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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 01A42C04EBD for ; Tue, 16 Oct 2018 12:05:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3B5C20869 for ; Tue, 16 Oct 2018 12:05:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B3B5C20869 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.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 S1727112AbeJPT4G (ORCPT ); Tue, 16 Oct 2018 15:56:06 -0400 Received: from mx2.suse.de ([195.135.220.15]:44056 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726718AbeJPT4G (ORCPT ); Tue, 16 Oct 2018 15:56:06 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id D06DEB030; Tue, 16 Oct 2018 12:05:54 +0000 (UTC) Date: Tue, 16 Oct 2018 14:05:54 +0200 From: Michal Hocko To: Kirill Tkhai Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, vdavydov.dev@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm: Convert mem_cgroup_id::ref to refcount_t type Message-ID: <20181016120554.GT18839@dhcp22.suse.cz> References: <153910718919.7006.13400779039257185427.stgit@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <153910718919.7006.13400779039257185427.stgit@localhost.localdomain> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 09-10-18 20:46:56, Kirill Tkhai wrote: > This will allow to use generic refcount_t interfaces > to check counters overflow instead of currently existing > VM_BUG_ON(). The only difference after the patch is > VM_BUG_ON() may cause BUG(), while refcount_t fires > with WARN(). But this seems not to be significant here, > since such the problems are usually caught by syzbot > with panic-on-warn enabled. > > Signed-off-by: Kirill Tkhai Acked-by: Michal Hocko > --- > include/linux/memcontrol.h | 2 +- > mm/memcontrol.c | 10 ++++------ > 2 files changed, 5 insertions(+), 7 deletions(-) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index 4399cc3f00e4..7ab2120155a4 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -78,7 +78,7 @@ struct mem_cgroup_reclaim_cookie { > > struct mem_cgroup_id { > int id; > - atomic_t ref; > + refcount_t ref; > }; > > /* > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 7bebe2ddec05..aa728d5b3d72 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4299,14 +4299,12 @@ static void mem_cgroup_id_remove(struct mem_cgroup *memcg) > > 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); > + refcount_add(n, &memcg->id.ref); > } > > 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)) { > + if (refcount_sub_and_test(n, &memcg->id.ref)) { > mem_cgroup_id_remove(memcg); > > /* Memcg ID pins CSS */ > @@ -4523,7 +4521,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css) > } > > /* Online state pins memcg ID, memcg ID pins CSS */ > - atomic_set(&memcg->id.ref, 1); > + refcount_set(&memcg->id.ref, 1); > css_get(css); > return 0; > } > @@ -6357,7 +6355,7 @@ subsys_initcall(mem_cgroup_init); > #ifdef CONFIG_MEMCG_SWAP > static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg) > { > - while (!atomic_inc_not_zero(&memcg->id.ref)) { > + while (!refcount_inc_not_zero(&memcg->id.ref)) { > /* > * The root cgroup cannot be destroyed, so it's refcount must > * always be >= 1. -- Michal Hocko SUSE Labs