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_ALIGN(sizeof(rec) + *recovery_size, tdb->page_size) - sizeof(rec);
 734         *recovery_offset = tdb->map_size;
 735         recovery_head = *recovery_offset;
 736
 737         if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
 738                                      (tdb->map_size - tdb->transaction->old_map_size) +
 739                                      sizeof(rec) + *recovery_max_size) == -1) {
 740                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to create recovery area\n"));
 741                 return -1;
 742         }
 743
 744         /* remap the file (if using mmap) */
 745         methods->tdb_oob(tdb, tdb->map_size, 1, 1);
 746
 747         /* we have to reset the old map size so that we don't try to expand the file
 748            again in the transaction commit, which would destroy the recovery area */
 749         tdb->transaction->old_map_size = tdb->map_size;
 750
 751         /* write the recovery header offset and sync - we can sync without a race here
 752            as the magic ptr in the recovery record has not been set */
 753         CONVERT(recovery_head);
 754         if (methods->tdb_write(tdb, TDB_RECOVERY_HEAD,
 755                                &recovery_head, sizeof(tdb_off_t)) == -1) {
 756                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to write recovery head\n"));
 757                 return -1;
 758         }
 759         if (transaction_write_existing(tdb, TDB_RECOVERY_HEAD, &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
 764         return 0;
 765 }
 766
 767
 768 /*
 769   setup the recovery data that will be used on a crash during commit
 770 */
 771 static int transaction_setup_recovery(struct tdb_context *tdb,
 772                                       tdb_off_t *magic_offset)
 773 {
 774         tdb_len_t recovery_size;
 775         unsigned char *data, *p;
 776         const struct tdb_methods *methods = tdb->transaction->io_methods;
 777         struct tdb_record *rec;
 778         tdb_off_t recovery_offset, recovery_max_size;
 779         tdb_off_t old_map_size = tdb->transaction->old_map_size;
 780         uint32_t magic, tailer;
 781         int i;
 782
 783         /*
 784           check that the recovery area has enough space
 785         */
 786         if (tdb_recovery_allocate(tdb, &recovery_size,
 787                                   &recovery_offset, &recovery_max_size) == -1) {
 788                 return -1;
 789         }
 790
 791         data = (unsigned char *)malloc(recovery_size + sizeof(*rec));
 792         if (data == NULL) {
 793                 tdb->ecode = TDB_ERR_OOM;
 794                 return -1;
 795         }
 796
 797         rec = (struct tdb_record *)data;
 798         memset(rec, 0, sizeof(*rec));
 799
 800         rec->magic    = TDB_RECOVERY_INVALID_MAGIC;
 801         rec->data_len = recovery_size;
 802         rec->rec_len  = recovery_max_size;
 803         rec->key_len  = old_map_size;
 804         CONVERT(*rec);
 805
 806         /* build the recovery data into a single blob to allow us to do a single
 807            large write, which should be more efficient */
 808         p = data + sizeof(*rec);
 809         for (i=0;i<tdb->transaction->num_blocks;i++) {
 810                 tdb_off_t offset;
 811                 tdb_len_t length;
 812
 813                 if (tdb->transaction->blocks[i] == NULL) {
 814                         continue;
 815                 }
 816
 817                 offset = i * tdb->transaction->block_size;
 818                 length = tdb->transaction->block_size;
 819                 if (i == tdb->transaction->num_blocks-1) {
 820                         length = tdb->transaction->last_block_size;
 821                 }
 822
 823                 if (offset >= old_map_size) {
 824                         continue;
 825                 }
 826                 if (offset + length > tdb->transaction->old_map_size) {
 827                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: transaction data over new region boundary\n"));
 828                         free(data);
 829                         tdb->ecode = TDB_ERR_CORRUPT;
 830                         return -1;
 831                 }
 832                 memcpy(p, &offset, 4);
 833                 memcpy(p+4, &length, 4);
 834                 if (DOCONV()) {
 835                         tdb_convert(p, 8);
 836                 }
 837                 /* the recovery area contains the old data, not the
 838                    new data, so we have to call the original tdb_read
 839                    method to get it */
 840                 if (methods->tdb_read(tdb, offset, p + 8, length, 0) != 0) {
 841                         free(data);
 842                         tdb->ecode = TDB_ERR_IO;
 843                         return -1;
 844                 }
 845                 p += 8 + length;
 846         }
 847
 848         /* and the tailer */
 849         tailer = sizeof(*rec) + recovery_max_size;
 850         memcpy(p, &tailer, 4);
 851         if (DOCONV()) {
 852                 tdb_convert(p, 4);
 853         }
 854
 855         /* write the recovery data to the recovery area */
 856         if (methods->tdb_write(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
 857                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery data\n"));
 858                 free(data);
 859                 tdb->ecode = TDB_ERR_IO;
