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

[Vladimir Davydov]

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@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Glauber Costa <glommer@xxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
---
 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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