e2fsck/recovery.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * linux/fs/jbd2/recovery.c
   4  *
   5  * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
   6  *
   7  * Copyright 1999-2000 Red Hat Software --- All Rights Reserved
   8  *
   9  * Journal recovery routines for the generic filesystem journaling code;
  10  * part of the ext2fs journaling system.
  11  */
  12
  13 #ifndef __KERNEL__
  14 #include "jfs_user.h"
  15 #else
  16 #include <linux/time.h>
  17 #include <linux/fs.h>
  18 #include <linux/jbd2.h>
  19 #include <linux/errno.h>
  20 #include <linux/crc32.h>
  21 #include <linux/blkdev.h>
  22 #endif
  23
  24 /*
  25  * Maintain information about the progress of the recovery job, so that
  26  * the different passes can carry information between them.
  27  */
  28 struct recovery_info
  29 {
  30         tid_t           start_transaction;
  31         tid_t           end_transaction;
  32
  33         int             nr_replays;
  34         int             nr_revokes;
  35         int             nr_revoke_hits;
  36 };
  37
  38 enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
  39 static int do_one_pass(journal_t *journal,
  40                                 struct recovery_info *info, enum passtype pass);
  41 static int scan_revoke_records(journal_t *, struct buffer_head *,
  42                                 tid_t, struct recovery_info *);
  43
  44 #ifdef __KERNEL__
  45
  46 /* Release readahead buffers after use */
  47 static void journal_brelse_array(struct buffer_head *b[], int n)
  48 {
  49         while (--n >= 0)
  50                 brelse (b[n]);
  51 }
  52
  53
  54 /*
  55  * When reading from the journal, we are going through the block device
  56  * layer directly and so there is no readahead being done for us.  We
  57  * need to implement any readahead ourselves if we want it to happen at
  58  * all.  Recovery is basically one long sequential read, so make sure we
  59  * do the IO in reasonably large chunks.
  60  *
  61  * This is not so critical that we need to be enormously clever about
  62  * the readahead size, though.  128K is a purely arbitrary, good-enough
  63  * fixed value.
  64  */
  65
  66 #define MAXBUF 8
  67 static int do_readahead(journal_t *journal, unsigned int start)
  68 {
  69         int err;
  70         unsigned int max, nbufs, next;
  71         unsigned long long blocknr;
  72         struct buffer_head *bh;
  73
  74         struct buffer_head * bufs[MAXBUF];
  75
  76         /* Do up to 128K of readahead */
  77         max = start + (128 * 1024 / journal->j_blocksize);
  78         if (max > journal->j_maxlen)
  79                 max = journal->j_maxlen;
  80
  81         /* Do the readahead itself.  We'll submit MAXBUF buffer_heads at
  82          * a time to the block device IO layer. */
  83
  84         nbufs = 0;
  85
  86         for (next = start; next < max; next++) {
  87                 err = jbd2_journal_bmap(journal, next, &blocknr);
  88
  89                 if (err) {
  90                         printk(KERN_ERR "JBD2: bad block at offset %u\n",
  91                                 next);
  92                         goto failed;
  93                 }
  94
  95                 bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
  96                 if (!bh) {
  97                         err = -ENOMEM;
  98                         goto failed;
  99                 }
 100
 101                 if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
 102                         bufs[nbufs++] = bh;
 103                         if (nbufs == MAXBUF) {
 104                                 ll_rw_block(REQ_OP_READ, 0, nbufs, bufs);
 105                                 journal_brelse_array(bufs, nbufs);
 106                                 nbufs = 0;
 107                         }
 108                 } else
 109                         brelse(bh);
 110         }
 111
 112         if (nbufs)
 113                 ll_rw_block(REQ_OP_READ, 0, nbufs, bufs);
 114         err = 0;
 115
 116 failed:
 117         if (nbufs)
 118                 journal_brelse_array(bufs, nbufs);
 119         return err;
 120 }
 121
 122 #endif /* __KERNEL__ */
 123
 124
 125 /*
 126  * Read a block from the journal
 127  */
 128
 129 static int jread(struct buffer_head **bhp, journal_t *journal,
 130                  unsigned int offset)
 131 {
 132         int err;
 133         unsigned long long blocknr;
 134         struct buffer_head *bh;
 135
 136         *bhp = NULL;
 137
 138         if (offset >= journal->j_maxlen) {
 139                 printk(KERN_ERR "JBD2: corrupted journal superblock\n");
 140                 return -EFSCORRUPTED;
 141         }
 142
 143         err = jbd2_journal_bmap(journal, offset, &blocknr);
 144
 145         if (err) {
 146                 printk(KERN_ERR "JBD2: bad block at offset %u\n",
 147                         offset);
 148                 return err;
 149         }
 150
 151         bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
 152         if (!bh)
 153                 return -ENOMEM;
 154
 155         if (!buffer_uptodate(bh)) {
 156                 /* If this is a brand new buffer, start readahead.
