From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756305AbaJXOtO (ORCPT ); Fri, 24 Oct 2014 10:49:14 -0400 Received: from mx2.parallels.com ([199.115.105.18]:46924 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753499AbaJXOtM (ORCPT ); Fri, 24 Oct 2014 10:49:12 -0400 Date: Fri, 24 Oct 2014 18:49:03 +0400 From: Vladimir Davydov To: Johannes Weiner CC: Andrew Morton , Michal Hocko , , , Subject: Re: [patch 2/3] mm: memcontrol: pull the NULL check from __mem_cgroup_same_or_subtree() Message-ID: <20141024144903.GB28055@esperanza> References: <1414158589-26094-1-git-send-email-hannes@cmpxchg.org> <1414158589-26094-2-git-send-email-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1414158589-26094-2-git-send-email-hannes@cmpxchg.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 24, 2014 at 09:49:48AM -0400, Johannes Weiner wrote: > The NULL in mm_match_cgroup() comes from a possibly exiting mm->owner. > It makes a lot more sense to check where it's looked up, rather than > check for it in __mem_cgroup_same_or_subtree() where it's unexpected. > > No other callsite passes NULL to __mem_cgroup_same_or_subtree(). > > Signed-off-by: Johannes Weiner Reviewed-by: Vladimir Davydov > --- > include/linux/memcontrol.h | 5 +++-- > mm/memcontrol.c | 2 +- > 2 files changed, 4 insertions(+), 3 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index ea007615e8f9..e32ab948f589 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -83,11 +83,12 @@ static inline > bool mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *memcg) > { > struct mem_cgroup *task_memcg; > - bool match; > + bool match = false; > > rcu_read_lock(); > task_memcg = mem_cgroup_from_task(rcu_dereference(mm->owner)); > - match = __mem_cgroup_same_or_subtree(memcg, task_memcg); > + if (task_memcg) > + match = __mem_cgroup_same_or_subtree(memcg, task_memcg); > rcu_read_unlock(); > return match; > } > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index bdf8520979cf..15b1c5110a8f 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1316,7 +1316,7 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg, > { > if (root_memcg == memcg) > return true; > - if (!root_memcg->use_hierarchy || !memcg) > + if (!root_memcg->use_hierarchy) > return false; > return cgroup_is_descendant(memcg->css.cgroup, root_memcg->css.cgroup); > } > -- > 2.1.2 >