Re: [PATCH] selftests/bpf: Fix flaky file_reader test

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 6/3/26 7:39 AM, Mykyta Yatsenko wrote:
> From: Mykyta Yatsenko <yatsenko@meta.com>
> 
> file_reader/on_open_expect_fault test expects page fault
> when reading pages from the test harness executable.
> It is not guaranteed that those are paged out, even
> after madvise(MADV_PAGEOUT).
> Relax the condition in the test to succeed with both
> 0 and -EFAULT returned.
> 
> Fixes: 784cdf931543 ("selftests/bpf: add file dynptr tests")
> Reported-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
> Closes: https://lore.kernel.org/all/ah6g7JSYOWGp2oAG@u94a/
> Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>

Hi Mykyta,

I tried the patch on libbpf/libbpf CI, the test was consistently
failing there. It works [1], thanks!

Tested-by: Ihor Solodrai <ihor.solodrai@linux.dev>

[1] https://github.com/libbpf/libbpf/actions/runs/27032965962

> ---
>  tools/testing/selftests/bpf/progs/file_reader.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/progs/file_reader.c b/tools/testing/selftests/bpf/progs/file_reader.c
> index 462712ff3b8a..aa2c05cce2b3 100644
> --- a/tools/testing/selftests/bpf/progs/file_reader.c
> +++ b/tools/testing/selftests/bpf/progs/file_reader.c
> @@ -50,7 +50,7 @@ int on_open_expect_fault(void *c)
>  		goto out;
>  
>  	local_err = bpf_dynptr_read(tmp_buf, user_buf_sz, &dynptr, user_buf_sz, 0);
> -	if (local_err == -EFAULT) { /* Expect page fault */
> +	if (local_err == -EFAULT || local_err == 0) { /* Expect page fault or success */
>  		local_err = 0;
>  		run_success = 1;
>  	}
> 
> ---
> base-commit: 245da8192c073820390f7fa1cc1e834b32119bce
> change-id: 20260603-file_reader_flake-bf0753be6b2e
> 
> Best regards,
> --  
> Mykyta Yatsenko <yatsenko@meta.com>
>