fs/jbd2/recovery.c

   1 /*
   2  * linux/fs/jbd2/recovery.c
   3  *
   4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
   5  *
   6  * Copyright 1999-2000 Red Hat Software --- All Rights Reserved
   7  *
   8  * This file is part of the Linux kernel and is made available under
   9  * the terms of the GNU General Public License, version 2, or at your
  10  * option, any later version, incorporated herein by reference.
  11  *
  12  * Journal recovery routines for the generic filesystem journaling code;
  13  * part of the ext2fs journaling system.
  14  */
  15
  16 #ifndef __KERNEL__
  17 #include "jfs_user.h"
  18 #else
  19 #include <linux/time.h>
  20 #include <linux/fs.h>
  21 #include <linux/jbd2.h>
  22 #include <linux/errno.h>
  23 #include <linux/slab.h>
  24 #include <linux/crc32.h>
  25 #endif
  26
  27 /*
  28  * Maintain information about the progress of the recovery job, so that
  29  * the different passes can carry information between them.
  30  */
  31 struct recovery_info
  32 {
  33         tid_t           start_transaction;
  34         tid_t           end_transaction;
  35
  36         int             nr_replays;
  37         int             nr_revokes;
  38         int             nr_revoke_hits;
  39 };
  40
  41 enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
  42 static int do_one_pass(journal_t *journal,
  43                                 struct recovery_info *info, enum passtype pass);
  44 static int scan_revoke_records(journal_t *, struct buffer_head *,
  45                                 tid_t, struct recovery_info *);
  46
  47 #ifdef __KERNEL__
  48
  49 /* Release readahead buffers after use */
  50 static void journal_brelse_array(struct buffer_head *b[], int n)
  51 {
  52         while (--n >= 0)
  53                 brelse (b[n]);
  54 }
  55
  56
  57 /*
  58  * When reading from the journal, we are going through the block device
  59  * layer directly and so there is no readahead being done for us.  We
  60  * need to implement any readahead ourselves if we want it to happen at
  61  * all.  Recovery is basically one long sequential read, so make sure we
  62  * do the IO in reasonably large chunks.
  63  *
  64  * This is not so critical that we need to be enormously clever about
  65  * the readahead size, though.  128K is a purely arbitrary, good-enough
  66  * fixed value.
  67  */
  68
  69 #define MAXBUF 8
  70 static int do_readahead(journal_t *journal, unsigned int start)
  71 {
  72         int err;
  73         unsigned int max, nbufs, next;
  74         unsigned long long blocknr;
  75         struct buffer_head *bh;
  76
  77         struct buffer_head * bufs[MAXBUF];
  78
  79         /* Do up to 128K of readahead */
  80         max = start + (128 * 1024 / journal->j_blocksize);
  81         if (max > journal->j_maxlen)
  82                 max = journal->j_maxlen;
  83
  84         /* Do the readahead itself.  We'll submit MAXBUF buffer_heads at
  85          * a time to the block device IO layer. */
  86
  87         nbufs = 0;
  88
  89         for (next = start; next < max; next++) {
  90                 err = jbd2_journal_bmap(journal, next, &blocknr);
  91
  92                 if (err) {
  93                         printk (KERN_ERR "JBD: bad block at offset %u\n",
  94                                 next);
  95                         goto failed;
  96                 }
  97
  98                 bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
  99                 if (!bh) {
 100                         err = -ENOMEM;
 101                         goto failed;
 102                 }
 103
 104                 if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
 105                         bufs[nbufs++] = bh;
 106                         if (nbufs == MAXBUF) {
 107                                 ll_rw_block(READ, nbufs, bufs);
 108                                 journal_brelse_array(bufs, nbufs);
 109                                 nbufs = 0;
 110                         }
 111                 } else
 112                         brelse(bh);
 113         }
 114
 115         if (nbufs)
 116                 ll_rw_block(READ, nbufs, bufs);
 117         err = 0;
 118
 119 failed:
 120         if (nbufs)
 121                 journal_brelse_array(bufs, nbufs);
 122         return err;
 123 }
 124
 125 #endif /* __KERNEL__ */
 126
 127
 128 /*
 129  * Read a block from the journal
 130  */
 131
 132 static int jread(struct buffer_head **bhp, journal_t *journal,
 133                  unsigned int offset)
 134 {
 135         int err;
 136         unsigned long long blocknr;
 137         struct buffer_head *bh;
 138
 139         *bhp = NULL;
 140
 141         if (offset >= journal->j_maxlen) {
 142                 printk(KERN_ERR "JBD: corrupted journal superblock\n");
 143                 return -EIO;
 144         }
 145
 146         err = jbd2_journal_bmap(journal, offset, &blocknr);
 147
 148         if (err) {
 149                 printk (KERN_ERR "JBD: bad block at offset %u\n",
 150                         offset);
 151                 return err;
 152         }
 153
 154         bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
 155         if (!bh)
 156                 return -ENOMEM;
 157
 158         if (!buffer_uptodate(bh)) {
 159                 /* If this is a brand new buffer, start readahead.
