[ 3.5.y.z extended stable ] Patch "mm/hotplug: correctly add new zone to all other nodes' zone" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    mm/hotplug: correctly add new zone to all other nodes' zone

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 5945e570620711249a54509dea2f7675f6a9cfb0 Mon Sep 17 00:00:00 2001
From: Jiang Liu <jiang.liu at huawei.com>
Date: Tue, 31 Jul 2012 16:43:30 -0700
Subject: [PATCH] mm/hotplug: correctly add new zone to all other nodes' zone
 lists

commit 08dff7b7d629807dbb1f398c68dd9cd58dd657a1 upstream.

When online_pages() is called to add new memory to an empty zone, it
rebuilds all zone lists by calling build_all_zonelists().  But there's a
bug which prevents the new zone to be added to other nodes' zone lists.

online_pages() {
	build_all_zonelists()
	.....
	node_set_state(zone_to_nid(zone), N_HIGH_MEMORY)
}

Here the node of the zone is put into N_HIGH_MEMORY state after calling
build_all_zonelists(), but build_all_zonelists() only adds zones from
nodes in N_HIGH_MEMORY state to the fallback zone lists.
build_all_zonelists()

    ->__build_all_zonelists()
	->build_zonelists()
	    ->find_next_best_node()
		->for_each_node_state(n, N_HIGH_MEMORY)

So memory in the new zone will never be used by other nodes, and it may
cause strange behavor when system is under memory pressure.  So put node
into N_HIGH_MEMORY state before calling build_all_zonelists().

Signed-off-by: Jianguo Wu <wujianguo at huawei.com>
Signed-off-by: Jiang Liu <liuj97 at gmail.com>
Cc: Mel Gorman <mgorman at suse.de>
Cc: Michal Hocko <mhocko at suse.cz>
Cc: Minchan Kim <minchan at kernel.org>
Cc: Rusty Russell <rusty at rustcorp.com.au>
Cc: Yinghai Lu <yinghai at kernel.org>
Cc: Tony Luck <tony.luck at intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro at jp.fujitsu.com>
Cc: David Rientjes <rientjes at google.com>
Cc: Keping Chen <chenkeping at huawei.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
[ luis: backported to 3.5 ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 mm/memory_hotplug.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 0086ac9..17651cd 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -516,19 +516,20 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages)

 	zone->present_pages += onlined_pages;
 	zone->zone_pgdat->node_present_pages += onlined_pages;
-	if (need_zonelists_rebuild)
-		build_all_zonelists(zone);
-	else
-		zone_pcp_update(zone);
+	if (onlined_pages) {
+		node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
+		if (need_zonelists_rebuild)
+			build_all_zonelists(zone);
+		else
+			zone_pcp_update(zone);
+	}

 	mutex_unlock(&zonelists_mutex);

 	init_per_zone_wmark_min();

-	if (onlined_pages) {
+	if (onlined_pages)
 		kswapd_run(zone_to_nid(zone));
-		node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
-	}

 	vm_total_pages = nr_free_pagecache_pages();

--
1.8.1.2