mm/sl[aou]b: Common alignment code

Extract the code to do object alignment from the allocators.
Do the alignment calculations in slab_common so that the
__kmem_cache_create functions of the allocators do not have
to deal with alignment.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

mm/slab_common.c

@@ -72,6 +72,34 @@ static inline int kmem_cache_sanity_check(const char *name, size_t size)
 }
 #endif
 
+/*
+ * Figure out what the alignment of the objects will be given a set of
+ * flags, a user specified alignment and the size of the objects.
+ */
+unsigned long calculate_alignment(unsigned long flags,
+		unsigned long align, unsigned long size)
+{
+	/*
+	 * If the user wants hardware cache aligned objects then follow that
+	 * suggestion if the object is sufficiently large.
+	 *
+	 * The hardware cache alignment cannot override the specified
+	 * alignment though. If that is greater then use it.
+	 */
+	if (flags & SLAB_HWCACHE_ALIGN) {
+		unsigned long ralign = cache_line_size();
+		while (size <= ralign / 2)
+			ralign /= 2;
+		align = max(align, ralign);
+	}
+
+	if (align < ARCH_SLAB_MINALIGN)
+		align = ARCH_SLAB_MINALIGN;
+
+	return ALIGN(align, sizeof(void *));
+}
+
+
 /*
  * kmem_cache_create - Create a cache.
  * @name: A string which is used in /proc/slabinfo to identify this cache.
@@ -124,7 +152,7 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size, size_t align
 	s = kmem_cache_zalloc(kmem_cache, GFP_KERNEL);
 	if (s) {
 		s->object_size = s->size = size;
-		s->align = align;
+		s->align = calculate_alignment(flags, align, size);
 		s->ctor = ctor;
 		s->name = kstrdup(name, GFP_KERNEL);
 		if (!s->name) {
@@ -211,7 +239,7 @@ void __init create_boot_cache(struct kmem_cache *s, const char *name, size_t siz
 
 	s->name = name;
 	s->size = s->object_size = size;
-	s->align = ARCH_KMALLOC_MINALIGN;
+	s->align = calculate_alignment(flags, ARCH_KMALLOC_MINALIGN, size);
 	err = __kmem_cache_create(s, flags);
 
 	if (err)