linux-kernel - Re: [PATCH for-4.6-fixes] memcg: remove lru_add_drain_all() invocation from mem_cgroup_move

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Message-ID: <20160421032704.GA15585@dhcp22.suse.cz>
Date:	Wed, 20 Apr 2016 23:27:05 -0400
From:	Michal Hocko <mhocko@...nel.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Petr Mladek <pmladek@...e.com>, cgroups@...r.kernel.org,
	Cyril Hrubis <chrubis@...e.cz>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH for-4.6-fixes] memcg: remove lru_add_drain_all()
 invocation from mem_cgroup_move_charge()

On Wed 20-04-16 17:29:22, Tejun Heo wrote:
> Hello, Michal.
> 
> On Sun, Apr 17, 2016 at 08:07:48AM -0400, Michal Hocko wrote:
[...]
> > I liked your proposal when mem_cgroup_move_charge would be called from a
> > context which doesn't hold the problematic rwsem much more. Would that
> > be too intrusive for the stable backport?
> 
> Yeah, I'm working on the fix but let's plug this one first as it seems
> really easy to trigger.  I got a couple off-list reports (in and
> outside fb) of this triggering.

Sure, I think we can use this for an immediate workaround. Nevertheless
we want to have a full fix and do not rely on this being the only
problem. I would eventually like to reintroduce the draining later when
we have a better fix because even though this is not a correctness
problem I think we should try hard to not leave anything behind.

That being said:
Acked-by: Michal Hocko <mhocko@...e.com>
-- 
Michal Hocko
SUSE Labs