From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754433AbaFCNXA (ORCPT ); Tue, 3 Jun 2014 09:23:00 -0400 Received: from cantor2.suse.de ([195.135.220.15]:41075 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754359AbaFCNW6 (ORCPT ); Tue, 3 Jun 2014 09:22:58 -0400 Date: Tue, 3 Jun 2014 15:22:55 +0200 From: Michal Hocko To: Johannes Weiner Cc: Andrew Morton , Hugh Dickins , Tejun Heo , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch 05/10] mm: memcontrol: catch root bypass in move precharge Message-ID: <20140603132255.GJ1321@dhcp22.suse.cz> References: <1401380162-24121-1-git-send-email-hannes@cmpxchg.org> <1401380162-24121-6-git-send-email-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1401380162-24121-6-git-send-email-hannes@cmpxchg.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 29-05-14 12:15:57, Johannes Weiner wrote: > When mem_cgroup_try_charge() returns -EINTR, it bypassed the charge to > the root memcg. But move precharging does not catch this and treats > this case as if no charge had happened, thus leaking a charge against > root. Because of an old optimization, the root memcg's res_counter is > not actually charged right now, but it's still an imbalance and > subsequent patches will charge the root memcg again. > > Catch those bypasses to the root memcg and properly cancel them before > giving up the move. > > Signed-off-by: Johannes Weiner Acked-by: Michal Hocko > --- > mm/memcontrol.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 8957d6c945b8..184e67cce4e4 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6485,8 +6485,15 @@ one_by_one: > cond_resched(); > } > ret = mem_cgroup_try_charge(memcg, GFP_KERNEL, 1, false); > + /* > + * In case of failure, any residual charges against > + * mc.to will be dropped by mem_cgroup_clear_mc() > + * later on. However, cancel any charges that are > + * bypassed to root right away or they'll be lost. > + */ > + if (ret == -EINTR) > + __mem_cgroup_cancel_charge(root_mem_cgroup, 1); > if (ret) > - /* mem_cgroup_clear_mc() will do uncharge later */ > return ret; > mc.precharge++; > } > -- > 1.9.3 > -- Michal Hocko SUSE Labs