// SPDX-License-Identifier: GPL-2.0+
/*
 * linux/fs/jbd2/recovery.c
 *
 * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
 *
 * Copyright 1999-2000 Red Hat Software --- All Rights Reserved
 *
 * Journal recovery routines for the generic filesystem journaling code;
 * part of the ext2fs journaling system.
 */

#ifndef __KERNEL__
#include "jfs_user.h"
#else
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/jbd2.h>
#include <linux/errno.h>
#include <linux/crc32.h>
#include <linux/blkdev.h>
#endif

/*
 * Maintain information about the progress of the recovery job, so that
 * the different passes can carry information between them.
 */
struct recovery_info
{
        tid_t           start_transaction;
        tid_t           end_transaction;

        int             nr_replays;
        int             nr_revokes;
        int             nr_revoke_hits;
};

enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
static int do_one_pass(journal_t *journal,
                                struct recovery_info *info, enum passtype pass);
static int scan_revoke_records(journal_t *, struct buffer_head *,
                                tid_t, struct recovery_info *);

#ifdef __KERNEL__

/* Release readahead buffers after use */
static void journal_brelse_array(struct buffer_head *b[], int n)
{
        while (--n >= 0)
                brelse (b[n]);
}


/*
 * When reading from the journal, we are going through the block device
 * layer directly and so there is no readahead being done for us.  We
 * need to implement any readahead ourselves if we want it to happen at
 * all.  Recovery is basically one long sequential read, so make sure we
 * do the IO in reasonably large chunks.
 *
 * This is not so critical that we need to be enormously clever about
 * the readahead size, though.  128K is a purely arbitrary, good-enough
 * fixed value.
 */

#define MAXBUF 8
static int do_readahead(journal_t *journal, unsigned int start)
{
        int err;
        unsigned int max, nbufs, next;
        unsigned long long blocknr;
        struct buffer_head *bh;

        struct buffer_head * bufs[MAXBUF];

        /* Do up to 128K of readahead */
        max = start + (128 * 1024 / journal->j_blocksize);
        if (max > journal->j_maxlen)
                max = journal->j_maxlen;

        /* Do the readahead itself.  We'll submit MAXBUF buffer_heads at
         * a time to the block device IO layer. */

        nbufs = 0;

        for (next = start; next < max; next++) {
                err = jbd2_journal_bmap(journal, next, &blocknr);

                if (err) {
                        printk(KERN_ERR "JBD2: bad block at offset %u\n",
                                next);
                        goto failed;
                }

                bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
                if (!bh) {
                        err = -ENOMEM;
                        goto failed;
                }

                if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
                        bufs[nbufs++] = bh;
                        if (nbufs == MAXBUF) {
                                ll_rw_block(REQ_OP_READ, 0, nbufs, bufs);
                                journal_brelse_array(bufs, nbufs);
                                nbufs = 0;
                        }
                } else
                        brelse(bh);
        }

        if (nbufs)
                ll_rw_block(REQ_OP_READ, 0, nbufs, bufs);
        err = 0;

failed:
        if (nbufs)
                journal_brelse_array(bufs, nbufs);
        return err;
}

#endif /* __KERNEL__ */


/*
 * Read a block from the journal
 */

static int jread(struct buffer_head **bhp, journal_t *journal,
                 unsigned int offset)
{
        int err;
        unsigned long long blocknr;
        struct buffer_head *bh;

        *bhp = NULL;

        if (offset >= journal->j_maxlen) {
                printk(KERN_ERR "JBD2: corrupted journal superblock\n");
                return -EFSCORRUPTED;
        }

        err = jbd2_journal_bmap(journal, offset, &blocknr);

        if (err) {
                printk(KERN_ERR "JBD2: bad block at offset %u\n",
                        offset);
                return err;
        }

        bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
        if (!bh)
                return -ENOMEM;

        if (!buffer_uptodate(bh)) {
                /* If this is a brand new buffer, start readahead.
                   Otherwise, we assume we are already reading it.  */
                if (!buffer_req(bh))
                        do_readahead(journal, offset);
                wait_on_buffer(bh);
        }

        if (!buffer_uptodate(bh)) {
                printk(KERN_ERR "JBD2: Failed to read block at offset %u\n",
                        offset);
                brelse(bh);
                return -EIO;
        }

