         }
 278                         if (tdb->transaction->io_methods->tdb_read(tdb, blk * tdb->transaction->block_size,
 279                                                                    tdb->transaction->blocks[blk],
 280                                                                    len2, 0) != 0) {
 281                                 SAFE_FREE(tdb->transaction->blocks[blk]);
 282                                 tdb->ecode = TDB_ERR_IO;
 283                                 goto fail;
 284                         }
 285                         if (blk == tdb->transaction->num_blocks-1) {
 286                                 tdb->transaction->last_block_size = len2;
 287                         }
 288                 }
 289         }
 290
 291         /* overwrite part of an existing block */
 292         if (buf == NULL) {
 293                 memset(tdb->transaction->blocks[blk] + off, 0, len);
 294         } else {
 295                 memcpy(tdb->transaction->blocks[blk] + off, buf, len);
 296         }
 297         if (blk == tdb->transaction->num_blocks-1) {
 298                 if (len + off > tdb->transaction->last_block_size) {
 299                         tdb->transaction->last_block_size = len + off;
 300                 }
 301         }
 302
 303         return 0;
 304
 305 fail:
 306         TDB_LOG((tdb, TDB_DEBUG_FATAL, "transaction_write: failed at off=%d len=%d\n",
 307                  (blk*tdb->transaction->block_size) + off, len));
 308         tdb->transaction->transaction_error = 1;
 309         return -1;
 310 }
 311
 312
 313 /*
 314   write while in a transaction - this variant never expands the transaction blocks, it only
 315   updates existing blocks. This means it cannot change the recovery size
 316 */
 317 static int transaction_write_existing(struct tdb_context *tdb, tdb_off_t off,
 318                                       const void *buf, tdb_len_t len)
 319 {
 320         uint32_t blk;
 321
 322         /* break it up into block sized chunks */
 323         while (len + (off % tdb->transaction->block_size) > tdb->transaction->block_size) {
 324                 tdb_len_t len2 = tdb->transaction->block_size - (off % tdb->transaction->block_size);
 325                 if (transaction_write_existing(tdb, off, buf, len2) != 0) {
 326                         return -1;
 327                 }
 328                 len -= len2;
 329                 off += len2;
 330                 if (buf != NULL) {
 331                         buf = (const void *)(len2 + (const char *)buf);
 332                 }
 333         }
 334
 335         if (len == 0) {
 336                 return 0;
 337         }
 338
 339         blk = off / tdb->transaction->block_size;
 340         off = off % tdb->transaction->block_size;
 341
 342         if (tdb->transaction->num_blocks <= blk ||
 343             tdb->transaction->blocks[blk] == NULL) {
 344                 return 0;
 345         }
 346
 347         if (blk == tdb->transaction->num_blocks-1 &&
 348             off + len > tdb->transaction->last_block_size) {
 349                 if (off >= tdb->transaction->last_block_size) {
 350                         return 0;
 351                 }
 352                 len = tdb->transaction->last_block_size - off;
 353         }
 354
 355         /* overwrite part of an existing block */
 356         memcpy(tdb->transaction->blocks[blk] + off, buf, len);
 357
 358         return 0;
 359 }
 360
 361
 362 /*
 363   accelerated hash chain head search, using the cached hash heads
 364 */
 365 static void transaction_next_hash_chain(struct tdb_context *tdb, uint32_t *chain)
 366 {
 367         uint32_t h = *chain;
 368         for (;h < tdb->hash_size;h++) {
 369                 /* the +1 takes account of the freelist */
 370                 if (0 != tdb->transaction->hash_heads[h+1]) {
 371                         break;
 372                 }
 373         }
 374         (*chain) = h;
 375 }
 376
 377 /*
 378   out of bounds check during a transaction
 379 */
 380 static int transaction_oob(struct tdb_context *tdb, tdb_off_t off,
 381                            tdb_len_t len, int probe)
 382 {
 383         if (off + len >= off && off + len <= tdb->map_size) {
 384                 return 0;
 385         }
 386         tdb->ecode = TDB_ERR_IO;
 387         return -1;
 388 }
 389
 390 /*
 391   transaction version of tdb_expand().
