linux-kernel - Re: [PATCH man-pages 1/5] ioctl_userfaultfd.2: update description of shared memory areas

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Message-Id: <20170502093110.GA5910@rapoport-lnx>
Date:   Tue, 2 May 2017 12:31:11 +0300
From:   Mike Rapoport <rppt@...ux.vnet.ibm.com>
To:     "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
Cc:     Andrea Arcangeli <aarcange@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-man@...r.kernel.org
Subject: Re: [PATCH man-pages 1/5] ioctl_userfaultfd.2: update description of
 shared memory areas

On Mon, May 01, 2017 at 08:33:31PM +0200, Michael Kerrisk (man-pages) wrote:
> Hello Mike,
> 
> I've applied this patch, but  have a question.
> 
> On 05/01/2017 07:43 AM, Mike Rapoport wrote:
> > Signed-off-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>
> > ---
> >  man2/ioctl_userfaultfd.2 | 13 +++++++++++--
> >  1 file changed, 11 insertions(+), 2 deletions(-)
> > 
> > diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2
> > index 889feb9..6edd396 100644
> > --- a/man2/ioctl_userfaultfd.2
> > +++ b/man2/ioctl_userfaultfd.2
> > @@ -181,8 +181,17 @@ virtual memory areas
> >  .TP
> >  .B UFFD_FEATURE_MISSING_SHMEM
> >  If this feature bit is set,
> > -the kernel supports registering userfaultfd ranges on tmpfs
> > -virtual memory areas
> > +the kernel supports registering userfaultfd ranges on shared memory areas.
> > +This includes all kernel shared memory APIs:
> > +System V shared memory,
> > +tmpfs,
> > +/dev/zero,
> > +.BR mmap(2)
> > +with
> > +.I MAP_SHARED
> > +flag set,
> > +.BR memfd_create (2),
> > +etc.
> >  
> >  The returned
> >  .I ioctls
> 
> Does the change in this patch represent a change that occurred in
> Linux 4.11? If so, I think this needs to be said explicitly in the text.

The patch only extends the description of UFFD_FEATURE_MISSING_SHMEM. The
feature is indeed available from 4.11, but that is said a few lives above
(line 136 in ioctl_userfaultfd.2)
 
> Cheers,
> 
> Michael
> 
> 
> 
> -- 
> Michael Kerrisk
> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
> Linux/UNIX System Programming Training: http://man7.org/training/
>