memory hotplug: memmap_init_zone called twice

__add_zone calls memmap_init_zone twice if memory gets attached to an empty
zone.  Once via init_currently_empty_zone and once explictly right after that
call.

Looks like this is currently not a bug, however the call is superfluous and
might lead to subtle bugs if memmap_init_zone gets changed.  So make sure it
is called only once.

Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -167,13 +167,9 @@ static int __add_zone(struct zone *zone, unsigned long phys_start_pfn)
 	int zone_type;
 
 	zone_type = zone - pgdat->node_zones;
-	if (!zone->wait_table) {
-		int ret = 0;
-		ret = init_currently_empty_zone(zone, phys_start_pfn,
+	if (!zone->wait_table)
+		return init_currently_empty_zone(zone, phys_start_pfn,
 						 nr_pages, MEMMAP_HOTPLUG);
-		if (ret < 0)
-			return ret;
-	}
 	memmap_init_zone(nr_pages, nid, zone_type,
 			 phys_start_pfn, MEMMAP_HOTPLUG);
 	return 0;