memcg: use __GFP_NOWARN in page cgroup allocation

page_cgroup's page allocation at init/memory hotplug uses kmalloc() and
vmalloc(). If kmalloc() failes, vmalloc() is used.

This is because vmalloc() is very limited resource on 32bit systems.
We want to use kmalloc() first.

But in this kind of call, __GFP_NOWARN should be specified.
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: 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/page_cgroup.c

@@ -114,7 +114,8 @@ static int __init_refok init_section_page_cgroup(unsigned long pfn)
 		nid = page_to_nid(pfn_to_page(pfn));
 		table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
 		if (slab_is_available()) {
-			base = kmalloc_node(table_size, GFP_KERNEL, nid);
+			base = kmalloc_node(table_size,
+					GFP_KERNEL | __GFP_NOWARN, nid);
 			if (!base)
 				base = vmalloc_node(table_size, nid);
 		} else {