slub: Make the order configurable for each slab cache

Makes /sys/kernel/slab/<slabname>/order writable. The allocation
order can then be changed dynamically during runtime.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
 mm/slub.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2008-02-15 14:32:03.186628435 -0800
+++ linux-2.6/mm/slub.c	2008-02-15 14:39:15.063180225 -0800
@@ -2368,7 +2368,7 @@ static int calculate_sizes(struct kmem_c
 	/*
 	 * Determine the number of objects per slab
 	 */
-	s->objects = (PAGE_SIZE << s->order) / size;
+	s->objects = max_t(unsigned long, s->objects, (PAGE_SIZE << s->order) / size);
 	s->objects0 = PAGE_SIZE / size;
 
 	return !!s->objects;
@@ -3839,11 +3839,24 @@ static ssize_t objs_per_slab_show(struct
 }
 SLAB_ATTR_RO(objs_per_slab);
 
+static ssize_t order_store(struct kmem_cache *s,
+				const char *buf, size_t length)
+{
+	int order = simple_strtoul(buf, NULL, 10);
+
+	if (order > slub_max_order)
+		return -EINVAL;
+
+	s->order = order;
+	calculate_sizes(s);
+	return length;
+}
+
 static ssize_t order_show(struct kmem_cache *s, char *buf)
 {
 	return sprintf(buf, "%d\n", s->order);
 }
-SLAB_ATTR_RO(order);
+SLAB_ATTR(order);
 
 static ssize_t ctor_show(struct kmem_cache *s, char *buf)
 {