 392 */
 393 static int transaction_expand_file(struct tdb_context *tdb, tdb_off_t size,
 394                                    tdb_off_t addition)
 395 {
 396         /* add a write to the transaction elements, so subsequent
 397            reads see the zero data */
 398         if (transaction_write(tdb, size, NULL, addition) != 0) {
 399                 return -1;
 400         }
 401
 402         tdb->transaction->expanded = true;
 403
 404         return 0;
 405 }
 406
 407 static const struct tdb_methods transaction_methods = {
 408         transaction_read,
 409         transaction_write,
 410         transaction_next_hash_chain,
 411         transaction_oob,
 412         transaction_expand_file,
 413 };
 414
 415
 416 /*
 417   start a tdb transaction. No token is returned, as only a single
 418   transaction is allowed to be pending per tdb_context
 419 */
 420 static int _tdb_transaction_start(struct tdb_context *tdb,
 421                                   enum tdb_lock_flags lockflags)
 422 {
 423         /* some sanity checks */
 424         if (tdb->read_only || (tdb->flags & TDB_INTERNAL) || tdb->traverse_read) {
 425                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction on a read-only or internal db\n"));
 426                 tdb->ecode = TDB_ERR_EINVAL;
 427                 return -1;
 428         }
 429
 430         /* cope with nested tdb_transaction_start() calls */
 431         if (tdb->transaction != NULL) {
 432                 if (!(tdb->flags & TDB_ALLOW_NESTING)) {
 433                         tdb->ecode = TDB_ERR_NESTING;
 434                         return -1;
 435                 }
 436                 tdb->transaction->nesting++;
 437                 TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_start: nesting %d\n",
 438                          tdb->transaction->nesting));
 439                 return 0;
 440         }
 441
 442         if (tdb_have_extra_locks(tdb)) {
 443                 /* the caller must not have any locks when starting a
 444                    transaction as otherwise we'll be screwed by lack
 445                    of nested locks in posix */
 446                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction with locks held\n"));
 447                 tdb->ecode = TDB_ERR_LOCK;
 448                 return -1;
 449         }
 450
 451         if (tdb->travlocks.next != NULL) {
 452                 /* you cannot use transactions inside a traverse (although you can use
 453                    traverse inside a transaction) as otherwise you can end up with
 454                    deadlock */
 455                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction within a traverse\n"));
 456                 tdb->ecode = TDB_ERR_LOCK;
 457                 return -1;
 458         }
 459
 460         tdb->transaction = (struct tdb_transaction *)
 461                 calloc(sizeof(struct tdb_transaction), 1);
 462         if (tdb->transaction == NULL) {
 463                 tdb->ecode = TDB_ERR_OOM;
 464                 return -1;
 465         }
 466
 467         /* a page at a time seems like a reasonable compromise between compactness and efficiency */
 468         tdb->transaction->block_size = tdb->page_size;
 469
 470         /* get the transaction write lock. This is a blocking lock. As
 471            discussed with Volker, there are a number of ways we could
 472            make this async, which we will probably do in the future */
 473         if (tdb_transaction_lock(tdb, F_WRLCK, lockflags) == -1) {
 474                 SAFE_FREE(tdb->transaction->blocks);
 475                 SAFE_FREE(tdb->transaction);
 476                 if ((lockflags & TDB_LOCK_WAIT) == 0) {
 477                         tdb->ecode = TDB_ERR_NOLOCK;
 478                 }
 479                 return -1;
 480         }
 481
 482         /* get a read lock from the freelist to the end of file. This
 483            is upgraded to a write lock during the commit */
 484         if (tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, true) == -1) {
 485                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: failed to get hash locks\n"));
 486                 goto fail_allrecord_lock;
 487         }
 488
 489         /* setup a copy of the hash table heads so the hash scan in
 490            traverse can be fast */
 491         tdb->transaction->hash_heads = (uint32_t *)
 492                 calloc(tdb->hash_size+1, sizeof(uint32_t));
 493         if (tdb->transaction->hash_heads == NULL) {
 494                 tdb->ecode = TDB_ERR_OOM;
 495                 goto fail;
 496         }
 497         if (tdb->methods->tdb_read(tdb, FREELIST_TOP, tdb->transaction->hash_heads,
 498                                    TDB_HASHTABLE_SIZE(tdb), 0) != 0) {
 499                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_start: failed to read hash heads\n"));
 500                 tdb->ecode = TDB_ERR_IO;
 501                 goto fail;
 502         }
 503
 504         /* make sure we know about any file expansions already done by
 505            anyone else */
 506         tdb->methods->tdb_oob(tdb, tdb->map_size, 1, 1);
