[PATCH v7 mm-new 08/10] selftests/bpf: add test case to update THP policy

[Yafang Shao <laoar.shao@xxxxxxxxx>]

EBUSY is returned when attempting to install a new BPF program while one is
already running, though updates to existing programs are permitted.

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
 .../selftests/bpf/prog_tests/thp_adjust.c     | 23 +++++++++++++++++++
 .../selftests/bpf/progs/test_thp_adjust.c     | 14 +++++++++++
 2 files changed, 37 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/thp_adjust.c b/tools/testing/selftests/bpf/prog_tests/thp_adjust.c
index a4a34ee28301..30172f2ee5d5 100644
--- a/tools/testing/selftests/bpf/prog_tests/thp_adjust.c
+++ b/tools/testing/selftests/bpf/prog_tests/thp_adjust.c
@@ -170,6 +170,27 @@ static void subtest_thp_policy(void)
 	bpf_link__destroy(ops_link);
 }
 
+static void subtest_thp_policy_update(void)
+{
+	struct bpf_link *old_link, *new_link;
+	int err;
+
+	old_link = bpf_map__attach_struct_ops(skel->maps.swap_ops);
+	if (!ASSERT_OK_PTR(old_link, "attach_old_link"))
+		return;
+
+	new_link = bpf_map__attach_struct_ops(skel->maps.khugepaged_ops);
+	if (!ASSERT_NULL(new_link, "attach_new_link"))
+		goto destory_old;
+	ASSERT_EQ(errno, EBUSY, "attach_new_link");
+
+	err = bpf_link__update_map(old_link, skel->maps.khugepaged_ops);
+	ASSERT_EQ(err, 0, "update_old_link");
+
+destory_old:
+	bpf_link__destroy(old_link);
+}
+
 static int thp_adjust_setup(void)
 {
 	int err, cgrp_fd, cgrp_id, pmd_order;
@@ -249,6 +270,8 @@ void test_thp_adjust(void)
 
 	if (test__start_subtest("alloc_in_khugepaged"))
 		subtest_thp_policy();
+	if (test__start_subtest("policy_update"))
+		subtest_thp_policy_update();
 
 	thp_adjust_destroy();
 }
diff --git a/tools/testing/selftests/bpf/progs/test_thp_adjust.c b/tools/testing/selftests/bpf/progs/test_thp_adjust.c
index 93c7927e827a..175e65c5899f 100644
--- a/tools/testing/selftests/bpf/progs/test_thp_adjust.c
+++ b/tools/testing/selftests/bpf/progs/test_thp_adjust.c
@@ -98,3 +98,17 @@ SEC(".struct_ops.link")
 struct bpf_thp_ops khugepaged_ops = {
 	.thp_get_order = (void *)alloc_in_khugepaged,
 };
+
+SEC("struct_ops/thp_get_order")
+int BPF_PROG(alloc_not_in_swap, struct vm_area_struct *vma, enum bpf_thp_vma_type vma_type,
+	     enum tva_type tva_type, unsigned long orders)
+{
+	if (tva_type == TVA_SWAP)
+		return 0;
+	return -1;
+}
+
+SEC(".struct_ops.link")
+struct bpf_thp_ops swap_ops = {
+	.thp_get_order = (void *)alloc_not_in_swap,
+};
-- 
2.47.3