mm, memory_hotplug: remove explicit build_all_zonelists from try_online_node

try_online_node calls hotadd_new_pgdat which already calls
build_all_zonelists.  So the additional call is redundant.  Even though
hotadd_new_pgdat will only initialize zonelists of the new node this is
the right thing to do because such a node doesn't have any memory so
other zonelists would ignore all the zones from this node anyway.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Michal Hocko <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Toshi Kani <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Shaohua Li <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Michal Hocko

mm/memory_hotplug.c

@@ -1081,13 +1081,6 @@ int try_online_node(int nid)
 	node_set_online(nid);
 	ret = register_one_node(nid);
 	BUG_ON(ret);
-
-	if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
-		mutex_lock(&zonelists_mutex);
-		build_all_zonelists(NULL);
-		mutex_unlock(&zonelists_mutex);
-	}
-
 out:
 	mem_hotplug_done();
 	return ret;