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

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Message-ID: <1586d8ea-342c-c652-86f4-a7fafc8c7be6@gmail.com>
Date:   Tue, 2 May 2017 22:23:28 +0200
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Mike Rapoport <rppt@...ux.vnet.ibm.com>
Cc:     mtk.manpages@...il.com, 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 05/02/2017 11:31 AM, Mike Rapoport wrote:
> 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)

Okay -- thanks for the clarification.

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/