[PATCH v3 2/2] mem-hotplug: Reset node present pages when hot-adding a new pgdat.

[Tang Chen <tangchen@cn.fujitsu.com>]

When memory is hot-added, all the memory is in offline state. So
clear all zones' present_pages because they will be updated in
online_pages() and offline_pages(). Otherwise, /proc/zoneinfo
will corrupt:

When the memory of node2 is offline:
# cat /proc/zoneinfo
......
Node 2, zone   Movable
......
        spanned  8388608
        present  8388608
        managed  0

When we online memory on node2:
# cat /proc/zoneinfo
......
Node 2, zone   Movable
......
        spanned  8388608
        present  16777216
        managed  8388608

Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: stable@vger.kernel.org # 3.16+
---
 mm/memory_hotplug.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 8aba12b..d0c9b7c 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1067,6 +1067,16 @@ out:
 }
 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
 
+static void reset_node_present_pages(pg_data_t *pgdat)
+{
+	struct zone *z;
+
+	for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
+		z->present_pages = 0;
+
+	pgdat->node_present_pages = 0;
+}
+
 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
 static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
 {
@@ -1105,6 +1115,13 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
 	 */
 	reset_node_managed_pages(pgdat);
 
+	/*
+	 * When memory is hot-added, all the memory is in offline state. So
+	 * clear all zones' present_pages because they will be updated in
+	 * online_pages() and offline_pages().
+	 */
+	reset_node_present_pages(pgdat);
+
 	return pgdat;
 }
 
-- 
1.8.3.1

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