[PATCH v4] sched/numa, mm: do not try to migrate memory to memoryless nodes

[Byungchul Park]

Memoryless nodes do not have any memory to migrate to, so stop trying
it.

Signed-off-by: Byungchul Park <byungchul@xxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
---
 kernel/sched/fair.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d7a3c63a2171..3e3b44ae72d1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1828,6 +1828,12 @@ bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio,
 	int dst_nid = cpu_to_node(dst_cpu);
 	int last_cpupid, this_cpupid;
 
+	/*
+	 * Cannot migrate to memoryless nodes.
+	 */
+	if (!node_state(dst_nid, N_MEMORY))
+		return false;
+
 	/*
 	 * The pages in slow memory node should be migrated according
 	 * to hot/cold instead of private/shared.
-- 
2.17.1