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
