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 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         /* did we expand in this transaction */
 142         bool expanded;
 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 off,
 386                            tdb_len_t len, int probe)
 387 {
 388         if (off + len >= off && off + len <= tdb->map_size) {
 389                 return 0;
 390         }
 391         tdb->ecode = TDB_ERR_IO;
 392         return -1;
 393 }
 394
 395 /*
 396   transaction version of tdb_expand().
 397 */
 398 static int transaction_expand_file(struct tdb_context *tdb, tdb_off_t size,
 399                                    tdb_off_t addition)
 400 {
 401         /* add a write to the transaction elements, so subsequent
 402            reads see the zero data */
 403         if (transaction_write(tdb, size, NULL, addition) != 0) {
 404                 return -1;
 405         }
 406
 407         tdb->transaction->expanded = true;
 408
 409         return 0;
 410 }
 411
 412 static const struct tdb_methods transaction_methods = {
 413         transaction_read,
 414         transaction_write,
 415         transaction_next_hash_chain,
 416         transaction_oob,
 417         transaction_expand_file,
 418 };
 419
 420
 421 /*
 422   start a tdb transaction. No token is returned, as only a single
 423   transaction is allowed to be pending per tdb_context
 424 */
 425 static int _tdb_transaction_start(struct tdb_context *tdb,
 426                                   enum tdb_lock_flags lockflags)
 427 {
 428         /* some sanity checks */
 429         if (tdb->read_only || (tdb->flags & TDB_INTERNAL) || tdb->traverse_read) {
 430                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction on a read-only or internal db\n"));
 431                 tdb->ecode = TDB_ERR_EINVAL;
 432                 return -1;
 433         }
 434
 435         /* cope with nested tdb_transaction_start() calls */
 436         if (tdb->transaction != NULL) {
 437                 if (!(tdb->flags & TDB_ALLOW_NESTING)) {
 438                         tdb->ecode = TDB_ERR_NESTING;
 439                         return -1;
 440                 }
 441                 tdb->transaction->nesting++;
 442                 TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_start: nesting %d\n",
 443                          tdb->transaction->nesting));
 444                 return 0;
 445         }
 446
 447         if (tdb_have_extra_locks(tdb)) {
 448                 /* the caller must not have any locks when starting a
 449                    transaction as otherwise we'll be screwed by lack
 450                    of nested locks in posix */
 451                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction with locks held\n"));
 452                 tdb->ecode = TDB_ERR_LOCK;
 453                 return -1;
 454         }
 455
 456         if (tdb->travlocks.next != NULL) {
 457                 /* you cannot use transactions inside a traverse (although you can use
 458                    traverse inside a transaction) as otherwise you can end up with
 459                    deadlock */
 460                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: cannot start a transaction within a traverse\n"));
 461                 tdb->ecode = TDB_ERR_LOCK;
 462                 return -1;
 463         }
 464
 465         tdb->transaction = (struct tdb_transaction *)
 466                 calloc(sizeof(struct tdb_transaction), 1);
 467         if (tdb->transaction == NULL) {
 468                 tdb->ecode = TDB_ERR_OOM;
 469                 return -1;
 470         }
 471
 472         /* a page at a time seems like a reasonable compromise between compactness and efficiency */
 473         tdb->transaction->block_size = tdb->page_size;
 474
 475         /* get the transaction write lock. This is a blocking lock. As
 476            discussed with Volker, there are a number of ways we could
 477            make this async, which we will probably do in the future */
 478         if (tdb_transaction_lock(tdb, F_WRLCK, lockflags) == -1) {
 479                 SAFE_FREE(tdb->transaction->blocks);
 480                 SAFE_FREE(tdb->transaction);
 481                 if ((lockflags & TDB_LOCK_WAIT) == 0) {
 482                         tdb->ecode = TDB_ERR_NOLOCK;
 483                 }
 484                 return -1;
 485         }
 486
 487         /* get a read lock from the freelist to the end of file. This