 160                    Otherwise, we assume we are already reading it.  */
 161                 if (!buffer_req(bh))
 162                         do_readahead(journal, offset);
 163                 wait_on_buffer(bh);
 164         }
 165
 166         if (!buffer_uptodate(bh)) {
 167                 printk (KERN_ERR "JBD: Failed to read block at offset %u\n",
 168                         offset);
 169                 brelse(bh);
 170                 return -EIO;
 171         }
 172
 173         *bhp = bh;
 174         return 0;
 175 }
 176
 177
 178 /*
 179  * Count the number of in-use tags in a journal descriptor block.
 180  */
 181
 182 static int count_tags(journal_t *journal, struct buffer_head *bh)
 183 {
 184         char *                  tagp;
 185         journal_block_tag_t *   tag;
 186         int                     nr = 0, size = journal->j_blocksize;
 187         int                     tag_bytes = journal_tag_bytes(journal);
 188
 189         tagp = &bh->b_data[sizeof(journal_header_t)];
 190
 191         while ((tagp - bh->b_data + tag_bytes) <= size) {
 192                 tag = (journal_block_tag_t *) tagp;
 193
 194                 nr++;
 195                 tagp += tag_bytes;
 196                 if (!(tag->t_flags & cpu_to_be32(JBD2_FLAG_SAME_UUID)))
 197                         tagp += 16;
 198
 199                 if (tag->t_flags & cpu_to_be32(JBD2_FLAG_LAST_TAG))
 200                         break;
 201         }
 202
 203         return nr;
 204 }
 205
 206
 207 /* Make sure we wrap around the log correctly! */
 208 #define wrap(journal, var)                                              \
 209 do {                                                                    \
 210         if (var >= (journal)->j_last)                                   \
 211                 var -= ((journal)->j_last - (journal)->j_first);        \
 212 } while (0)
 213
 214 /**
 215  * jbd2_journal_recover - recovers a on-disk journal
 216  * @journal: the journal to recover
 217  *
 218  * The primary function for recovering the log contents when mounting a
 219  * journaled device.
 220  *
 221  * Recovery is done in three passes.  In the first pass, we look for the
 222  * end of the log.  In the second, we assemble the list of revoke
 223  * blocks.  In the third and final pass, we replay any un-revoked blocks
 224  * in the log.
 225  */
 226 int jbd2_journal_recover(journal_t *journal)
 227 {
 228         int                     err;
 229         journal_superblock_t *  sb;
 230
 231         struct recovery_info    info;
 232
 233         memset(&info, 0, sizeof(info));
 234         sb = journal->j_superblock;
 235
 236         /*
 237          * The journal superblock's s_start field (the current log head)
 238          * is always zero if, and only if, the journal was cleanly
 239          * unmounted.
 240          */
 241
 242         if (!sb->s_start) {
 243                 jbd_debug(1, "No recovery required, last transaction %d\n",
 244                           be32_to_cpu(sb->s_sequence));
 245                 journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
 246                 return 0;
 247         }
 248
 249         err = do_one_pass(journal, &info, PASS_SCAN);
 250         if (!err)
 251                 err = do_one_pass(journal, &info, PASS_REVOKE);
 252         if (!err)
 253                 err = do_one_pass(journal, &info, PASS_REPLAY);
 254
 255         jbd_debug(1, "JBD: recovery, exit status %d, "
 256                   "recovered transactions %u to %u\n",
 257                   err, info.start_transaction, info.end_transaction);
 258         jbd_debug(1, "JBD: Replayed %d and revoked %d/%d blocks\n",
 259                   info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
 260
 261         /* Restart the log at the next transaction ID, thus invalidating
 262          * any existing commit records in the log. */
 263         journal->j_transaction_sequence = ++info.end_transaction;
 264
 265         jbd2_journal_clear_revoke(journal);
 266         sync_blockdev(journal->j_fs_dev);
 267         return err;
 268 }
 269
 270 /**
 271  * jbd2_journal_skip_recovery - Start journal and wipe exiting records
 272  * @journal: journal to startup
 273  *
 274  * Locate any valid recovery information from the journal and set up the
 275  * journal structures in memory to ignore it (presumably because the
 276  * caller has evidence that it is out of date).