 157                    Otherwise, we assume we are already reading it.  */
 158                 if (!buffer_req(bh))
 159                         do_readahead(journal, offset);
 160                 wait_on_buffer(bh);
 161         }
 162
 163         if (!buffer_uptodate(bh)) {
 164                 printk(KERN_ERR "JBD2: Failed to read block at offset %u\n",
 165                         offset);
 166                 brelse(bh);
 167                 return -EIO;
 168         }
 169
 170         *bhp = bh;
 171         return 0;
 172 }
 173
 174 static int jbd2_descriptor_block_csum_verify(journal_t *j, void *buf)
 175 {
 176         struct jbd2_journal_block_tail *tail;
 177         __be32 provided;
 178         __u32 calculated;
 179
 180         if (!jbd2_journal_has_csum_v2or3(j))
 181                 return 1;
 182
 183         tail = (struct jbd2_journal_block_tail *)((char *)buf + j->j_blocksize -
 184                         sizeof(struct jbd2_journal_block_tail));
 185         provided = tail->t_checksum;
 186         tail->t_checksum = 0;
 187         calculated = jbd2_chksum(j, j->j_csum_seed, buf, j->j_blocksize);
 188         tail->t_checksum = provided;
 189
 190         return provided == cpu_to_be32(calculated);
 191 }
 192
 193 /*
 194  * Count the number of in-use tags in a journal descriptor block.
 195  */
 196
 197 static int count_tags(journal_t *journal, struct buffer_head *bh)
 198 {
 199         char *                  tagp;
 200         journal_block_tag_t *   tag;
 201         int                     nr = 0, size = journal->j_blocksize;
 202         int                     tag_bytes = journal_tag_bytes(journal);
 203
 204         if (jbd2_journal_has_csum_v2or3(journal))
 205                 size -= sizeof(struct jbd2_journal_block_tail);
 206
 207         tagp = &bh->b_data[sizeof(journal_header_t)];
 208
 209         while ((tagp - bh->b_data + tag_bytes) <= size) {
 210                 tag = (journal_block_tag_t *) tagp;
 211
 212                 nr++;
 213                 tagp += tag_bytes;
 214                 if (!(tag->t_flags & cpu_to_be16(JBD2_FLAG_SAME_UUID)))
 215                         tagp += 16;
 216
 217                 if (tag->t_flags & cpu_to_be16(JBD2_FLAG_LAST_TAG))
 218                         break;
 219         }
 220
 221         return nr;
 222 }
 223
 224
 225 /* Make sure we wrap around the log correctly! */
 226 #define wrap(journal, var)                                              \
 227 do {                                                                    \
 228         if (var >= (journal)->j_last)                                   \
 229                 var -= ((journal)->j_last - (journal)->j_first);        \
 230 } while (0)
 231
 232 /**
 233  * jbd2_journal_recover - recovers a on-disk journal
 234  * @journal: the journal to recover
 235  *
 236  * The primary function for recovering the log contents when mounting a
 237  * journaled device.
 238  *
 239  * Recovery is done in three passes.  In the first pass, we look for the
 240  * end of the log.  In the second, we assemble the list of revoke
 241  * blocks.  In the third and final pass, we replay any un-revoked blocks
 242  * in the log.
 243  */
 244 int jbd2_journal_recover(journal_t *journal)
 245 {
 246         int                     err, err2;
 247         journal_superblock_t *  sb;
 248
 249         struct recovery_info    info;
 250
 251         memset(&info, 0, sizeof(info));
 252         sb = journal->j_superblock;
 253
 254         /*
 255          * The journal superblock's s_start field (the current log head)
 256          * is always zero if, and only if, the journal was cleanly
 257          * unmounted.
