On Mon 18-12-23 22:18:14, Baokun Li wrote:
> When bb_free is not 0 but bb_fragments is 0, return directly to avoid
> system crash due to division by zero.
How could this possibly happen? bb_fragments is the number of free space
extents and bb_free is the number of free blocks. No free space extents =>
no free blocks seems pretty obvious? You can see the logic in
ext4_mb_generate_buddy()...
Honza
>
> Fixes: 83e80a6e3543 ("ext4: use buckets for cr 1 block scan instead of rbtree")
> CC: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
> ---
> fs/ext4/mballoc.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 2fbee0f0f5c3..e2a167240335 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -845,6 +845,9 @@ mb_update_avg_fragment_size(struct super_block *sb, struct ext4_group_info *grp)
> if (!test_opt2(sb, MB_OPTIMIZE_SCAN) || grp->bb_free == 0)
> return;
>
> + if (unlikely(grp->bb_fragments == 0))
> + return;
> +
> new_order = mb_avg_fragment_size_order(sb,
> grp->bb_free / grp->bb_fragments);
> if (new_order == grp->bb_avg_fragment_size_order)
> --
> 2.31.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
