[PATCH] mm/memory_hotplug: just build zonelist for new added node

[Wei Yang]

In commit (9adb62a5df9c0fbef7) "mm/hotplug: correctly setup fallback
zonelists when creating new pgdat" tries to build the correct zonelist for
a new added node, while it is not necessary to rebuild it for already exist
nodes.

In build_zonelists(), it will iterate on nodes with memory. For a new added
node, it will have memory until node_states_set_node() is called in
online_pages().

This patch will avoid to rebuild the zonelists for already exist nodes.

Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
---
 mm/page_alloc.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 560eafe8234d..fc8181b44fd8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5200,15 +5200,17 @@ static int __build_all_zonelists(void *data)
 	memset(node_load, 0, sizeof(node_load));
 #endif
 
-	if (self && !node_online(self->node_id)) {
+	/* This node is hotadded and no memory preset yet.
+	 * So just build zonelists is fine, no need to touch other nodes.
+	 */
+	if (self && !node_online(self->node_id))
 		build_zonelists(self);
-	}
-
-	for_each_online_node(nid) {
-		pg_data_t *pgdat = NODE_DATA(nid);
+	else
+		for_each_online_node(nid) {
+			pg_data_t *pgdat = NODE_DATA(nid);
 
-		build_zonelists(pgdat);
-	}
+			build_zonelists(pgdat);
+		}
 
 	/*
 	 * Initialize the boot_pagesets that are going to be used
-- 
2.11.0