 258          */
 259
 260         if (!sb->s_start) {
 261                 jbd_debug(1, "No recovery required, last transaction %d\n",
 262                           be32_to_cpu(sb->s_sequence));
 263                 journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
 264                 return 0;
 265         }
 266
 267         err = do_one_pass(journal, &info, PASS_SCAN);
 268         if (!err)
 269                 err = do_one_pass(journal, &info, PASS_REVOKE);
 270         if (!err)
 271                 err = do_one_pass(journal, &info, PASS_REPLAY);
 272
 273         jbd_debug(1, "JBD2: recovery, exit status %d, "
 274                   "recovered transactions %u to %u\n",
 275                   err, info.start_transaction, info.end_transaction);
 276         jbd_debug(1, "JBD2: Replayed %d and revoked %d/%d blocks\n",
 277                   info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
 278
 279         /* Restart the log at the next transaction ID, thus invalidating
 280          * any existing commit records in the log. */
 281         journal->j_transaction_sequence = ++info.end_transaction;
 282
 283         jbd2_journal_clear_revoke(journal);
 284         err2 = sync_blockdev(journal->j_fs_dev);
 285         if (!err)
 286                 err = err2;
 287         /* Make sure all replayed data is on permanent storage */
 288         if (journal->j_flags & JBD2_BARRIER) {
 289                 err2 = blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
 290                 if (!err)
 291                         err = err2;
 292         }
 293         return err;
 294 }
 295
 296 /**
 297  * jbd2_journal_skip_recovery - Start journal and wipe exiting records
 298  * @journal: journal to startup
 299  *
 300  * Locate any valid recovery information from the journal and set up the
 301  * journal structures in memory to ignore it (presumably because the
 302  * caller has evidence that it is out of date).
 303  * This function doesn't appear to be exported..
 304  *
 305  * We perform one pass over the journal to allow us to tell the user how
 306  * much recovery information is being erased, and to let us initialise
 307  * the journal transaction sequence numbers to the next unused ID.
 308  */
 309 int jbd2_journal_skip_recovery(journal_t *journal)
 310 {
 311         int                     err;
 312
 313         struct recovery_info    info;
 314
 315         memset (&info, 0, sizeof(info));
 316
 317         err = do_one_pass(journal, &info, PASS_SCAN);
 318
 319         if (err) {
 320                 printk(KERN_ERR "JBD2: error %d scanning journal\n", err);
 321                 ++journal->j_transaction_sequence;
 322         } else {
 323 #ifdef CONFIG_JBD2_DEBUG
 324                 int dropped = info.end_transaction -
 325                         be32_to_cpu(journal->j_superblock->s_sequence);
 326                 jbd_debug(1,
 327                           "JBD2: ignoring %d transaction%s from the journal.\n",
 328                           dropped, (dropped == 1) ? "" : "s");
 329 #endif
 330                 journal->j_transaction_sequence = ++info.end_transaction;
 331         }
 332
 333         journal->j_tail = 0;
 334         return err;
 335 }
 336
 337 static inline unsigned long long read_tag_block(journal_t *journal,
 338                                                 journal_block_tag_t *tag)
 339 {
 340         unsigned long long block = be32_to_cpu(tag->t_blocknr);
 341         if (jbd2_has_feature_64bit(journal))
 342                 block |= (u64)be32_to_cpu(tag->t_blocknr_high) << 32;
 343         return block;
 344 }
 345
 346 /*
 347  * calc_chksums calculates the checksums for the blocks described in the
 348  * descriptor block.
