fs/jbd2/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         unsigned long   head_block;
  33
  34         int             nr_replays;
  35         int             nr_revokes;
  36         int             nr_revoke_hits;
  37 };
  38
  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_total_len)
  79                 max = journal->j_total_len;
  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                                 bh_readahead_batch(nbufs, bufs, 0);
 105                                 journal_brelse_array(bufs, nbufs);
 106                                 nbufs = 0;
 107                         }
 108                 } else
 109                         brelse(bh);
 110         }
 111
 112         if (nbufs)
 113                 bh_readahead_batch(nbufs, bufs, 0);
 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_total_len) {
 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                 /*
 157                  * If this is a brand new buffer, start readahead.
 158                  * Otherwise, we assume we are already reading it.
 159                  */
 160                 bool need_readahead = !buffer_req(bh);
 161
 162                 bh_read_nowait(bh, 0);
 163                 if (need_readahead)
 164                         do_readahead(journal, offset);
 165                 wait_on_buffer(bh);
 166         }
 167
 168         if (!buffer_uptodate(bh)) {
 169                 printk(KERN_ERR "JBD2: Failed to read block at offset %u\n",
 170                         offset);
 171                 brelse(bh);
 172                 return -EIO;
 173         }
 174
 175         *bhp = bh;
 176         return 0;
 177 }
 178
 179 static int jbd2_descriptor_block_csum_verify(journal_t *j, void *buf)
 180 {
 181         struct jbd2_journal_block_tail *tail;
 182         __be32 provided;
 183         __u32 calculated;
 184
 185         if (!jbd2_journal_has_csum_v2or3(j))
 186                 return 1;
 187
 188         tail = (struct jbd2_journal_block_tail *)((char *)buf +
 189                 j->j_blocksize - sizeof(struct jbd2_journal_block_tail));
 190         provided = tail->t_checksum;
 191         tail->t_checksum = 0;
 192         calculated = jbd2_chksum(j, j->j_csum_seed, buf, j->j_blocksize);
 193         tail->t_checksum = provided;
 194
 195         return provided == cpu_to_be32(calculated);
 196 }
 197
 198 /*
 199  * Count the number of in-use tags in a journal descriptor block.
 200  */
 201
 202 static int count_tags(journal_t *journal, struct buffer_head *bh)
 203 {
 204         char *                  tagp;
 205         journal_block_tag_t     tag;
 206         int                     nr = 0, size = journal->j_blocksize;
 207         int                     tag_bytes = journal_tag_bytes(journal);
 208
 209         if (jbd2_journal_has_csum_v2or3(journal))
 210                 size -= sizeof(struct jbd2_journal_block_tail);
 211
 212         tagp = &bh->b_data[sizeof(journal_header_t)];
 213
 214         while ((tagp - bh->b_data + tag_bytes) <= size) {
 215                 memcpy(&tag, tagp, sizeof(tag));
 216
 217                 nr++;
 218                 tagp += tag_bytes;
 219                 if (!(tag.t_flags & cpu_to_be16(JBD2_FLAG_SAME_UUID)))
 220                         tagp += 16;
 221
 222                 if (tag.t_flags & cpu_to_be16(JBD2_FLAG_LAST_TAG))
 223                         break;
 224         }
 225
 226         return nr;
 227 }
 228
 229
 230 /* Make sure we wrap around the log correctly! */
 231 #define wrap(journal, var)                                              \
 232 do {                                                                    \
 233         if (var >= (journal)->j_last)                                   \
 234                 var -= ((journal)->j_last - (journal)->j_first);        \
 235 } while (0)
 236
 237 static int fc_do_one_pass(journal_t *journal,
 238                           struct recovery_info *info, enum passtype pass)
 239 {
 240         unsigned int expected_commit_id = info->end_transaction;
 241         unsigned long next_fc_block;
 242         struct buffer_head *bh;
 243         int err = 0;
 244
 245         next_fc_block = journal->j_fc_first;
 246         if (!journal->j_fc_replay_callback)
 247                 return 0;
 248
 249         while (next_fc_block <= journal->j_fc_last) {
 250                 jbd2_debug(3, "Fast commit replay: next block %ld\n",
 251                           next_fc_block);
 252                 err = jread(&bh, journal, next_fc_block);
 253                 if (err) {
 254                         jbd2_debug(3, "Fast commit replay: read error\n");
 255                         break;
 256                 }
 257
 258                 err = journal->j_fc_replay_callback(journal, bh, pass,
 259                                         next_fc_block - journal->j_fc_first,
 260                                         expected_commit_id);
 261                 brelse(bh);
 262                 next_fc_block++;
 263                 if (err < 0 || err == JBD2_FC_REPLAY_STOP)
 264                         break;
 265                 err = 0;
 266         }
 267
 268         if (err)
 269                 jbd2_debug(3, "Fast commit replay failed, err = %d\n", err);
 270
 271         return err;
 272 }
 273
 274 /**
 275  * jbd2_journal_recover - recovers a on-disk journal
 276  * @journal: the journal to recover
 277  *
 278  * The primary function for recovering the log contents when mounting a
 279  * journaled device.
