Add a kunit test for the functionality of damon_apply_min_nr_regions().

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/tests/core-kunit.h | 52 +++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index 92ea25e2dc9e3..4c19ccac5a2ee 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -1241,6 +1241,57 @@ static void damon_test_set_filters_default_reject(struct kunit *test)
 	damos_free_filter(target_filter);
 }
 
+static void damon_test_apply_min_nr_regions_for(struct kunit *test,
+		unsigned long sz_regions, unsigned long min_region_sz,
+		unsigned long min_nr_regions,
+		unsigned long max_region_sz_expect,
+		unsigned long nr_regions_expect)
+{
+	struct damon_ctx *ctx;
+	struct damon_target *t;
+	struct damon_region *r;
+	unsigned long max_region_size;
+
+	ctx = damon_new_ctx();
+	if (!ctx)
+		kunit_skip(test, "ctx alloc fail\n");
+	t = damon_new_target();
+	if (!t) {
+		damon_destroy_ctx(ctx);
+		kunit_skip(test, "target alloc fail\n");
+	}
+	damon_add_target(ctx, t);
+	r = damon_new_region(0, sz_regions);
+	if (!r) {
+		damon_destroy_ctx(ctx);
+		kunit_skip(test, "region alloc fail\n");
+	}
+	damon_add_region(r, t);
+
+	ctx->min_region_sz = min_region_sz;
+	ctx->attrs.min_nr_regions = min_nr_regions;
+	max_region_size = damon_apply_min_nr_regions(ctx);
+
+	KUNIT_EXPECT_EQ(test, max_region_size, max_region_sz_expect);
+	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), nr_regions_expect);
+
+	damon_destroy_ctx(ctx);
+}
+
+static void damon_test_apply_min_nr_regions(struct kunit *test)
+{
+	/* common, expected setup */
+	damon_test_apply_min_nr_regions_for(test, 10, 1, 10, 1, 10);
+	/* no zero size limit */
+	damon_test_apply_min_nr_regions_for(test, 10, 1, 15, 1, 10);
+	/* max size should be aligned by min_region_sz */
+	damon_test_apply_min_nr_regions_for(test, 10, 2, 2, 6, 2);
+	/*
+	 * when min_nr_regions and min_region_sz conflicts, min_region_sz wins.
+	 */
+	damon_test_apply_min_nr_regions_for(test, 10, 2, 10, 2, 5);
+}
+
 static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damon_test_target),
 	KUNIT_CASE(damon_test_regions),
@@ -1267,6 +1318,7 @@ static struct kunit_case damon_test_cases[] = {
 	KUNIT_CASE(damos_test_filter_out),
 	KUNIT_CASE(damon_test_feed_loop_next_input),
 	KUNIT_CASE(damon_test_set_filters_default_reject),
+	KUNIT_CASE(damon_test_apply_min_nr_regions),
 	{},
 };
 
-- 
2.47.3