 349  */
 350 static int calc_chksums(journal_t *journal, struct buffer_head *bh,
 351                         unsigned long *next_log_block, __u32 *crc32_sum)
 352 {
 353         int i, num_blks, err;
 354         unsigned long io_block;
 355         struct buffer_head *obh;
 356
 357         num_blks = count_tags(journal, bh);
 358         /* Calculate checksum of the descriptor block. */
 359         *crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);
 360
 361         for (i = 0; i < num_blks; i++) {
 362                 io_block = (*next_log_block)++;
 363                 wrap(journal, *next_log_block);
 364                 err = jread(&obh, journal, io_block);
 365                 if (err) {
 366                         printk(KERN_ERR "JBD2: IO error %d recovering block "
 367                                 "%lu in log\n", err, io_block);
 368                         return 1;
 369                 } else {
 370                         *crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
 371                                      obh->b_size);
 372                 }
 373                 put_bh(obh);
 374         }
 375         return 0;
 376 }
 377
 378 static int jbd2_commit_block_csum_verify(journal_t *j, void *buf)
 379 {
 380         struct commit_header *h;
 381         __be32 provided;
 382         __u32 calculated;
 383
 384         if (!jbd2_journal_has_csum_v2or3(j))
 385                 return 1;
 386
 387         h = buf;
 388         provided = h->h_chksum[0];
 389         h->h_chksum[0] = 0;
 390         calculated = jbd2_chksum(j, j->j_csum_seed, buf, j->j_blocksize);
 391         h->h_chksum[0] = provided;
 392
 393         return provided == cpu_to_be32(calculated);
 394 }
 395
 396 static int jbd2_block_tag_csum_verify(journal_t *j, journal_block_tag_t *tag,
 397                                       void *buf, __u32 sequence)
 398 {
 399         journal_block_tag3_t *tag3 = (journal_block_tag3_t *)tag;
 400         __u32 csum32;
 401         __be32 seq;
 402
 403         if (!jbd2_journal_has_csum_v2or3(j))
 404                 return 1;
 405
 406         seq = cpu_to_be32(sequence);
 407         csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&seq, sizeof(seq));
 408         csum32 = jbd2_chksum(j, csum32, buf, j->j_blocksize);
 409
 410         if (jbd2_has_feature_csum3(j))
 411                 return tag3->t_checksum == cpu_to_be32(csum32);
 412         else
 413                 return tag->t_checksum == cpu_to_be16(csum32);
 414 }
 415
 416 static int do_one_pass(journal_t *journal,
 417                         struct recovery_info *info, enum passtype pass)
 418 {
 419         unsigned int            first_commit_ID, next_commit_ID;
 420         unsigned long           next_log_block;
 421         int                     err, success = 0;
 422         journal_superblock_t *  sb;
 423         journal_header_t *      tmp;
 424         struct buffer_head *    bh;
 425         unsigned int            sequence;
 426         int                     blocktype;
 427         int                     tag_bytes = journal_tag_bytes(journal);
 428         __u32                   crc32_sum = ~0; /* Transactional Checksums */
 429         int                     descr_csum_size = 0;
 430         int                     block_error = 0;
 431
 432         /*
 433          * First thing is to establish what we expect to find in the log
 434          * (in terms of transaction IDs), and where (in terms of log
 435          * block offsets): query the superblock.
 436          */
 437
 438         sb = journal->j_superblock;
 439         next_commit_ID = be32_to_cpu(sb->s_sequence);
 440         next_log_block = be32_to_cpu(sb->s_start);
 441
 442         first_commit_ID = next_commit_ID;
 443         if (pass == PASS_SCAN)
 444                 info->start_transaction = first_commit_ID;
 445
 446         jbd_debug(1, "Starting recovery pass %d\n", pass);
 447
 448         /*
 449          * Now we walk through the log, transaction by transaction,
 450          * making sure that each transaction has a commit block in the
 451          * expected place.  Each complete transaction gets replayed back
 452          * into the main filesystem.
 453          */
 454
 455         while (1) {
 456                 int                     flags;
 457                 char *                  tagp;
 458                 journal_block_tag_t *   tag;
 459                 struct buffer_head *    obh;
 460                 struct buffer_head *    nbh;
 461
 462                 cond_resched();
 463
 464                 /* If we already know where to stop the log traversal,
 465                  * check right now that we haven't gone past the end of
 466                  * the log. */
 467
 468                 if (pass != PASS_SCAN)
 469                         if (tid_geq(next_commit_ID, info->end_transaction))
 470                                 break;
 471
 472                 jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
 473                           next_commit_ID, next_log_block, journal->j_last);
 474
 475                 /* Skip over each chunk of the transaction looking
 476                  * either the next descriptor block or the final commit
 477                  * record. */
 478
 479                 jbd_debug(3, "JBD2: checking block %ld\n", next_log_block);
 480                 err = jread(&bh, journal, next_log_block);
 481                 if (err)
 482                         goto failed;
 483
 484                 next_log_block++;
 485                 wrap(journal, next_log_block);
 486
 487                 /* What kind of buffer is it?