 507         tdb->transaction->old_map_size = tdb->map_size;
 508
 509         /* finally hook the io methods, replacing them with
 510            transaction specific methods */
 511         tdb->transaction->io_methods = tdb->methods;
 512         tdb->methods = &transaction_methods;
 513
 514         /* Trace at the end, so we get sequence number correct. */
 515         tdb_trace(tdb, "tdb_transaction_start");
 516         return 0;
 517
 518 fail:
 519         tdb_allrecord_unlock(tdb, F_RDLCK, false);
 520 fail_allrecord_lock:
 521         tdb_transaction_unlock(tdb, F_WRLCK);
 522         SAFE_FREE(tdb->transaction->blocks);
 523         SAFE_FREE(tdb->transaction->hash_heads);
 524         SAFE_FREE(tdb->transaction);
 525         return -1;
 526 }
 527
 528 _PUBLIC_ int tdb_transaction_start(struct tdb_context *tdb)
 529 {
 530         return _tdb_transaction_start(tdb, TDB_LOCK_WAIT);
 531 }
 532
 533 _PUBLIC_ int tdb_transaction_start_nonblock(struct tdb_context *tdb)
 534 {
 535         return _tdb_transaction_start(tdb, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE);
 536 }
 537
 538 /*
 539   sync to disk
 540 */
 541 static int transaction_sync(struct tdb_context *tdb, tdb_off_t offset, tdb_len_t length)
 542 {
 543         if (tdb->flags & TDB_NOSYNC) {
 544                 return 0;
 545         }
 546
 547 #ifdef HAVE_FDATASYNC
 548         if (fdatasync(tdb->fd) != 0) {
 549 #else
 550         if (fsync(tdb->fd) != 0) {
 551 #endif
 552                 tdb->ecode = TDB_ERR_IO;
 553                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: fsync failed\n"));
 554                 return -1;
 555         }
 556 #ifdef HAVE_MMAP
 557         if (tdb->map_ptr) {
 558                 tdb_off_t moffset = offset & ~(tdb->page_size-1);
 559                 if (msync(moffset + (char *)tdb->map_ptr,
 560                           length + (offset - moffset), MS_SYNC) != 0) {
 561                         tdb->ecode = TDB_ERR_IO;
 562                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: msync failed - %s\n",
 563                                  strerror(errno)));
 564                         return -1;
 565                 }
 566         }
 567 #endif
 568         return 0;
 569 }
 570
 571
 572 static int _tdb_transaction_cancel(struct tdb_context *tdb)
 573 {
 574         int i, ret = 0;
 575
 576         if (tdb->transaction == NULL) {
 577                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_cancel: no transaction\n"));
 578                 return -1;
 579         }
 580
 581         if (tdb->transaction->nesting != 0) {
 582                 tdb->transaction->transaction_error = 1;
 583                 tdb->transaction->nesting--;
 584                 return 0;
 585         }
 586
 587         tdb->map_size = tdb->transaction->old_map_size;
 588
 589         /* free all the transaction blocks */
 590         for (i=0;i<tdb->transaction->num_blocks;i++) {
 591                 if (tdb->transaction->blocks[i] != NULL) {
 592                         free(tdb->transaction->blocks[i]);
 593                 }
 594         }
 595         SAFE_FREE(tdb->transaction->blocks);
 596
 597         if (tdb->transaction->magic_offset) {
 598                 const struct tdb_methods *methods = tdb->transaction->io_methods;
 599                 const uint32_t invalid = TDB_RECOVERY_INVALID_MAGIC;
 600
 601                 /* remove the recovery marker */
 602                 if (methods->tdb_write(tdb, tdb->transaction->magic_offset, &invalid, 4) == -1 ||
 603                 transaction_sync(tdb, tdb->transaction->magic_offset, 4) == -1) {
 604                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_cancel: failed to remove recovery magic\n"));
 605                         ret = -1;
 606                 }
 607         }
 608
 609         /* This also removes the OPEN_LOCK, if we have it. */
 610         tdb_release_transaction_locks(tdb);
 611
 612         /* restore the normal io methods */
 613         tdb->methods = tdb->transaction->io_methods;
 614
 615         SAFE_FREE(tdb->transaction->hash_heads);
 616         SAFE_FREE(tdb->transaction);
 617
 618         return ret;
 619 }
 620
 621 /*
 622   cancel the current transaction
 623 */
 624 _PUBLIC_ int tdb_transaction_cancel(struct tdb_context *tdb)
 625 {
 626         tdb_trace(tdb, "tdb_transaction_cancel");
 627         return _tdb_transaction_cancel(tdb);
 628 }
 629
 630 /*
 631   work out how much space the linearised recovery data will consume
 632 */
 633 static tdb_len_t tdb_recovery_size(struct tdb_context *tdb)
 634 {
 635         tdb_len_t recovery_size = 0;
 636         int i;
 637
 638         recovery_size = sizeof(uint32_t);
 639         for (i=0;i<tdb->transaction->num_blocks;i++) {
 640                 if (i * tdb->transaction->block_size >= tdb->transaction->old_map_size) {
 641                         break;
 642                 }
 643                 if (tdb->transaction->blocks[i] == NULL) {
 644                         continue;
 645                 }
 646                 recovery_size += 2*sizeof(tdb_off_t);
