On 2019/1/17 下午10:30, David Sterba wrote:
> On Thu, Jan 17, 2019 at 09:04:13AM +0800, Qu Wenruo wrote:
>>
>>
>> On 2019/1/17 上午12:00, Josef Bacik wrote:
>>> qgroups will do the old roots lookup at delayed ref time, which could be
>>> while walking down the extent root while running a delayed ref.  This
>>> should be fine, except we specifically lock eb's in the backref walking
>>> code irrespective of path->skip_locking, which deadlocks the system.
>>> Fix up the backref code to honor path->skip_locking, nobody will be
>>> modifying the commit_root when we're searching so it's completely safe
>>> to do.  Thanks,
>>>
>>> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
>>
>> Reviewed-by: Qu Wenruo <wqu@suse.com>
> 
> What can we use from https://patchwork.kernel.org/patch/10725371/ to
> add to the changelog? Is the deadlock caused by fb235dc06fac?

The error and cause part should be the same.

Just Josef's is much better than my patch.

Only the [FIX] part needs some update.

Thanks
Qu

> The fix
> applies to stable 4.19+ directly and to 4.14 with context fixups.
> Thanks.
>