memory_hotplug: check for walk_memory_resource() failure in online_pages()

Add a check to online_pages() to test for failure of
walk_memory_resource().  This fixes a condition where a failure
of walk_memory_resource() can lead to online_pages() returning
success without the requested pages being onlined.
Signed-off-by: NGeoff Levand <geoffrey.levand@am.sony.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Keith Mannthey <kmannth@us.ibm.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -404,8 +404,15 @@ int online_pages(unsigned long pfn, unsigned long nr_pages)
 	if (!populated_zone(zone))
 		need_zonelists_rebuild = 1;
 
-	walk_memory_resource(pfn, nr_pages, &onlined_pages,
+	ret = walk_memory_resource(pfn, nr_pages, &onlined_pages,
 		online_pages_range);
+	if (ret) {
+		printk(KERN_DEBUG "online_pages %lx at %lx failed\n",
+			nr_pages, pfn);
+		memory_notify(MEM_CANCEL_ONLINE, &arg);
+		return ret;
+	}
+
 	zone->present_pages += onlined_pages;
 	zone->zone_pgdat->node_present_pages += onlined_pages;