[PATCH 2/6] mm/damon/core-test: test max_nr_accesses overflow caused divide-by-zero

[SeongJae Park]

Commit 35f5d94187a6 ("mm/damon: implement a function for max nr_accesses
safe calculation") has fixed an overflow bug that could cause
divide-by-zero.  Add a kunit test for the bug to ensure similar bugs are
not introduced again.

Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
---
 mm/damon/core-test.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mm/damon/core-test.h b/mm/damon/core-test.h
index 876e398557b0..0cee634f3544 100644
--- a/mm/damon/core-test.h
+++ b/mm/damon/core-test.h
@@ -302,6 +302,16 @@ static void damon_test_set_regions(struct kunit *test)
 	damon_destroy_target(t);
 }
 
+static void damon_test_nr_accesses_to_accesses_bp(struct kunit *test)
+{
+	struct damon_attrs attrs = {
+		.sample_interval = 10,
+		.aggr_interval = ((unsigned long)UINT_MAX + 1) * 10
+	};
+
+	KUNIT_EXPECT_EQ(test, damon_nr_accesses_to_accesses_bp(123, &attrs), 0);
+}
+
 static void damon_test_update_monitoring_result(struct kunit *test)
 {
 	struct damon_attrs old_attrs = {
@@ -487,6 +497,7 @@ static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damon_test_split_regions_of),
 	KUNIT_CASE(damon_test_ops_registration),
 	KUNIT_CASE(damon_test_set_regions),
+	KUNIT_CASE(damon_test_nr_accesses_to_accesses_bp),
 	KUNIT_CASE(damon_test_update_monitoring_result),
 	KUNIT_CASE(damon_test_set_attrs),
 	KUNIT_CASE(damon_test_moving_sum),
-- 
2.34.1