[PATCH 028/270] ext4: remove erroneous ext4_superblock_csum_set() in update_backups()

[Ben Hutchings]

On Mon, 2012-11-26 at 14:55 -0200, Herton Ronaldo Krzesinski wrote:
> 3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Tao Ma <boyu.mt at taobao.com>
> 
> commit bef53b01faeb791e27605cba1a71ba21364cb23e upstream.
> 
> The update_backups() function is used to backup all the metadata
> blocks, so we should not take it for granted that 'data' is pointed to
> a super block and use ext4_superblock_csum_set to calculate the
> checksum there.  In case where the data is a group descriptor block,
> it will corrupt the last group descriptor, and then e2fsck will
> complain about it it.
> 
> As all the metadata checksums should already be OK when we do the
> backup, remove the wrong ext4_superblock_csum_set and it should be
> just fine.
> 
> Reported-by: "Theodore Ts'o" <tytso at mit.edu>
> Signed-off-by: Tao Ma <boyu.mt at taobao.com>
> Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
> [ herton: adjust context ]
> Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>

This should also be applicable to 3.6.

Ben.

> ---
>  fs/ext4/resize.c |    2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index b0bdd10..dc1affc 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -979,8 +979,6 @@ static void update_backups(struct super_block *sb,
>  		goto exit_err;
>  	}
>  
> -	ext4_superblock_csum_set(sb, (struct ext4_super_block *)data);
> -
>  	while ((group = ext4_list_backups(sb, &three, &five, &seven)) < last) {
>  		struct buffer_head *bh;
>  

-- 
Ben Hutchings
Never attribute to conspiracy what can adequately be explained by stupidity.
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