 647                 if (i == tdb->transaction->num_blocks-1) {
 648                         recovery_size += tdb->transaction->last_block_size;
 649                 } else {
 650                         recovery_size += tdb->transaction->block_size;
 651                 }
 652         }
 653
 654         return recovery_size;
 655 }
 656
 657 int tdb_recovery_area(struct tdb_context *tdb,
 658                       const struct tdb_methods *methods,
 659                       tdb_off_t *recovery_offset,
 660                       struct tdb_record *rec)
 661 {
 662         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, recovery_offset) == -1) {
 663                 return -1;
 664         }
 665
 666         if (*recovery_offset == 0) {
 667                 rec->rec_len = 0;
 668                 return 0;
 669         }
 670
 671         if (methods->tdb_read(tdb, *recovery_offset, rec, sizeof(*rec),
 672                               DOCONV()) == -1) {
 673                 return -1;
 674         }
 675
 676         /* ignore invalid recovery regions: can happen in crash */
 677         if (rec->magic != TDB_RECOVERY_MAGIC &&
 678             rec->magic != TDB_RECOVERY_INVALID_MAGIC) {
 679                 *recovery_offset = 0;
 680                 rec->rec_len = 0;
 681         }
 682         return 0;
 683 }
 684
 685 /*
 686   allocate the recovery area, or use an existing recovery area if it is
 687   large enough
 688 */
 689 static int tdb_recovery_allocate(struct tdb_context *tdb,
 690                                  tdb_len_t *recovery_size,
 691                                  tdb_off_t *recovery_offset,
 692                                  tdb_len_t *recovery_max_size)
 693 {
 694         struct tdb_record rec;
 695         const struct tdb_methods *methods = tdb->transaction->io_methods;
 696         tdb_off_t recovery_head, new_end;
 697
 698         if (tdb_recovery_area(tdb, methods, &recovery_head, &rec) == -1) {
 699                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery head\n"));
 700                 return -1;
 701         }
 702
 703         *recovery_size = tdb_recovery_size(tdb);
 704
 705         /* Existing recovery area? */
 706         if (recovery_head != 0 && *recovery_size <= rec.rec_len) {
 707                 /* it fits in the existing area */
 708                 *recovery_max_size = rec.rec_len;
 709                 *recovery_offset = recovery_head;
 710                 return 0;
 711         }
 712
 713         /* If recovery area in middle of file, we need a new one. */
 714         if (recovery_head == 0
 715             || recovery_head + sizeof(rec) + rec.rec_len != tdb->map_size) {
 716                 /* we need to free up the old recovery area, then allocate a
 717                    new one at the end of the file. Note that we cannot use
 718                    tdb_allocate() to allocate the new one as that might return
 719                    us an area that is being currently used (as of the start of
 720                    the transaction) */
 721                 if (recovery_head) {
 722                         if (tdb_free(tdb, recovery_head, &rec) == -1) {
 723                                 TDB_LOG((tdb, TDB_DEBUG_FATAL,
 724                                          "tdb_recovery_allocate: failed to"
 725                                          " free previous recovery area\n"));
 726                                 return -1;
 727                         }
 728
 729                         /* the tdb_free() call might have increased
 730                          * the recovery size */
 731                         *recovery_size = tdb_recovery_size(tdb);
 732                 }
 733
 734                 /* New head will be at end of file. */
 735                 recovery_head = tdb->map_size;
 736         }
 737
 738         /* Now we know where it will be. */
 739         *recovery_offset = recovery_head;
 740
 741         /* Expand by more than we need, so we don't do it often. */
 742         *recovery_max_size = tdb_expand_adjust(tdb->map_size,
 743                                                *recovery_size,
 744                                                tdb->page_size)
 745                 - sizeof(rec);
 746
 747         new_end = recovery_head + sizeof(rec) + *recovery_max_size;
 748
 749         if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
 750                                      new_end - tdb->transaction->old_map_size)
 751             == -1) {
 752                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to create recovery area\n"));
 753                 return -1;
 754         }
 755
 756         /* remap the file (if using mmap) */
 757         methods->tdb_oob(tdb, tdb->map_size, 1, 1);
 758
 759         /* we have to reset the old map size so that we don't try to expand the file
 760            again in the transaction commit, which would destroy the recovery area */
 761         tdb->transaction->old_map_size = tdb->map_size;
 762
 763         /* write the recovery header offset and sync - we can sync without a race here
 764            as the magic ptr in the recovery record has not been set */
