On Sun, Sep 23, 2012 at 05:54:18PM +0800, Miao Xie wrote:

quoted

quoted

@@ -2347,7 +2335,8 @@ static int chunk_usage_filter(struct btrfs_fs_info *fs_info, u64 chunk_offset,
 	cache = btrfs_lookup_block_group(fs_info, chunk_offset);
 	chunk_used = btrfs_block_group_used(&cache->item);
 
-	user_thresh = div_factor_fine(cache->key.offset, bargs->usage);
+	BUG_ON(bargs->usage < 0 || bargs->usage > 100);

otherwise it reliably crashes here

Sorry, I don't know why it will crash here if we input 0. I tried to input 0,
and it worked well.

My oversight, sorry.

I think the only case we must take into account is the users might input the wrong value (>100 or <0)
on the old kernel, and it can be stored into the filesystem. If we mount this filesystem
on the new kernel, some problems may happen.

So better avoid a BUG_ON.