 277  * This function does'nt appear to be exorted..
 278  *
 279  * We perform one pass over the journal to allow us to tell the user how
 280  * much recovery information is being erased, and to let us initialise
 281  * the journal transaction sequence numbers to the next unused ID.
 282  */
 283 int jbd2_journal_skip_recovery(journal_t *journal)
 284 {
 285         int                     err;
 286         journal_superblock_t *  sb;
 287
 288         struct recovery_info    info;
 289
 290         memset (&info, 0, sizeof(info));
 291         sb = journal->j_superblock;
 292
 293         err = do_one_pass(journal, &info, PASS_SCAN);
 294
 295         if (err) {
 296                 printk(KERN_ERR "JBD: error %d scanning journal\n", err);
 297                 ++journal->j_transaction_sequence;
 298         } else {
 299 #ifdef CONFIG_JBD2_DEBUG
 300                 int dropped = info.end_transaction - be32_to_cpu(sb->s_sequence);
 301 #endif
 302                 jbd_debug(1,
 303                           "JBD: ignoring %d transaction%s from the journal.\n",
 304                           dropped, (dropped == 1) ? "" : "s");
 305                 journal->j_transaction_sequence = ++info.end_transaction;
 306         }
 307
 308         journal->j_tail = 0;
 309         return err;
 310 }
 311
 312 static inline unsigned long long read_tag_block(int tag_bytes, journal_block_tag_t *tag)
 313 {
 314         unsigned long long block = be32_to_cpu(tag->t_blocknr);
 315         if (tag_bytes > JBD2_TAG_SIZE32)
 316                 block |= (u64)be32_to_cpu(tag->t_blocknr_high) << 32;
 317         return block;
 318 }
 319
 320 /*
 321  * calc_chksums calculates the checksums for the blocks described in the
 322  * descriptor block.
 323  */
 324 static int calc_chksums(journal_t *journal, struct buffer_head *bh,
 325                         unsigned long *next_log_block, __u32 *crc32_sum)
 326 {
 327         int i, num_blks, err;
 328         unsigned long io_block;
 329         struct buffer_head *obh;
 330
 331         num_blks = count_tags(journal, bh);
 332         /* Calculate checksum of the descriptor block. */
 333         *crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);
 334
 335         for (i = 0; i < num_blks; i++) {
 336                 io_block = (*next_log_block)++;
 337                 wrap(journal, *next_log_block);
 338                 err = jread(&obh, journal, io_block);
 339                 if (err) {
 340                         printk(KERN_ERR "JBD: IO error %d recovering block "
 341                                 "%lu in log\n", err, io_block);
 342                         return 1;
 343                 } else {
 344                         *crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
 345                                      obh->b_size);
 346                 }
 347         }
 348         return 0;
 349 }
 350
 351 static int do_one_pass(journal_t *journal,
 352                         struct recovery_info *info, enum passtype pass)
 353 {
 354         unsigned int            first_commit_ID, next_commit_ID;
 355         unsigned long           next_log_block;
 356         int                     err, success = 0;
 357         journal_superblock_t *  sb;
 358         journal_header_t *      tmp;
 359         struct buffer_head *    bh;
 360         unsigned int            sequence;
 361         int                     blocktype;
 362         int                     tag_bytes = journal_tag_bytes(journal);
 363         __u32                   crc32_sum = ~0; /* Transactional Checksums */
 364
 365         /* Precompute the maximum metadata descriptors in a descriptor block */
 366         int                     MAX_BLOCKS_PER_DESC;
 367         MAX_BLOCKS_PER_DESC = ((journal->j_blocksize-sizeof(journal_header_t))
 368                                / tag_bytes);
 369
 370         /*
 371          * First thing is to establish what we expect to find in the log
 372          * (in terms of transaction IDs), and where (in terms of log
 373          * block offsets): query the superblock.
