linux/fs/jbd2/recovery.c
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   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/crc32.h>
  24#endif
  25
  26/*
  27 * Maintain information about the progress of the recovery job, so that
  28 * the different passes can carry information between them.
  29 */
  30struct recovery_info
  31{
  32        tid_t           start_transaction;
  33        tid_t           end_transaction;
  34
  35        int             nr_replays;
  36        int             nr_revokes;
  37        int             nr_revoke_hits;
  38};
  39
  40enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
  41static int do_one_pass(journal_t *journal,
  42                                struct recovery_info *info, enum passtype pass);
  43static int scan_revoke_records(journal_t *, struct buffer_head *,
  44                                tid_t, struct recovery_info *);
  45
  46#ifdef __KERNEL__
  47
  48/* Release readahead buffers after use */
  49static void journal_brelse_array(struct buffer_head *b[], int n)
  50{
  51        while (--n >= 0)
  52                brelse (b[n]);
  53}
  54
  55
  56/*
  57 * When reading from the journal, we are going through the block device
  58 * layer directly and so there is no readahead being done for us.  We
  59 * need to implement any readahead ourselves if we want it to happen at
  60 * all.  Recovery is basically one long sequential read, so make sure we
  61 * do the IO in reasonably large chunks.
  62 *
  63 * This is not so critical that we need to be enormously clever about
  64 * the readahead size, though.  128K is a purely arbitrary, good-enough
  65 * fixed value.
  66 */
  67
  68#define MAXBUF 8
  69static int do_readahead(journal_t *journal, unsigned int start)
  70{
  71        int err;
  72        unsigned int max, nbufs, next;
  73        unsigned long long blocknr;
  74        struct buffer_head *bh;
  75
  76        struct buffer_head * bufs[MAXBUF];
  77
  78        /* Do up to 128K of readahead */
  79        max = start + (128 * 1024 / journal->j_blocksize);
  80        if (max > journal->j_maxlen)
  81                max = journal->j_maxlen;
  82
  83        /* Do the readahead itself.  We'll submit MAXBUF buffer_heads at
  84         * a time to the block device IO layer. */
  85
  86        nbufs = 0;
  87
  88        for (next = start; next < max; next++) {
  89                err = jbd2_journal_bmap(journal, next, &blocknr);
  90
  91                if (err) {
  92                        printk(KERN_ERR "JBD2: bad block at offset %u\n",
  93                                next);
  94                        goto failed;
  95                }
  96
  97                bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
  98                if (!bh) {
  99                        err = -ENOMEM;
 100                        goto failed;
 101                }
 102
 103                if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
 104                        bufs[nbufs++] = bh;
 105                        if (nbufs == MAXBUF) {
 106                                ll_rw_block(READ, nbufs, bufs);
 107                                journal_brelse_array(bufs, nbufs);
 108                                nbufs = 0;
 109                        }
 110                } else
 111                        brelse(bh);
 112        }
 113
 114        if (nbufs)
 115                ll_rw_block(READ, nbufs, bufs);
 116        err = 0;
 117
 118failed:
 119        if (nbufs)
 120                journal_brelse_array(bufs, nbufs);
 121        return err;
 122}
 123
 124#endif /* __KERNEL__ */
 125
 126
 127/*
 128 * Read a block from the journal
 129 */
 130
 131static int jread(struct buffer_head **bhp, journal_t *journal,
 132                 unsigned int offset)
 133{
 134        int err;
 135        unsigned long long blocknr;
 136        struct buffer_head *bh;
 137
 138        *bhp = NULL;
 139
 140        if (offset >= journal->j_maxlen) {
 141                printk(KERN_ERR "JBD2: corrupted journal superblock\n");
 142                return -EIO;
 143        }
 144
 145        err = jbd2_journal_bmap(journal, offset, &blocknr);
 146
 147        if (err) {
 148                printk(KERN_ERR "JBD2: bad block at offset %u\n",
 149                        offset);
 150                return err;
 151        }
 152
 153        bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
 154        if (!bh)
 155                return -ENOMEM;
 156
 157        if (!buffer_uptodate(bh)) {
 158                /* If this is a brand new buffer, start readahead.
