mm/slab.c: replace open-coded round-up code with ALIGN

Link: http://lkml.kernel.org/r/20170616072918epcms5p4ff16c24ef8472b4c3b4371823cd87856@epcms5p4
Signed-off-by: Canjiang Lu <canjiang.lu@samsung.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>

mm/slab.c

@@ -2040,17 +2040,13 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
 	 * unaligned accesses for some archs when redzoning is used, and makes
 	 * sure any on-slab bufctl's are also correctly aligned.
 	 */
-	if (size & (BYTES_PER_WORD - 1)) {
-		size += (BYTES_PER_WORD - 1);
-		size &= ~(BYTES_PER_WORD - 1);
-	}
+	size = ALIGN(size, BYTES_PER_WORD);
 
 	if (flags & SLAB_RED_ZONE) {
 		ralign = REDZONE_ALIGN;
 		/* If redzoning, ensure that the second redzone is suitably
 		 * aligned, by adjusting the object size accordingly. */
-		size += REDZONE_ALIGN - 1;
-		size &= ~(REDZONE_ALIGN - 1);
+		size = ALIGN(size, REDZONE_ALIGN);
 	}
 
 	/* 3) caller mandated alignment */