 488            is upgraded to a write lock during the commit */
 489         if (tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, true) == -1) {
 490                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: failed to get hash locks\n"));
 491                 goto fail_allrecord_lock;
 492         }
 493
 494         /* setup a copy of the hash table heads so the hash scan in
 495            traverse can be fast */
 496         tdb->transaction->hash_heads = (uint32_t *)
 497                 calloc(tdb->header.hash_size+1, sizeof(uint32_t));
 498         if (tdb->transaction->hash_heads == NULL) {
 499                 tdb->ecode = TDB_ERR_OOM;
 500                 goto fail;
 501         }
 502         if (tdb->methods->tdb_read(tdb, FREELIST_TOP, tdb->transaction->hash_heads,
 503                                    TDB_HASHTABLE_SIZE(tdb), 0) != 0) {
 504                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_start: failed to read hash heads\n"));
 505                 tdb->ecode = TDB_ERR_IO;
 506                 goto fail;
 507         }
 508
 509         /* make sure we know about any file expansions already done by
 510            anyone else */
 511         tdb->methods->tdb_oob(tdb, tdb->map_size, 1, 1);
 512         tdb->transaction->old_map_size = tdb->map_size;
 513
 514         /* finally hook the io methods, replacing them with
 515            transaction specific methods */
 516         tdb->transaction->io_methods = tdb->methods;
 517         tdb->methods = &transaction_methods;
 518
 519         /* Trace at the end, so we get sequence number correct. */
 520         tdb_trace(tdb, "tdb_transaction_start");
 521         return 0;
 522
 523 fail:
 524         tdb_allrecord_unlock(tdb, F_RDLCK, false);
 525 fail_allrecord_lock:
 526         tdb_transaction_unlock(tdb, F_WRLCK);
 527         SAFE_FREE(tdb->transaction->blocks);
 528         SAFE_FREE(tdb->transaction->hash_heads);
 529         SAFE_FREE(tdb->transaction);
 530         return -1;
 531 }
 532
 533 _PUBLIC_ int tdb_transaction_start(struct tdb_context *tdb)
 534 {
 535         return _tdb_transaction_start(tdb, TDB_LOCK_WAIT);
 536 }
 537
 538 _PUBLIC_ int tdb_transaction_start_nonblock(struct tdb_context *tdb)
 539 {
 540         return _tdb_transaction_start(tdb, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE);
 541 }
 542
 543 /*
 544   sync to disk
 545 */
 546 static int transaction_sync(struct tdb_context *tdb, tdb_off_t offset, tdb_len_t length)
 547 {
 548         if (tdb->flags & TDB_NOSYNC) {
 549                 return 0;
 550         }
 551
 552 #ifdef HAVE_FDATASYNC
 553         if (fdatasync(tdb->fd) != 0) {
 554 #else
 555         if (fsync(tdb->fd) != 0) {
 556 #endif
 557                 tdb->ecode = TDB_ERR_IO;
 558                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: fsync failed\n"));
 559                 return -1;
 560         }
 561 #ifdef HAVE_MMAP
 562         if (tdb->map_ptr) {
 563                 tdb_off_t moffset = offset & ~(tdb->page_size-1);
 564                 if (msync(moffset + (char *)tdb->map_ptr,
 565                           length + (offset - moffset), MS_SYNC) != 0) {
 566                         tdb->ecode = TDB_ERR_IO;
 567                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction: msync failed - %s\n",
 568                                  strerror(errno)));
 569                         return -1;
 570                 }
 571         }
 572 #endif
 573         return 0;
 574 }
 575
 576
 577 static int _tdb_transaction_cancel(struct tdb_context *tdb)
 578 {
 579         int i, ret = 0;
 580
 581         if (tdb->transaction == NULL) {
 582                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_cancel: no transaction\n"));
 583                 return -1;
 584         }
 585
 586         if (tdb->transaction->nesting != 0) {
 587                 tdb->transaction->transaction_error = 1;
 588                 tdb->transaction->nesting--;
 589                 return 0;
 590         }
 591
 592         tdb->map_size = tdb->transaction->old_map_size;
 593
 594         /* free all the transaction blocks */
 595         for (i=0;i<tdb->transaction->num_blocks;i++) {
 596                 if (tdb->transaction->blocks[i] != NULL) {
 597                         free(tdb->transaction->blocks[i]);
 598                 }
 599         }
 600         SAFE_FREE(tdb->transaction->blocks);
 601
 602         if (tdb->transaction->magic_offset) {
 603                 const struct tdb_methods *methods = tdb->transaction->io_methods;