        *bhp = bh;
        return 0;
}

static int jbd2_descriptor_block_csum_verify(journal_t *j, void *buf)
{
        struct jbd2_journal_block_tail *tail;
        __be32 provided;
        __u32 calculated;

        if (!jbd2_journal_has_csum_v2or3(j))
                return 1;

        tail = (struct jbd2_journal_block_tail *)(buf + j->j_blocksize -
                        sizeof(struct jbd2_journal_block_tail));
        provided = tail->t_checksum;
        tail->t_checksum = 0;
        calculated = jbd2_chksum(j, j->j_csum_seed, buf, j->j_blocksize);
        tail->t_checksum = provided;

        return provided == cpu_to_be32(calculated);
}

/*
 * Count the number of in-use tags in a journal descriptor block.
 */

static int count_tags(journal_t *journal, struct buffer_head *bh)
{
        char *                  tagp;
        journal_block_tag_t *   tag;
        int                     nr = 0, size = journal->j_blocksize;
        int                     tag_bytes = journal_tag_bytes(journal);

        if (jbd2_journal_has_csum_v2or3(journal))
                size -= sizeof(struct jbd2_journal_block_tail);

        tagp = &bh->b_data[sizeof(journal_header_t)];

        while ((tagp - bh->b_data + tag_bytes) <= size) {
                tag = (journal_block_tag_t *) tagp;

                nr++;
                tagp += tag_bytes;
                if (!(tag->t_flags & cpu_to_be16(JBD2_FLAG_SAME_UUID)))
                        tagp += 16;

                if (tag->t_flags & cpu_to_be16(JBD2_FLAG_LAST_TAG))
                        break;
        }

        return nr;
}


/* Make sure we wrap around the log correctly! */
#define wrap(journal, var)                                              \
do {                                                                    \
        if (var >= (journal)->j_last)                                   \
                var -= ((journal)->j_last - (journal)->j_first);        \
} while (0)

/**
 * jbd2_journal_recover - recovers a on-disk journal
 * @journal: the journal to recover
 *
 * The primary function for recovering the log contents when mounting a
 * journaled device.
 *
 * Recovery is done in three passes.  In the first pass, we look for the
 * end of the log.  In the second, we assemble the list of revoke
 * blocks.  In the third and final pass, we replay any un-revoked blocks
 * in the log.
 */
int jbd2_journal_recover(journal_t *journal)
{
        int                     err, err2;
        journal_superblock_t *  sb;

        struct recovery_info    info;

        memset(&info, 0, sizeof(info));
        sb = journal->j_superblock;

        /*
         * The journal superblock's s_start field (the current log head)
         * is always zero if, and only if, the journal was cleanly
         * unmounted.
         */

        if (!sb->s_start) {
                jbd_debug(1, "No recovery required, last transaction %d\n",
                          be32_to_cpu(sb->s_sequence));
                journal->j_transaction_sequence = be32_to_cpu(sb->s_sequence) + 1;
                return 0;
        }

        err = do_one_pass(journal, &info, PASS_SCAN);
        if (!err)
                err = do_one_pass(journal, &info, PASS_REVOKE);
        if (!err)
                err = do_one_pass(journal, &info, PASS_REPLAY);

        jbd_debug(1, "JBD2: recovery, exit status %d, "
                  "recovered transactions %u to %u\n",
                  err, info.start_transaction, info.end_transaction);
        jbd_debug(1, "JBD2: Replayed %d and revoked %d/%d blocks\n",
                  info.nr_replays, info.nr_revoke_hits, info.nr_revokes);

        /* Restart the log at the next transaction ID, thus invalidating
         * any existing commit records in the log. */
        journal->j_transaction_sequence = ++info.end_transaction;

        jbd2_journal_clear_revoke(journal);
        err2 = sync_blockdev(journal->j_fs_dev);
        if (!err)
                err = err2;
        /* Make sure all replayed data is on permanent storage */
        if (journal->j_flags & JBD2_BARRIER) {
                err2 = blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
                if (!err)
                        err = err2;
        }
        return err;
}

