[PATCH 2/2] selftests/migration: Disable NUMA balancing and check migration status

[Alistair Popple <apopple@nvidia.com>]

The migration selftest was only checking the return code and not the
status array for migration success/failure. Update the test to check
both. This uncovered a bug in the return code handling of
do_pages_move().

Also disable NUMA balancing as that can lead to unexpected migration
failures.

Signed-off-by: Alistair Popple <apopple@nvidia.com>
Suggested-by: Ryan Roberts <ryan.roberts@arm.com>
---

Ryan, this will still cause the test to fail if a migration failed. I
was unable to reproduce a migration failure for any cases on my system
once I disabled NUMA balancing though so I'd be curious if you are
still seeing failures with this patch applied. AFAIK there shouldn't
be anything else that would be causing migration failure so would like
to know what is causing failures. Thanks!

 tools/testing/selftests/mm/migration.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/migration.c b/tools/testing/selftests/mm/migration.c
index 379581567f27..cf079af5799b 100644
--- a/tools/testing/selftests/mm/migration.c
+++ b/tools/testing/selftests/mm/migration.c
@@ -51,6 +51,12 @@ FIXTURE_SETUP(migration)
 	ASSERT_NE(self->threads, NULL);
 	self->pids = malloc(self->nthreads * sizeof(*self->pids));
 	ASSERT_NE(self->pids, NULL);
+
+	/*
+	 * Disable NUMA balancing which can cause migration
+	 * failures.
+	 */
+	numa_set_membind(numa_all_nodes_ptr);
 };
 
 FIXTURE_TEARDOWN(migration)
@@ -62,13 +68,14 @@ FIXTURE_TEARDOWN(migration)
 int migrate(uint64_t *ptr, int n1, int n2)
 {
 	int ret, tmp;
-	int status = 0;
 	struct timespec ts1, ts2;
 
 	if (clock_gettime(CLOCK_MONOTONIC, &ts1))
 		return -1;
 
 	while (1) {
+		int status = NUMA_NUM_NODES + 1;
+
 		if (clock_gettime(CLOCK_MONOTONIC, &ts2))
 			return -1;
 
@@ -85,6 +92,15 @@ int migrate(uint64_t *ptr, int n1, int n2)
 			return -2;
 		}
 
+		/*
+		 * Note we should never see this because move_pages() should
+		 * have indicated a page couldn't migrate above.
+		 */
+		if (status < 0) {
+			printf("Page didn't migrate, error %d\n", status);
+			return -2;
+		}
+
 		tmp = n2;
 		n2 = n1;
 		n1 = tmp;
-- 
2.39.2