 280  *
 281  * Recovery is done in three passes.  In the first pass, we look for the
 282  * end of the log.  In the second, we assemble the list of revoke
 283  * blocks.  In the third and final pass, we replay any un-revoked blocks
 284  * in the log.
 285  */
 286 int jbd2_journal_recover(journal_t *journal)
 287 {
 288         int                     err, err2;
 289         journal_superblock_t *  sb;
 290
 291         struct recovery_info    info;
 292
 293         memset(&info, 0, sizeof(info));
 294         sb = journal->j_superblock;
 295
 296         /*
 297          * The journal superblock's s_start field (the current log head)
 298          * is always zero if, and only if, the journal was cleanly
 299          * unmounted.
 300          */
 301         if (!sb->s_start) {
 302                 jbd2_debug(1, "No recovery required, last transaction %d, head block %u\n",
 303                           be32_to_cpu(sb->s_sequence), be32_to_cpu(sb->s_head));
 304                 journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
 305                 journal->j_head = be32_to_cpu(sb->s_head);
 306                 return 0;
 307         }
 308
 309         err = do_one_pass(journal, &info, PASS_SCAN);
 310         if (!err)
 311                 err = do_one_pass(journal, &info, PASS_REVOKE);
 312         if (!err)
 313                 err = do_one_pass(journal, &info, PASS_REPLAY);
 314
 315         jbd2_debug(1, "JBD2: recovery, exit status %d, "
 316                   "recovered transactions %u to %u\n",
 317                   err, info.start_transaction, info.end_transaction);
 318         jbd2_debug(1, "JBD2: Replayed %d and revoked %d/%d blocks\n",
 319                   info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
 320
 321         /* Restart the log at the next transaction ID, thus invalidating
 322          * any existing commit records in the log. */
 323         journal->j_transaction_sequence = ++info.end_transaction;
 324         journal->j_head = info.head_block;
 325         jbd2_debug(1, "JBD2: last transaction %d, head block %lu\n",
 326                   journal->j_transaction_sequence, journal->j_head);
 327
 328         jbd2_journal_clear_revoke(journal);
 329         err2 = sync_blockdev(journal->j_fs_dev);
 330         if (!err)
 331                 err = err2;
 332         err2 = jbd2_check_fs_dev_write_error(journal);
 333         if (!err)
 334                 err = err2;
 335         /* Make sure all replayed data is on permanent storage */
 336         if (journal->j_flags & JBD2_BARRIER) {
 337                 err2 = blkdev_issue_flush(journal->j_fs_dev);
 338                 if (!err)
 339                         err = err2;
 340         }
 341         return err;
 342 }
 343
 344 /**
 345  * jbd2_journal_skip_recovery - Start journal and wipe exiting records
 346  * @journal: journal to startup
 347  *
 348  * Locate any valid recovery information from the journal and set up the
 349  * journal structures in memory to ignore it (presumably because the
 350  * caller has evidence that it is out of date).
 351  * This function doesn't appear to be exported..
 352  *
 353  * We perform one pass over the journal to allow us to tell the user how
 354  * much recovery information is being erased, and to let us initialise
 355  * the journal transaction sequence numbers to the next unused ID.