 488                  *
 489                  * If it is a descriptor block, check that it has the
 490                  * expected sequence number.  Otherwise, we're all done
 491                  * here. */
 492
 493                 tmp = (journal_header_t *)bh->b_data;
 494
 495                 if (tmp->h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER)) {
 496                         brelse(bh);
 497                         break;
 498                 }
 499
 500                 blocktype = be32_to_cpu(tmp->h_blocktype);
 501                 sequence = be32_to_cpu(tmp->h_sequence);
 502                 jbd_debug(3, "Found magic %d, sequence %d\n",
 503                           blocktype, sequence);
 504
 505                 if (sequence != next_commit_ID) {
 506                         brelse(bh);
 507                         break;
 508                 }
 509
 510                 /* OK, we have a valid descriptor block which matches
 511                  * all of the sequence number checks.  What are we going
 512                  * to do with it?  That depends on the pass... */
 513
 514                 switch(blocktype) {
 515                 case JBD2_DESCRIPTOR_BLOCK:
 516                         /* Verify checksum first */
 517                         if (jbd2_journal_has_csum_v2or3(journal))
 518                                 descr_csum_size =
 519                                         sizeof(struct jbd2_journal_block_tail);
 520                         if (descr_csum_size > 0 &&
 521                             !jbd2_descriptor_block_csum_verify(journal,
 522                                                                bh->b_data)) {
 523                                 err = -EFSBADCRC;
 524                                 brelse(bh);
 525                                 goto failed;
 526                         }
 527
 528                         /* If it is a valid descriptor block, replay it
 529                          * in pass REPLAY; if journal_checksums enabled, then
 530                          * calculate checksums in PASS_SCAN, otherwise,
 531                          * just skip over the blocks it describes. */
 532                         if (pass != PASS_REPLAY) {
 533                                 if (pass == PASS_SCAN &&
 534                                     jbd2_has_feature_checksum(journal) &&
 535                                     !info->end_transaction) {
 536                                         if (calc_chksums(journal, bh,
 537                                                         &next_log_block,
 538                                                         &crc32_sum)) {
 539                                                 put_bh(bh);
 540                                                 break;
 541                                         }
 542                                         put_bh(bh);
 543                                         continue;
 544                                 }
 545                                 next_log_block += count_tags(journal, bh);
 546                                 wrap(journal, next_log_block);
 547                                 put_bh(bh);
 548                                 continue;
 549                         }
 550
 551                         /* A descriptor block: we can now write all of
 552                          * the data blocks.  Yay, useful work is finally
 553                          * getting done here! */
 554
 555                         tagp = &bh->b_data[sizeof(journal_header_t)];
 556                         while ((tagp - bh->b_data + tag_bytes)
 557                                <= journal->j_blocksize - descr_csum_size) {
 558                                 unsigned long io_block;
 559
 560                                 tag = (journal_block_tag_t *) tagp;
 561                                 flags = be16_to_cpu(tag->t_flags);
 562
 563                                 io_block = next_log_block++;
 564                                 wrap(journal, next_log_block);
 565                                 err = jread(&obh, journal, io_block);
 566                                 if (err) {
 567                                         /* Recover what we can, but
 568                                          * report failure at the end. */
 569                                         success = err;
 570                                         printk(KERN_ERR
 571                                                 "JBD2: IO error %d recovering "
 572                                                 "block %ld in log\n",
 573                                                 err, io_block);
 574                                 } else {
 575                                         unsigned long long blocknr;
 576
 577                                         J_ASSERT(obh != NULL);
 578                                         blocknr = read_tag_block(journal,
 579                                                                  tag);
 580
 581                                         /* If the block has been
 582                                          * revoked, then we're all done
 583                                          * here. */
 584                                         if (jbd2_journal_test_revoke
 585                                             (journal, blocknr,
 586                                              next_commit_ID)) {
 587                                                 brelse(obh);
 588                                                 ++info->nr_revoke_hits;
 589                                                 goto skip_write;
 590                                         }
 591
 592                                         /* Look for block corruption */
 593                                         if (!jbd2_block_tag_csum_verify(
 594                                                 journal, tag, obh->b_data,
 595                                                 be32_to_cpu(tmp->h_sequence))) {
 596                                                 brelse(obh);
 597                                                 success = -EFSBADCRC;
 598                                                 printk(KERN_ERR "JBD2: Invalid "
 599                                                        "checksum recovering "
 600                                                        "data block %llu in "
 601                                                        "log\n", blocknr);
 602                                                 block_error = 1;
 603                                                 goto skip_write;
 604                                         }
 605
 606                                         /* Find a buffer for the new
 607                                          * data being restored */