/**
 * jbd2_journal_skip_recovery - Start journal and wipe exiting records
 * @journal: journal to startup
 *
 * Locate any valid recovery information from the journal and set up the
 * journal structures in memory to ignore it (presumably because the
 * caller has evidence that it is out of date).
 * This function doesn't appear to be exported..
 *
 * We perform one pass over the journal to allow us to tell the user how
 * much recovery information is being erased, and to let us initialise
 * the journal transaction sequence numbers to the next unused ID.
 */
int jbd2_journal_skip_recovery(journal_t *journal)
{
        int                     err;

        struct recovery_info    info;

        memset (&info, 0, sizeof(info));

        err = do_one_pass(journal, &info, PASS_SCAN);

        if (err) {
                printk(KERN_ERR "JBD2: error %d scanning journal\n", err);
                ++journal->j_transaction_sequence;
        } else {
#ifdef CONFIG_JBD2_DEBUG
                int dropped = info.end_transaction - 
                        be32_to_cpu(journal->j_superblock->s_sequence);
                jbd_debug(1,
                          "JBD2: ignoring %d transaction%s from the journal.\n",
                          dropped, (dropped == 1) ? "" : "s");
#endif
                journal->j_transaction_sequence = ++info.end_transaction;
        }

        journal->j_tail = 0;
        return err;
}

static inline unsigned long long read_tag_block(journal_t *journal,
                                                journal_block_tag_t *tag)
{
        unsigned long long block = be32_to_cpu(tag->t_blocknr);
        if (jbd2_has_feature_64bit(journal))
                block |= (u64)be32_to_cpu(tag->t_blocknr_high) << 32;
        return block;
}

/*
 * calc_chksums calculates the checksums for the blocks described in the
 * descriptor block.
 */
static int calc_chksums(journal_t *journal, struct buffer_head *bh,
                        unsigned long *next_log_block, __u32 *crc32_sum)
{
        int i, num_blks, err;
        unsigned long io_block;
        struct buffer_head *obh;

        num_blks = count_tags(journal, bh);
        /* Calculate checksum of the descriptor block. */
        *crc32_sum = crc32_be(*crc32_sum, (void *)bh->b_data, bh->b_size);

        for (i = 0; i < num_blks; i++) {
                io_block = (*next_log_block)++;
                wrap(journal, *next_log_block);
                err = jread(&obh, journal, io_block);
                if (err) {
                        printk(KERN_ERR "JBD2: IO error %d recovering block "
                                "%lu in log\n", err, io_block);
                        return 1;
                } else {
                        *crc32_sum = crc32_be(*crc32_sum, (void *)obh->b_data,
                                     obh->b_size);
                }
                put_bh(obh);
        }
        return 0;
}

static int jbd2_commit_block_csum_verify(journal_t *j, void *buf)
{
        struct commit_header *h;
        __be32 provided;
        __u32 calculated;

        if (!jbd2_journal_has_csum_v2or3(j))
                return 1;

        h = buf;
        provided = h->h_chksum[0];
        h->h_chksum[0] = 0;
        calculated = jbd2_chksum(j, j->j_csum_seed, buf, j->j_blocksize);
        h->h_chksum[0] = provided;

        return provided == cpu_to_be32(calculated);
}

static int jbd2_block_tag_csum_verify(journal_t *j, journal_block_tag_t *tag,
                                      void *buf, __u32 sequence)
{
        journal_block_tag3_t *tag3 = (journal_block_tag3_t *)tag;
        __u32 csum32;
        __be32 seq;

        if (!jbd2_journal_has_csum_v2or3(j))
                return 1;

        seq = cpu_to_be32(sequence);
        csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&seq, sizeof(seq));
        csum32 = jbd2_chksum(j, csum32, buf, j->j_blocksize);

        if (jbd2_has_feature_csum3(j))
                return tag3->t_checksum == cpu_to_be32(csum32);
        else
                return tag->t_checksum == cpu_to_be16(csum32);
}

static int do_one_pass(journal_t *journal,
                        struct recovery_info *info, enum passtype pass)
{
        unsigned int            first_commit_ID, next_commit_ID;
        unsigned long           next_log_block;
        int                     err, success = 0;
        journal_superblock_t *  sb;
        journal_header_t *      tmp;
        struct buffer_head *    bh;
        unsigned int            sequence;
        int                     blocktype;
        int                     tag_bytes = journal_tag_bytes(journal);
        __u32                   crc32_sum = ~0; /* Transactional Checksums */
        int                     descr_csum_size = 0;
        int                     block_error = 0;

