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    Subject[PATCH 4.2.y-ckt 045/211] [PATCH] fix calculation of meta_bg descriptor backups
    Date
    4.2.8-ckt1 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Andy Leiserson <andy@leiserson.org>

    commit 904dad4742d211b7a8910e92695c0fa957483836 upstream.

    "group" is the group where the backup will be placed, and is
    initialized to zero in the declaration. This meant that backups for
    meta_bg descriptors were erroneously written to the backup block group
    descriptors in groups 1 and (desc_per_block-1).

    Reproduction information:
    mke2fs -Fq -t ext4 -b 1024 -O ^resize_inode /tmp/foo.img 16G
    truncate -s 24G /tmp/foo.img
    losetup /dev/loop0 /tmp/foo.img
    mount /dev/loop0 /mnt
    resize2fs /dev/loop0
    umount /dev/loop0
    dd if=/dev/zero of=/dev/loop0 bs=1024 count=2
    e2fsck -fy /dev/loop0
    losetup -d /dev/loop0

    Signed-off-by: Andy Leiserson <andy@leiserson.org>
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    fs/ext4/resize.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
    index cf0c472..c7c53fd 100644
    --- a/fs/ext4/resize.c
    +++ b/fs/ext4/resize.c
    @@ -1040,7 +1040,7 @@ exit_free:
    * do not copy the full number of backups at this time. The resize
    * which changed s_groups_count will backup again.
    */
    -static void update_backups(struct super_block *sb, int blk_off, char *data,
    +static void update_backups(struct super_block *sb, sector_t blk_off, char *data,
    int size, int meta_bg)
    {
    struct ext4_sb_info *sbi = EXT4_SB(sb);
    @@ -1065,7 +1065,7 @@ static void update_backups(struct super_block *sb, int blk_off, char *data,
    group = ext4_list_backups(sb, &three, &five, &seven);
    last = sbi->s_groups_count;
    } else {
    - group = ext4_meta_bg_first_group(sb, group) + 1;
    + group = ext4_get_group_number(sb, blk_off) + 1;
    last = (ext4_group_t)(group + EXT4_DESC_PER_BLOCK(sb) - 2);
    }

    --
    1.9.1


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