 608                                         nbh = __getblk(journal->j_fs_dev,
 609                                                         blocknr,
 610                                                         journal->j_blocksize);
 611                                         if (nbh == NULL) {
 612                                                 printk(KERN_ERR
 613                                                        "JBD2: Out of memory "
 614                                                        "during recovery.\n");
 615                                                 err = -ENOMEM;
 616                                                 brelse(bh);
 617                                                 brelse(obh);
 618                                                 goto failed;
 619                                         }
 620
 621                                         lock_buffer(nbh);
 622                                         memcpy(nbh->b_data, obh->b_data,
 623                                                         journal->j_blocksize);
 624                                         if (flags & JBD2_FLAG_ESCAPE) {
 625                                                 *((__be32 *)nbh->b_data) =
 626                                                 cpu_to_be32(JBD2_MAGIC_NUMBER);
 627                                         }
 628
 629                                         BUFFER_TRACE(nbh, "marking dirty");
 630                                         set_buffer_uptodate(nbh);
 631                                         mark_buffer_dirty(nbh);
 632                                         BUFFER_TRACE(nbh, "marking uptodate");
 633                                         ++info->nr_replays;
 634                                         /* ll_rw_block(WRITE, 1, &nbh); */
 635                                         unlock_buffer(nbh);
 636                                         brelse(obh);
 637                                         brelse(nbh);
 638                                 }
 639
 640                         skip_write:
 641                                 tagp += tag_bytes;
 642                                 if (!(flags & JBD2_FLAG_SAME_UUID))
 643                                         tagp += 16;
 644
 645                                 if (flags & JBD2_FLAG_LAST_TAG)
 646                                         break;
 647                         }
 648
 649                         brelse(bh);
 650                         continue;
 651
 652                 case JBD2_COMMIT_BLOCK:
 653                         /*     How to differentiate between interrupted commit
 654                          *               and journal corruption ?
 655                          *
 656                          * {nth transaction}
 657                          *        Checksum Verification Failed
 658                          *                       |
 659                          *               ____________________
 660                          *              |                    |
 661                          *      async_commit             sync_commit
 662                          *              |                    |
 663                          *              | GO TO NEXT    "Journal Corruption"
 664                          *              | TRANSACTION
 665                          *              |
 666                          * {(n+1)th transaction}
 667                          *              |
 668                          *       _______|______________
 669                          *      |                     |
 670                          * Commit block found   Commit block not found
 671                          *      |                     |
 672                          * "Journal Corruption"       |
 673                          *               _____________|_________
 674                          *              |                       |
 675                          *      nth trans corrupt       OR   nth trans
 676                          *      and (n+1)th interrupted     interrupted
 677                          *      before commit block
 678                          *      could reach the disk.
 679                          *      (Cannot find the difference in above
 680                          *       mentioned conditions. Hence assume
 681                          *       "Interrupted Commit".)
 682                          */
 683
 684                         /* Found an expected commit block: if checksums
 685                          * are present verify them in PASS_SCAN; else not
 686                          * much to do other than move on to the next sequence
 687                          * number. */
 688                         if (pass == PASS_SCAN &&
 689                             jbd2_has_feature_checksum(journal)) {
 690                                 int chksum_err, chksum_seen;
 691                                 struct commit_header *cbh =
 692                                         (struct commit_header *)bh->b_data;
 693                                 unsigned found_chksum =
 694                                         be32_to_cpu(cbh->h_chksum[0]);
 695
 696                                 chksum_err = chksum_seen = 0;
 697
 698                                 if (info->end_transaction) {
 699                                         journal->j_failed_commit =
 700                                                 info->end_transaction;
 701                                         brelse(bh);
 702                                         break;
 703                                 }
 704
 705                                 if (crc32_sum == found_chksum &&
 706                                     cbh->h_chksum_type == JBD2_CRC32_CHKSUM &&
 707                                     cbh->h_chksum_size ==
 708                                                 JBD2_CRC32_CHKSUM_SIZE)
 709                                        chksum_seen = 1;
 710                                 else if (!(cbh->h_chksum_type == 0 &&
 711                                              cbh->h_chksum_size == 0 &&
 712                                              found_chksum == 0 &&
 713                                              !chksum_seen))
 714                                 /*
 715                                  * If fs is mounted using an old kernel and then
 716                                  * kernel with journal_chksum is used then we
 717                                  * get a situation where the journal flag has
 718                                  * checksum flag set but checksums are not
 719                                  * present i.e chksum = 0, in the individual
 720                                  * commit blocks.