        /*
         * First thing is to establish what we expect to find in the log
         * (in terms of transaction IDs), and where (in terms of log
         * block offsets): query the superblock.
         */

        sb = journal->j_superblock;
        next_commit_ID = be32_to_cpu(sb->s_sequence);
        next_log_block = be32_to_cpu(sb->s_start);

        first_commit_ID = next_commit_ID;
        if (pass == PASS_SCAN)
                info->start_transaction = first_commit_ID;

        jbd_debug(1, "Starting recovery pass %d\n", pass);

        /*
         * Now we walk through the log, transaction by transaction,
         * making sure that each transaction has a commit block in the
         * expected place.  Each complete transaction gets replayed back
         * into the main filesystem.
         */

        while (1) {
                int                     flags;
                char *                  tagp;
                journal_block_tag_t *   tag;
                struct buffer_head *    obh;
                struct buffer_head *    nbh;

                cond_resched();

                /* If we already know where to stop the log traversal,
                 * check right now that we haven't gone past the end of
                 * the log. */

                if (pass != PASS_SCAN)
                        if (tid_geq(next_commit_ID, info->end_transaction))
                                break;

                jbd_debug(2, "Scanning for sequence ID %u at %lu/%lu\n",
                          next_commit_ID, next_log_block, journal->j_last);

                /* Skip over each chunk of the transaction looking
                 * either the next descriptor block or the final commit
                 * record. */

                jbd_debug(3, "JBD2: checking block %ld\n", next_log_block);
                err = jread(&bh, journal, next_log_block);
                if (err)
                        goto failed;

                next_log_block++;
                wrap(journal, next_log_block);

                /* What kind of buffer is it?
                 *
                 * If it is a descriptor block, check that it has the
                 * expected sequence number.  Otherwise, we're all done
                 * here. */

                tmp = (journal_header_t *)bh->b_data;

                if (tmp->h_magic != cpu_to_be32(JBD2_MAGIC_NUMBER)) {
                        brelse(bh);
                        break;
                }

                blocktype = be32_to_cpu(tmp->h_blocktype);
                sequence = be32_to_cpu(tmp->h_sequence);
                jbd_debug(3, "Found magic %d, sequence %d\n",
                          blocktype, sequence);

                if (sequence != next_commit_ID) {
                        brelse(bh);
                        break;
                }

                /* OK, we have a valid descriptor block which matches
                 * all of the sequence number checks.  What are we going
                 * to do with it?  That depends on the pass... */

                switch(blocktype) {
                case JBD2_DESCRIPTOR_BLOCK:
                        /* Verify checksum first */
                        if (jbd2_journal_has_csum_v2or3(journal))
                                descr_csum_size =
                                        sizeof(struct jbd2_journal_block_tail);
                        if (descr_csum_size > 0 &&
                            !jbd2_descriptor_block_csum_verify(journal,
                                                               bh->b_data)) {
                                printk(KERN_ERR "JBD2: Invalid checksum "
                                       "recovering block %lu in log\n",
                                       next_log_block);
                                err = -EFSBADCRC;
                                brelse(bh);
                                goto failed;
                        }

                        /* If it is a valid descriptor block, replay it
                         * in pass REPLAY; if journal_checksums enabled, then
                         * calculate checksums in PASS_SCAN, otherwise,
                         * just skip over the blocks it describes. */
                        if (pass != PASS_REPLAY) {
                                if (pass == PASS_SCAN &&
                                    jbd2_has_feature_checksum(journal) &&
                                    !info->end_transaction) {
                                        if (calc_chksums(journal, bh,
                                                        &next_log_block,
                                                        &crc32_sum)) {
                                                put_bh(bh);
                                                break;
                                        }
                                        put_bh(bh);
                                        continue;
                                }
                                next_log_block += count_tags(journal, bh);
                                wrap(journal, next_log_block);
                                put_bh(bh);
                                continue;
                        }

                        /* A descriptor block: we can now write all of
                         * the data blocks.  Yay, useful work is finally
                         * getting done here! */

                        tagp = &bh->b_data[sizeof(journal_header_t)];
                        while ((tagp - bh->b_data + tag_bytes)
                               <= journal->j_blocksize - descr_csum_size) {
                                unsigned long io_block;

                                tag = (journal_block_tag_t *) tagp;
                                flags = be16_to_cpu(tag->t_flags);

                                io_block = next_log_block++;
                                wrap(journal, next_log_block);
                                err = jread(&obh, journal, io_block);
                                if (err) {
                                        /* Recover what we can, but
                                         * report failure at the end. */
                                        success = err;
                                        printk(KERN_ERR
                                                "JBD2: IO error %d recovering "
                                                "block %ld in log\n",
                                                err, io_block);
                                } else {
                                        unsigned long long blocknr;

