memory_hotplug: use pgdat_resize_lock() in online_pages()

mmzone.h documents node_size_lock (which pgdat_resize_lock() locks) as
follows:

        * Must be held any time you expect node_start_pfn, node_present_pages
        * or node_spanned_pages stay constant.  [...]

So actually hold it when we update node_present_pages in online_pages().

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 1ad92b46753e..527c51084bb8 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -918,6 +918,7 @@ static void node_states_set_node(int node, struct memory_notify *arg)
 
 int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_type)
 {
+        unsigned long flags;
         unsigned long onlined_pages = 0;
         struct zone *zone;
         int need_zonelists_rebuild = 0;
@@ -996,7 +997,11 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 
         zone->managed_pages += onlined_pages;
         zone->present_pages += onlined_pages;
+
+        pgdat_resize_lock(zone->zone_pgdat, &flags);
         zone->zone_pgdat->node_present_pages += onlined_pages;
+        pgdat_resize_unlock(zone->zone_pgdat, &flags);
+
         if (onlined_pages) {
                 node_states_set_node(zone_to_nid(zone), &arg);
                 if (need_zonelists_rebuild)