From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f70.google.com (mail-lf0-f70.google.com [209.85.215.70]) by kanga.kvack.org (Postfix) with ESMTP id 862096B025E for ; Tue, 2 Aug 2016 13:30:14 -0400 (EDT) Received: by mail-lf0-f70.google.com with SMTP id e7so98872461lfe.0 for ; Tue, 02 Aug 2016 10:30:14 -0700 (PDT) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id c6si3671208wjq.184.2016.08.02.10.30.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 02 Aug 2016 10:30:13 -0700 (PDT) Date: Tue, 2 Aug 2016 13:27:36 -0400 From: Johannes Weiner Subject: Re: [PATCH v2 3/3] mm: memcontrol: add sanity checks for memcg->id.ref on get/put Message-ID: <20160802172736.GC6637@cmpxchg.org> References: <32402ace75b459c8523f5b237a62061e1df7a3b5.1470149524.git.vdavydov@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <32402ace75b459c8523f5b237a62061e1df7a3b5.1470149524.git.vdavydov@virtuozzo.com> Sender: owner-linux-mm@kvack.org List-ID: To: Vladimir Davydov Cc: Andrew Morton , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Tue, Aug 02, 2016 at 06:00:50PM +0300, Vladimir Davydov wrote: > Signed-off-by: Vladimir Davydov > --- > mm/memcontrol.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 67109d556a4a..32b2f33865f9 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4033,6 +4033,7 @@ static DEFINE_IDR(mem_cgroup_idr); > > static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n) > { > + VM_BUG_ON(atomic_read(&memcg->id.ref) <= 0); > atomic_add(n, &memcg->id.ref); > } > > @@ -4056,6 +4057,7 @@ static struct mem_cgroup *mem_cgroup_id_get_active(struct mem_cgroup *memcg) > > static void mem_cgroup_id_put_many(struct mem_cgroup *memcg, unsigned int n) > { > + VM_BUG_ON(atomic_read(&memcg->id.ref) < n); > if (atomic_sub_and_test(n, &memcg->id.ref)) { > idr_remove(&mem_cgroup_idr, memcg->id.id); > memcg->id.id = 0; > @@ -4176,6 +4178,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void) > INIT_LIST_HEAD(&memcg->cgwb_list); > #endif > idr_replace(&mem_cgroup_idr, memcg, memcg->id.id); > + atomic_set(&memcg->id.ref, 1); > return memcg; > fail: > if (memcg->id.id > 0) > @@ -4245,7 +4248,6 @@ fail: > static int mem_cgroup_css_online(struct cgroup_subsys_state *css) > { > /* Online state pins memcg ID, memcg ID pins CSS */ > - mem_cgroup_id_get(mem_cgroup_from_css(css)); > css_get(css); > return 0; This comment and code is no very, very confusing. Can you move the atomic_set(&memcg->id.ref, 1) down here instead? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org