[PATCH] nommu: use compound page in slab allocator

The earlier patch to consolidate mmu and nommu page allocation and
refcounting by using compound pages for nommu allocations had a bug:
kmalloc slabs who's pages were initially allocated by a non-__GFP_COMP
allocator could be passed into mm/nommu.c kmalloc allocations which really
wanted __GFP_COMP underlying pages.  Fix that by having nommu pass
__GFP_COMP to all higher order slab allocations.
Signed-off-by: NLuke Yang <luke.adi@gmail.com>
Acked-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

mm/slab.c

@@ -1456,7 +1456,14 @@ static void *kmem_getpages(struct kmem_cache *cachep, gfp_t flags, int nodeid)
 	int i;
 
 	flags |= cachep->gfpflags;
+#ifndef CONFIG_MMU
+	/* nommu uses slab's for process anonymous memory allocations, so
+	 * requires __GFP_COMP to properly refcount higher order allocations"
+	 */
+	page = alloc_pages_node(nodeid, (flags | __GFP_COMP), cachep->gfporder);
+#else
 	page = alloc_pages_node(nodeid, flags, cachep->gfporder);
+#endif
 	if (!page)
 		return NULL;
 	addr = page_address(page);