 604                 const uint32_t invalid = TDB_RECOVERY_INVALID_MAGIC;
 605
 606                 /* remove the recovery marker */
 607                 if (methods->tdb_write(tdb, tdb->transaction->magic_offset, &invalid, 4) == -1 ||
 608                 transaction_sync(tdb, tdb->transaction->magic_offset, 4) == -1) {
 609                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_cancel: failed to remove recovery magic\n"));
 610                         ret = -1;
 611                 }
 612         }
 613
 614         /* This also removes the OPEN_LOCK, if we have it. */
 615         tdb_release_transaction_locks(tdb);
 616
 617         /* restore the normal io methods */
 618         tdb->methods = tdb->transaction->io_methods;
 619
 620         SAFE_FREE(tdb->transaction->hash_heads);
 621         SAFE_FREE(tdb->transaction);
 622
 623         return ret;
 624 }
 625
 626 /*
 627   cancel the current transaction
 628 */
 629 _PUBLIC_ int tdb_transaction_cancel(struct tdb_context *tdb)
 630 {
 631         tdb_trace(tdb, "tdb_transaction_cancel");
 632         return _tdb_transaction_cancel(tdb);
 633 }
 634
 635 /*
 636   work out how much space the linearised recovery data will consume
 637 */
 638 static tdb_len_t tdb_recovery_size(struct tdb_context *tdb)
 639 {
 640         tdb_len_t recovery_size = 0;
 641         int i;
 642
 643         recovery_size = sizeof(uint32_t);
 644         for (i=0;i<tdb->transaction->num_blocks;i++) {
 645                 if (i * tdb->transaction->block_size >= tdb->transaction->old_map_size) {
 646                         break;
 647                 }
 648                 if (tdb->transaction->blocks[i] == NULL) {
 649                         continue;
 650                 }
 651                 recovery_size += 2*sizeof(tdb_off_t);
 652                 if (i == tdb->transaction->num_blocks-1) {
 653                         recovery_size += tdb->transaction->last_block_size;
 654                 } else {
 655                         recovery_size += tdb->transaction->block_size;
 656                 }
 657         }
 658
 659         return recovery_size;
 660 }
 661
 662 int tdb_recovery_area(struct tdb_context *tdb,
 663                       const struct tdb_methods *methods,
 664                       tdb_off_t *recovery_offset,
 665                       struct tdb_record *rec)
 666 {
 667         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, recovery_offset) == -1) {
 668                 return -1;
 669         }
 670
 671         if (*recovery_offset == 0) {
 672                 rec->rec_len = 0;
 673                 return 0;
 674         }
 675
 676         if (methods->tdb_read(tdb, *recovery_offset, rec, sizeof(*rec),
 677                               DOCONV()) == -1) {
 678                 return -1;
 679         }
 680
 681         /* ignore invalid recovery regions: can happen in crash */
 682         if (rec->magic != TDB_RECOVERY_MAGIC &&
 683             rec->magic != TDB_RECOVERY_INVALID_MAGIC) {
 684                 *recovery_offset = 0;
 685                 rec->rec_len = 0;
 686         }
 687         return 0;
 688 }
 689
 690 /*
 691   allocate the recovery area, or use an existing recovery area if it is
 692   large enough
 693 */
 694 static int tdb_recovery_allocate(struct tdb_context *tdb,
 695                                  tdb_len_t *recovery_size,
 696                                  tdb_off_t *recovery_offset,
 697                                  tdb_len_t *recovery_max_size)
 698 {
 699         struct tdb_record rec;
 700         const struct tdb_methods *methods = tdb->transaction->io_methods;
 701         tdb_off_t recovery_head;
 702
 703         if (tdb_recovery_area(tdb, methods, &recovery_head, &rec) == -1) {
 704                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery head\n"));
 705                 return -1;
 706         }
 707
 708         *recovery_size = tdb_recovery_size(tdb);
 709
 710         if (recovery_head != 0 && *recovery_size <= rec.rec_len) {
 711                 /* it fits in the existing area */
 712                 *recovery_max_size = rec.rec_len;
 713                 *recovery_offset = recovery_head;
 714                 return 0;
 715         }
 716
 717         /* we need to free up the old recovery area, then allocate a
 718            new one at the end of the file. Note that we cannot use
 719            tdb_allocate() to allocate the new one as that might return