 765         CONVERT(recovery_head);
 766         if (methods->tdb_write(tdb, TDB_RECOVERY_HEAD,
 767                                &recovery_head, sizeof(tdb_off_t)) == -1) {
 768                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
 769                 return -1;
 770         }
 771         if (transaction_write_existing(tdb, TDB_RECOVERY_HEAD, &recovery_head, sizeof(tdb_off_t)) == -1) {
 772                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
 773                 return -1;
 774         }
 775
 776         return 0;
 777 }
 778
 779
 780 /*
 781   setup the recovery data that will be used on a crash during commit
 782 */
 783 static int transaction_setup_recovery(struct tdb_context *tdb,
 784                                       tdb_off_t *magic_offset)
 785 {
 786         tdb_len_t recovery_size;
 787         unsigned char *data, *p;
 788         const struct tdb_methods *methods = tdb->transaction->io_methods;
 789         struct tdb_record *rec;
 790         tdb_off_t recovery_offset, recovery_max_size;
 791         tdb_off_t old_map_size = tdb->transaction->old_map_size;
 792         uint32_t magic, tailer;
 793         int i;
 794
 795         /*
 796           check that the recovery area has enough space
 797         */
 798         if (tdb_recovery_allocate(tdb, &recovery_size,
 799                                   &recovery_offset, &recovery_max_size) == -1) {
 800                 return -1;
 801         }
 802
 803         data = (unsigned char *)malloc(recovery_size + sizeof(*rec));
 804         if (data == NULL) {
 805                 tdb->ecode = TDB_ERR_OOM;
 806                 return -1;
 807         }
 808
 809         rec = (struct tdb_record *)data;
 810         memset(rec, 0, sizeof(*rec));
 811
 812         rec->magic    = TDB_RECOVERY_INVALID_MAGIC;
 813         rec->data_len = recovery_size;
 814         rec->rec_len  = recovery_max_size;
 815         rec->key_len  = old_map_size;
 816         CONVERT(*rec);
 817
 818         /* build the recovery data into a single blob to allow us to do a single
 819            large write, which should be more efficient */
 820         p = data + sizeof(*rec);
 821         for (i=0;i<tdb->transaction->num_blocks;i++) {
 822                 tdb_off_t offset;
 823                 tdb_len_t length;
 824
 825                 if (tdb->transaction->blocks[i] == NULL) {
 826                         continue;
 827                 }
 828
 829                 offset = i * tdb->transaction->block_size;
 830                 length = tdb->transaction->block_size;
 831                 if (i == tdb->transaction->num_blocks-1) {
 832                         length = tdb->transaction->last_block_size;
 833                 }
 834
 835                 if (offset >= old_map_size) {
 836                         continue;
 837                 }
 838                 if (offset + length > tdb->transaction->old_map_size) {
 839                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: transaction data over new region boundary\n"));
 840                         free(data);
 841                         tdb->ecode = TDB_ERR_CORRUPT;
 842                         return -1;
 843                 }
 844                 memcpy(p, &offset, 4);
 845                 memcpy(p+4, &length, 4);
 846                 if (DOCONV()) {
 847                         tdb_convert(p, 8);
 848                 }
 849                 /* the recovery area contains the old data, not the
 850                    new data, so we have to call the original tdb_read
 851                    method to get it */
 852                 if (methods->tdb_read(tdb, offset, p + 8, length, 0) != 0) {
 853                         free(data);
 854                         tdb->ecode = TDB_ERR_IO;
 855                         return -1;
 856                 }
 857                 p += 8 + length;
 858         }
 859
 860         /* and the tailer */
 861         tailer = sizeof(*rec) + recovery_max_size;
 862         memcpy(p, &tailer, 4);
 863         if (DOCONV()) {
 864                 tdb_convert(p, 4);
 865         }
 866
 867         /* write the recovery data to the recovery area */
 868         if (methods->tdb_write(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
 869                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery data\n"));
 870                 free(data);
 871                 tdb->ecode = TDB_ERR_IO;
 872                 return -1;
 873         }
 874         if (transaction_write_existing(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
 875                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery data\n"));
 876                 free(data);
 877                 tdb->ecode = TDB_ERR_IO;
 878                 return -1;
 879         }
 880
 881         /* as we don't have ordered writes, we have to sync the recovery
 882            data before we update the magic to indicate that the recovery
 883            data is present */
 884         if (transaction_sync(tdb, recovery_offset, sizeof(*rec) + recovery_size) == -1) {
 885                 free(data);
 886                 return -1;
 887         }
