mm: do not overwrite reserved pages counter at show_mem()

Minor fixlet to perform the reserved pages counter aggregation for each
node, at show_mem()
Signed-off-by: Rafael Aquini <aquini@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Johannes Weiner <jweiner@redhat.com>
Acked-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/show_mem.c

@@ -28,7 +28,7 @@ void show_mem(unsigned int filter)
 				continue;
 
 			total += zone->present_pages;
-			reserved = zone->present_pages - zone->managed_pages;
+			reserved += zone->present_pages - zone->managed_pages;
 
 			if (is_highmem_idx(zoneid))
 				highmem += zone->present_pages;