Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752107AbbLRWkJ (ORCPT ); Fri, 18 Dec 2015 17:40:09 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:40358 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751408AbbLRWkF (ORCPT ); Fri, 18 Dec 2015 17:40:05 -0500 Date: Fri, 18 Dec 2015 14:40:04 -0800 From: Andrew Morton To: Vladimir Davydov Cc: Johannes Weiner , , Michal Hocko , , Subject: Re: [PATCH v2] mm: memcontrol: fix possible memcg leak due to interrupted reclaim Message-Id: <20151218144004.6ec6189817b64e04d9405001@linux-foundation.org> In-Reply-To: <20151218162405.GU28521@esperanza> References: <1450182697-11049-1-git-send-email-vdavydov@virtuozzo.com> <20151217150217.a02c264ce9b5335b02bae888@linux-foundation.org> <20151218153202.GS28521@esperanza> <20151218160041.GA4201@cmpxchg.org> <20151218162405.GU28521@esperanza> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2008 Lines: 59 On Fri, 18 Dec 2015 19:24:05 +0300 Vladimir Davydov wrote: > > OK, got it, thanks. Here goes the incremental patch (it should also fix > the warning regarding unused cmpxchg returned value): > --- > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index fc25dc211eaf..908c075e04eb 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -864,7 +864,7 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, > * might block it. So we clear iter->position right > * away. > */ > - cmpxchg(&iter->position, pos, NULL); > + (void)cmpxchg(&iter->position, pos, NULL); No, this doesn't actually squish the __must_check warning. Can anyone think of anything smarter than this? --- a/mm/memcontrol.c~mm-memcontrol-fix-possible-memcg-leak-due-to-interrupted-reclaim-fix-fix +++ a/mm/memcontrol.c @@ -851,6 +851,9 @@ static struct mem_cgroup *get_mem_cgroup return memcg; } +/* Move this to compiler.h if it proves worthy */ +#define defeat_must_check(expr) do { if (expr) ; } while (0) + /** * mem_cgroup_iter - iterate over memory cgroup hierarchy * @root: hierarchy root @@ -915,7 +918,7 @@ struct mem_cgroup *mem_cgroup_iter(struc * might block it. So we clear iter->position right * away. */ - (void)cmpxchg(&iter->position, pos, NULL); + defeat_must_check(cmpxchg(&iter->position, pos, NULL)); } } @@ -967,7 +970,7 @@ struct mem_cgroup *mem_cgroup_iter(struc * thread, so check that the value hasn't changed since we read * it to avoid reclaiming from the same cgroup twice. */ - (void)cmpxchg(&iter->position, pos, memcg); + defeat_must_check(cmpxchg(&iter->position, pos, memcg)); /* * pairs with css_tryget when dereferencing iter->position _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/