 888
 889         free(data);
 890
 891         magic = TDB_RECOVERY_MAGIC;
 892         CONVERT(magic);
 893
 894         *magic_offset = recovery_offset + offsetof(struct tdb_record, magic);
 895
 896         if (methods->tdb_write(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
 897                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery magic\n"));
 898                 tdb->ecode = TDB_ERR_IO;
 899                 return -1;
 900         }
 901         if (transaction_write_existing(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
 902                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery magic\n"));
 903                 tdb->ecode = TDB_ERR_IO;
 904                 return -1;
 905         }
 906
 907         /* ensure the recovery magic marker is on disk */
 908         if (transaction_sync(tdb, *magic_offset, sizeof(magic)) == -1) {
 909                 return -1;
 910         }
 911
 912         return 0;
 913 }
 914
 915 static int _tdb_transaction_prepare_commit(struct tdb_context *tdb)
 916 {
 917         const struct tdb_methods *methods;
 918
 919         if (tdb->transaction == NULL) {
 920                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: no transaction\n"));
 921                 return -1;
 922         }
 923
 924         if (tdb->transaction->prepared) {
 925                 tdb->ecode = TDB_ERR_EINVAL;
 926                 _tdb_transaction_cancel(tdb);
 927                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction already prepared\n"));
 928                 return -1;
 929         }
 930
 931         if (tdb->transaction->transaction_error) {
 932                 tdb->ecode = TDB_ERR_IO;
 933                 _tdb_transaction_cancel(tdb);
 934                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction error pending\n"));
 935                 return -1;
 936         }
 937
 938
 939         if (tdb->transaction->nesting != 0) {
 940                 return 0;
 941         }
 942
 943         /* check for a null transaction */
 944         if (tdb->transaction->blocks == NULL) {
 945                 return 0;
 946         }
 947
 948         methods = tdb->transaction->io_methods;
 949
 950         /* if there are any locks pending then the caller has not
 951            nested their locks properly, so fail the transaction */
 952         if (tdb_have_extra_locks(tdb)) {
 953                 tdb->ecode = TDB_ERR_LOCK;
 954                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: locks pending on commit\n"));
 955                 _tdb_transaction_cancel(tdb);
 956                 return -1;
 957         }
 958
 959         /* upgrade the main transaction lock region to a write lock */
 960         if (tdb_allrecord_upgrade(tdb) == -1) {
 961                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to upgrade hash locks\n"));
 962                 _tdb_transaction_cancel(tdb);
 963                 return -1;
 964         }
 965
 966         /* get the open lock - this prevents new users attaching to the database
 967            during the commit */
 968         if (tdb_nest_lock(tdb, OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT) == -1) {
 969                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to get open lock\n"));
 970                 _tdb_transaction_cancel(tdb);
 971                 return -1;
 972         }
 973
 974         /* write the recovery data to the end of the file */
 975         if (transaction_setup_recovery(tdb, &tdb->transaction->magic_offset) == -1) {
 976                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: failed to setup recovery data\n"));
 977                 _tdb_transaction_cancel(tdb);
 978                 return -1;
 979         }
 980
 981         tdb->transaction->prepared = true;
 982
 983         /* expand the file to the new size if needed */
 984         if (tdb->map_size != tdb->transaction->old_map_size) {
 985                 if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
 986                                              tdb->map_size -
 987                                              tdb->transaction->old_map_size) == -1) {
 988                         tdb->ecode = TDB_ERR_IO;
 989                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: expansion failed\n"));
 990                         _tdb_transaction_cancel(tdb);
 991                         return -1;
 992                 }
 993                 tdb->map_size = tdb->transaction->old_map_size;
 994                 methods->tdb_oob(tdb, tdb->map_size, 1, 1);
 995         }
 996
 997         /* Keep the open lock until the actual commit */
 998
 999         return 0;
1000 }
1001
1002 /*
1003    prepare to commit the current transaction
1004 */
1005 _PUBLIC_ int tdb_transaction_prepare_commit(struct tdb_context *tdb)
1006 {
1007         tdb_trace(tdb, "tdb_transaction_prepare_commit");
1008         return _tdb_transaction_prepare_commit(tdb);
1009 }
1010
1011 /* A repack is worthwhile if the largest is less than half total free. */
1012 static bool repack_worthwhile(struct tdb_context *tdb)
1013 {
