memory-hotplug: build zonelists when offlining pages

online_pages() does build_all_zonelists() and zone_pcp_update(), I think
offline_pages() should do it too.

When the zone has no memory to allocate, remove it from other nodes'
zonelists.  zone_batchsize() depends on zone's present pages, if zone's
present pages are changed, zone's pcp should be updated.
Signed-off-by: NXishi Qiu <qiuxishi@huawei.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -970,8 +970,13 @@ static int __ref offline_pages(unsigned long start_pfn,
 
 	init_per_zone_wmark_min();
 
-	if (!populated_zone(zone))
+	if (!populated_zone(zone)) {
 		zone_pcp_reset(zone);
+		mutex_lock(&zonelists_mutex);
+		build_all_zonelists(NULL, NULL);
+		mutex_unlock(&zonelists_mutex);
+	} else
+		zone_pcp_update(zone);
 
 	if (!node_present_pages(node)) {
 		node_clear_state(node, N_HIGH_MEMORY);