 159                   Otherwise, we assume we are already reading it.  */
 160                if (!buffer_req(bh))
 161                        do_readahead(journal, offset);
 162                wait_on_buffer(bh);
 163        }
 164
 165        if (!buffer_uptodate(bh)) {
 166                printk(KERN_ERR "JBD2: Failed to read block at offset %u\n",
 167                        offset);
 168                brelse(bh);
 169                return -EIO;
 170        }
 171
 172        *bhp = bh;
 173        return 0;
 174}
 175
 176
 177/*
 178 * Count the number of in-use tags in a journal descriptor block.
 179 */
 180
 181static int count_tags(journal_t *journal, struct buffer_head *bh)
 182{
 183        char *                  tagp;
 184        journal_block_tag_t *   tag;
 185        int                     nr = 0, size = journal->j_blocksize;
 186        int                     tag_bytes = journal_tag_bytes(journal);
 187
 188        tagp = &bh->b_data[sizeof(journal_header_t)];
 189
 190        while ((tagp - bh->b_data + tag_bytes) <= size) {
 191                tag = (journal_block_tag_t *) tagp;
 192
 193                nr++;
 194                tagp += tag_bytes;
 195                if (!(tag->t_flags & cpu_to_be32(JBD2_FLAG_SAME_UUID)))
 196                        tagp += 16;
 197
 198                if (tag->t_flags & cpu_to_be32(JBD2_FLAG_LAST_TAG))
 199                        break;
 200        }
 201
 202        return nr;
 203}
 204
 205
 206/* Make sure we wrap around the log correctly! */
 207#define wrap(journal, var)                                              \
 208do {                                                                    \
 209        if (var >= (journal)->j_last)                                   \
 210                var -= ((journal)->j_last - (journal)->j_first);        \
 211} while (0)
 212
 213/**
 214 * jbd2_journal_recover - recovers a on-disk journal
 215 * @journal: the journal to recover
 216 *
 217 * The primary function for recovering the log contents when mounting a
 218 * journaled device.
 219 *
 220 * Recovery is done in three passes.  In the first pass, we look for the
 221 * end of the log.  In the second, we assemble the list of revoke
 222 * blocks.  In the third and final pass, we replay any un-revoked blocks
 223 * in the log.
 224 */
 225int jbd2_journal_recover(journal_t *journal)
 226{
 227        int                     err, err2;
 228        journal_superblock_t *  sb;
 229
 230        struct recovery_info    info;
 231
 232        memset(&info, 0, sizeof(info));
 233        sb = journal->j_superblock;
 234
 235        /*
 236         * The journal superblock's s_start field (the current log head)
 237         * is always zero if, and only if, the journal was cleanly
 238         * unmounted.
 239         */
 240
 241        if (!sb->s_start) {
 242                jbd_debug(1, "No recovery required, last transaction %d\n",
 243                          be32_to_cpu(sb->s_sequence));
 244                journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
 245                return 0;
 246        }
 247
 248        err = do_one_pass(journal, &info, PASS_SCAN);
 249        if (!err)
 250                err = do_one_pass(journal, &info, PASS_REVOKE);
 251        if (!err)
 252                err = do_one_pass(journal, &info, PASS_REPLAY);
 253
 254        jbd_debug(1, "JBD2: recovery, exit status %d, "
 255                  "recovered transactions %u to %u\n",
 256                  err, info.start_transaction, info.end_transaction);
 257        jbd_debug(1, "JBD2: Replayed %d and revoked %d/%d blocks\n",
 258                  info.nr_replays, info.nr_revoke_hits, info.nr_revokes);
 259
 260        /* Restart the log at the next transaction ID, thus invalidating
 261         * any existing commit records in the log. */
 262        journal->j_transaction_sequence = ++info.end_transaction;
 263
 264        jbd2_journal_clear_revoke(journal);
 265        err2 = sync_blockdev(journal->j_fs_dev);
 266        if (!err)
 267                err = err2;
 268
 269        return err;
 270}
 271
 272/**
 273 * jbd2_journal_skip_recovery - Start journal and wipe exiting records
 274 * @journal: journal to startup
 275 *
 276 * Locate any valid recovery information from the journal and set up the
 277 * journal structures in memory to ignore it (presumably because the
 278 * caller has evidence that it is out of date).