 720            us an area that is being currently used (as of the start of
 721            the transaction) */
 722         if (recovery_head != 0) {
 723                 if (tdb_free(tdb, recovery_head, &rec) == -1) {
 724                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to free previous recovery area\n"));
 725                         return -1;
 726                 }
 727         }
 728
 729         /* the tdb_free() call might have increased the recovery size */
 730         *recovery_size = tdb_recovery_size(tdb);
 731
 732         /* round up to a multiple of page size */
 733         *recovery_max_size = tdb_expand_adjust(tdb->map_size,
 734                                                *recovery_size,
 735                                                tdb->page_size)
 736                 - sizeof(rec);
 737
 738         *recovery_offset = tdb->map_size;
 739         recovery_head = *recovery_offset;
 740
 741         if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
 742                                      (tdb->map_size - tdb->transaction->old_map_size) +
 743                                      sizeof(rec) + *recovery_max_size) == -1) {
 744                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to create recovery area\n"));
 745                 return -1;
 746         }
 747
 748         /* remap the file (if using mmap) */
 749         methods->tdb_oob(tdb, tdb->map_size, 1, 1);
 750
 751         /* we have to reset the old map size so that we don't try to expand the file
 752            again in the transaction commit, which would destroy the recovery area */
 753         tdb->transaction->old_map_size = tdb->map_size;
 754
 755         /* write the recovery header offset and sync - we can sync without a race here
 756            as the magic ptr in the recovery record has not been set */
 757         CONVERT(recovery_head);
 758         if (methods->tdb_write(tdb, TDB_RECOVERY_HEAD,
 759                                &recovery_head, sizeof(tdb_off_t)) == -1) {
 760                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
 761                 return -1;
 762         }
 763         if (transaction_write_existing(tdb, TDB_RECOVERY_HEAD, &recovery_head, sizeof(tdb_off_t)) == -1) {
 764                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
 765                 return -1;
 766         }
 767
 768         return 0;
 769 }
 770
 771
 772 /*
 773   setup the recovery data that will be used on a crash during commit
 774 */
 775 static int transaction_setup_recovery(struct tdb_context *tdb,
 776                                       tdb_off_t *magic_offset)
 777 {
 778         tdb_len_t recovery_size;
 779         unsigned char *data, *p;
 780         const struct tdb_methods *methods = tdb->transaction->io_methods;
 781         struct tdb_record *rec;
 782         tdb_off_t recovery_offset, recovery_max_size;
 783         tdb_off_t old_map_size = tdb->transaction->old_map_size;
 784         uint32_t magic, tailer;
 785         int i;
 786
 787         /*
 788           check that the recovery area has enough space
 789         */
 790         if (tdb_recovery_allocate(tdb, &recovery_size,
 791                                   &recovery_offset, &recovery_max_size) == -1) {
 792                 return -1;
 793         }
 794
 795         data = (unsigned char *)malloc(recovery_size + sizeof(*rec));
 796         if (data == NULL) {
 797                 tdb->ecode = TDB_ERR_OOM;
 798                 return -1;
 799         }
 800
 801         rec = (struct tdb_record *)data;
 802         memset(rec, 0, sizeof(*rec));
 803
 804         rec->magic    = TDB_RECOVERY_INVALID_MAGIC;
 805         rec->data_len = recovery_size;
 806         rec->rec_len  = recovery_max_size;
 807         rec->key_len  = old_map_size;
 808         CONVERT(*rec);
 809
 810         /* build the recovery data into a single blob to allow us to do a single
 811            large write, which should be more efficient */
 812         p = data + sizeof(*rec);
 813         for (i=0;i<tdb->transaction->num_blocks;i++) {
 814                 tdb_off_t offset;
 815                 tdb_len_t length;
 816
 817                 if (tdb->transaction->blocks[i] == NULL) {
 818                         continue;
 819                 }
 820
 821                 offset = i * tdb->transaction->block_size;
 822                 length = tdb->transaction->block_size;
 823                 if (i == tdb->transaction->num_blocks-1) {
