Re: [PATCH v2 6/8] ext4: avoid allocating blocks from corrupted group in ext4_mb_try_best_found()

[Jan Kara]

On Thu 21-12-23 23:05:56, Baokun Li wrote:
> Determine if the group block bitmap is corrupted before using ac_b_ex in
> ext4_mb_try_best_found() to avoid allocating blocks from a group with a
> corrupted block bitmap in the following concurrency and making the
> situation worse.
> 
> ext4_mb_regular_allocator
>   ext4_lock_group(sb, group)
>   ext4_mb_good_group
>    // check if the group bbitmap is corrupted
>   ext4_mb_complex_scan_group
>    // Scan group gets ac_b_ex but doesn't use it
>   ext4_unlock_group(sb, group)
>                            ext4_mark_group_bitmap_corrupted(group)
>                            // The block bitmap was corrupted during
>                            // the group unlock gap.
>   ext4_mb_try_best_found
>     ext4_lock_group(ac->ac_sb, group)
>     ext4_mb_use_best_found
>       mb_mark_used
>       // Allocating blocks in block bitmap corrupted group
> 
> Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza

> ---
>  fs/ext4/mballoc.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 03500aec43ac..2bb29f0077bd 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2303,6 +2303,9 @@ void ext4_mb_try_best_found(struct ext4_allocation_context *ac,
>  		return;
>  
>  	ext4_lock_group(ac->ac_sb, group);
> +	if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info)))
> +		goto out;
> +
>  	max = mb_find_extent(e4b, ex.fe_start, ex.fe_len, &ex);
>  
>  	if (max > 0) {
> @@ -2310,6 +2313,7 @@ void ext4_mb_try_best_found(struct ext4_allocation_context *ac,
>  		ext4_mb_use_best_found(ac, e4b);
>  	}
>  
> +out:
>  	ext4_unlock_group(ac->ac_sb, group);
>  	ext4_mb_unload_buddy(e4b);
>  }
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR