From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f69.google.com (mail-pl0-f69.google.com [209.85.160.69]) by kanga.kvack.org (Postfix) with ESMTP id 10E1F6B000C for ; Thu, 2 Aug 2018 04:13:34 -0400 (EDT) Received: by mail-pl0-f69.google.com with SMTP id 90-v6so922565pla.18 for ; Thu, 02 Aug 2018 01:13:34 -0700 (PDT) Received: from EUR01-VE1-obe.outbound.protection.outlook.com (mail-ve1eur01on0098.outbound.protection.outlook.com. [104.47.1.98]) by mx.google.com with ESMTPS id t10-v6si442249pgn.370.2018.08.02.01.13.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 02 Aug 2018 01:13:32 -0700 (PDT) Subject: [PATCH] memcg: Add comment to mem_cgroup_css_online() From: Kirill Tkhai References: <20180413115454.GL17484@dhcp22.suse.cz> <20180413121433.GM17484@dhcp22.suse.cz> <20180413125101.GO17484@dhcp22.suse.cz> <20180726162512.6056b5d7c1d2a5fbff6ce214@linux-foundation.org> <20180727193134.GA10996@cmpxchg.org> <20180729192621.py4znecoinw5mqcp@esperanza> <20180730153113.GB4567@cmpxchg.org> <20180731163908.603d7a27c6534341e1afa724@linux-foundation.org> <20180801155552.GA8600@cmpxchg.org> <20180801162235.j3v7xipyw5afnj4x@esperanza> <7a836e47-f0a4-6802-9b90-cc473e5ab90b@virtuozzo.com> Message-ID: <521f9e5f-c436-b388-fe83-4dc870bfb489@virtuozzo.com> Date: Thu, 2 Aug 2018 11:13:24 +0300 MIME-Version: 1.0 In-Reply-To: <7a836e47-f0a4-6802-9b90-cc473e5ab90b@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vladimir Davydov , Johannes Weiner Cc: Andrew Morton , Michal Hocko , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Explain relationships between allocation and expanding. Suggested-by: Vladimir Davydov Signed-off-by: Kirill Tkhai --- diff --git a/mm/memcontrol.c b/mm/memcontrol.c index d90993ef1d7d..34e5ff72ce87 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4703,6 +4703,11 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css) { struct mem_cgroup *memcg = mem_cgroup_from_css(css); + /* + * A memcg must be visible for memcg_expand_shrinker_maps() + * by the time the maps are allocated. So, we allocate maps + * here, when for_each_mem_cgroup() can't skip it. + */ if (memcg_alloc_shrinker_maps(memcg)) { mem_cgroup_id_remove(memcg); return -ENOMEM;