 824                         length = tdb->transaction->last_block_size;
 825                 }
 826
 827                 if (offset >= old_map_size) {
 828                         continue;
 829                 }
 830                 if (offset + length > tdb->transaction->old_map_size) {
 831                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: transaction data over new region boundary\n"));
 832                         free(data);
 833                         tdb->ecode = TDB_ERR_CORRUPT;
 834                         return -1;
 835                 }
 836                 memcpy(p, &offset, 4);
 837                 memcpy(p+4, &length, 4);
 838                 if (DOCONV()) {
 839                         tdb_convert(p, 8);
 840                 }
 841                 /* the recovery area contains the old data, not the
 842                    new data, so we have to call the original tdb_read
 843                    method to get it */
 844                 if (methods->tdb_read(tdb, offset, p + 8, length, 0) != 0) {
 845                         free(data);
 846                         tdb->ecode = TDB_ERR_IO;
 847                         return -1;
 848                 }
 849                 p += 8 + length;
 850         }
 851
 852         /* and the tailer */
 853         tailer = sizeof(*rec) + recovery_max_size;
 854         memcpy(p, &tailer, 4);
 855         if (DOCONV()) {
 856                 tdb_convert(p, 4);
 857         }
 858
 859         /* write the recovery data to the recovery area */
 860         if (methods->tdb_write(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
 861                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery data\n"));
 862                 free(data);
 863                 tdb->ecode = TDB_ERR_IO;
 864                 return -1;
 865         }
 866         if (transaction_write_existing(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
 867                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery data\n"));
 868                 free(data);
 869                 tdb->ecode = TDB_ERR_IO;
 870                 return -1;
 871         }
 872
 873         /* as we don't have ordered writes, we have to sync the recovery
 874            data before we update the magic to indicate that the recovery
 875            data is present */
 876         if (transaction_sync(tdb, recovery_offset, sizeof(*rec) + recovery_size) == -1) {
 877                 free(data);
 878                 return -1;
 879         }
 880
 881         free(data);
 882
 883         magic = TDB_RECOVERY_MAGIC;
 884         CONVERT(magic);
 885
 886         *magic_offset = recovery_offset + offsetof(struct tdb_record, magic);
 887
 888         if (methods->tdb_write(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
 889                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery magic\n"));
 890                 tdb->ecode = TDB_ERR_IO;
 891                 return -1;
 892         }
 893         if (transaction_write_existing(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
 894                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery magic\n"));
 895                 tdb->ecode = TDB_ERR_IO;
 896                 return -1;
 897         }
 898
 899         /* ensure the recovery magic marker is on disk */
 900         if (transaction_sync(tdb, *magic_offset, sizeof(magic)) == -1) {
 901                 return -1;
 902         }
 903
 904         return 0;
 905 }
 906
 907 static int _tdb_transaction_prepare_commit(struct tdb_context *tdb)
 908 {
 909         const struct tdb_methods *methods;
 910
 911         if (tdb->transaction == NULL) {
 912                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: no transaction\n"));
 913                 return -1;
 914         }
 915
 916         if (tdb->transaction->prepared) {
 917                 tdb->ecode = TDB_ERR_EINVAL;
 918                 _tdb_transaction_cancel(tdb);
 919                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction already prepared\n"));
 920                 return -1;
 921         }
 922
 923         if (tdb->transaction->transaction_error) {
 924                 tdb->ecode = TDB_ERR_IO;
 925                 _tdb_transaction_cancel(tdb);
 926                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction error pending\n"));
 927                 return -1;
 928         }
 929
 930
 931         if (tdb->transaction->nesting != 0) {
 932                 return 0;
 933         }
 934