 279 * This function does'nt appear to be exorted..
 280 *
 281 * We perform one pass over the journal to allow us to tell the user how
 282 * much recovery information is being erased, and to let us initialise
 283 * the journal transaction sequence numbers to the next unused ID.
 284 */
 285int jbd2_journal_skip_recovery(journal_t *journal)
 286{
 287        int                     err;
 288
 289        struct recovery_info    info;
 290
 291        memset (&info, 0, sizeof(info));
 292
 293        err = do_one_pass(journal, &info, PASS_SCAN);
 294
 295        if (err) {
 296                printk(KERN_ERR "JBD2: error %d scanning journal\n", err);
 297                ++journal->j_transaction_sequence;
 298        } else {
 299#ifdef CONFIG_JBD2_DEBUG
 300                int dropped = info.end_transaction - 
 301                        be32_to_cpu(journal->j_superblock->s_sequence);
 302                jbd_debug(1,
 303                          "JBD2: ignoring %d transaction%s from the journal.\n",
 304                          dropped, (dropped == 1) ? "" : "s");
 305#endif
 306                journal->j_transaction_sequence = ++info.end_transaction;
 307        }
 308
 309        journal->j_tail = 0;
 310        return err;
 311}
 312
 313static inline unsigned long long read_tag_block(int tag_bytes, journal_block_tag_t *tag)
 314{
 315        unsigned long long block = be32_to_cpu(tag->t_blocknr);
 316        if (tag_bytes > JBD2_TAG_SIZE32)
 317                block |= (u64)be32_to_cpu(tag->t_blocknr_high) << 32;
 318        return block;
 319}
 320
 321/*
 322 * calc_chksums calculates the checksums for the blocks described in the
 323 * descriptor block.
 324 */
 325static int calc_chksums(journal_t *journal, struct buffer_head *bh,
 326                        unsigned long *next_log_block, __u32 *crc32_sum)
 327{
 328        int i, num_blks, err;
 329        unsigned long io_block;
 330        struct buffer_head *obh;
 331
 332        num_blks = count_tags(journal, bh);
 333        /* Calculate checksum of the descriptor block. */
 334        *crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);
 335
 336        for (i = 0; i < num_blks; i++) {
 337                io_block = (*next_log_block)++;
 338                wrap(journal, *next_log_block);
 339                err = jread(&obh, journal, io_block);
 340                if (err) {
 341                        printk(KERN_ERR "JBD2: IO error %d recovering block "
 342                                "%lu in log\n", err, io_block);
 343                        return 1;
 344                } else {
 345                        *crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
 346                                     obh->b_size);
 347                }
 348                put_bh(obh);
 349        }
 350        return 0;
 351}
 352
 353static int do_one_pass(journal_t *journal,
 354                        struct recovery_info *info, enum passtype pass)
 355{
 356        unsigned int            first_commit_ID, next_commit_ID;
 357        unsigned long           next_log_block;
 358        int                     err, success = 0;
 359        journal_superblock_t *  sb;
 360        journal_header_t *      tmp;
 361        struct buffer_head *    bh;
 362        unsigned int            sequence;
 363        int                     blocktype;
 364        int                     tag_bytes = journal_tag_bytes(journal);
 365        __u32                   crc32_sum = ~0; /* Transactional Checksums */
 366
 367        /*
 368         * First thing is to establish what we expect to find in the log
 369         * (in terms of transaction IDs), and where (in terms of log
 370         * block offsets): query the superblock.
 371         */
 372
 373        sb = journal->j_superblock;
 374        next_commit_ID = be32_to_cpu(sb->s_sequence);
 375        next_log_block = be32_to_cpu(sb->s_start);
 376
 377        first_commit_ID = next_commit_ID;
 378        if (pass == PASS_SCAN)
 379                info->start_transaction = first_commit_ID;
 380
 381        jbd_debug(1, "Starting recovery pass %d\n", pass);
 382
 383        /*
 384         * Now we walk through the log, transaction by transaction,
 385         * making sure that each transaction has a commit block in the
 386         * expected place.  Each complete transaction gets replayed back
 387         * into the main filesystem.