 860                 return -1;
 861         }
 862         if (transaction_write_existing(tdb, recovery_offset, data, sizeof(*rec) + recovery_size) == -1) {
 863                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery data\n"));
 864                 free(data);
 865                 tdb->ecode = TDB_ERR_IO;
 866                 return -1;
 867         }
 868
 869         /* as we don't have ordered writes, we have to sync the recovery
 870            data before we update the magic to indicate that the recovery
 871            data is present */
 872         if (transaction_sync(tdb, recovery_offset, sizeof(*rec) + recovery_size) == -1) {
 873                 free(data);
 874                 return -1;
 875         }
 876
 877         free(data);
 878
 879         magic = TDB_RECOVERY_MAGIC;
 880         CONVERT(magic);
 881
 882         *magic_offset = recovery_offset + offsetof(struct tdb_record, magic);
 883
 884         if (methods->tdb_write(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
 885                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write recovery magic\n"));
 886                 tdb->ecode = TDB_ERR_IO;
 887                 return -1;
 888         }
 889         if (transaction_write_existing(tdb, *magic_offset, &magic, sizeof(magic)) == -1) {
 890                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_setup_recovery: failed to write secondary recovery magic\n"));
 891                 tdb->ecode = TDB_ERR_IO;
 892                 return -1;
 893         }
 894
 895         /* ensure the recovery magic marker is on disk */
 896         if (transaction_sync(tdb, *magic_offset, sizeof(magic)) == -1) {
 897                 return -1;
 898         }
 899
 900         return 0;
 901 }
 902
 903 static int _tdb_transaction_prepare_commit(struct tdb_context *tdb)
 904 {
 905         const struct tdb_methods *methods;
 906
 907         if (tdb->transaction == NULL) {
 908                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: no transaction\n"));
 909                 return -1;
 910         }
 911
 912         if (tdb->transaction->prepared) {
 913                 tdb->ecode = TDB_ERR_EINVAL;
 914                 _tdb_transaction_cancel(tdb);
 915                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction already prepared\n"));
 916                 return -1;
 917         }
 918
 919         if (tdb->transaction->transaction_error) {
 920                 tdb->ecode = TDB_ERR_IO;
 921                 _tdb_transaction_cancel(tdb);
 922                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: transaction error pending\n"));
 923                 return -1;
 924         }
 925
 926
 927         if (tdb->transaction->nesting != 0) {
 928                 return 0;
 929         }
 930
 931         /* check for a null transaction */
 932         if (tdb->transaction->blocks == NULL) {
 933                 return 0;
 934         }
 935
 936         methods = tdb->transaction->io_methods;
 937
 938         /* if there are any locks pending then the caller has not
 939            nested their locks properly, so fail the transaction */
 940         if (tdb_have_extra_locks(tdb)) {
 941                 tdb->ecode = TDB_ERR_LOCK;
 942                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: locks pending on commit\n"));
 943                 _tdb_transaction_cancel(tdb);
 944                 return -1;
 945         }
 946
 947         /* upgrade the main transaction lock region to a write lock */
 948         if (tdb_allrecord_upgrade(tdb) == -1) {
 949                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to upgrade hash locks\n"));
 950                 _tdb_transaction_cancel(tdb);
 951                 return -1;
 952         }
 953
 954         /* get the open lock - this prevents new users attaching to the database
 955            during the commit */
 956         if (tdb_nest_lock(tdb, OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT) == -1) {
 957                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to get open lock\n"));
 958                 _tdb_transaction_cancel(tdb);
 959                 return -1;
 960         }
 961
 962         if (!(tdb->flags & TDB_NOSYNC)) {
 963                 /* write the recovery data to the end of the file */
 964                 if (transaction_setup_recovery(tdb, &tdb->transaction->magic_offset) == -1) {
 965                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: failed to setup recovery data\n"));
 966                         _tdb_transaction_cancel(tdb);
 967                         return -1;
 968                 }
 969         }
 970
 971         tdb->transaction->prepared = true;
 972
 973         /* expand the file to the new size if needed */
 974         if (tdb->map_size != tdb->transaction->old_map_size) {
 975                 if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size,
 976                                              tdb->map_size -
 977                                              tdb->transaction->old_map_size) == -1) {
 978                         tdb->ecode = TDB_ERR_IO;
 979                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare_commit: expansion failed\n"));
 980                         _tdb_transaction_cancel(tdb);
 981                         return -1;
 982                 }
 983                 tdb->map_size = tdb->transaction->old_map_size;
