When the node is offlined, there is no memory/cpu on the node. If a
sleep task runs on a cpu of this node, it will be migrated to the
cpu on the other node. So we can clear cpu-to-node mapping.

Cc: Yasuaki Ishimatsu <isimatu.yasu...@jp.fujitsu.com>
Cc: David Rientjes <rient...@google.com>
Cc: Jiang Liu <liu...@gmail.com>
Cc: Minchan Kim <minchan....@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motoh...@jp.fujitsu.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Mel Gorman <m...@csn.ul.ie>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Tang Chen <tangc...@cn.fujitsu.com>
Signed-off-by: Wen Congyang <we...@cn.fujitsu.com>
---
 mm/memory_hotplug.c | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index b7c30bb..5ae86d7 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1669,6 +1669,34 @@ static int check_cpu_on_node(void *data)
        return 0;
 }
 
+static void unmap_cpu_on_node(void *data)
+{
+#ifdef CONFIG_ACPI_NUMA
+       struct pglist_data *pgdat = data;
+       int cpu;
+
+       for_each_possible_cpu(cpu)
+               if (cpu_to_node(cpu) == pgdat->node_id)
+                       numa_clear_node(cpu);
+#endif
+}
+
+static int check_and_unmap_cpu_on_node(void *data)
+{
+       int ret = check_cpu_on_node(data);
+
+       if (ret)
+               return ret;
+
+       /*
+        * the node will be offlined when we come here, so we can clear
+        * the cpu_to_node() now.
+        */
+
+       unmap_cpu_on_node(data);
+       return 0;
+}
+
 /* offline the node if all memory sections of this node are removed */
 void try_offline_node(int nid)
 {
@@ -1695,7 +1723,7 @@ void try_offline_node(int nid)
                return;
        }
 
-       if (stop_machine(check_cpu_on_node, NODE_DATA(nid), NULL))
+       if (stop_machine(check_and_unmap_cpu_on_node, NODE_DATA(nid), NULL))
                return;
 
        /*
-- 
1.8.0

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