Re: [PATCH v2] selftests/vm: fix errno handling in mrelease_test

[David Vernet <void@manifault.com>]

On Mon, Jul 04, 2022 at 07:33:51PM +0200, Adam Sindelar wrote:

Thanks for fixing this, Adam.

> mrelease_test should return KSFT_SKIP when process_mrelease is not
> defined, but due to a perror call consuming the errno, it returns
> KSFT_FAIL.
> 
> This patch decides the exit code before calling perror.
> 

We should probably also include a "Fixes" line here (see [0]):

Fixes: 33776141b812 ("selftests: vm: add process_mrelease tests")

[0]: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes

> Signed-off-by: Adam Sindelar <adam@wowsignal.io>
> ---
> v1->v2: Fixed second instance in the same file
> 
>  tools/testing/selftests/vm/mrelease_test.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/vm/mrelease_test.c b/tools/testing/selftests/vm/mrelease_test.c
> index 96671c2f7d48..e8b17258579b 100644
> --- a/tools/testing/selftests/vm/mrelease_test.c
> +++ b/tools/testing/selftests/vm/mrelease_test.c
> @@ -100,8 +100,10 @@ int main(void)
>  
>  	/* Test a wrong pidfd */
>  	if (!syscall(__NR_process_mrelease, -1, 0) || errno != EBADF) {
> +		/* perror overwrites errno, so this line must be first */
> +		res = (errno == ENOSYS ? KSFT_SKIP : KSFT_FAIL);
>  		perror("process_mrelease with wrong pidfd");
> -		exit(errno == ENOSYS ? KSFT_SKIP : KSFT_FAIL);
> +		exit(res);
>  	}
>  
>  	/* Start the test with 1MB child memory allocation */
> @@ -156,8 +158,9 @@ int main(void)
>  	run_negative_tests(pidfd);
>  
>  	if (kill(pid, SIGKILL)) {
> +		res = (errno == ENOSYS ? KSFT_SKIP : KSFT_FAIL);
>  		perror("kill");
> -		exit(errno == ENOSYS ? KSFT_SKIP : KSFT_FAIL);
> +		exit(res);
>  	}
>  
>  	success = (syscall(__NR_process_mrelease, pidfd, 0) == 0);
> -- 
> 2.35.1
> 

This looks good to me, but it looks like there are a couple of other places
where we're doing the wrong thing, i.e. in run_negative_tests() and after
calling waitpid(). Could you please fix those as well?

Also adding Suren to cc.

- David