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 <20230223005754.2700663-4-axelrasmussen@google.com> <F3D3DA6C-0AEC-4947-9E2F-7A9773296A5D@vmware.com>
In-Reply-To: <F3D3DA6C-0AEC-4947-9E2F-7A9773296A5D@vmware.com>
From:   Axel Rasmussen <axelrasmussen@google.com>
Date:   Thu, 23 Feb 2023 11:03:58 -0800
Message-ID: <CAJHvVcj_NKp8wOUL5D2GX61xp0Rvzy6Z8gvL_G=qogsJreiGTQ@mail.gmail.com>
Subject: Re: [PATCH v2 3/5] mm: userfaultfd: combine 'mode' and 'wp_copy' arguments
To:     Nadav Amit <namit@vmware.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, Jan Kara <jack@suse.cz>,
        "Liam R. Howlett" <Liam.Howlett@oracle.com>,
        Matthew Wilcox <willy@infradead.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Mike Rapoport <rppt@kernel.org>,
        Muchun Song <muchun.song@linux.dev>,
        Peter Xu <peterx@redhat.com>, Shuah Khan <shuah@kernel.org>,
        James Houghton <jthoughton@google.com>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kselftest@vger.kernel.org" <linux-kselftest@vger.kernel.org>
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On Thu, Feb 23, 2023 at 10:51 AM Nadav Amit <namit@vmware.com> wrote:
>
>
>
> > On Feb 22, 2023, at 4:57 PM, Axel Rasmussen <axelrasmussen@google.com> =
wrote:
> >
> > Many userfaultfd ioctl functions take both a 'mode' and a 'wp_copy'
> > argument. In future commits we plan to plumb the flags through to more
> > places, so we'd be proliferating the very long argument list even
> > further.
> >
> > Let's take the time to simplify the argument list. Combine the two
> > arguments into one - and generalize, so when we add more flags in the
> > future, it doesn't imply more function arguments.
> >
> > Since the modes (copy, zeropage, continue) are mutually exclusive, stor=
e
> > them as an integer value (0, 1, 2) in the low bits. Place combine-able
> > flag bits in the high bits.
> >
> > Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
>
> Hi Axel,
>
> I sent a patch a long time ago called =E2=80=9Cuserfaultfd: introduce uff=
d_flags=E2=80=9D.
> For some reason it does not appear on lore, but you were a recipient.
>
> It was pretty similar, but one thing that I preferred in my version is
> that it defined a different type to avoid confusion. Since =E2=80=9Cflags=
=E2=80=9D is
> a very generic name, perhaps you=E2=80=99d like to adapt this approach.

Oh! I must have missed it, or just forgot. I'll take a look and see
about making some improvements. I'll also be sure to credit you in the
commit message.

>