linux-kernel - Re: [PATCH 1/3] userfaultfd/selftests: fix feature support detection

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Date:   Tue, 21 Sep 2021 13:44:46 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Axel Rasmussen <axelrasmussen@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] userfaultfd/selftests: fix feature support detection

Hi, Axel,

On Tue, Sep 21, 2021 at 09:33:21AM -0700, Axel Rasmussen wrote:
> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> index 10ab56c2484a..2366caf90435 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -79,10 +79,6 @@ static int test_type;
>  #define ALARM_INTERVAL_SECS 10
>  static volatile bool test_uffdio_copy_eexist = true;
>  static volatile bool test_uffdio_zeropage_eexist = true;
> -/* Whether to test uffd write-protection */
> -static bool test_uffdio_wp = false;
> -/* Whether to test uffd minor faults */
> -static bool test_uffdio_minor = false;

IMHO it's not a fault to have these variables; they're still the fastest way to
do branching.  It's just that in some cases we should set them to "false"
rather than "true", am I right?

How about we just set them properly in set_test_type?  Say, we can fetch the
feature bits in set_test_type rather than assuming it's only related to the
type of memory.

Thanks,

-- 
Peter Xu