mm/memory_hotplug.c: spare unnecessary calls to node_set_state

In node_states_check_changes_online, we check if the node will have to be
set for any of the N_*_MEMORY states after the pages have been onlined.

Later on, we perform the activation in node_states_set_node.  Currently,
in node_states_set_node we set the node to N_MEMORY unconditionally.

This means that we call node_set_state for N_MEMORY every time pages go
online, but we only need to do it if the node has not yet been set for
N_MEMORY.

Fix this by checking status_change_nid.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Oscar Salvador <[email protected]>
Reviewed-by: Pavel Tatashin <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Jonathan Cameron <[email protected]>
Cc: <[email protected]>
Cc: Mathieu Malaterre <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/memory_hotplug.c

@@ -753,7 +753,8 @@ static void node_states_set_node(int node, struct memory_notify *arg)
 	if (arg->status_change_nid_high >= 0)
 		node_set_state(node, N_HIGH_MEMORY);
 
-	node_set_state(node, N_MEMORY);
+	if (arg->status_change_nid >= 0)
+		node_set_state(node, N_MEMORY);
 }
 
 static void __meminit resize_zone_range(struct zone *zone, unsigned long start_pfn,