 935         /* check for a null transaction */
 936         if (tdb->transaction->blocks == NULL) {
 937                 return 0;
 938         }
 939
 940         methods = tdb->transaction->io_methods;
 941
 942         /* if there are any locks pending then the caller has not
 943            nested their locks properly, so fail the transaction */
 944         if (tdb_have_extra_locks(tdb)) {
 945                 tdb->ecode = TDB_ERR_LOCK;
 946                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: locks pending on commit\n"));
 947                 _tdb_transaction_cancel(tdb);
 948                 return -1;
 949         }
 950
 951         /* upgrade the main transaction lock region to a write lock */
 952         if (tdb_allrecord_upgrade(tdb) == -1) {
 953                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to upgrade hash locks\n"));
 954                 _tdb_transaction_cancel(tdb);
 955                 return -1;
 956         }
 957
 958         /* get the open lock - this prevents new users attaching to the database
 959            during the commit */
 960         if (tdb_nest_lock(tdb, OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT) == -1) {
 961                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to get open lock\n"));
 962                 _tdb_transaction_cancel(tdb);
 963                 return -1;
 964         }
 965
 966         if (!(tdb->flags & TDB_NOSYNC)) {
 967                 /* write the recovery data to the end of the file */
 968                 if (transaction_setup_recovery(tdb, &tdb->transaction->magic_offset) == -1) {
 969                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: failed to setup recovery data\n"));
 970                         _tdb_transaction_cancel(tdb);
 971                         return -1;
 972                 }
 973         }
 974
 975         tdb->transaction->prepared = true;
 976
 977         /* expand the file to the new size if needed */
 978         if (tdb->map_size != tdb->transaction->old_map_size) {
 979                 if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
 980                                              tdb->map_size -
 981                                              tdb->transaction->old_map_size) == -1) {
 982                         tdb->ecode = TDB_ERR_IO;
 983                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: expansion failed\n"));
 984                         _tdb_transaction_cancel(tdb);
 985                         return -1;
 986                 }
 987                 tdb->map_size = tdb->transaction->old_map_size;
 988                 methods->tdb_oob(tdb, tdb->map_size, 1, 1);
 989         }
 990
 991         /* Keep the open lock until the actual commit */
 992
 993         return 0;
 994 }
 995
 996 /*
 997    prepare to commit the current transaction
 998 */
 999 _PUBLIC_ int tdb_transaction_prepare_commit(struct tdb_context *tdb)
1000 {
1001         tdb_trace(tdb, "tdb_transaction_prepare_commit");
1002         return _tdb_transaction_prepare_commit(tdb);
1003 }
1004
1005 /* A repack is worthwhile if the largest is less than half total free. */
1006 static bool repack_worthwhile(struct tdb_context *tdb)
1007 {
1008         tdb_off_t ptr;
1009         struct tdb_record rec;
1010         tdb_len_t total = 0, largest = 0;
1011
1012         if (tdb_ofs_read(tdb, FREELIST_TOP, &ptr) == -1) {
1013                 return false;
1014         }
1015
1016         while (ptr != 0 && tdb_rec_free_read(tdb, ptr, &rec) == 0) {
1017                 total += rec.rec_len;
1018                 if (rec.rec_len > largest) {
1019                         largest = rec.rec_len;
1020                 }
1021                 ptr = rec.next;
1022         }
1023
1024         return total > largest * 2;
1025 }
1026
1027 /*
1028   commit the current transaction
1029 */
1030 _PUBLIC_ int tdb_transaction_commit(struct tdb_context *tdb)
1031 {
1032         const struct tdb_methods *methods;
1033         int i;
1034         bool need_repack = false;
1035
1036         if (tdb->transaction == NULL) {
1037                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: no transaction\n"));
1038                 return -1;
1039         }
1040
1041         tdb_trace(tdb, "tdb_transaction_commit");
1042
1043         if (tdb->transaction->transaction_error) {
1044                 tdb->ecode = TDB_ERR_IO;
1045                 _tdb_transaction_cancel(tdb);
1046                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: transaction error pending\n"));