 388         */
 389
 390        while (1) {
 391                int                     flags;
 392                char *                  tagp;
 393                journal_block_tag_t *   tag;
 394                struct buffer_head *    obh;
 395                struct buffer_head *    nbh;
 396
 397                cond_resched();
 398
 399                /* If we already know where to stop the log traversal,
 400                 * check right now that we haven't gone past the end of
 401                 * the log. */
 402
 403                if (pass != PASS_SCAN)
 404                        if (tid_geq(next_commit_ID, info->end_transaction))
 405                                break;
 406
 407                jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
 408                          next_commit_ID, next_log_block, journal->j_last);
 409
 410                /* Skip over each chunk of the transaction looking
 411                 * either the next descriptor block or the final commit
 412                 * record. */
 413
 414                jbd_debug(3, "JBD2: checking block %ld\n", next_log_block);
 415                err = jread(&bh, journal, next_log_block);
 416                if (err)
 417                        goto failed;
 418
 419                next_log_block++;
 420                wrap(journal, next_log_block);
 421
 422                /* What kind of buffer is it?
 423                 *
 424                 * If it is a descriptor block, check that it has the
 425                 * expected sequence number.  Otherwise, we're all done
 426                 * here. */
 427
 428                tmp = (journal_header_t *)bh->b_data;
 429
 430                if (tmp->h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER)) {
 431                        brelse(bh);
 432                        break;
 433                }
 434
 435                blocktype = be32_to_cpu(tmp->h_blocktype);
 436                sequence = be32_to_cpu(tmp->h_sequence);
 437                jbd_debug(3, "Found magic %d, sequence %d\n",
 438                          blocktype, sequence);
 439
 440                if (sequence != next_commit_ID) {
 441                        brelse(bh);
 442                        break;
 443                }
 444
 445                /* OK, we have a valid descriptor block which matches
 446                 * all of the sequence number checks.  What are we going
 447                 * to do with it?  That depends on the pass... */
 448
 449                switch(blocktype) {
 450                case JBD2_DESCRIPTOR_BLOCK:
 451                        /* If it is a valid descriptor block, replay it
 452                         * in pass REPLAY; if journal_checksums enabled, then
 453                         * calculate checksums in PASS_SCAN, otherwise,
 454                         * just skip over the blocks it describes. */
 455                        if (pass != PASS_REPLAY) {
 456                                if (pass == PASS_SCAN &&
 457                                    JBD2_HAS_COMPAT_FEATURE(journal,
 458                                            JBD2_FEATURE_COMPAT_CHECKSUM) &&
 459                                    !info->end_transaction) {
 460                                        if (calc_chksums(journal, bh,
 461                                                        &next_log_block,
 462                                                        &crc32_sum)) {
 463                                                put_bh(bh);
 464                                                break;
 465                                        }
 466                                        put_bh(bh);
 467                                        continue;
 468                                }
 469                                next_log_block += count_tags(journal, bh);
 470                                wrap(journal, next_log_block);
 471                                put_bh(bh);
 472                                continue;
 473                        }
 474
 475                        /* A descriptor block: we can now write all of
 476                         * the data blocks.  Yay, useful work is finally
 477                         * getting done here! */
 478
 479                        tagp = &bh->b_data[sizeof(journal_header_t)];
 480                        while ((tagp - bh->b_data + tag_bytes)
 481                               <= journal->j_blocksize) {
 482                                unsigned long io_block;
 483
 484                                tag = (journal_block_tag_t *) tagp;
 485                                flags = be32_to_cpu(tag->t_flags);
 486
 487                                io_block = next_log_block++;
 488                                wrap(journal, next_log_block);
 489                                err = jread(&obh, journal, io_block);
 490                                if (err) {
 491                                        /* Recover what we can, but
 492                                         * report failure at the end. */
 493                                        success = err;
 494                                        printk(KERN_ERR
 495                                                "JBD2: IO error %d recovering "
 496                                                "block %ld in log\n",
 497                                                err, io_block);
 498                                } else {
 499                                        unsigned long long blocknr;
 500
 501                                        J_ASSERT(obh != NULL);
 502                                        blocknr = read_tag_block(tag_bytes,
 503                                                                 tag);
 504
 505                                        /* If the block has been
 506                                         * revoked, then we're all done
 507                                         * here. */
 508                                        if (jbd2_journal_test_revoke
 509                                            (journal, blocknr,
 510                                             next_commit_ID)) {
 511                                                brelse(obh);
 512                                                ++info->nr_revoke_hits;
 513                                                goto skip_write;
 514                                        }
 515
 516                                        /* Find a buffer for the new
 517                                         * data being restored */
 518                                        nbh = __getblk(journal->j_fs_dev,
