From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 28E626B004F for ; Wed, 14 Jan 2009 03:11:29 -0500 (EST) Message-ID: <496D9DFA.1050602@cn.fujitsu.com> Date: Wed, 14 Jan 2009 16:10:34 +0800 From: Li Zefan MIME-Version: 1.0 Subject: [PATCH] memcg: fix a race when setting memory.swappiness Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: KAMEZAWA Hiroyuki , Balbir Singh , Paul Menage , Daisuke Nishimura , LKML , "linux-mm@kvack.org" List-ID: (suppose: memcg->use_hierarchy == 0 and memcg->swappiness == 60) echo 10 > /memcg/0/swappiness | mem_cgroup_swappiness_write() | ... | echo 1 > /memcg/0/use_hierarchy | mkdir /mnt/0/1 | sub_memcg->swappiness = 60; memcg->swappiness = 10; | In the above scenario, we end up having 2 different swappiness values in a single hierarchy. We should hold cgroup_lock() when cheking cgrp->children list. Signed-off-by: Li Zefan Acked-by: KAMEZAWA Hiroyuki --- mm/memcontrol.c | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index fb62b43..bc8f101 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1992,6 +1992,7 @@ static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft, { struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp); struct mem_cgroup *parent; + if (val > 100) return -EINVAL; @@ -1999,15 +2000,22 @@ static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft, return -EINVAL; parent = mem_cgroup_from_cont(cgrp->parent); + + cgroup_lock(); + /* If under hierarchy, only empty-root can set this value */ if ((parent->use_hierarchy) || - (memcg->use_hierarchy && !list_empty(&cgrp->children))) + (memcg->use_hierarchy && !list_empty(&cgrp->children))) { + cgroup_unlock(); return -EINVAL; + } spin_lock(&memcg->reclaim_param_lock); memcg->swappiness = val; spin_unlock(&memcg->reclaim_param_lock); + cgroup_unlock(); + return 0; } -- 1.5.4.rc3 -- 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