memory_hotplug: use pgdat_resize_lock() in __offline_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 __offline_pages().

[akpm@linux-foundation.org: fix build]
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 527c51084bb8..a66d0023d219 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1492,6 +1492,7 @@ static int __ref __offline_pages(unsigned long start_pfn,
         unsigned long pfn, nr_pages, expire;
         long offlined_pages;
         int ret, drain, retry_max, node;
+        unsigned long flags;
         struct zone *zone;
         struct memory_notify arg;
 
@@ -1585,7 +1586,11 @@ repeat:
         /* removal success */
         zone->managed_pages -= offlined_pages;
         zone->present_pages -= offlined_pages;
+
+        pgdat_resize_lock(zone->zone_pgdat, &flags);
         zone->zone_pgdat->node_present_pages -= offlined_pages;
+        pgdat_resize_unlock(zone->zone_pgdat, &flags);
+
         totalram_pages -= offlined_pages;
 
         init_per_zone_wmark_min();