 374          */
 375
 376         sb = journal->j_superblock;
 377         next_commit_ID = be32_to_cpu(sb->s_sequence);
 378         next_log_block = be32_to_cpu(sb->s_start);
 379
 380         first_commit_ID = next_commit_ID;
 381         if (pass == PASS_SCAN)
 382                 info->start_transaction = first_commit_ID;
 383
 384         jbd_debug(1, "Starting recovery pass %d\n", pass);
 385
 386         /*
 387          * Now we walk through the log, transaction by transaction,
 388          * making sure that each transaction has a commit block in the
 389          * expected place.  Each complete transaction gets replayed back
 390          * into the main filesystem.
 391          */
 392
 393         while (1) {
 394                 int                     flags;
 395                 char *                  tagp;
 396                 journal_block_tag_t *   tag;
 397                 struct buffer_head *    obh;
 398                 struct buffer_head *    nbh;
 399
 400                 cond_resched();
 401
 402                 /* If we already know where to stop the log traversal,
 403                  * check right now that we haven't gone past the end of
 404                  * the log. */
 405
 406                 if (pass != PASS_SCAN)
 407                         if (tid_geq(next_commit_ID, info->end_transaction))
 408                                 break;
 409
 410                 jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
 411                           next_commit_ID, next_log_block, journal->j_last);
 412
 413                 /* Skip over each chunk of the transaction looking
 414                  * either the next descriptor block or the final commit
 415                  * record. */
 416
 417                 jbd_debug(3, "JBD: checking block %ld\n", next_log_block);
 418                 err = jread(&bh, journal, next_log_block);
 419                 if (err)
 420                         goto failed;
 421
 422                 next_log_block++;
 423                 wrap(journal, next_log_block);
 424
 425                 /* What kind of buffer is it?
 426                  *
 427                  * If it is a descriptor block, check that it has the
 428                  * expected sequence number.  Otherwise, we're all done
 429                  * here. */
 430
 431                 tmp = (journal_header_t *)bh->b_data;
 432
 433                 if (tmp->h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER)) {
 434                         brelse(bh);
 435                         break;
 436                 }
 437
 438                 blocktype = be32_to_cpu(tmp->h_blocktype);
 439                 sequence = be32_to_cpu(tmp->h_sequence);
 440                 jbd_debug(3, "Found magic %d, sequence %d\n",
 441                           blocktype, sequence);
 442
 443                 if (sequence != next_commit_ID) {
 444                         brelse(bh);
 445                         break;
 446                 }
 447
 448                 /* OK, we have a valid descriptor block which matches
 449                  * all of the sequence number checks.  What are we going
 450                  * to do with it?  That depends on the pass... */
 451
 452                 switch(blocktype) {
 453                 case JBD2_DESCRIPTOR_BLOCK:
 454                         /* If it is a valid descriptor block, replay it
 455                          * in pass REPLAY; if journal_checksums enabled, then
 456                          * calculate checksums in PASS_SCAN, otherwise,
 457                          * just skip over the blocks it describes. */
 458                         if (pass != PASS_REPLAY) {
 459                                 if (pass == PASS_SCAN &&
 460                                     JBD2_HAS_COMPAT_FEATURE(journal,
 461                                             JBD2_FEATURE_COMPAT_CHECKSUM) &&
 462                                     !info->end_transaction) {
 463                                         if (calc_chksums(journal, bh,
 464                                                         &next_log_block,
 465                                                         &crc32_sum)) {
 466                                                 put_bh(bh);
 467                                                 break;
 468                                         }
 469                                         put_bh(bh);
 470                                         continue;
 471                                 }
 472                                 next_log_block += count_tags(journal, bh);
 473                                 wrap(journal, next_log_block);
 474                                 put_bh(bh);
 475                                 continue;
 476                         }
 477
 478                         /* A descriptor block: we can now write all of
 479                          * the data blocks.  Yay, useful work is finally
 480                          * getting done here! */
 481
 482                         tagp = &bh->b_data[sizeof(journal_header_t)];
 483                         while ((tagp - bh->b_data + tag_bytes)
 484                                <= journal->j_blocksize) {
 485                                 unsigned long io_block;
 486
 487                                 tag = (journal_block_tag_t *) tagp;
 488                                 flags = be32_to_cpu(tag->t_flags);
 489
 490                                 io_block = next_log_block++;
 491                                 wrap(journal, next_log_block);
 492                                 err = jread(&obh, journal, io_block);
 493                                 if (err) {
 494                                         /* Recover what we can, but
 495                                          * report failure at the end. */
 496                                         success = err;