1014         tdb_off_t ptr;
1015         struct tdb_record rec;
1016         tdb_len_t total = 0, largest = 0;
1017
1018         if (tdb_ofs_read(tdb, FREELIST_TOP, &ptr) == -1) {
1019                 return false;
1020         }
1021
1022         while (ptr != 0 && tdb_rec_free_read(tdb, ptr, &rec) == 0) {
1023                 total += rec.rec_len;
1024                 if (rec.rec_len > largest) {
1025                         largest = rec.rec_len;
1026                 }
1027                 ptr = rec.next;
1028         }
1029
1030         return total > largest * 2;
1031 }
1032
1033 /*
1034   commit the current transaction
1035 */
1036 _PUBLIC_ int tdb_transaction_commit(struct tdb_context *tdb)
1037 {
1038         const struct tdb_methods *methods;
1039         int i;
1040         bool need_repack = false;
1041
1042         if (tdb->transaction == NULL) {
1043                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: no transaction\n"));
1044                 return -1;
1045         }
1046
1047         tdb_trace(tdb, "tdb_transaction_commit");
1048
1049         if (tdb->transaction->transaction_error) {
1050                 tdb->ecode = TDB_ERR_IO;
1051                 _tdb_transaction_cancel(tdb);
1052                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: transaction error pending\n"));
1053                 return -1;
1054         }
1055
1056
1057         if (tdb->transaction->nesting != 0) {
1058                 tdb->transaction->nesting--;
1059                 return 0;
1060         }
1061
1062         /* check for a null transaction */
1063         if (tdb->transaction->blocks == NULL) {
1064                 _tdb_transaction_cancel(tdb);
1065                 return 0;
1066         }
1067
1068         if (!tdb->transaction->prepared) {
1069                 int ret = _tdb_transaction_prepare_commit(tdb);
1070                 if (ret)
1071                         return ret;
1072         }
1073
1074         methods = tdb->transaction->io_methods;
1075
1076         /* perform all the writes */
1077         for (i=0;i<tdb->transaction->num_blocks;i++) {
1078                 tdb_off_t offset;
1079                 tdb_len_t length;
1080
1081                 if (tdb->transaction->blocks[i] == NULL) {
1082                         continue;
1083                 }
1084
1085                 offset = i * tdb->transaction->block_size;
1086                 length = tdb->transaction->block_size;
1087                 if (i == tdb->transaction->num_blocks-1) {
1088                         length = tdb->transaction->last_block_size;
1089                 }
1090
1091                 if (methods->tdb_write(tdb, offset, tdb->transaction->blocks[i], length) == -1) {
1092                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed during commit\n"));
1093
1094                         /* we've overwritten part of the data and
1095                            possibly expanded the file, so we need to
1096                            run the crash recovery code */
1097                         tdb->methods = methods;
1098                         tdb_transaction_recover(tdb);
1099
1100                         _tdb_transaction_cancel(tdb);
1101
1102                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed\n"));
1103                         return -1;
1104                 }
1105                 SAFE_FREE(tdb->transaction->blocks[i]);
1106         }
1107
1108         /* Do this before we drop lock or blocks. */
1109         if (tdb->transaction->expanded) {
1110                 need_repack = repack_worthwhile(tdb);
1111         }
1112
1113         SAFE_FREE(tdb->transaction->blocks);
1114         tdb->transaction->num_blocks = 0;
1115
1116         /* ensure the new data is on disk */
1117         if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1118                 return -1;
1119         }
1120
1121         /*
1122           TODO: maybe write to some dummy hdr field, or write to magic
1123           offset without mmap, before the last sync, instead of the
1124           utime() call
1125         */
1126
1127         /* on some systems (like Linux 2.6.x) changes via mmap/msync
1128            don't change the mtime of the file, this means the file may
1129            not be backed up (as tdb rounding to block sizes means that
1130            file size changes are quite rare too). The following forces
1131            mtime changes when a transaction completes */
1132 #ifdef HAVE_UTIME
1133         utime(tdb->name, NULL);
1134 #endif
1135
1136         /* use a transaction cancel to free memory and remove the
1137            transaction locks */
1138         _tdb_transaction_cancel(tdb);
1139
1140         if (need_repack) {
1141                 return tdb_repack(tdb);
1142         }
1143
1144         return 0;
1145 }
1146
1147
1148 /*
1149   recover from an aborted transaction. Must be called with exclusive
1150   database write access already established (including the open
1151   lock to prevent new processes attaching)
1152 */
1153 int tdb_transaction_recover(struct tdb_context *tdb)
1154 {
1155         tdb_off_t recovery_head, recovery_eof;
1156         unsigned char *data, *p;
