From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx138.postini.com [74.125.245.138]) by kanga.kvack.org (Postfix) with SMTP id 2A0796B0006 for ; Thu, 21 Mar 2013 05:08:53 -0400 (EDT) Date: Thu, 21 Mar 2013 10:08:49 +0100 From: Michal Hocko Subject: Re: [PATCH] memcg: fix memcg_cache_name() to use cgroup_name() Message-ID: <20130321090849.GF6094@dhcp22.suse.cz> References: <514A60CD.60208@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <514A60CD.60208@huawei.com> Sender: owner-linux-mm@kvack.org List-ID: To: Li Zefan Cc: Tejun Heo , LKML , Cgroups , linux-mm@kvack.org, KAMEZAWA Hiroyuki , Johannes Weiner , Glauber Costa On Thu 21-03-13 09:22:21, Li Zefan wrote: > As cgroup supports rename, it's unsafe to dereference dentry->d_name > without proper vfs locks. Fix this by using cgroup_name(). > > Signed-off-by: Li Zefan > --- > > This patch depends on "cgroup: fix cgroup_path() vs rename() race", > which has been queued for 3.10. > > --- > mm/memcontrol.c | 15 +++++++-------- > 1 file changed, 7 insertions(+), 8 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 53b8201..72be5c9 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3217,17 +3217,16 @@ void mem_cgroup_destroy_cache(struct kmem_cache *cachep) > static char *memcg_cache_name(struct mem_cgroup *memcg, struct kmem_cache *s) > { > char *name; > - struct dentry *dentry; > + > + name = (char *)__get_free_page(GFP_TEMPORARY); Ouch. Can we use a static temporary buffer instead? This is called from workqueue context so we do not have to be afraid of the deep call chain. It is also not a hot path AFAICS. Even GFP_ATOMIC for kasprintf would be an improvement IMO. > + if (!name) > + return NULL; > > rcu_read_lock(); > - dentry = rcu_dereference(memcg->css.cgroup->dentry); > + snprintf(name, PAGE_SIZE, "%s(%d:%s)", s->name, memcg_cache_id(memcg), > + cgroup_name(memcg->css.cgroup)); > rcu_read_unlock(); > > - BUG_ON(dentry == NULL); > - > - name = kasprintf(GFP_KERNEL, "%s(%d:%s)", s->name, > - memcg_cache_id(memcg), dentry->d_name.name); > - > return name; > } > > @@ -3247,7 +3246,7 @@ static struct kmem_cache *kmem_cache_dup(struct mem_cgroup *memcg, > if (new) > new->allocflags |= __GFP_KMEMCG; > > - kfree(name); > + free_page((unsigned long)name); > return new; > } > > -- > 1.8.0.2 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Michal Hocko SUSE Labs -- 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