releases/3.6.2/ext4-avoid-duplicate-writes-of-the-backup-bg-descriptor-blocks.patch

   1 From 2ebd1704ded88a8ae29b5f3998b13959c715c4be Mon Sep 17 00:00:00 2001
   2 From: Yongqiang Yang <xiaoqiangnk@gmail.com>
   3 Date: Wed, 5 Sep 2012 01:27:50 -0400
   4 Subject: ext4: avoid duplicate writes of the backup bg descriptor blocks
   5
   6 From: Yongqiang Yang <xiaoqiangnk@gmail.com>
   7
   8 commit 2ebd1704ded88a8ae29b5f3998b13959c715c4be upstream.
   9
  10 The resize code was needlessly writing the backup block group
  11 descriptor blocks multiple times (once per block group) during an
  12 online resize.
  13
  14 Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
  15 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
  16 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  17
  18 ---
  19  fs/ext4/resize.c |   10 ++++++----
  20  1 file changed, 6 insertions(+), 4 deletions(-)
  21
  22 --- a/fs/ext4/resize.c
  23 +++ b/fs/ext4/resize.c
  24 @@ -1358,13 +1358,15 @@ exit_journal:
  25                 err = err2;
  26
  27         if (!err) {
  28 -               int i;
  29 +               int gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
  30 +               int gdb_num_end = ((group + flex_gd->count - 1) /
  31 +                                  EXT4_DESC_PER_BLOCK(sb));
  32 +
  33                 update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
  34                                sizeof(struct ext4_super_block));
  35 -               for (i = 0; i < flex_gd->count; i++, group++) {
  36 +               for (; gdb_num <= gdb_num_end; gdb_num++) {
  37                         struct buffer_head *gdb_bh;
  38 -                       int gdb_num;
  39 -                       gdb_num = group / EXT4_BLOCKS_PER_GROUP(sb);
  40 +
  41                         gdb_bh = sbi->s_group_desc[gdb_num];
  42                         update_backups(sb, gdb_bh->b_blocknr, gdb_bh->b_data,
  43                                        gdb_bh->b_size);