page_cgroup should ignore empty nodes

Fix a total bootup freeze on ia64.
Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Tested-by: NLi Zefan <lizf@cn.fujitsu.com>
Reported-by: NLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/page_cgroup.c

@@ -49,6 +49,9 @@ static int __init alloc_node_page_cgroup(int nid)
 	start_pfn = NODE_DATA(nid)->node_start_pfn;
 	nr_pages = NODE_DATA(nid)->node_spanned_pages;
 
+	if (!nr_pages)
+		return 0;
+
 	table_size = sizeof(struct page_cgroup) * nr_pages;
 
 	base = __alloc_bootmem_node_nopanic(NODE_DATA(nid),