[RFC PATCH v1.2 09/12] mm/damon/tests/core-kunit: test damon_nr_samples_per_aggr()

damon_max_nr_accesses(), which is a previous version of
damon_nr_samples_per_aggr() before the renaming, was wrongly returning
zero or random overflowed values for extreme intervals setup.  Commit
35d4a3cf70a8 ("mm/damon/ops-common: handle extreme intervals in
damon_hot_score()") updated the function to return correct or more valid
values.  Add a kunit test to ensure it is working as expected.

Signed-off-by: SJ Park <[email protected]>
---
 mm/damon/tests/core-kunit.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index 252d81c30d6f1..c7bda8aadef3f 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -619,6 +619,27 @@ static void damon_test_set_regions(struct kunit *test)
 			(struct damon_addr_range[]){}, 0, -EINVAL);
 }
 
+static void damon_test_nr_samples_per_aggr(struct kunit *test)
+{
+	struct damon_attrs attrs = {
+		.sample_interval = 0,
+		.aggr_interval = 0,
+	};
+
+	/* Zero aggregation interval doesn't cause division by zero */
+	KUNIT_EXPECT_EQ(test, damon_nr_samples_per_aggr(&attrs), 1);
+
+	/*
+	 * Too large aggregation interval on 64 bit system doesn't cause
+	 * overflow
+	 */
+	if (ULONG_MAX > UINT_MAX) {
+		attrs.aggr_interval = (unsigned long)UINT_MAX + 1;
+		KUNIT_EXPECT_EQ(test, damon_nr_samples_per_aggr(&attrs),
+				UINT_MAX);
+	}
+}
+
 static void damon_test_update_monitoring_result(struct kunit *test)
 {
 	struct damon_attrs old_attrs = {
@@ -1670,6 +1691,7 @@ static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damon_test_split_above_half_progresses),
 	KUNIT_CASE(damon_test_ops_registration),
 	KUNIT_CASE(damon_test_set_regions),
+	KUNIT_CASE(damon_test_nr_samples_per_aggr),
 	KUNIT_CASE(damon_test_update_monitoring_result),
 	KUNIT_CASE(damon_test_set_attrs),
 	KUNIT_CASE(damon_test_mvsum),
-- 
2.47.3