 356  */
 357 int jbd2_journal_skip_recovery(journal_t *journal)
 358 {
 359         int                     err;
 360
 361         struct recovery_info    info;
 362
 363         memset (&info, 0, sizeof(info));
 364
 365         err = do_one_pass(journal, &info, PASS_SCAN);
 366
 367         if (err) {
 368                 printk(KERN_ERR "JBD2: error %d scanning journal\n", err);
 369                 ++journal->j_transaction_sequence;
 370                 journal->j_head = journal->j_first;
 371         } else {
 372 #ifdef CONFIG_JBD2_DEBUG
 373                 int dropped = info.end_transaction -
 374                         be32_to_cpu(journal->j_superblock->s_sequence);
 375                 jbd2_debug(1,
 376                           "JBD2: ignoring %d transaction%s from the journal.\n",
 377                           dropped, (dropped == 1) ? "" : "s");
 378 #endif
 379                 journal->j_transaction_sequence = ++info.end_transaction;
 380                 journal->j_head = info.head_block;
 381         }
 382
 383         journal->j_tail = 0;
 384         return err;
 385 }
 386
 387 static inline unsigned long long read_tag_block(journal_t *journal,
 388                                                 journal_block_tag_t *tag)
 389 {
 390         unsigned long long block = be32_to_cpu(tag->t_blocknr);
 391         if (jbd2_has_feature_64bit(journal))
 392                 block |= (u64)be32_to_cpu(tag->t_blocknr_high) << 32;
 393         return block;
 394 }
 395
 396 /*
 397  * calc_chksums calculates the checksums for the blocks described in the
 398  * descriptor block.
 399  */
 400 static int calc_chksums(journal_t *journal, struct buffer_head *bh,
 401                         unsigned long *next_log_block, __u32 *crc32_sum)
 402 {
 403         int i, num_blks, err;
 404         unsigned long io_block;
 405         struct buffer_head *obh;
 406
 407         num_blks = count_tags(journal, bh);
 408         /* Calculate checksum of the descriptor block. */
 409         *crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);
 410
 411         for (i = 0; i < num_blks; i++) {
 412                 io_block = (*next_log_block)++;
 413                 wrap(journal, *next_log_block);
 414                 err = jread(&obh, journal, io_block);
 415                 if (err) {
 416                         printk(KERN_ERR "JBD2: IO error %d recovering block "
 417                                 "%lu in log\n", err, io_block);
 418                         return 1;
 419                 } else {
 420                         *crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
 421                                      obh->b_size);
 422                 }
 423                 put_bh(obh);
 424         }
 425         return 0;
 426 }
 427
 428 static int jbd2_commit_block_csum_verify(journal_t *j, void *buf)
 429 {
 430         struct commit_header *h;
 431         __be32 provided;
 432         __u32 calculated;
 433
 434         if (!jbd2_journal_has_csum_v2or3(j))
 435                 return 1;
 436
 437         h = buf;
 438         provided = h->h_chksum[0];
 439         h->h_chksum[0] = 0;
 440         calculated = jbd2_chksum(j, j->j_csum_seed, buf, j->j_blocksize);
 441         h->h_chksum[0] = provided;
 442
 443         return provided == cpu_to_be32(calculated);
 444 }
 445
 446 static int jbd2_block_tag_csum_verify(journal_t *j, journal_block_tag_t *tag,
 447                                       journal_block_tag3_t *tag3,
 448                                       void *buf, __u32 sequence)
 449 {
 450         __u32 csum32;
 451         __be32 seq;
 452
 453         if (!jbd2_journal_has_csum_v2or3(j))
 454                 return 1;
 455
 456         seq = cpu_to_be32(sequence);
 457         csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&seq, sizeof(seq));
 458         csum32 = jbd2_chksum(j, csum32, buf, j->j_blocksize);
 459
 460         if (jbd2_has_feature_csum3(j))
 461                 return tag3->t_checksum == cpu_to_be32(csum32);
 462         else
 463                 return tag->t_checksum == cpu_to_be16(csum32);
 464 }
 465
 466 static int do_one_pass(journal_t *journal,
 467                         struct recovery_info *info, enum passtype pass)
 468 {
 469         unsigned int            first_commit_ID, next_commit_ID;
 470         unsigned long           next_log_block, head_block;
 471         int                     err, success = 0;
 472         journal_superblock_t *  sb;
 473         journal_header_t *      tmp;
 474         struct buffer_head *    bh;
 475         unsigned int            sequence;
 476         int                     blocktype;
 477         int                     tag_bytes = journal_tag_bytes(journal);
 478         __u32                   crc32_sum = ~0; /* Transactional Checksums */
 479         int                     descr_csum_size = 0;
 480         int                     block_error = 0;
 481         bool                    need_check_commit_time = false;
 482         __u64                   last_trans_commit_time = 0, commit_time;
 483
 484         /*
 485          * First thing is to establish what we expect to find in the log
 486          * (in terms of transaction IDs), and where (in terms of log
 487          * block offsets): query the superblock.
