linux-kernel - Re: [PATCH] ioctl_userfaultfd.2: Corrections for returned .ioctls members

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Message-ID: <CAJHvVch=vO6gwyn+swyeHEQ4mUccL6T+Vt3G9akeEjXZ6XKM-A@mail.gmail.com>
Date:   Tue, 22 Mar 2022 09:23:38 -0700
From:   Axel Rasmussen <axelrasmussen@...gle.com>
To:     "Alejandro Colomar (man-pages)" <alx.manpages@...il.com>
Cc:     Peter Xu <peterx@...hat.com>, Ian Abbott <abbotti@....co.uk>,
        linux-man@...r.kernel.org,
        Michael Kerrisk <mtk.manpages@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ioctl_userfaultfd.2: Corrections for returned .ioctls members

On Tue, Mar 22, 2022 at 5:32 AM Alejandro Colomar (man-pages)
<alx.manpages@...il.com> wrote:
>
> Hi Ian and Peter,
>
> On 3/21/22 07:10, Peter Xu wrote:
> > On Fri, Mar 18, 2022 at 07:13:43PM +0000, Ian Abbott wrote:
> >> Support for the `UFFDIO_WRITEPROTECT` operation is not indicated in the
> >> `ioctls` member of `struct uffdio_api`.  It is indicated in the `ioctls`
> >> member of `struct uffdio_register` along with indications of support for
> >> the `UFFDIO_COPY`, `UFFDIO_WAKE` and `UFFDIO_ZEROPAGE` operations (and
> >> also the `UFFDIO_CONTINUE` operation supported since Linux 5.13 but
> >> that is not documented by this man page yet.)
> >
> > I thought it should have landed but indeed it's not.  Copying Axel.

Ah, I mistakenly thought it got merged, but there were a few remaining
issues Alejandro wanted addressed first. I'll send a v3 of it later
today.

For what it's worth, as part of adding minor fault handling, we pretty
significantly change the ioctl field's behavior, and I rewrote a lot
of the documentation around it. So, it may conflict with this patch.
:/ Sorry about that.

> >
> >>
> >> Fixes: f559fa36a678 ("ioctl_userfaultfd.2: Add write-protect mode docs")
> >> Signed-off-by: Ian Abbott <abbotti@....co.uk>
>
> Patch applied.
>
> >
> > The patch looks correct to me, thanks for fixing it.
> >
> > Acked-by: Peter Xu <peterx@...hat.com>
>
> And tag appended.
>
> Thank you both!
>
> Alex
>
> >
> >> ---
> >>   man2/ioctl_userfaultfd.2 | 27 ++++++++++++++++++++-------
> >>   1 file changed, 20 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2
> >> index 504f61d4b..e930af520 100644
> >> --- a/man2/ioctl_userfaultfd.2
> >> +++ b/man2/ioctl_userfaultfd.2
> >> @@ -235,11 +235,6 @@ operation is supported.
> >>   The
> >>   .B UFFDIO_UNREGISTER
> >>   operation is supported.
> >> -.TP
> >> -.B 1 << _UFFDIO_WRITEPROTECT
> >> -The
> >> -.B UFFDIO_WRITEPROTECT
> >> -operation is supported.
> >>   .PP
> >>   This
> >>   .BR ioctl (2)
> >> @@ -333,8 +328,26 @@ If the operation is successful, the kernel modifies the
> >>   bit-mask field to indicate which
> >>   .BR ioctl (2)
> >>   operations are available for the specified range.
> >> -This returned bit mask is as for
> >> -.BR UFFDIO_API .
> >> +This returned bit mask can contain the following bits:
> >> +.TP
> >> +.B 1 << _UFFDIO_COPY
> >> +The
> >> +.B UFFDIO_COPY
> >> +operation is supported.
> >> +.TP
> >> +.B 1 << _UFFDIO_WAKE
> >> +The
> >> +.B UFFDIO_WAKE
> >> +operation is supported.
> >> +.TP
> >> +.B 1 << _UFFDIO_WRITEPROTECT
> >> +The
> >> +.B UFFDIO_WRITEPROTECT
> >> +.TP
> >> +.B 1 << _UFFDIO_ZEROPAGE
> >> +The
> >> +.B UFFDIO_ZEROPAGE
> >> +operation is supported.
> >>   .PP
> >>   This
> >>   .BR ioctl (2)
> >> --
> >
>
> --
> Alejandro Colomar
> Linux man-pages comaintainer; http://www.kernel.org/doc/man-pages/
> http://www.alejandro-colomar.es/