linux-kernel - Re: [PATCH] ext4: Fixed corruption when online resizing a fs with 1K block size

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Message-ID: <20130508135825.GA3810@quack.suse.cz>
Date:	Wed, 8 May 2013 15:58:25 +0200
From:	Jan Kara <jack@...e.cz>
To:	Maarten ter Huurne <maarten@...ewalker.org>
Cc:	Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ext4: Fixed corruption when online resizing a fs with 1K
 block size

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 <jack@...e.cz>

								Honza
> 
> Signed-off-by: Maarten ter Huurne <maarten@...ewalker.org>
> ---
>  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 <jack@...e.cz>
SUSE Labs, CR
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