memory-hotplug: fix zone stat mismatch

During memory-hotplug, I found NR_ISOLATED_[ANON|FILE] are increasing,
causing the kernel to hang.  When the system doesn't have enough free
pages, it enters reclaim but never reclaim any pages due to
too_many_isolated()==true and loops forever.

The cause is that when we do memory-hotadd after memory-remove,
__zone_pcp_update() clears a zone's ZONE_STAT_ITEMS in setup_pageset()
although the vm_stat_diff of all CPUs still have values.

In addtion, when we offline all pages of the zone, we reset them in
zone_pcp_reset without draining so we loss some zone stat item.

Reviewed-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9b8e6243a524..5485f0ef4ec3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5916,6 +5916,7 @@ static int __meminit __zone_pcp_update(void *data)
                 local_irq_save(flags);
                 if (pcp->count > 0)
                         free_pcppages_bulk(zone, pcp->count, pcp);
+                drain_zonestat(zone, pset);
                 setup_pageset(pset, batch);
                 local_irq_restore(flags);
         }
@@ -5932,10 +5933,16 @@ void __meminit zone_pcp_update(struct zone *zone)
 void zone_pcp_reset(struct zone *zone)
 {
         unsigned long flags;
+        int cpu;
+        struct per_cpu_pageset *pset;
 
         /* avoid races with drain_pages()  */
         local_irq_save(flags);
         if (zone->pageset != &boot_pageset) {
+                for_each_online_cpu(cpu) {
+                        pset = per_cpu_ptr(zone->pageset, cpu);
+                        drain_zonestat(zone, pset);
+                }
                 free_percpu(zone->pageset);
                 zone->pageset = &boot_pageset;
         }