From: Lai Jiangshan <redacted>

Now, memory management can handle movable node or nodes which don't have
any normal memory, so we can dynamic configure and add movable node by:
	online a ZONE_MOVABLE memory from a previous offline node
	offline the last normal memory which result a non-normal-memory-node

movable-node is very important for power-saving,
hardware partitioning and high-available-system(hardware fault management).

...

--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c

@@ -589,11 +589,19 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 	return 0;
 }
 
+#ifdef CONFIG_MOVABLE_NODE
+/* when CONFIG_MOVABLE_NODE, we allow online node don't have normal memory */

+static bool can_online_high_movable(struct zone *zone)
+{
+	return true;
+}
+#else /* #ifdef CONFIG_MOVABLE_NODE */
 /* ensure every online node has NORMAL memory */
 static bool can_online_high_movable(struct zone *zone)
 {
 	return node_state(zone_to_nid(zone), N_NORMAL_MEMORY);
 }
+#endif /* #ifdef CONFIG_MOVABLE_NODE */
 
 /* check which state of node_states will be changed when online memory */
 static void node_states_check_changes_online(unsigned long nr_pages,

@@ -1097,6 +1105,13 @@ check_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
 	return offlined;
 }
 
+#ifdef CONFIG_MOVABLE_NODE
+/* when CONFIG_MOVABLE_NODE, we allow online node don't have normal memory */

+static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
+{
+	return true;
+}
+#else /* #ifdef CONFIG_MOVABLE_NODE */
 /* ensure the node has NORMAL memory if it is still online */
 static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
 {

@@ -1120,6 +1135,7 @@ static bool can_offline_normal(struct zone *zone, unsigned long nr_pages)
 	 */
 	return present_pages == 0;
 }
+#endif /* #ifdef CONFIG_MOVABLE_NODE */