[PATCH v3] sched/numa, mm: do not promote folios to nodes not set N_MEMORY

[Byungchul Park]

A numa node might not have its local memory but CPUs. Promoting a folio
to the node's local memory is nonsense. So avoid nodes not set N_MEMORY
from getting promoted.

Signed-off-by: Byungchul Park <byungchul@xxxxxx>
---
 kernel/sched/fair.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d7a3c63a2171..7ed9ef3c0134 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1828,6 +1828,13 @@ 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;
 
+	/*
+	 * A node of dst_nid might not have its local memory. Promoting
+	 * a folio to the node is meaningless.
+	 */
+	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