fixed-corruption-when-online-resizing-1k-block-size

   1 ext4: fix corruption when online resizing a fs with 1K block size
   2
   3 From: Maarten ter Huurne <maarten@treewalker.org>
   4
   5 Subtracting the number of the first data block places the superblock
   6 backups one block too early, corrupting the file system. When the block
   7 size is larger than 1K, the first data block is 0, so the subtraction
   8 has no effect and no corruption occurs.
   9
  10 Signed-off-by: Maarten ter Huurne <maarten@treewalker.org>
  11 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
  12 Reviewed-by: Jan Kara <jack@suse.cz>
  13 ---
  14  fs/ext4/resize.c |    4 +---
  15  1 file changed, 1 insertion(+), 3 deletions(-)
  16
  17 diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
  18 index c169477..116c80d 100644
  19 --- a/fs/ext4/resize.c
  20 +++ b/fs/ext4/resize.c
  21 @@ -1654,12 +1654,10 @@ errout:
  22                 err = err2;
  23
  24         if (!err) {
  25 -               ext4_fsblk_t first_block;
  26 -               first_block = ext4_group_first_block_no(sb, 0);
  27                 if (test_opt(sb, DEBUG))
  28                         printk(KERN_DEBUG "EXT4-fs: extended group to %llu "
  29                                "blocks\n", ext4_blocks_count(es));
  30 -               update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr - first_block,
  31 +               update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr,
  32                                (char *)es, sizeof(struct ext4_super_block), 0);
  33         }
  34         return err;
  35 --
  36 1.7.10.4
  37
  38