 488          */
 489
 490         sb = journal->j_superblock;
 491         next_commit_ID = be32_to_cpu(sb->s_sequence);
 492         next_log_block = be32_to_cpu(sb->s_start);
 493         head_block = next_log_block;
 494
 495         first_commit_ID = next_commit_ID;
 496         if (pass == PASS_SCAN)
 497                 info->start_transaction = first_commit_ID;
 498
 499         jbd2_debug(1, "Starting recovery pass %d\n", pass);
 500
 501         /*
 502          * Now we walk through the log, transaction by transaction,
 503          * making sure that each transaction has a commit block in the
 504          * expected place.  Each complete transaction gets replayed back
 505          * into the main filesystem.
 506          */
 507
 508         while (1) {
 509                 int                     flags;
 510                 char *                  tagp;
 511                 journal_block_tag_t     tag;
 512                 struct buffer_head *    obh;
 513                 struct buffer_head *    nbh;
 514
 515                 cond_resched();
 516
 517                 /* If we already know where to stop the log traversal,
 518                  * check right now that we haven't gone past the end of
 519                  * the log. */
 520
 521                 if (pass != PASS_SCAN)
 522                         if (tid_geq(next_commit_ID, info->end_transaction))
 523                                 break;
 524
 525                 jbd2_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
 526                           next_commit_ID, next_log_block, journal->j_last);
 527
 528                 /* Skip over each chunk of the transaction looking
 529                  * either the next descriptor block or the final commit
 530                  * record. */
 531
 532                 jbd2_debug(3, "JBD2: checking block %ld\n", next_log_block);
 533                 err = jread(&bh, journal, next_log_block);
 534                 if (err)
 535                         goto failed;
 536
 537                 next_log_block++;
 538                 wrap(journal, next_log_block);
 539
 540                 /* What kind of buffer is it?
 541                  *
 542                  * If it is a descriptor block, check that it has the
 543                  * expected sequence number.  Otherwise, we're all done
 544                  * here. */
 545
 546                 tmp = (journal_header_t *)bh->b_data;
 547
 548                 if (tmp->h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER)) {
 549                         brelse(bh);
 550                         break;
 551                 }
 552
 553                 blocktype = be32_to_cpu(tmp->h_blocktype);
 554                 sequence = be32_to_cpu(tmp->h_sequence);
 555                 jbd2_debug(3, "Found magic %d, sequence %d\n",
 556                           blocktype, sequence);
 557
 558                 if (sequence != next_commit_ID) {
 559                         brelse(bh);
 560                         break;
 561                 }
 562
 563                 /* OK, we have a valid descriptor block which matches
 564                  * all of the sequence number checks.  What are we going
 565                  * to do with it?  That depends on the pass... */
 566
 567                 switch(blocktype) {
 568                 case JBD2_DESCRIPTOR_BLOCK:
 569                         /* Verify checksum first */
 570                         if (jbd2_journal_has_csum_v2or3(journal))
 571                                 descr_csum_size =
 572                                         sizeof(struct jbd2_journal_block_tail);
 573                         if (descr_csum_size > 0 &&
 574                             !jbd2_descriptor_block_csum_verify(journal,
 575                                                                bh->b_data)) {
 576                                 /*
 577                                  * PASS_SCAN can see stale blocks due to lazy
 578                                  * journal init. Don't error out on those yet.
