Re: [PATCH bpf-next v2] selftests/bpf: Avoid flaky resize value test for percpu data

> diff --git a/tools/testing/selftests/bpf/prog_tests/global_data_init.c b/tools/testing/selftests/bpf/prog_tests/global_data_init.c
> index 5671c31085cd..2b69290bcc3e 100644
> --- a/tools/testing/selftests/bpf/prog_tests/global_data_init.c
> +++ b/tools/testing/selftests/bpf/prog_tests/global_data_init.c

[ ... ]

> @@ -236,6 +223,57 @@ static void test_global_percpu_data_lskel(void)
>  	test_global_percpu_data_lskel__destroy(lskel);
>  }
>
> +#define PAGE_SIZE 4096
> +
> +static void test_global_percpu_data_map_resize(void)
> +{
> +	const __u32 desired_sz = sysconf(_SC_PAGE_SIZE) * 2;
> +	struct test_global_percpu_data *skel;
> +	const int arr_value = -1;
> +	struct bpf_map *map;
> +	int err, prog_fd;
> +	size_t data_sz;
> +
> +	if (sysconf(_SC_PAGE_SIZE) != PAGE_SIZE) {
> +		test__skip();
> +		return;
> +	}
> +
> +	skel = test_global_percpu_data__open();
> +	if (!ASSERT_OK_PTR(skel, "test_global_percpu_data__open"))
> +		return;
> +
> +	map = skel->maps.percpu_arr;
> +	skel->percpu_arr->arr[0] = arr_value;
> +	err = bpf_map__set_value_size(map, desired_sz);

This isn't a bug, but since the guard above already pins the page size to
4096, would `const __u32 desired_sz = PAGE_SIZE * 2;` read more directly
here - and is the unguarded `#define PAGE_SIZE 4096` preferable to the
`#ifndef PAGE_SIZE` form used in sockopt.c?

> +	if (!ASSERT_OK(err, "bpf_map__set_value_size"))
> +		goto out;
> +	if (!ASSERT_EQ(bpf_map__value_size(map), desired_sz, "bpf_map__value_size"))
> +		goto out;
> +	if (!ASSERT_NEQ(bpf_map__btf_value_type_id(map), 0, "bpf_map__btf_value_type_id"))
> +		goto out;
> +
> +	skel->percpu_arr = bpf_map__initial_value(map, &data_sz);
> +	if (!ASSERT_EQ(data_sz, desired_sz, "data_sz"))
> +		goto out;
> +	if (!ASSERT_OK_PTR(skel->percpu_arr, "skel->percpu_arr"))
> +		goto out;

This isn't a bug, but would it read more consistently with
test_global_percpu_data_init() to check ASSERT_OK_PTR(skel->percpu_arr)
before ASSERT_EQ(data_sz, desired_sz)? The block this replaces checked
pointer-then-size, and the surviving test_global_percpu_data_init() at the
same file still does pointer-then-size.

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/32156312094