slub: min order when debug_guardpage_minorder > 0

Disable slub debug facilities and allocate slabs at minimal order when
debug_guardpage_minorder > 0 to increase probability to catch random
memory corruption by cpu exception.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/slub.c

@@ -3654,6 +3654,9 @@ void __init kmem_cache_init(void)
 	struct kmem_cache *temp_kmem_cache_node;
 	unsigned long kmalloc_size;
 
+	if (debug_guardpage_minorder())
+		slub_max_order = 0;
+
 	kmem_size = offsetof(struct kmem_cache, node) +
 				nr_node_ids * sizeof(struct kmem_cache_node *);