[PATCH v3 3/4] memory_hotplug: use pgdat_resize_lock() in online_pages()

[Cody P Schafer]

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@xxxxxxxxxxxxxxxxxx>
---
 mm/memory_hotplug.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a221fac..0bdca10 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -915,6 +915,7 @@ 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;
@@ -993,7 +994,11 @@ 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)
-- 
1.8.2.2

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