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Subject[PATCH 2/4] mm/hotplug: correctly add new zone to all other nodes' zone lists
Date
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: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Jiang Liu <liuj97@gmail.com>
---
mm/memory_hotplug.c | 15 ++++++++-------
1 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index f93c5b5..bce80c7 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -512,19 +512,20 @@ 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(NULL, 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(NULL, 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();

--
1.7.1



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