damon_register_ops
int damon_register_ops(struct damon_operations *ops);
return damon_register_ops(&ops);
KUNIT_EXPECT_EQ(test, damon_register_ops(&bak), 0);
KUNIT_EXPECT_EQ(test, damon_register_ops(&ops), -EINVAL);
KUNIT_EXPECT_EQ(test, damon_register_ops(&ops), 0);
KUNIT_EXPECT_EQ(test, damon_register_ops(&ops), -EINVAL);
err = damon_register_ops(&ops);
return damon_register_ops(&ops_fvaddr);