 497                                         printk (KERN_ERR
 498                                                 "JBD: IO error %d recovering "
 499                                                 "block %ld in log\n",
 500                                                 err, io_block);
 501                                 } else {
 502                                         unsigned long long blocknr;
 503
 504                                         J_ASSERT(obh != NULL);
 505                                         blocknr = read_tag_block(tag_bytes,
 506                                                                  tag);
 507
 508                                         /* If the block has been
 509                                          * revoked, then we're all done
 510                                          * here. */
 511                                         if (jbd2_journal_test_revoke
 512                                             (journal, blocknr,
 513                                              next_commit_ID)) {
 514                                                 brelse(obh);
 515                                                 ++info->nr_revoke_hits;
 516                                                 goto skip_write;
 517                                         }
 518
 519                                         /* Find a buffer for the new
 520                                          * data being restored */
 521                                         nbh = __getblk(journal->j_fs_dev,
 522                                                         blocknr,
 523                                                         journal->j_blocksize);
 524                                         if (nbh == NULL) {
 525                                                 printk(KERN_ERR
 526                                                        "JBD: Out of memory "
 527                                                        "during recovery.\n");
 528                                                 err = -ENOMEM;
 529                                                 brelse(bh);
 530                                                 brelse(obh);
 531                                                 goto failed;
 532                                         }
 533
 534                                         lock_buffer(nbh);
 535                                         memcpy(nbh->b_data, obh->b_data,
 536                                                         journal->j_blocksize);
 537                                         if (flags & JBD2_FLAG_ESCAPE) {
 538                                                 *((__be32 *)nbh->b_data) =
 539                                                 cpu_to_be32(JBD2_MAGIC_NUMBER);
 540                                         }
 541
 542                                         BUFFER_TRACE(nbh, "marking dirty");
 543                                         set_buffer_uptodate(nbh);
 544                                         mark_buffer_dirty(nbh);
 545                                         BUFFER_TRACE(nbh, "marking uptodate");
 546                                         ++info->nr_replays;
 547                                         /* ll_rw_block(WRITE, 1, &nbh); */
 548                                         unlock_buffer(nbh);
 549                                         brelse(obh);
 550                                         brelse(nbh);
 551                                 }
 552
 553                         skip_write:
 554                                 tagp += tag_bytes;
 555                                 if (!(flags & JBD2_FLAG_SAME_UUID))
 556                                         tagp += 16;
 557
 558                                 if (flags & JBD2_FLAG_LAST_TAG)
 559                                         break;
 560                         }
 561
 562                         brelse(bh);
 563                         continue;
 564
 565                 case JBD2_COMMIT_BLOCK:
 566                         /*     How to differentiate between interrupted commit
 567                          *               and journal corruption ?
 568                          *
 569                          * {nth transaction}
 570                          *        Checksum Verification Failed
 571                          *                       |
 572                          *               ____________________
 573                          *              |                    |
 574                          *      async_commit             sync_commit
 575                          *              |                    |
 576                          *              | GO TO NEXT    "Journal Corruption"
 577                          *              | TRANSACTION
 578                          *              |
 579                          * {(n+1)th transanction}
 580                          *              |
 581                          *       _______|______________
 582                          *      |                     |
 583                          * Commit block found   Commit block not found
 584                          *      |                     |
 585                          * "Journal Corruption"       |
 586                          *               _____________|_________
 587                          *              |                       |
 588                          *      nth trans corrupt       OR   nth trans
 589                          *      and (n+1)th interrupted     interrupted
 590                          *      before commit block
 591                          *      could reach the disk.
 592                          *      (Cannot find the difference in above
 593                          *       mentioned conditions. Hence assume
 594                          *       "Interrupted Commit".)
