fix-resize-nonstd-blocks-per-group

   1 ext4: fix online resize with a non-standard blocks per group setting
   2
   3 The set_flexbg_block_bitmap() function assumed that the number of
   4 blocks in a blockgroup was sb->blocksize * 8, which is normally true,
   5 but not always!  Use EXT4_BLOCKS_PER_GROUP(sb) instead, to fix block
   6 bitmap corruption after:
   7
   8 mke2fs -t ext4 -g 3072 -i 4096 /dev/vdd 1G
   9 mount -t ext4 /dev/vdd /vdd
  10 resize2fs /dev/vdd 8G
  11
  12 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
  13 Reported-by: Jon Bernard <jbernard@tuxion.com>
  14 Cc: stable@vger.kernel.org
  15 ---
  16  fs/ext4/resize.c | 2 +-
  17  1 file changed, 1 insertion(+), 1 deletion(-)
  18
  19 diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
  20 index 69a6261..f3b84cd 100644
  21 --- a/fs/ext4/resize.c
  22 +++ b/fs/ext4/resize.c
  23 @@ -409,7 +409,7 @@ static int set_flexbg_block_bitmap(struct super_block *sb, handle_t *handle,
  24                 start = ext4_group_first_block_no(sb, group);
  25                 group -= flex_gd->groups[0].group;
  26
  27 -               count2 = sb->s_blocksize * 8 - (block - start);
  28 +               count2 = EXT4_BLOCKS_PER_GROUP(sb) - (block - start);
  29                 if (count2 > count)
  30                         count2 = count;
  31