                                        J_ASSERT(obh != NULL);
                                        blocknr = read_tag_block(journal,
                                                                 tag);

                                        /* If the block has been
                                         * revoked, then we're all done
                                         * here. */
                                        if (jbd2_journal_test_revoke
                                            (journal, blocknr,
                                             next_commit_ID)) {
                                                brelse(obh);
                                                ++info->nr_revoke_hits;
                                                goto skip_write;
                                        }

                                        /* Look for block corruption */
                                        if (!jbd2_block_tag_csum_verify(
                                                journal, tag, obh->b_data,
                                                be32_to_cpu(tmp->h_sequence))) {
                                                brelse(obh);
                                                success = -EFSBADCRC;
                                                printk(KERN_ERR "JBD2: Invalid "
                                                       "checksum recovering "
                                                       "data block %llu in "
                                                       "log\n", blocknr);
                                                block_error = 1;
                                                goto skip_write;
                                        }

                                        /* Find a buffer for the new
                                         * data being restored */
                                        nbh = __getblk(journal->j_fs_dev,
                                                        blocknr,
                                                        journal->j_blocksize);
                                        if (nbh == NULL) {
                                                printk(KERN_ERR
                                                       "JBD2: Out of memory "
                                                       "during recovery.\n");
                                                err = -ENOMEM;
                                                brelse(bh);
                                                brelse(obh);
                                                goto failed;
                                        }

                                        lock_buffer(nbh);
                                        memcpy(nbh->b_data, obh->b_data,
                                                        journal->j_blocksize);
                                        if (flags & JBD2_FLAG_ESCAPE) {
                                                *((__be32 *)nbh->b_data) =
                                                cpu_to_be32(JBD2_MAGIC_NUMBER);
                                        }

                                        BUFFER_TRACE(nbh, "marking dirty");
                                        set_buffer_uptodate(nbh);
                                        mark_buffer_dirty(nbh);
                                        BUFFER_TRACE(nbh, "marking uptodate");
                                        ++info->nr_replays;
                                        /* ll_rw_block(WRITE, 1, &nbh); */
                                        unlock_buffer(nbh);
                                        brelse(obh);
                                        brelse(nbh);
                                }

                        skip_write:
                                tagp += tag_bytes;
                                if (!(flags & JBD2_FLAG_SAME_UUID))
                                        tagp += 16;

                                if (flags & JBD2_FLAG_LAST_TAG)
                                        break;
                        }

                        brelse(bh);
                        continue;

                case JBD2_COMMIT_BLOCK:
                        /*     How to differentiate between interrupted commit
                         *               and journal corruption ?
                         *
                         * {nth transaction}
                         *        Checksum Verification Failed
                         *                       |
                         *               ____________________
                         *              |                    |
                         *      async_commit             sync_commit
                         *              |                    |
                         *              | GO TO NEXT    "Journal Corruption"
                         *              | TRANSACTION
                         *              |
                         * {(n+1)th transanction}
                         *              |
                         *       _______|______________
                         *      |                     |
                         * Commit block found   Commit block not found
                         *      |                     |
                         * "Journal Corruption"       |
                         *               _____________|_________
                         *              |                       |
                         *      nth trans corrupt       OR   nth trans
                         *      and (n+1)th interrupted     interrupted
                         *      before commit block
                         *      could reach the disk.
                         *      (Cannot find the difference in above
                         *       mentioned conditions. Hence assume
                         *       "Interrupted Commit".)
                         */

                        /* Found an expected commit block: if checksums
                         * are present verify them in PASS_SCAN; else not
                         * much to do other than move on to the next sequence
                         * number. */
                        if (pass == PASS_SCAN &&
                            jbd2_has_feature_checksum(journal)) {
                                int chksum_err, chksum_seen;
                                struct commit_header *cbh =
                                        (struct commit_header *)bh->b_data;
                                unsigned found_chksum =
                                        be32_to_cpu(cbh->h_chksum[0]);

                                chksum_err = chksum_seen = 0;

                                if (info->end_transaction) {
                                        journal->j_failed_commit =
                                                info->end_transaction;
                                        brelse(bh);
                                        break;
                                }