 579                                  */
 580                                 if (pass != PASS_SCAN) {
 581                                         pr_err("JBD2: Invalid checksum recovering block %lu in log\n",
 582                                                next_log_block);
 583                                         err = -EFSBADCRC;
 584                                         brelse(bh);
 585                                         goto failed;
 586                                 }
 587                                 need_check_commit_time = true;
 588                                 jbd2_debug(1,
 589                                         "invalid descriptor block found in %lu\n",
 590                                         next_log_block);
 591                         }
 592
 593                         /* If it is a valid descriptor block, replay it
 594                          * in pass REPLAY; if journal_checksums enabled, then
 595                          * calculate checksums in PASS_SCAN, otherwise,
 596                          * just skip over the blocks it describes. */
 597                         if (pass != PASS_REPLAY) {
 598                                 if (pass == PASS_SCAN &&
 599                                     jbd2_has_feature_checksum(journal) &&
 600                                     !need_check_commit_time &&
 601                                     !info->end_transaction) {
 602                                         if (calc_chksums(journal, bh,
 603                                                         &next_log_block,
 604                                                         &crc32_sum)) {
 605                                                 put_bh(bh);
 606                                                 break;
 607                                         }
 608                                         put_bh(bh);
 609                                         continue;
 610                                 }
 611                                 next_log_block += count_tags(journal, bh);
 612                                 wrap(journal, next_log_block);
 613                                 put_bh(bh);
 614                                 continue;
 615                         }
 616
 617                         /* A descriptor block: we can now write all of
 618                          * the data blocks.  Yay, useful work is finally
 619                          * getting done here! */
 620
 621                         tagp = &bh->b_data[sizeof(journal_header_t)];
 622                         while ((tagp - bh->b_data + tag_bytes)
 623                                <= journal->j_blocksize - descr_csum_size) {
 624                                 unsigned long io_block;
 625
 626                                 memcpy(&tag, tagp, sizeof(tag));
 627                                 flags = be16_to_cpu(tag.t_flags);
 628
 629                                 io_block = next_log_block++;
 630                                 wrap(journal, next_log_block);
 631                                 err = jread(&obh, journal, io_block);
 632                                 if (err) {
 633                                         /* Recover what we can, but
 634                                          * report failure at the end. */
 635                                         success = err;
 636                                         printk(KERN_ERR
 637                                                 "JBD2: IO error %d recovering "
 638                                                 "block %lu in log\n",
 639                                                 err, io_block);
 640                                 } else {
 641                                         unsigned long long blocknr;
 642
 643                                         J_ASSERT(obh != NULL);
 644                                         blocknr = read_tag_block(journal,
 645                                                                  &tag);
 646
 647                                         /* If the block has been
 648                                          * revoked, then we're all done
 649                                          * here. */
 650                                         if (jbd2_journal_test_revoke
 651                                             (journal, blocknr,
 652                                              next_commit_ID)) {
 653                                                 brelse(obh);
 654                                                 ++info->nr_revoke_hits;
 655                                                 goto skip_write;
 656                                         }
 657
 658                                         /* Look for block corruption */
 659                                         if (!jbd2_block_tag_csum_verify(
 660                         journal, &tag, (journal_block_tag3_t *)tagp,
 661                         obh->b_data, be32_to_cpu(tmp->h_sequence))) {
 662                                                 brelse(obh);
 663                                                 success = -EFSBADCRC;
 664                                                 printk(KERN_ERR "JBD2: Invalid "
 665                                                        "checksum recovering "
 666                                                        "data block %llu in "
 667                                                        "journal block %lu\n",
 668                                                        blocknr, io_block);
 669                                                 block_error = 1;
 670                                                 goto skip_write;
 671                                         }
 672
 673                                         /* Find a buffer for the new
 674                                          * data being restored */
 675                                         nbh = __getblk(journal->j_fs_dev,
 676                                                         blocknr,
 677                                                         journal->j_blocksize);
 678                                         if (nbh == NULL) {
 679                                                 printk(KERN_ERR
 680                                                        "JBD2: Out of memory "
 681                                                        "during recovery.\n");
 682                                                 err = -ENOMEM;
 683                                                 brelse(bh);
 684                                                 brelse(obh);
 685                                                 goto failed;
 686                                         }
 687
 688                                         lock_buffer(nbh);
 689                                         memcpy(nbh->b_data, obh->b_data,
 690                                                         journal->j_blocksize);
 691                                         if (flags & JBD2_FLAG_ESCAPE) {
 692                                                 *((__be32 *)nbh->b_data) =
 693                                                 cpu_to_be32(JBD2_MAGIC_NUMBER);
 694                                         }
 695
 696                                         BUFFER_TRACE(nbh, "marking dirty");
 697                                         set_buffer_uptodate(nbh);
 698                                         mark_buffer_dirty(nbh);
 699                                         BUFFER_TRACE(nbh, "marking uptodate");
 700                                         ++info->nr_replays;
 701                                         unlock_buffer(nbh);
 702                                         brelse(obh);
 703                                         brelse(nbh);
 704                                 }
 705
 706                         skip_write:
 707                                 tagp += tag_bytes;
 708                                 if (!(flags & JBD2_FLAG_SAME_UUID))
 709                                         tagp += 16;
 710
 711                                 if (flags & JBD2_FLAG_LAST_TAG)
 712                                         break;
 713                         }
 714
 715                         brelse(bh);
 716                         continue;
 717
 718                 case JBD2_COMMIT_BLOCK:
 719                         /*     How to differentiate between interrupted commit
 720                          *               and journal corruption ?