 519                                                        blocknr,
 520                                                        journal->j_blocksize);
 521                                        if (nbh == NULL) {
 522                                                printk(KERN_ERR
 523                                                       "JBD2: Out of memory "
 524                                                       "during recovery.\n");
 525                                                err = -ENOMEM;
 526                                                brelse(bh);
 527                                                brelse(obh);
 528                                                goto failed;
 529                                        }
 530
 531                                        lock_buffer(nbh);
 532                                        memcpy(nbh->b_data, obh->b_data,
 533                                                        journal->j_blocksize);
 534                                        if (flags & JBD2_FLAG_ESCAPE) {
 535                                                *((__be32 *)nbh->b_data) =
 536                                                cpu_to_be32(JBD2_MAGIC_NUMBER);
 537                                        }
 538
 539                                        BUFFER_TRACE(nbh, "marking dirty");
 540                                        set_buffer_uptodate(nbh);
 541                                        mark_buffer_dirty(nbh);
 542                                        BUFFER_TRACE(nbh, "marking uptodate");
 543                                        ++info->nr_replays;
 544                                        /* ll_rw_block(WRITE, 1, &nbh); */
 545                                        unlock_buffer(nbh);
 546                                        brelse(obh);
 547                                        brelse(nbh);
 548                                }
 549
 550                        skip_write:
 551                                tagp += tag_bytes;
 552                                if (!(flags & JBD2_FLAG_SAME_UUID))
 553                                        tagp += 16;
 554
 555                                if (flags & JBD2_FLAG_LAST_TAG)
 556                                        break;
 557                        }
 558
 559                        brelse(bh);
 560                        continue;
 561
 562                case JBD2_COMMIT_BLOCK:
 563                        /*     How to differentiate between interrupted commit
 564                         *               and journal corruption ?
 565                         *
 566                         * {nth transaction}
 567                         *        Checksum Verification Failed
 568                         *                       |
 569                         *               ____________________
 570                         *              |                    |
 571                         *      async_commit             sync_commit
 572                         *              |                    |
 573                         *              | GO TO NEXT    "Journal Corruption"
 574                         *              | TRANSACTION
 575                         *              |
 576                         * {(n+1)th transanction}
 577                         *              |
 578                         *       _______|______________
 579                         *      |                     |
 580                         * Commit block found   Commit block not found
 581                         *      |                     |
 582                         * "Journal Corruption"       |
 583                         *               _____________|_________
 584                         *              |                       |
 585                         *      nth trans corrupt       OR   nth trans
 586                         *      and (n+1)th interrupted     interrupted
 587                         *      before commit block
 588                         *      could reach the disk.
 589                         *      (Cannot find the difference in above
 590                         *       mentioned conditions. Hence assume
 591                         *       "Interrupted Commit".)
 592                         */
 593
 594                        /* Found an expected commit block: if checksums
 595                         * are present verify them in PASS_SCAN; else not
 596                         * much to do other than move on to the next sequence
 597                         * number. */
 598                        if (pass == PASS_SCAN &&
 599                            JBD2_HAS_COMPAT_FEATURE(journal,
 600                                    JBD2_FEATURE_COMPAT_CHECKSUM)) {
 601                                int chksum_err, chksum_seen;
 602                                struct commit_header *cbh =
 603                                        (struct commit_header *)bh->b_data;
 604                                unsigned found_chksum =
 605                                        be32_to_cpu(cbh->h_chksum[0]);
 606
 607                                chksum_err = chksum_seen = 0;
 608
 609                                if (info->end_transaction) {
 610                                        journal->j_failed_commit =
 611                                                info->end_transaction;
 612                                        brelse(bh);
 613                                        break;
 614                                }
 615
 616                                if (crc32_sum == found_chksum &&
 617                                    cbh->h_chksum_type == JBD2_CRC32_CHKSUM &&
 618                                    cbh->h_chksum_size ==
 619                                                JBD2_CRC32_CHKSUM_SIZE)
 620                                       chksum_seen = 1;
 621                                else if (!(cbh->h_chksum_type == 0 &&
 622                                             cbh->h_chksum_size == 0 &&
 623                                             found_chksum == 0 &&
 624                                             !chksum_seen))
 625                                /*
 626                                 * If fs is mounted using an old kernel and then
 627                                 * kernel with journal_chksum is used then we
 628                                 * get a situation where the journal flag has
 629                                 * checksum flag set but checksums are not
 630                                 * present i.e chksum = 0, in the individual
 631                                 * commit blocks.
