slab: replace smp_read_barrier_depends() with lockless_dereference()

Recently lockless_dereference() was added which can be used in place of
hard-coding smp_read_barrier_depends().  The following PATCH makes the
change.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/slab.h b/mm/slab.h
index 53a55c7..078acbc 100644 (file)
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -209,15 +209,15 @@ cache_from_memcg_idx(struct kmem_cache *s, int idx)
 
        rcu_read_lock();
        params = rcu_dereference(s->memcg_params);
-       cachep = params->memcg_caches[idx];
-       rcu_read_unlock();
 
        /*
         * Make sure we will access the up-to-date value. The code updating
         * memcg_caches issues a write barrier to match this (see
         * memcg_register_cache()).
         */
-       smp_read_barrier_depends();
+       cachep = lockless_dereference(params->memcg_caches[idx]);
+       rcu_read_unlock();
+
        return cachep;
 }