 721                          *
 722                          * {nth transaction}
 723                          *        Checksum Verification Failed
 724                          *                       |
 725                          *               ____________________
 726                          *              |                    |
 727                          *      async_commit             sync_commit
 728                          *              |                    |
 729                          *              | GO TO NEXT    "Journal Corruption"
 730                          *              | TRANSACTION
 731                          *              |
 732                          * {(n+1)th transanction}
 733                          *              |
 734                          *       _______|______________
 735                          *      |                     |
 736                          * Commit block found   Commit block not found
 737                          *      |                     |
 738                          * "Journal Corruption"       |
 739                          *               _____________|_________
 740                          *              |                       |
 741                          *      nth trans corrupt       OR   nth trans
 742                          *      and (n+1)th interrupted     interrupted
 743                          *      before commit block
 744                          *      could reach the disk.
 745                          *      (Cannot find the difference in above
 746                          *       mentioned conditions. Hence assume
 747                          *       "Interrupted Commit".)
 748                          */
 749                         commit_time = be64_to_cpu(
 750                                 ((struct commit_header *)bh->b_data)->h_commit_sec);
 751                         /*
 752                          * If need_check_commit_time is set, it means we are in
 753                          * PASS_SCAN and csum verify failed before. If
 754                          * commit_time is increasing, it's the same journal,
 755                          * otherwise it is stale journal block, just end this
 756                          * recovery.
 757                          */
 758                         if (need_check_commit_time) {
 759                                 if (commit_time >= last_trans_commit_time) {
 760                                         pr_err("JBD2: Invalid checksum found in transaction %u\n",
 761                                                next_commit_ID);
 762                                         err = -EFSBADCRC;
 763                                         brelse(bh);
 764                                         goto failed;
 765                                 }
 766                         ignore_crc_mismatch:
 767                                 /*
 768                                  * It likely does not belong to same journal,
 769                                  * just end this recovery with success.
 770                                  */
 771                                 jbd2_debug(1, "JBD2: Invalid checksum ignored in transaction %u, likely stale data\n",
 772                                           next_commit_ID);
 773                                 brelse(bh);
 774                                 goto done;
 775                         }
 776
 777                         /*
 778                          * Found an expected commit block: if checksums
 779                          * are present, verify them in PASS_SCAN; else not
 780                          * much to do other than move on to the next sequence
 781                          * number.
 782                          */
 783                         if (pass == PASS_SCAN &&
 784                             jbd2_has_feature_checksum(journal)) {
 785                                 struct commit_header *cbh =
 786                                         (struct commit_header *)bh->b_data;
 787                                 unsigned found_chksum =
 788                                         be32_to_cpu(cbh->h_chksum[0]);
 789
 790                                 if (info->end_transaction) {
 791                                         journal->j_failed_commit =
 792                                                 info->end_transaction;
 793                                         brelse(bh);
 794                                         break;
 795                                 }
 796
 797                                 /* Neither checksum match nor unused? */
 798                                 if (!((crc32_sum == found_chksum &&
 799                                        cbh->h_chksum_type ==
 800                                                 JBD2_CRC32_CHKSUM &&
 801                                        cbh->h_chksum_size ==
 802                                                 JBD2_CRC32_CHKSUM_SIZE) ||
 803                                       (cbh->h_chksum_type == 0 &&
 804                                        cbh->h_chksum_size == 0 &&
 805                                        found_chksum == 0)))
 806                                         goto chksum_error;
 807
 808                                 crc32_sum = ~0;
 809                         }
 810                         if (pass == PASS_SCAN &&
 811                             !jbd2_commit_block_csum_verify(journal,
 812                                                            bh->b_data)) {
 813                         chksum_error:
 814                                 if (commit_time < last_trans_commit_time)
 815                                         goto ignore_crc_mismatch;
 816                                 info->end_transaction = next_commit_ID;
 817                                 info->head_block = head_block;
 818
 819                                 if (!jbd2_has_feature_async_commit(journal)) {
 820                                         journal->j_failed_commit =
 821                                                 next_commit_ID;
 822                                         brelse(bh);
 823                                         break;
 824                                 }
 825                         }
 826                         if (pass == PASS_SCAN) {
 827                                 last_trans_commit_time = commit_time;
 828                                 head_block = next_log_block;
 829                         }
 830                         brelse(bh);
 831                         next_commit_ID++;
 832                         continue;
 833
 834                 case JBD2_REVOKE_BLOCK:
 835                         /*
 836                          * Check revoke block crc in pass_scan, if csum verify
 837                          * failed, check commit block time later.