 595                          */
 596
 597                         /* Found an expected commit block: if checksums
 598                          * are present verify them in PASS_SCAN; else not
 599                          * much to do other than move on to the next sequence
 600                          * number. */
 601                         if (pass == PASS_SCAN &&
 602                             JBD2_HAS_COMPAT_FEATURE(journal,
 603                                     JBD2_FEATURE_COMPAT_CHECKSUM)) {
 604                                 int chksum_err, chksum_seen;
 605                                 struct commit_header *cbh =
 606                                         (struct commit_header *)bh->b_data;
 607                                 unsigned found_chksum =
 608                                         be32_to_cpu(cbh->h_chksum[0]);
 609
 610                                 chksum_err = chksum_seen = 0;
 611
 612                                 if (info->end_transaction) {
 613                                         printk(KERN_ERR "JBD: Transaction %u "
 614                                                 "found to be corrupt.\n",
 615                                                 next_commit_ID - 1);
 616                                         brelse(bh);
 617                                         break;
 618                                 }
 619
 620                                 if (crc32_sum == found_chksum &&
 621                                     cbh->h_chksum_type == JBD2_CRC32_CHKSUM &&
 622                                     cbh->h_chksum_size ==
 623                                                 JBD2_CRC32_CHKSUM_SIZE)
 624                                        chksum_seen = 1;
 625                                 else if (!(cbh->h_chksum_type == 0 &&
 626                                              cbh->h_chksum_size == 0 &&
 627                                              found_chksum == 0 &&
 628                                              !chksum_seen))
 629                                 /*
 630                                  * If fs is mounted using an old kernel and then
 631                                  * kernel with journal_chksum is used then we
 632                                  * get a situation where the journal flag has
 633                                  * checksum flag set but checksums are not
 634                                  * present i.e chksum = 0, in the individual
 635                                  * commit blocks.
 636                                  * Hence to avoid checksum failures, in this
 637                                  * situation, this extra check is added.
 638                                  */
 639                                                 chksum_err = 1;
 640
 641                                 if (chksum_err) {
 642                                         info->end_transaction = next_commit_ID;
 643
 644                                         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 645                                            JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)){
 646                                                 printk(KERN_ERR
 647                                                        "JBD: Transaction %u "
 648                                                        "found to be corrupt.\n",
 649                                                        next_commit_ID);
 650                                                 brelse(bh);
 651                                                 break;
 652                                         }
 653                                 }
 654                                 crc32_sum = ~0;
 655                         }
 656                         brelse(bh);
 657                         next_commit_ID++;
 658                         continue;
 659
 660                 case JBD2_REVOKE_BLOCK:
 661                         /* If we aren't in the REVOKE pass, then we can
 662                          * just skip over this block. */
 663                         if (pass != PASS_REVOKE) {
 664                                 brelse(bh);
 665                                 continue;
 666                         }
 667
 668                         err = scan_revoke_records(journal, bh,
 669                                                   next_commit_ID, info);
 670                         brelse(bh);
 671                         if (err)
 672                                 goto failed;
 673                         continue;
 674
 675                 default:
 676                         jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
 677                                   blocktype);
 678                         brelse(bh);
 679                         goto done;
 680                 }
 681         }
 682
 683  done:
 684         /*
 685          * We broke out of the log scan loop: either we came to the
 686          * known end of the log or we found an unexpected block in the
 687          * log.  If the latter happened, then we know that the "current"
 688          * transaction marks the end of the valid log.
 689          */
 690
 691         if (pass == PASS_SCAN) {
 692                 if (!info->end_transaction)
 693                         info->end_transaction = next_commit_ID;
 694         } else {
 695                 /* It's really bad news if different passes end up at
 696                  * different places (but possible due to IO errors). */
 697                 if (info->end_transaction != next_commit_ID) {
 698                         printk (KERN_ERR "JBD: recovery pass %d ended at "
 699                                 "transaction %u, expected %u\n",
 700                                 pass, next_commit_ID, info->end_transaction);
 701                         if (!success)
 702                                 success = -EIO;
 703                 }
 704         }
 705
 706         return success;
 707
 708  failed:
 709         return err;
 710 }
 711
 712
 713 /* Scan a revoke record, marking all blocks mentioned as revoked. */
 714
 715 static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 716                                tid_t sequence, struct recovery_info *info)
 717 {
 718         jbd2_journal_revoke_header_t *header;
 719         int offset, max;
 720         int record_len = 4;
 721
 722         header = (jbd2_journal_revoke_header_t *) bh->b_data;
 723         offset = sizeof(jbd2_journal_revoke_header_t);
 724         max = be32_to_cpu(header->r_count);
 725
 726         if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
 727                 record_len = 8;
 728
 729         while (offset + record_len <= max) {
 730                 unsigned long long blocknr;
 731                 int err;
 732
 733                 if (record_len == 4)
 734                         blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
 735                 else
 736                         blocknr = be64_to_cpu(* ((__be64 *) (bh->b_data+offset)));
 737                 offset += record_len;
 738                 err = jbd2_journal_set_revoke(journal, blocknr, sequence);
 739                 if (err)
 740                         return err;
 741                 ++info->nr_revokes;
 742         }
 743         return 0;
 744 }