 721                                  * Hence to avoid checksum failures, in this
 722                                  * situation, this extra check is added.
 723                                  */
 724                                                 chksum_err = 1;
 725
 726                                 if (chksum_err) {
 727                                         info->end_transaction = next_commit_ID;
 728
 729                                         if (!jbd2_has_feature_async_commit(journal)) {
 730                                                 journal->j_failed_commit =
 731                                                         next_commit_ID;
 732                                                 brelse(bh);
 733                                                 break;
 734                                         }
 735                                 }
 736                                 crc32_sum = ~0;
 737                         }
 738                         if (pass == PASS_SCAN &&
 739                             !jbd2_commit_block_csum_verify(journal,
 740                                                            bh->b_data)) {
 741                                 info->end_transaction = next_commit_ID;
 742
 743                                 if (!jbd2_has_feature_async_commit(journal)) {
 744                                         journal->j_failed_commit =
 745                                                 next_commit_ID;
 746                                         brelse(bh);
 747                                         break;
 748                                 }
 749                         }
 750                         brelse(bh);
 751                         next_commit_ID++;
 752                         continue;
 753
 754                 case JBD2_REVOKE_BLOCK:
 755                         /* If we aren't in the REVOKE pass, then we can
 756                          * just skip over this block. */
 757                         if (pass != PASS_REVOKE) {
 758                                 brelse(bh);
 759                                 continue;
 760                         }
 761
 762                         err = scan_revoke_records(journal, bh,
 763                                                   next_commit_ID, info);
 764                         brelse(bh);
 765                         if (err)
 766                                 goto failed;
 767                         continue;
 768
 769                 default:
 770                         jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
 771                                   blocktype);
 772                         brelse(bh);
 773                         goto done;
 774                 }
 775         }
 776
 777  done:
 778         /*
 779          * We broke out of the log scan loop: either we came to the
 780          * known end of the log or we found an unexpected block in the
 781          * log.  If the latter happened, then we know that the "current"
 782          * transaction marks the end of the valid log.
 783          */
 784
 785         if (pass == PASS_SCAN) {
 786                 if (!info->end_transaction)
 787                         info->end_transaction = next_commit_ID;
 788         } else {
 789                 /* It's really bad news if different passes end up at
 790                  * different places (but possible due to IO errors). */
 791                 if (info->end_transaction != next_commit_ID) {
 792                         printk(KERN_ERR "JBD2: recovery pass %d ended at "
 793                                 "transaction %u, expected %u\n",
 794                                 pass, next_commit_ID, info->end_transaction);
 795                         if (!success)
 796                                 success = -EIO;
 797                 }
 798         }
 799         if (block_error && success == 0)
 800                 success = -EIO;
 801         return success;
 802
 803  failed:
 804         return err;
 805 }
 806
 807 /* Scan a revoke record, marking all blocks mentioned as revoked. */
 808
 809 static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 810                                tid_t sequence, struct recovery_info *info)
 811 {
 812         jbd2_journal_revoke_header_t *header;
 813         int offset, max;
 814         unsigned csum_size = 0;
 815         __u32 rcount;
 816         int record_len = 4;
 817
 818         header = (jbd2_journal_revoke_header_t *) bh->b_data;
 819         offset = sizeof(jbd2_journal_revoke_header_t);
 820         rcount = be32_to_cpu(header->r_count);
 821
 822         if (!jbd2_descriptor_block_csum_verify(journal, header))
 823                 return -EFSBADCRC;
 824
 825         if (jbd2_journal_has_csum_v2or3(journal))
 826                 csum_size = sizeof(struct jbd2_journal_block_tail);
 827         if (rcount > journal->j_blocksize - csum_size)
 828                 return -EINVAL;
 829         max = rcount;
 830
 831         if (jbd2_has_feature_64bit(journal))
 832                 record_len = 8;
 833
 834         while (offset + record_len <= max) {
 835                 unsigned long long blocknr;
 836                 int err;
 837
 838                 if (record_len == 4)
 839                         blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
 840                 else
 841                         blocknr = be64_to_cpu(* ((__be64 *) (bh->b_data+offset)));
 842                 offset += record_len;
 843                 err = jbd2_journal_set_revoke(journal, blocknr, sequence);
 844                 if (err)
 845                         return err;
 846                 ++info->nr_revokes;
 847         }
 848         return 0;
 849 }