slub: fix high order page allocation problem with __GFP_NOFAIL

SLUB already try to allocate high order page with clearing __GFP_NOFAIL.
But, when allocating shadow page for kmemcheck, it missed clearing
the flag. This trigger WARN_ON_ONCE() reported by Christian Casteyde.

https://bugzilla.kernel.org/show_bug.cgi?id=65991
https://lkml.org/lkml/2013/12/3/764

This patch fix this situation by using same allocation flag as original
allocation.

Reported-by: Christian Casteyde <casteyde.christian@free.fr>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

mm/slub.c

@@ -1350,11 +1350,12 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 	page = alloc_slab_page(alloc_gfp, node, oo);
 	if (unlikely(!page)) {
 		oo = s->min;
+		alloc_gfp = flags;
 		/*
 		 * Allocation may have failed due to fragmentation.
 		 * Try a lower order alloc if possible
 		 */
-		page = alloc_slab_page(flags, node, oo);
+		page = alloc_slab_page(alloc_gfp, node, oo);
 
 		if (page)
 			stat(s, ORDER_FALLBACK);
@@ -1364,7 +1365,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 		&& !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) {
 		int pages = 1 << oo_order(oo);
 
-		kmemcheck_alloc_shadow(page, oo_order(oo), flags, node);
+		kmemcheck_alloc_shadow(page, oo_order(oo), alloc_gfp, node);
 
 		/*
 		 * Objects from caches that have a constructor don't get