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Date:   Tue, 12 Apr 2022 13:41:59 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Axel Rasmussen <axelrasmussen@google.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        "Dmitry V . Levin" <ldv@altlinux.org>,
        Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Nadav Amit <namit@vmware.com>, Peter Xu <peterx@redhat.com>,
        Shuah Khan <shuah@kernel.org>, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-kselftest@vger.kernel.org
Subject: Re: [PATCH 2/2] userfaultfd: selftests: modify selftest to use
 /dev/userfaultfd
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On Tue, 12 Apr 2022 13:29:42 -0700 Axel Rasmussen <axelrasmussen@google.com> wrote:

> Prefer this new interface, but if using it fails for any reason just
> fall back to using userfaultfd(2) as before.

This seems a poor idea - the old interface will henceforth be untested.

Why not tweak the code to test both interfaces?