 984                 methods->tdb_oob(tdb, tdb->map_size, 1, 1);
 985         }
 986
 987         /* Keep the open lock until the actual commit */
 988
 989         return 0;
 990 }
 991
 992 /*
 993    prepare to commit the current transaction
 994 */
 995 _PUBLIC_ int tdb_transaction_prepare_commit(struct tdb_context *tdb)
 996 {
 997         tdb_trace(tdb, "tdb_transaction_prepare_commit");
 998         return _tdb_transaction_prepare_commit(tdb);
 999 }
1000
1001 /* A repack is worthwhile if the largest is less than half total free. */
1002 static bool repack_worthwhile(struct tdb_context *tdb)
1003 {
1004         tdb_off_t ptr;
1005         struct tdb_record rec;
1006         tdb_len_t total = 0, largest = 0;
1007
1008         if (tdb_ofs_read(tdb, FREELIST_TOP, &ptr) == -1) {
1009                 return false;
1010         }
1011
1012         while (ptr != 0 && tdb_rec_free_read(tdb, ptr, &rec) == 0) {
1013                 total += rec.rec_len;
1014                 if (rec.rec_len > largest) {
1015                         largest = rec.rec_len;
1016                 }
1017                 ptr = rec.next;
1018         }
1019
1020         return total > largest * 2;
1021 }
1022
1023 /*
1024   commit the current transaction
1025 */
1026 _PUBLIC_ int tdb_transaction_commit(struct tdb_context *tdb)
1027 {
1028         const struct tdb_methods *methods;
1029         int i;
1030         bool need_repack = false;
1031
1032         if (tdb->transaction == NULL) {
1033                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: no transaction\n"));
1034                 return -1;
1035         }
1036
1037         tdb_trace(tdb, "tdb_transaction_commit");
1038
1039         if (tdb->transaction->transaction_error) {
1040                 tdb->ecode = TDB_ERR_IO;
1041                 _tdb_transaction_cancel(tdb);
1042                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: transaction error pending\n"));
1043                 return -1;
1044         }
1045
1046
1047         if (tdb->transaction->nesting != 0) {
1048                 tdb->transaction->nesting--;
1049                 return 0;
1050         }
1051
1052         /* check for a null transaction */
1053         if (tdb->transaction->blocks == NULL) {
1054                 _tdb_transaction_cancel(tdb);
1055                 return 0;
1056         }
1057
1058         if (!tdb->transaction->prepared) {
1059                 int ret = _tdb_transaction_prepare_commit(tdb);
1060                 if (ret)
1061                         return ret;
1062         }
1063
1064         methods = tdb->transaction->io_methods;
1065
1066         /* perform all the writes */
1067         for (i=0;i<tdb->transaction->num_blocks;i++) {
1068                 tdb_off_t offset;
1069                 tdb_len_t length;
1070
1071                 if (tdb->transaction->blocks[i] == NULL) {
1072                         continue;
1073                 }
1074
1075                 offset = i * tdb->transaction->block_size;
1076                 length = tdb->transaction->block_size;
1077                 if (i == tdb->transaction->num_blocks-1) {
1078                         length = tdb->transaction->last_block_size;
1079                 }
1080
1081                 if (methods->tdb_write(tdb, offset, tdb->transaction->blocks[i], length) == -1) {
1082                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed during commit\n"));
1083
1084                         /* we've overwritten part of the data and
1085                            possibly expanded the file, so we need to
1086                            run the crash recovery code */
1087                         tdb->methods = methods;
1088                         tdb_transaction_recover(tdb);
1089
1090                         _tdb_transaction_cancel(tdb);
1091
1092                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: write failed\n"));
1093                         return -1;
1094                 }
1095                 SAFE_FREE(tdb->transaction->blocks[i]);
1096         }
1097
1098         /* Do this before we drop lock or blocks. */
1099         if (tdb->transaction->expanded) {
1100                 need_repack = repack_worthwhile(tdb);
1101         }
1102
1103         SAFE_FREE(tdb->transaction->blocks);
1104         tdb->transaction->num_blocks = 0;
1105
1106         /* ensure the new data is on disk */
1107         if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1108                 return -1;
1109         }
1110
1111         /*
1112           TODO: maybe write to some dummy hdr field, or write to magic
1113           offset without mmap, before the last sync, instead of the
1114           utime() call
1115         */
1116
1117         /* on some systems (like Linux 2.6.x) changes via mmap/msync
1118            don't change the mtime of the file, this means the file may
1119            not be backed up (as tdb rounding to block sizes means that
1120            file size changes are quite rare too). The following forces
1121            mtime changes when a transaction completes */
1122 #ifdef HAVE_UTIME
1123         utime(tdb->name, NULL);
1124 #endif
1125
1126         /* use a transaction cancel to free memory and remove the
1127            transaction locks */
1128         _tdb_transaction_cancel(tdb);
1129
1130         if (need_repack) {
1131                 return tdb_repack(tdb);
1132         }
1133
1134         return 0;
1135 }
1136
1137
1138 /*
1139   recover from an aborted transaction. Must be called with exclusive
