linux-kernel - Re: [PATCH 2/2] kselftests: mm: Fail the test if userfaultfd syscall isn't found

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Message-ID: <3b700650-159d-45ad-91a3-59fca3019766@linuxfoundation.org>
Date: Thu, 12 Sep 2024 10:10:04 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Shuah Khan <shuah@...nel.org>
Cc: kernel@...labora.com, linux-mm@...ck.org,
 linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH 2/2] kselftests: mm: Fail the test if userfaultfd syscall
 isn't found

On 9/12/24 04:31, Muhammad Usama Anjum wrote:
> The userfaultfd is enabled in the config fragment of mm selftest suite.
> It must always be present. If it isn't present, we should throw error
> and not just skip. This would have helped us catch the test breakage.

Please elaborate on this to help understand the what breakage was
missed.

Also this commit log doesn't look right to me. syscall() could
fail for any reason. Do you mean to see skip is incorrect in this
error leg? Please see comments below.

> Adding this now to catch the future breakages.
> 
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
> ---
>   tools/testing/selftests/mm/pagemap_ioctl.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/mm/pagemap_ioctl.c b/tools/testing/selftests/mm/pagemap_ioctl.c
> index bcc73b4e805c6..d83dda8edf62c 100644
> --- a/tools/testing/selftests/mm/pagemap_ioctl.c
> +++ b/tools/testing/selftests/mm/pagemap_ioctl.c
> @@ -95,7 +95,7 @@ int init_uffd(void)
>   
>   	uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
>   	if (uffd == -1)
> -		return uffd;
> +		ksft_exit_fail_perror("Userfaultfd syscall failed");

This looks wrong to me - Is missing config the only reason this syscall
would fail?

>   
>   	uffdio_api.api = UFFD_API;
>   	uffdio_api.features = UFFD_FEATURE_WP_UNPOPULATED | UFFD_FEATURE_WP_ASYNC |

thanks,
-- Shuah