slab, slub: use page->rcu_head instead of page->lru plus cast

We have properly typed page->rcu_head, no need to cast page->lru.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slab.c

@@ -1889,21 +1889,10 @@ static void slab_destroy(struct kmem_cache *cachep, struct page *page)
 
 	freelist = page->freelist;
 	slab_destroy_debugcheck(cachep, page);
-	if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU)) {
-		struct rcu_head *head;
-
-		/*
-		 * RCU free overloads the RCU head over the LRU.
-		 * slab_page has been overloeaded over the LRU,
-		 * however it is not used from now on so that
-		 * we can use it safely.
-		 */
-		head = (void *)&page->rcu_head;
-		call_rcu(head, kmem_rcu_free);
-
-	} else {
+	if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU))
+		call_rcu(&page->rcu_head, kmem_rcu_free);
+	else
 		kmem_freepages(cachep, page);
-	}
 
 	/*
 	 * From now on, we don't use freelist

mm/slub.c

@@ -1507,10 +1507,7 @@ static void free_slab(struct kmem_cache *s, struct page *page)
 			VM_BUG_ON(s->reserved != sizeof(*head));
 			head = page_address(page) + offset;
 		} else {
-			/*
-			 * RCU free overloads the RCU head over the LRU
-			 */
-			head = (void *)&page->lru;
+			head = &page->rcu_head;
 		}
 
 		call_rcu(head, rcu_free_slab);