Re: [PATCH v2] btrfs: qgroup: Try our best to delete qgroup relations

[David Sterba <dsterba@suse.cz>]

On Tue, Aug 06, 2019 at 10:05:07PM +0800, Qu Wenruo wrote:
> When we try to delete qgroups, we're pretty cautious, we make sure both
> qgroups exist and there is a relationship between them, then try to
> delete the relation.
> 
> This behavior is OK, but the problem is we need to two relation items,
> and if we failed the first item deletion, we error out, leaving the
> other relation item in qgroup tree.
> 
> Sometimes the error from del_qgroup_relation_item() could just be
> -ENOENT, thus we can ignore that error and continue without any problem.
> 
> Further more, such cautious behavior makes qgroup relation deletion
> impossible for orphan relation items.
> 
> This patch will enhance __del_qgroup_relation():
> - If both qgroups and their relation items exist
>   Go the regular deletion routine and update their accounting if needed.
> 
> - If any qgroup or relation item doesn't exist
>   Then we still try to delete the orphan items anyway, but don't trigger
>   the accounting update.
> 
> By this, we try our best to remove relation items, and can handle orphan
> relation items properly, while still keep the existing behavior for good
> qgroup tree.
> 
> Reported-by: Andrei Borzenkov <arvidjaar@gmail.com>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
> changelog:
> v2:
> - Fix a condition for checking either @parent or @member is not found

Patch replaced in misc-next, thanks.