On Thu 21-12-23 23:05:54, Baokun Li wrote:
> After updating bb_free in mb_free_blocks, it is possible to return without
> updating bb_fragments because the block being freed is found to have
> already been freed, which leads to inconsistency between bb_free and
> bb_fragments.
>
> Since the group may be unlocked in ext4_grp_locked_error(), this can lead
> to problems such as dividing by zero when calculating the average fragment
> length. Hence move the update of bb_free to after the block double-free
> check guarantees that the corresponding statistics are updated only after
> the core block bitmap is modified.
>
> Fixes: eabe0444df90 ("ext4: speed-up releasing blocks on commit")
> CC: stable@xxxxxxxxxxxxxxx # 3.10
> Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
Just one nit below but regardless of that feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
> @@ -1941,10 +1936,16 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
> EXT4_GROUP_INFO_BBITMAP_CORRUPT);
> } else {
> mb_regenerate_buddy(e4b);
> + goto check;
> }
> - goto done;
> + return;
> }
I think this might be more readable when we revert the condition like:
/*
* Fastcommit replay can free already freed blocks which
* corrupts allocation info. Regenerate it.
*/
if (sbi->s_mount_state & EXT4_FC_REPLAY) {
mb_regenerate_buddy(e4b);
goto check;
}
ext4_grp_locked_error(sb, e4b->bd_group,
inode ? inode->i_ino : 0, blocknr,
"freeing already freed block (bit %u); block bitmap corrupt.",
block);
ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group,
EXT4_GROUP_INFO_BBITMAP_CORRUPT);
return;
}
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