1140   database write access already established (including the open
1141   lock to prevent new processes attaching)
1142 */
1143 int tdb_transaction_recover(struct tdb_context *tdb)
1144 {
1145         tdb_off_t recovery_head, recovery_eof;
1146         unsigned char *data, *p;
1147         uint32_t zero = 0;
1148         struct tdb_record rec;
1149
1150         /* find the recovery area */
1151         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
1152                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery head\n"));
1153                 tdb->ecode = TDB_ERR_IO;
1154                 return -1;
1155         }
1156
1157         if (recovery_head == 0) {
1158                 /* we have never allocated a recovery record */
1159                 return 0;
1160         }
1161
1162         /* read the recovery record */
1163         if (tdb->methods->tdb_read(tdb, recovery_head, &rec,
1164                                    sizeof(rec), DOCONV()) == -1) {
1165                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery record\n"));
1166                 tdb->ecode = TDB_ERR_IO;
1167                 return -1;
1168         }
1169
1170         if (rec.magic != TDB_RECOVERY_MAGIC) {
1171                 /* there is no valid recovery data */
1172                 return 0;
1173         }
1174
1175         if (tdb->read_only) {
1176                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: attempt to recover read only database\n"));
1177                 tdb->ecode = TDB_ERR_CORRUPT;
1178                 return -1;
1179         }
1180
1181         recovery_eof = rec.key_len;
1182
1183         data = (unsigned char *)malloc(rec.data_len);
1184         if (data == NULL) {
1185                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to allocate recovery data\n"));
1186                 tdb->ecode = TDB_ERR_OOM;
1187                 return -1;
1188         }
1189
1190         /* read the full recovery data */
1191         if (tdb->methods->tdb_read(tdb, recovery_head + sizeof(rec), data,
1192                                    rec.data_len, 0) == -1) {
1193                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to read recovery data\n"));
1194                 tdb->ecode = TDB_ERR_IO;
1195                 return -1;
1196         }
1197
1198         /* recover the file data */
1199         p = data;
1200         while (p+8 < data + rec.data_len) {
1201                 uint32_t ofs, len;
1202                 if (DOCONV()) {
1203                         tdb_convert(p, 8);
1204                 }
1205                 memcpy(&ofs, p, 4);
1206                 memcpy(&len, p+4, 4);
1207
1208                 if (tdb->methods->tdb_write(tdb, ofs, p+8, len) == -1) {
1209                         free(data);
1210                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to recover %d bytes at offset %d\n", len, ofs));
1211                         tdb->ecode = TDB_ERR_IO;
1212                         return -1;
1213                 }
1214                 p += 8 + len;
1215         }
1216
1217         free(data);
1218
1219         if (transaction_sync(tdb, 0, tdb->map_size) == -1) {
1220                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync recovery\n"));
1221                 tdb->ecode = TDB_ERR_IO;
1222                 return -1;
1223         }
1224
1225         /* if the recovery area is after the recovered eof then remove it */
1226         if (recovery_eof <= recovery_head) {
1227                 if (tdb_ofs_write(tdb, TDB_RECOVERY_HEAD, &zero) == -1) {
1228                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery head\n"));
1229                         tdb->ecode = TDB_ERR_IO;
1230                         return -1;
1231                 }
1232         }
1233
1234         /* remove the recovery magic */
1235         if (tdb_ofs_write(tdb, recovery_head + offsetof(struct tdb_record, magic),
1236                           &zero) == -1) {
1237                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to remove recovery magic\n"));
1238                 tdb->ecode = TDB_ERR_IO;
1239                 return -1;
1240         }
1241
1242         if (transaction_sync(tdb, 0, recovery_eof) == -1) {
1243                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_recover: failed to sync2 recovery\n"));
1244                 tdb->ecode = TDB_ERR_IO;
1245                 return -1;
1246         }
1247
1248         TDB_LOG((tdb, TDB_DEBUG_TRACE, "tdb_transaction_recover: recovered %d byte database\n",
1249                  recovery_eof));
1250
1251         /* all done */
1252         return 0;
1253 }
1254
1255 /* Any I/O failures we say "needs recovery". */
1256 bool tdb_needs_recovery(struct tdb_context *tdb)
1257 {
1258         tdb_off_t recovery_head;
1259         struct tdb_record rec;
1260
1261         /* find the recovery area */
1262         if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
1263                 return true;
1264         }
1265
1266         if (recovery_head == 0) {
1267                 /* we have never allocated a recovery record */
1268                 return false;
1269         }
1270
1271         /* read the recovery record */
1272         if (tdb->methods->tdb_read(tdb, recovery_head, &rec,
1273                                    sizeof(rec), DOCONV()) == -1) {
1274                 return true;
1275         }
1276
1277         return (rec.magic == TDB_RECOVERY_MAGIC);
1278 }