linux-kernel - [PATCH -mm 12/12] slub: make sure all memcg caches have unique names on sysfs

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Message-ID: <c19e2143ba98d26f3898489bf6ab55ed3764c1a1.1393423762.git.vdavydov@parallels.com>
Date:	Wed, 26 Feb 2014 19:05:17 +0400
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	<akpm@...ux-foundation.org>
CC:	<hannes@...xchg.org>, <mhocko@...e.cz>, <glommer@...il.com>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<devel@...nvz.org>, Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>
Subject: [PATCH -mm 12/12] slub: make sure all memcg caches have unique names on sysfs

Since memcg caches are now reparented on memcg offline, a memcg cache
can outlive its cgroup. If the memcg id is then reused for a new cgroup
with the same name, we can get cache name collision, which will result
in failures while trying to add a sysfs entry for a new cgroup's cache.
Let's fix this by appending the cache address to sysfs names of all
memcg caches so that they are guaranteed to have unique names.

Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Michal Hocko <mhocko@...e.cz>
Cc: Glauber Costa <glommer@...il.com>
Cc: Christoph Lameter <cl@...ux-foundation.org>
Cc: Pekka Enberg <penberg@...nel.org>
---
 mm/slub.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index d8b8659bfa64..cdeea794bba5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5234,7 +5234,18 @@ static int sysfs_slab_add(struct kmem_cache *s)
 	}
 
 	s->kobj.kset = cache_kset(s);
-	err = kobject_init_and_add(&s->kobj, &slab_ktype, NULL, "%s", name);
+	/*
+	 * A memcg cache can outlive its cgroup. If the memcg id is then reused
+	 * for a new cgroup with the same name, we can get cache name
+	 * collision. To make sure all memcg caches have unique names on sysfs,
+	 * we append the cache address to its name.
+	 */
+	if (is_root_cache(s))
+		err = kobject_init_and_add(&s->kobj, &slab_ktype,
+					   NULL, "%s", name);
+	else
+		err = kobject_init_and_add(&s->kobj, &slab_ktype,
+					   NULL, "%s-%p", name, s);
 	if (err) {
 		kobject_put(&s->kobj);
 		return err;
-- 
1.7.10.4

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