2013-05-06 16:06:07

by Maarten ter Huurne

Subject: [PATCH] ext4: Fixed corruption when online resizing a fs with 1K block size

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.

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

2013-05-08 13:58:25

by Jan Kara

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 <[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

2013-06-17 13:07:03

by Theodore Ts'o

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

On Wed, May 08, 2013 at 03:58:25PM +0200, Jan Kara wrote:
> 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]>

Applied, thanks.

- Ted