On Mon 06-05-13 18:06:07, Maarten ter Huurne wrote:
> Subtracting the number of the first data block places the superblock
> backups one block too early, corrupting the file system. When the block
> size is larger than 1K, the first data block is 0, so the subtraction
> has no effect and no corruption occurs.
  Looking where mke2fs places backup super blocks you are right. You can
add:
Reviewed-by: Jan Kara <[email protected]>

                                                                Honza
> 
> Signed-off-by: Maarten ter Huurne <[email protected]>
> ---
>  fs/ext4/resize.c |    4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index c169477..116c80d 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -1654,12 +1654,10 @@ errout:
>               err = err2;
>  
>       if (!err) {
> -             ext4_fsblk_t first_block;
> -             first_block = ext4_group_first_block_no(sb, 0);
>               if (test_opt(sb, DEBUG))
>                       printk(KERN_DEBUG "EXT4-fs: extended group to %llu "
>                              "blocks\n", ext4_blocks_count(es));
> -             update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr - first_block,
> +             update_backups(sb, EXT4_SB(sb)->s_sbh->b_blocknr,
>                              (char *)es, sizeof(struct ext4_super_block), 0);
>       }
>       return err;
> -- 
> 1.7.10.4
> 
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-- 
Jan Kara <[email protected]>
SUSE Labs, CR
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