On Wed 16-11-22 15:28:02, Baokun Li wrote:
> When a backup superblock is updated in update_backups(), the primary
> superblock's offset in the group (that is, sbi->s_sbh->b_blocknr) is used
> as the backup superblock's offset in its group. However, when the block
> size is 1K and bigalloc is enabled, the two offsets are not equal. This
> causes the backup group descriptors to be overwritten by the superblock
> in update_backups(). Moreover, if meta_bg is enabled, the file system will
> be corrupted because this feature uses backup group descriptors.
>
> To solve this issue, we use a more accurate ext4_group_first_block_no() as
> the offset of the backup superblock in its group.
>
> Fixes: d77147ff443b ("ext4: add support for online resizing with bigalloc")
> Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
The patch looks good to me. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> V1->V2:
> Replace s_first_data_block with ext4_group_first_block_no() to avoid
> type warning.(Reported-by: kernel test robot <lkp@xxxxxxxxx>)
>
> fs/ext4/resize.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index 32fbfc173571..98e544c2f97d 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -1591,8 +1591,8 @@ static int ext4_flex_group_add(struct super_block *sb,
> int meta_bg = ext4_has_feature_meta_bg(sb);
> sector_t old_gdb = 0;
>
> - update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
> - sizeof(struct ext4_super_block), 0);
> + update_backups(sb, ext4_group_first_block_no(sb, 0),
> + (char *)es, sizeof(struct ext4_super_block), 0);
> for (; gdb_num <= gdb_num_end; gdb_num++) {
> struct buffer_head *gdb_bh;
>
> @@ -1803,7 +1803,7 @@ static int ext4_group_extend_no_check(struct super_block *sb,
> 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,
> + update_backups(sb, ext4_group_first_block_no(sb, 0),
> (char *)es, sizeof(struct ext4_super_block), 0);
> }
> return err;
> --
> 2.31.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
