slab: factor out initialization of array cache

Factor out initialization of array cache to use it in following patch.
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slab.c

@@ -791,13 +791,8 @@ static void start_cpu_timer(int cpu)
 	}
 }
 
-static struct array_cache *alloc_arraycache(int node, int entries,
-					    int batchcount, gfp_t gfp)
+static void init_arraycache(struct array_cache *ac, int limit, int batch)
 {
-	int memsize = sizeof(void *) * entries + sizeof(struct array_cache);
-	struct array_cache *nc = NULL;
-
-	nc = kmalloc_node(memsize, gfp, node);
 	/*
 	 * The array_cache structures contain pointers to free object.
 	 * However, when such objects are allocated or transferred to another
@@ -805,15 +800,25 @@ static struct array_cache *alloc_arraycache(int node, int entries,
 	 * valid references during a kmemleak scan. Therefore, kmemleak must
 	 * not scan such objects.
 	 */
-	kmemleak_no_scan(nc);
-	if (nc) {
-		nc->avail = 0;
-		nc->limit = entries;
-		nc->batchcount = batchcount;
-		nc->touched = 0;
-		spin_lock_init(&nc->lock);
-	}
-	return nc;
+	kmemleak_no_scan(ac);
+	if (ac) {
+		ac->avail = 0;
+		ac->limit = limit;
+		ac->batchcount = batch;
+		ac->touched = 0;
+		spin_lock_init(&ac->lock);
+	}
+}
+
+static struct array_cache *alloc_arraycache(int node, int entries,
+					    int batchcount, gfp_t gfp)
+{
+	int memsize = sizeof(void *) * entries + sizeof(struct array_cache);
+	struct array_cache *ac = NULL;
+
+	ac = kmalloc_node(memsize, gfp, node);
+	init_arraycache(ac, entries, batchcount);
+	return ac;
 }
 
 static inline bool is_slab_pfmemalloc(struct page *page)