                                if (crc32_sum == found_chksum &&
                                    cbh->h_chksum_type == JBD2_CRC32_CHKSUM &&
                                    cbh->h_chksum_size ==
                                                JBD2_CRC32_CHKSUM_SIZE)
                                       chksum_seen = 1;
                                else if (!(cbh->h_chksum_type == 0 &&
                                             cbh->h_chksum_size == 0 &&
                                             found_chksum == 0 &&
                                             !chksum_seen))
                                /*
                                 * If fs is mounted using an old kernel and then
                                 * kernel with journal_chksum is used then we
                                 * get a situation where the journal flag has
                                 * checksum flag set but checksums are not
                                 * present i.e chksum = 0, in the individual
                                 * commit blocks.
                                 * Hence to avoid checksum failures, in this
                                 * situation, this extra check is added.
                                 */
                                                chksum_err = 1;

                                if (chksum_err) {
                                        info->end_transaction = next_commit_ID;

                                        if (!jbd2_has_feature_async_commit(journal)) {
                                                journal->j_failed_commit =
                                                        next_commit_ID;
                                                brelse(bh);
                                                break;
                                        }
                                }
                                crc32_sum = ~0;
                        }
                        if (pass == PASS_SCAN &&
                            !jbd2_commit_block_csum_verify(journal,
                                                           bh->b_data)) {
                                info->end_transaction = next_commit_ID;

                                if (!jbd2_has_feature_async_commit(journal)) {
                                        journal->j_failed_commit =
                                                next_commit_ID;
                                        brelse(bh);
                                        break;
                                }
                        }
                        brelse(bh);
                        next_commit_ID++;
                        continue;

                case JBD2_REVOKE_BLOCK:
                        /* If we aren't in the REVOKE pass, then we can
                         * just skip over this block. */
                        if (pass != PASS_REVOKE) {
                                brelse(bh);
                                continue;
                        }

                        err = scan_revoke_records(journal, bh,
                                                  next_commit_ID, info);
                        brelse(bh);
                        if (err)
                                goto failed;
                        continue;

                default:
                        jbd_debug(3, "Unrecognised magic %d, end of scan.\n",
                                  blocktype);
                        brelse(bh);
                        goto done;
                }
        }

 done:
        /*
         * We broke out of the log scan loop: either we came to the
         * known end of the log or we found an unexpected block in the
         * log.  If the latter happened, then we know that the "current"
         * transaction marks the end of the valid log.
         */

        if (pass == PASS_SCAN) {
                if (!info->end_transaction)
                        info->end_transaction = next_commit_ID;
        } else {
                /* It's really bad news if different passes end up at
                 * different places (but possible due to IO errors). */
                if (info->end_transaction != next_commit_ID) {
                        printk(KERN_ERR "JBD2: recovery pass %d ended at "
                                "transaction %u, expected %u\n",
                                pass, next_commit_ID, info->end_transaction);
                        if (!success)
                                success = -EIO;
                }
        }
        if (block_error && success == 0)
                success = -EIO;
        return success;

 failed:
        return err;
}

/* Scan a revoke record, marking all blocks mentioned as revoked. */

static int scan_revoke_records(journal_t *journal, struct buffer_head *bh,
                               tid_t sequence, struct recovery_info *info)
{
        jbd2_journal_revoke_header_t *header;
        int offset, max;
        int csum_size = 0;
        __u32 rcount;
        int record_len = 4;

        header = (jbd2_journal_revoke_header_t *) bh->b_data;
        offset = sizeof(jbd2_journal_revoke_header_t);
        rcount = be32_to_cpu(header->r_count);

        if (!jbd2_descriptor_block_csum_verify(journal, header))
                return -EFSBADCRC;

        if (jbd2_journal_has_csum_v2or3(journal))
                csum_size = sizeof(struct jbd2_journal_block_tail);
        if (rcount > journal->j_blocksize - csum_size)
                return -EINVAL;
        max = rcount;

        if (jbd2_has_feature_64bit(journal))
                record_len = 8;

        while (offset + record_len <= max) {
                unsigned long long blocknr;
                int err;

                if (record_len == 4)
                        blocknr = be32_to_cpu(* ((__be32 *) (bh->b_data+offset)));
                else
                        blocknr = be64_to_cpu(* ((__be64 *) (bh->b_data+offset)));
                offset += record_len;
                err = jbd2_journal_set_revoke(journal, blocknr, sequence);
                if (err)
                        return err;
                ++info->nr_revokes;
        }
        return 0;
}