slab: fix starting index for finding another object

In array cache, there is a object at index 0, check it.
Signed-off-by: Joonsoo Kim <js1304@gmail.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: David Miller <davem@davemloft.net>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slab.c

@@ -983,7 +983,7 @@ static void *__ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac,
 		}
 
 		/* The caller cannot use PFMEMALLOC objects, find another one */
-		for (i = 1; i < ac->avail; i++) {
+		for (i = 0; i < ac->avail; i++) {
 			/* If a !PFMEMALLOC object is found, swap them */
 			if (!is_obj_pfmemalloc(ac->entry[i])) {
 				objp = ac->entry[i];