1157         uint32_t zero = 0;
1158         struct tdb_record rec;
1159
1160         /* find the recovery area */
1161         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
1162                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery head\n"));
1163                 tdb->ecode = TDB_ERR_IO;
1164                 return -1;
1165         }
1166
1167         if (recovery_head == 0) {
1168                 /* we have never allocated a recovery record */
1169                 return 0;
1170         }
1171
1172         /* read the recovery record */
1173         if (tdb->methods->tdb_read(tdb, recovery_head, &rec,
1174                                    sizeof(rec), DOCONV()) == -1) {
1175                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery record\n"));
1176                 tdb->ecode = TDB_ERR_IO;
1177                 return -1;
1178         }
1179
1180         if (rec.magic != TDB_RECOVERY_MAGIC) {
1181                 /* there is no valid recovery data */
1182                 return 0;
1183         }
1184
1185         if (tdb->read_only) {
1186                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: attempt to recover read only database\n"));
1187                 tdb->ecode = TDB_ERR_CORRUPT;
1188                 return -1;
1189         }
1190
1191         recovery_eof = rec.key_len;
1192
1193         data = (unsigned char *)malloc(rec.data_len);
1194         if (data == NULL) {
1195                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to allocate recovery data\n"));
1196                 tdb->ecode = TDB_ERR_OOM;
1197                 return -1;
1198         }
1199
1200         /* read the full recovery data */
1201         if (tdb->methods->tdb_read(tdb, recovery_head + sizeof(rec), data,
1202                                    rec.data_len, 0) == -1) {
1203                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery data\n"));
1204                 tdb->ecode = TDB_ERR_IO;
1205                 return -1;
1206         }
1207
1208         /* recover the file data */
1209         p = data;
1210         while (p+8 < data + rec.data_len) {
1211                 uint32_t ofs, len;
1212                 if (DOCONV()) {
1213                         tdb_convert(p, 8);
1214                 }
1215                 memcpy(&ofs, p, 4);
1216                 memcpy(&len, p+4, 4);
1217
1218                 if (tdb->methods->tdb_write(tdb, ofs, p+8, len) == -1) {
1219                         free(data);
1220                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to recover %d bytes at offset %d\n", len, ofs));
1221                         tdb->ecode = TDB_ERR_IO;
1222                         return -1;
1223                 }
1224                 p += 8 + len;
1225         }
1226
1227         free(data);
1228
1229         if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1230                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync recovery\n"));
1231                 tdb->ecode = TDB_ERR_IO;
1232                 return -1;
1233         }
1234
1235         /* if the recovery area is after the recovered eof then remove it */
1236         if (recovery_eof <= recovery_head) {
1237                 if (tdb_ofs_write(tdb, TDB_RECOVERY_HEAD, &zero) == -1) {
1238                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery head\n"));
1239                         tdb->ecode = TDB_ERR_IO;
1240                         return -1;
1241                 }
1242         }
1243
1244         /* remove the recovery magic */
1245         if (tdb_ofs_write(tdb, recovery_head + offsetof(struct tdb_record, magic),
1246                           &zero) == -1) {
1247                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery magic\n"));
1248                 tdb->ecode = TDB_ERR_IO;
1249                 return -1;
1250         }
1251
1252         if (transaction_sync(tdb, 0, recovery_eof) == -1) {
1253                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync2 recovery\n"));
1254                 tdb->ecode = TDB_ERR_IO;
1255                 return -1;
1256         }
1257
1258         TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_recover: recovered %d byte database\n",
1259                  recovery_eof));
1260
1261         /* all done */
1262         return 0;
1263 }
1264
1265 /* Any I/O failures we say "needs recovery". */
1266 bool tdb_needs_recovery(struct tdb_context *tdb)
1267 {
1268         tdb_off_t recovery_head;
1269         struct tdb_record rec;
1270
1271         /* find the recovery area */
1272         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
1273                 return true;
1274         }
1275
1276         if (recovery_head == 0) {
1277                 /* we have never allocated a recovery record */
1278                 return false;
1279         }
1280
1281         /* read the recovery record */
1282         if (tdb->methods->tdb_read(tdb, recovery_head, &rec,
1283                                    sizeof(rec), DOCONV()) == -1) {
1284                 return true;
1285         }
1286
1287         return (rec.magic == TDB_RECOVERY_MAGIC);
1288 }