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>

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 527c51084bb8f8dc2907062ebf4bf2a930e031f5..a66d0023d21912a187c49a9328ef9ff1e92847c3 100644 (file)
--- 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();