1047                 return -1;
1048         }
1049
1050
1051         if (tdb->transaction->nesting != 0) {
1052                 tdb->transaction->nesting--;
1053                 return 0;
1054         }
1055
1056         /* check for a null transaction */
1057         if (tdb->transaction->blocks == NULL) {
1058                 _tdb_transaction_cancel(tdb);
1059                 return 0;
1060         }
1061
1062         if (!tdb->transaction->prepared) {
1063                 int ret = _tdb_transaction_prepare_commit(tdb);
1064                 if (ret)
1065                         return ret;
1066         }
1067
1068         methods = tdb->transaction->io_methods;
1069
1070         /* perform all the writes */
1071         for (i=0;i<tdb->transaction->num_blocks;i++) {
1072                 tdb_off_t offset;
1073                 tdb_len_t length;
1074
1075                 if (tdb->transaction->blocks[i] == NULL) {
1076                         continue;
1077                 }
1078
1079                 offset = i * tdb->transaction->block_size;
1080                 length = tdb->transaction->block_size;
1081                 if (i == tdb->transaction->num_blocks-1) {
1082                         length = tdb->transaction->last_block_size;
1083                 }
1084
1085                 if (methods->tdb_write(tdb, offset, tdb->transaction->blocks[i], length) == -1) {
1086                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed during commit\n"));
1087
1088                         /* we've overwritten part of the data and
1089                            possibly expanded the file, so we need to
1090                            run the crash recovery code */
1091                         tdb->methods = methods;
1092                         tdb_transaction_recover(tdb);
1093
1094                         _tdb_transaction_cancel(tdb);
1095
1096                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed\n"));
1097                         return -1;
1098                 }
1099                 SAFE_FREE(tdb->transaction->blocks[i]);
1100         }
1101
1102         /* Do this before we drop lock or blocks. */
1103         if (tdb->transaction->expanded) {
1104                 need_repack = repack_worthwhile(tdb);
1105         }
1106
1107         SAFE_FREE(tdb->transaction->blocks);
1108         tdb->transaction->num_blocks = 0;
1109
1110         /* ensure the new data is on disk */
1111         if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1112                 return -1;
1113         }
1114
1115         /*
1116           TODO: maybe write to some dummy hdr field, or write to magic
1117           offset without mmap, before the last sync, instead of the
1118           utime() call
1119         */
1120
1121         /* on some systems (like Linux 2.6.x) changes via mmap/msync
1122            don't change the mtime of the file, this means the file may
1123            not be backed up (as tdb rounding to block sizes means that
1124            file size changes are quite rare too). The following forces
1125            mtime changes when a transaction completes */
1126 #ifdef HAVE_UTIME
1127         utime(tdb->name, NULL);
1128 #endif
1129
1130         /* use a transaction cancel to free memory and remove the
1131            transaction locks */
1132         _tdb_transaction_cancel(tdb);
1133
1134         if (need_repack) {
1135                 return tdb_repack(tdb);
1136         }
1137
1138         return 0;
1139 }
1140
1141
1142 /*
1143   recover from an aborted transaction. Must be called with exclusive
1144   database write access already established (including the open
1145   lock to prevent new processes attaching)
1146 */
1147 int tdb_transaction_recover(struct tdb_context *tdb)
1148 {
1149         tdb_off_t recovery_head, recovery_eof;
1150         unsigned char *data, *p;
1151         uint32_t zero = 0;
1152         struct tdb_record rec;
1153
1154         /* find the recovery area */
1155         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
1156                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery head\n"));
1157                 tdb->ecode = TDB_ERR_IO;
1158                 return -1;
1159         }
1160
1161         if (recovery_head == 0) {
1162                 /* we have never allocated a recovery record */
1163                 return 0;
1164         }
1165
1166         /* read the recovery record */
1167         if (tdb->methods->tdb_read(tdb, recovery_head, &rec,
