Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751989Ab3C0Ig6 (ORCPT ); Wed, 27 Mar 2013 04:36:58 -0400 Received: from cantor2.suse.de ([195.135.220.15]:35351 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750822Ab3C0Ig4 (ORCPT ); Wed, 27 Mar 2013 04:36:56 -0400 From: Michal Hocko To: Tejun Heo Cc: Glauber Costa , Li Zefan , KAMEZAWA Hiroyuki , Johannes Weiner , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] memcg: fix memcg_cache_name() to use cgroup_name() Date: Wed, 27 Mar 2013 09:36:39 +0100 Message-Id: <1364373399-17397-1-git-send-email-mhocko@suse.cz> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3751 Lines: 115 As cgroup supports rename, it's unsafe to dereference dentry->d_name without proper vfs locks. Fix this by using cgroup_name() rather than dentry directly. Also open code memcg_cache_name because it is called only from kmem_cache_dup which frees the returned name right after kmem_cache_create_memcg makes a copy of it. Such a short-lived allocation doesn't make too much sense. So replace it by a static buffer as kmem_cache_dup is called with memcg_cache_mutex. Signed-off-by: Li Zefan Signed-off-by: Michal Hocko Acked-by: Glauber Costa --- mm/memcontrol.c | 64 ++++++++++++++++++++++++++++--------------------------- 1 file changed, 33 insertions(+), 31 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index f608546..b30547b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3364,52 +3364,54 @@ void mem_cgroup_destroy_cache(struct kmem_cache *cachep) schedule_work(&cachep->memcg_params->destroy); } -static char *memcg_cache_name(struct mem_cgroup *memcg, struct kmem_cache *s) -{ - char *name; - struct dentry *dentry; - - rcu_read_lock(); - dentry = rcu_dereference(memcg->css.cgroup->dentry); - 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; -} +/* + * This lock protects updaters, not readers. We want readers to be as fast as + * they can, and they will either see NULL or a valid cache value. Our model + * allow them to see NULL, in which case the root memcg will be selected. + * + * We need this lock because multiple allocations to the same cache from a non + * will span more than one worker. Only one of them can create the cache. + */ +static DEFINE_MUTEX(memcg_cache_mutex); +/* + * Called with memcg_cache_mutex held + */ static struct kmem_cache *kmem_cache_dup(struct mem_cgroup *memcg, struct kmem_cache *s) { - char *name; struct kmem_cache *new; + static char *tmp_name = NULL; - name = memcg_cache_name(memcg, s); - if (!name) - return NULL; + lockdep_assert_held(&memcg_cache_mutex); + + /* + * kmem_cache_create_memcg duplicates the given name and + * cgroup_name for this name requires RCU context. + * This static temporary buffer is used to prevent from + * pointless shortliving allocation. + */ + if (!tmp_name) { + tmp_name = kmalloc(PAGE_SIZE, GFP_KERNEL); + WARN_ON_ONCE(!tmp_name); + if (!tmp_name) + return NULL; + } + + rcu_read_lock(); + snprintf(tmp_name, PAGE_SIZE, "%s(%d:%s)", s->name, + memcg_cache_id(memcg), cgroup_name(memcg->css.cgroup)); + rcu_read_unlock(); - new = kmem_cache_create_memcg(memcg, name, s->object_size, s->align, + new = kmem_cache_create_memcg(memcg, tmp_name, s->object_size, s->align, (s->flags & ~SLAB_PANIC), s->ctor, s); if (new) new->allocflags |= __GFP_KMEMCG; - kfree(name); return new; } -/* - * This lock protects updaters, not readers. We want readers to be as fast as - * they can, and they will either see NULL or a valid cache value. Our model - * allow them to see NULL, in which case the root memcg will be selected. - * - * We need this lock because multiple allocations to the same cache from a non - * will span more than one worker. Only one of them can create the cache. - */ -static DEFINE_MUTEX(memcg_cache_mutex); static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg, struct kmem_cache *cachep) { -- 1.7.10.4 -- 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/