 632                                 * Hence to avoid checksum failures, in this
 633                                 * situation, this extra check is added.
 634                                 */
 635                                                chksum_err = 1;
 636
 637                                if (chksum_err) {
 638                                        info->end_transaction = next_commit_ID;
 639
 640                                        if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 641                                           JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)){
 642                                                journal->j_failed_commit =
 643                                                        next_commit_ID;
 644                                                brelse(bh);
 645                                                break;
 646                                        }
 647                                }
 648                                crc32_sum = ~0;
 649                        }
 650                        brelse(bh);
 651                        next_commit_ID++;
 652                        continue;
 653
 654                case JBD2_REVOKE_BLOCK:
 655                        /* If we aren't in the REVOKE pass, then we can
 656                         * just skip over this block. */
 657                        if (pass != PASS_REVOKE) {
 658                                brelse(bh);
 659                                continue;
 660                        }
 661
 662                        err = scan_revoke_records(journal, bh,
 663                                                  next_commit_ID, info);
 664                        brelse(bh);
 665                        if (err)
 666                                goto failed;
 667                        continue;
 668
 669                default:
 670                        jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
 671                                  blocktype);
 672                        brelse(bh);
 673                        goto done;
 674                }
 675        }
 676
 677 done:
 678        /*
 679         * We broke out of the log scan loop: either we came to the
 680         * known end of the log or we found an unexpected block in the
 681         * log.  If the latter happened, then we know that the "current"
 682         * transaction marks the end of the valid log.
 683         */
 684
 685        if (pass == PASS_SCAN) {
 686                if (!info->end_transaction)
 687                        info->end_transaction = next_commit_ID;
 688        } else {
 689                /* It's really bad news if different passes end up at
 690                 * different places (but possible due to IO errors). */
 691                if (info->end_transaction != next_commit_ID) {
 692                        printk(KERN_ERR "JBD2: recovery pass %d ended at "
 693                                "transaction %u, expected %u\n",
 694                                pass, next_commit_ID, info->end_transaction);
 695                        if (!success)
 696                                success = -EIO;
 697                }
 698        }
 699
 700        return success;
 701
 702 failed:
 703        return err;
 704}
 705
 706
 707/* Scan a revoke record, marking all blocks mentioned as revoked. */
 708
 709static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
 710                               tid_t sequence, struct recovery_info *info)
 711{
 712        jbd2_journal_revoke_header_t *header;
 713        int offset, max;
 714        int record_len = 4;
 715
 716        header = (jbd2_journal_revoke_header_t *) bh->b_data;
 717        offset = sizeof(jbd2_journal_revoke_header_t);
 718        max = be32_to_cpu(header->r_count);
 719
 720        if (JBD2_HAS_INCOMPAT_FEATURE(journal, JBD2_FEATURE_INCOMPAT_64BIT))
 721                record_len = 8;
 722
 723        while (offset + record_len <= max) {
 724                unsigned long long blocknr;
 725                int err;
 726
 727                if (record_len == 4)
 728                        blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
 729                else
 730                        blocknr = be64_to_cpu(* ((__be64 *) (bh->b_data+offset)));
 731                offset += record_len;
 732                err = jbd2_journal_set_revoke(journal, blocknr, sequence);
 733                if (err)
 734                        return err;
 735                ++info->nr_revokes;
 736        }
 737        return 0;
 738}
 739