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    Subject[ 048/122] ext4: avoid duplicate writes of the backup bg descriptor blocks
    Date
    3.6-stable review patch.  If anyone has any objections, please let me know.

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

    From: Yongqiang Yang <xiaoqiangnk@gmail.com>

    commit 2ebd1704ded88a8ae29b5f3998b13959c715c4be upstream.

    The resize code was needlessly writing the backup block group
    descriptor blocks multiple times (once per block group) during an
    online resize.

    Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
    Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ext4/resize.c | 10 ++++++----
    1 file changed, 6 insertions(+), 4 deletions(-)

    --- a/fs/ext4/resize.c
    +++ b/fs/ext4/resize.c
    @@ -1358,13 +1358,15 @@ exit_journal:
    err = err2;

    if (!err) {
    - int i;
    + int gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
    + int gdb_num_end = ((group + flex_gd->count - 1) /
    + EXT4_DESC_PER_BLOCK(sb));
    +
    update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
    sizeof(struct ext4_super_block));
    - for (i = 0; i < flex_gd->count; i++, group++) {
    + for (; gdb_num <= gdb_num_end; gdb_num++) {
    struct buffer_head *gdb_bh;
    - int gdb_num;
    - gdb_num = group / EXT4_BLOCKS_PER_GROUP(sb);
    +
    gdb_bh = sbi->s_group_desc[gdb_num];
    update_backups(sb, gdb_bh->b_blocknr, gdb_bh->b_data,
    gdb_bh->b_size);



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