linux-kernel - Re: [PATCH v2 1/4] userfaultfd: selftest: Fix checking of userfaultfd

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Message-Id: <20180807065023.GA20140@rapoport-lnx>
Date:   Tue, 7 Aug 2018 09:50:25 +0300
From:   Mike Rapoport <rppt@...ux.vnet.ibm.com>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Cc:     linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <shuah@...nel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Prakash Sangappa <prakash.sangappa@...cle.com>
Subject: Re: [PATCH v2 1/4] userfaultfd: selftest: Fix checking of
 userfaultfd_open() result

On Fri, Aug 03, 2018 at 07:00:43PM -0300, Thiago Jung Bauermann wrote:
> If the userfaultfd test is run on a kernel with CONFIG_USERFAULTFD=n, it
> will report that the system call is not available yet go ahead and continue
> anyway:
> 
>   # ./userfaultfd anon 30 1
>   nr_pages: 480, nr_pages_per_cpu: 120
>   userfaultfd syscall not available in this kernel
>   bounces: 0, mode:, register failure
> 
> This is because userfaultfd_open() returns 0 on success and 1 on error but
> all callers assume that it returns < 0 on error.
> 
> Since the convention of the test as a whole is the one used by
> userfault_open(), fix its callers instead. Now the test behaves correctly:
> 
>   # ./userfaultfd anon 30 1
>   nr_pages: 480, nr_pages_per_cpu: 120
>   userfaultfd syscall not available in this kernel
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>

Reviewed-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>

> ---
>  tools/testing/selftests/vm/userfaultfd.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> index 7b8171e3128a..e4099afe7557 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -859,7 +859,7 @@ static int userfaultfd_zeropage_test(void)
>  	if (uffd_test_ops->release_pages(area_dst))
>  		return 1;
> 
> -	if (userfaultfd_open(0) < 0)
> +	if (userfaultfd_open(0))
>  		return 1;
>  	uffdio_register.range.start = (unsigned long) area_dst;
>  	uffdio_register.range.len = nr_pages * page_size;
> @@ -902,7 +902,7 @@ static int userfaultfd_events_test(void)
> 
>  	features = UFFD_FEATURE_EVENT_FORK | UFFD_FEATURE_EVENT_REMAP |
>  		UFFD_FEATURE_EVENT_REMOVE;
> -	if (userfaultfd_open(features) < 0)
> +	if (userfaultfd_open(features))
>  		return 1;
>  	fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
> 
> @@ -961,7 +961,7 @@ static int userfaultfd_sig_test(void)
>  		return 1;
> 
>  	features = UFFD_FEATURE_EVENT_FORK|UFFD_FEATURE_SIGBUS;
> -	if (userfaultfd_open(features) < 0)
> +	if (userfaultfd_open(features))
>  		return 1;
>  	fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
> 
> @@ -1027,7 +1027,7 @@ static int userfaultfd_stress(void)
>  	if (!area_dst)
>  		return 1;
> 
> -	if (userfaultfd_open(0) < 0)
> +	if (userfaultfd_open(0))
>  		return 1;
> 
>  	count_verify = malloc(nr_pages * sizeof(unsigned long long));

-- 
Sincerely yours,
Mike.