 838                          */
 839                         if (pass == PASS_SCAN &&
 840                             !jbd2_descriptor_block_csum_verify(journal,
 841                                                                bh->b_data)) {
 842                                 jbd2_debug(1, "JBD2: invalid revoke block found in %lu\n",
 843                                           next_log_block);
 844                                 need_check_commit_time = true;
 845                         }
 846                         /* If we aren't in the REVOKE pass, then we can
 847                          * just skip over this block. */
 848                         if (pass != PASS_REVOKE) {
 849                                 brelse(bh);
 850                                 continue;
 851                         }
 852
 853                         err = scan_revoke_records(journal, bh,
 854                                                   next_commit_ID, info);
 855                         brelse(bh);
 856                         if (err)
 857                                 goto failed;
 858                         continue;
 859
 860                 default:
 861                         jbd2_debug(3, "Unrecognised magic %d, end of scan.\n",
 862                                   blocktype);
 863                         brelse(bh);
 864                         goto done;
 865                 }
 866         }
 867
 868  done:
 869         /*
 870          * We broke out of the log scan loop: either we came to the
 871          * known end of the log or we found an unexpected block in the
 872          * log.  If the latter happened, then we know that the "current"
 873          * transaction marks the end of the valid log.
 874          */
 875
 876         if (pass == PASS_SCAN) {
 877                 if (!info->end_transaction)
 878                         info->end_transaction = next_commit_ID;
 879                 if (!info->head_block)
 880                         info->head_block = head_block;
 881         } else {
 882                 /* It's really bad news if different passes end up at
 883                  * different places (but possible due to IO errors). */
 884                 if (info->end_transaction != next_commit_ID) {
 885                         printk(KERN_ERR "JBD2: recovery pass %d ended at "
 886                                 "transaction %u, expected %u\n",
 887                                 pass, next_commit_ID, info->end_transaction);
 888                         if (!success)
 889                                 success = -EIO;
 890                 }
 891         }
 892
 893         if (jbd2_has_feature_fast_commit(journal) &&  pass != PASS_REVOKE) {
 894                 err = fc_do_one_pass(journal, info, pass);
 895                 if (err)
 896                         success = err;
 897         }
 898
 899         if (block_error && success == 0)
 900                 success = -EIO;
 901         return success;
 902
 903  failed:
 904         return err;
 905 }
 906
 907 /* Scan a revoke record, marking all blocks mentioned as revoked. */
 908
 909 static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 910                                tid_t sequence, struct recovery_info *info)
 911 {
 912         jbd2_journal_revoke_header_t *header;
 913         int offset, max;
 914         unsigned csum_size = 0;
 915         __u32 rcount;
 916         int record_len = 4;
 917
 918         header = (jbd2_journal_revoke_header_t *) bh->b_data;
 919         offset = sizeof(jbd2_journal_revoke_header_t);
 920         rcount = be32_to_cpu(header->r_count);
 921
 922         if (jbd2_journal_has_csum_v2or3(journal))
 923                 csum_size = sizeof(struct jbd2_journal_block_tail);
 924         if (rcount > journal->j_blocksize - csum_size)
 925                 return -EINVAL;
 926         max = rcount;
 927
 928         if (jbd2_has_feature_64bit(journal))
 929                 record_len = 8;
 930
 931         while (offset + record_len <= max) {
 932                 unsigned long long blocknr;
 933                 int err;
 934
 935                 if (record_len == 4)
 936                         blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
 937                 else
 938                         blocknr = be64_to_cpu(* ((__be64 *) (bh->b_data+offset)));
 939                 offset += record_len;
 940                 err = jbd2_journal_set_revoke(journal, blocknr, sequence);
 941                 if (err)
 942                         return err;
 943                 ++info->nr_revokes;
 944         }
 945         return 0;
 946 }