From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9F70CC43142 for ; Tue, 31 Jul 2018 23:39:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F68320894 for ; Tue, 31 Jul 2018 23:39:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F68320894 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732839AbeHABVw (ORCPT ); Tue, 31 Jul 2018 21:21:52 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:53146 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732813AbeHABVw (ORCPT ); Tue, 31 Jul 2018 21:21:52 -0400 Received: from localhost.localdomain (c-24-4-125-7.hsd1.ca.comcast.net [24.4.125.7]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 79D9829; Tue, 31 Jul 2018 23:39:10 +0000 (UTC) Date: Tue, 31 Jul 2018 16:39:08 -0700 From: Andrew Morton To: Johannes Weiner Cc: Vladimir Davydov , Michal Hocko , Kirill Tkhai , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] memcg: Remove memcg_cgroup::id from IDR on mem_cgroup_css_alloc() failure Message-Id: <20180731163908.603d7a27c6534341e1afa724@linux-foundation.org> In-Reply-To: <20180730153113.GB4567@cmpxchg.org> References: <6dbc33bb-f3d5-1a46-b454-13c6f5865fcd@virtuozzo.com> <20180413113855.GI17484@dhcp22.suse.cz> <8a81c801-35c8-767d-54b0-df9f1ca0abc0@virtuozzo.com> <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> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 30 Jul 2018 11:31:13 -0400 Johannes Weiner wrote: > Subject: [PATCH] mm: memcontrol: simplify memcg idr allocation and error > unwinding > > The memcg ID is allocated early in the multi-step memcg creation > process, which needs 2-step ID allocation and IDR publishing, as well > as two separate IDR cleanup/unwind sites on error. > > Defer the IDR allocation until the last second during onlining to > eliminate all this complexity. There is no requirement to have the ID > and IDR entry earlier than that. And the root reference to the ID is > put in the offline path, so this matches nicely. This patch isn't aware of Kirill's later "mm, memcg: assign memcg-aware shrinkers bitmap to memcg", which altered mem_cgroup_css_online(): @@ -4356,6 +4470,11 @@ static int mem_cgroup_css_online(struct { struct mem_cgroup *memcg = mem_cgroup_from_css(css); + if (memcg_alloc_shrinker_maps(memcg)) { + mem_cgroup_id_remove(memcg); + return -ENOMEM; + } + /* Online state pins memcg ID, memcg ID pins CSS */ atomic_set(&memcg->id.ref, 1); css_get(css);