1168                                    sizeof(rec), DOCONV()) == -1) {
1169                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery record\n"));
1170                 tdb->ecode = TDB_ERR_IO;
1171                 return -1;
1172         }
1173
1174         if (rec.magic != TDB_RECOVERY_MAGIC) {
1175                 /* there is no valid recovery data */
1176                 return 0;
1177         }
1178
1179         if (tdb->read_only) {
1180                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: attempt to recover read only database\n"));
1181                 tdb->ecode = TDB_ERR_CORRUPT;
1182                 return -1;
1183         }
1184
1185         recovery_eof = rec.key_len;
1186
1187         data = (unsigned char *)malloc(rec.data_len);
1188         if (data == NULL) {
1189                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to allocate recovery data\n"));
1190                 tdb->ecode = TDB_ERR_OOM;
1191                 return -1;
1192         }
1193
1194         /* read the full recovery data */
1195         if (tdb->methods->tdb_read(tdb, recovery_head + sizeof(rec), data,
1196                                    rec.data_len, 0) == -1) {
1197                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery data\n"));
1198                 tdb->ecode = TDB_ERR_IO;
1199                 return -1;
1200         }
1201
1202         /* recover the file data */
1203         p = data;
1204         while (p+8 < data + rec.data_len) {
1205                 uint32_t ofs, len;
1206                 if (DOCONV()) {
1207                         tdb_convert(p, 8);
1208                 }
1209                 memcpy(&ofs, p, 4);
1210                 memcpy(&len, p+4, 4);
1211
1212                 if (tdb->methods->tdb_write(tdb, ofs, p+8, len) == -1) {
1213                         free(data);
1214                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to recover %d bytes at offset %d\n", len, ofs));
1215                         tdb->ecode = TDB_ERR_IO;
1216                         return -1;
1217                 }
1218                 p += 8 + len;
1219         }
1220
1221         free(data);
1222
1223         if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1224                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync recovery\n"));
1225                 tdb->ecode = TDB_ERR_IO;
1226                 return -1;
1227         }
1228
1229         /* if the recovery area is after the recovered eof then remove it */
1230         if (recovery_eof <= recovery_head) {
1231                 if (tdb_ofs_write(tdb, TDB_RECOVERY_HEAD, &zero) == -1) {
1232                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery head\n"));
1233                         tdb->ecode = TDB_ERR_IO;
1234                         return -1;
1235                 }
1236         }
1237
1238         /* remove the recovery magic */
1239         if (tdb_ofs_write(tdb, recovery_head + offsetof(struct tdb_record, magic),
1240                           &zero) == -1) {
1241                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery magic\n"));
1242                 tdb->ecode = TDB_ERR_IO;
1243                 return -1;
1244         }
1245
1246         if (transaction_sync(tdb, 0, recovery_eof) == -1) {
1247                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync2 recovery\n"));
1248                 tdb->ecode = TDB_ERR_IO;
1249                 return -1;
1250         }
1251
1252         TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_recover: recovered %d byte database\n",
1253                  recovery_eof));
1254
1255         /* all done */
1256         return 0;
1257 }
1258
1259 /* Any I/O failures we say "needs recovery". */
1260 bool tdb_needs_recovery(struct tdb_context *tdb)
1261 {
1262         tdb_off_t recovery_head;
1263         struct tdb_record rec;
1264
1265         /* find the recovery area */
1266         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
1267                 return true;
1268         }
1269
1270         if (recovery_head == 0) {
1271                 /* we have never allocated a recovery record */
1272                 return false;
1273         }
1274
1275         /* read the recovery record */
1276         if (tdb->methods->tdb_read(tdb, recovery_head, &rec,
1277                                    sizeof(rec), DOCONV()) == -1) {
1278                 return true;
1279         }
1280
1281         return (rec.magic == TDB_RECOVERY_MAGIC);
1282 }