From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx112.postini.com [74.125.245.112]) by kanga.kvack.org (Postfix) with SMTP id 7B4596B00B5 for ; Wed, 3 Apr 2013 04:08:01 -0400 (EDT) Message-ID: <515BE38B.2060602@parallels.com> Date: Wed, 3 Apr 2013 12:08:43 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCH -v2] memcg: don't do cleanup manually if mem_cgroup_css_online() fails References: <515A8A40.6020406@huawei.com> <20130402121600.GK24345@dhcp22.suse.cz> <20130402141646.GQ24345@dhcp22.suse.cz> <515AE948.1000704@parallels.com> <20130402142825.GA32520@dhcp22.suse.cz> <515AEC3A.2030401@parallels.com> <20130402150422.GB32520@dhcp22.suse.cz> In-Reply-To: <20130402150422.GB32520@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Li Zefan , Johannes Weiner , KAMEZAWA Hiroyuki , LKML , Cgroups , linux-mm@kvack.org On 04/02/2013 07:04 PM, Michal Hocko wrote: > On Tue 02-04-13 18:33:30, Glauber Costa wrote: >> On 04/02/2013 06:28 PM, Michal Hocko wrote: >>> On Tue 02-04-13 18:20:56, Glauber Costa wrote: >>>> On 04/02/2013 06:16 PM, Michal Hocko wrote: >>>>> mem_cgroup_css_online >>>>> memcg_init_kmem >>>>> mem_cgroup_get # refcnt = 2 >>>>> memcg_update_all_caches >>>>> memcg_update_cache_size # fails with ENOMEM >>>> >>>> Here is the thing: this one in kmem only happens for kmem enabled >>>> memcgs. For those, we tend to do a get once, and put only when the last >>>> kmem reference is gone. >>>> >>>> For non-kmem memcgs, refcnt will be 1 here, and will be balanced out by >>>> the mem_cgroup_put() in css_free. >>> >>> So we need this, right? >>> --- >>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >>> index f608546..2ef875d 100644 >>> --- a/mm/memcontrol.c >>> +++ b/mm/memcontrol.c >>> @@ -5306,6 +5306,8 @@ static int memcg_propagate_kmem(struct mem_cgroup *memcg) >>> ret = memcg_update_cache_sizes(memcg); >>> mutex_unlock(&set_limit_mutex); >>> out: >>> + if (ret) >>> + mem_cgroup_put(memcg); >>> return ret; >>> } >>> #endif /* CONFIG_MEMCG_KMEM */ >>> @@ -6417,16 +6419,6 @@ mem_cgroup_css_online(struct cgroup *cont) >>> >>> error = memcg_init_kmem(memcg, &mem_cgroup_subsys); >>> mutex_unlock(&memcg_create_mutex); >>> - if (error) { >>> - /* >>> - * We call put now because our (and parent's) refcnts >>> - * are already in place. mem_cgroup_put() will internally >>> - * call __mem_cgroup_free, so return directly >>> - */ >>> - mem_cgroup_put(memcg); >>> - if (parent->use_hierarchy) >>> - mem_cgroup_put(parent); >>> - } >>> return error; >>> } >>> >>> >> Yes, indeed you are very right - and thanks for looking at such depth. > > So what about the patch bellow? It seems that I provoked all this mess > but my brain managed to push it away so I do not remember why I thought > the parent needs reference drop... It is "only" 3.9 thing fortunately. > --- Li being fine with it, I am fine with it. -- 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