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>

1 files changed, 30 insertions, 2 deletions

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 497b45c25bae..a8e76d79ee65 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -73,6 +73,34 @@ 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.
  * @size: The size of objects to be created in 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)