linux-kernel - Re: [PATCH 0/5] {ioctl_}userfaultfd.2: initial updates for 4.11

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Date:   Wed, 26 Apr 2017 09:23:45 +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 0/5] {ioctl_}userfaultfd.2: initial updates for 4.11

Hello Mike,

On 04/25/2017 06:29 PM, Mike Rapoport wrote:
> Hello Michael,
> 
> These patches are some kind of brief highlights of the changes to the
> userfaultfd pages.

Thanks for the patches. All merged. A few tweaks made,
and pushed to Git.

> The changes to userfaultfd functionality are also described at update to
> Documentation/vm/userfaultfd.txt [1].
> 
> In general, there were three major additions:
> * hugetlbfs support
> * shmem support
> * non-page fault events
> 
> I think we should add some details about using userfaultfd with different
> memory types, describe meaning of each feature bits and add some text about
> the new events.

Agreed.

> I haven't updated 'struct uffd_msg' yet, and I hesitate whether it's
> description belongs to userfaultfd.2 or ioctl_userfaultfd.2

My guess is userfaultfd.2. But, maybe I missed something.
What suggests to you that it could be ioctl_userfaultfd.2 instead?

> As for the userfaultfd.7 we've discussed earlier, I believe it would
> repeat Documentation/vm/userfaultfd.txt in way, so I'm not really sure it
> is required.

The thing about kernel Doc files is they are a lot less visible.
It would be best I think to have the user-space visible
API fully described in man pages...

Cheers,

Michael


> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5a02026d390ea1bb0c16a0e214e45613a3e3d885
> 
> Mike Rapoport (5):
>   userfaultfd.2: describe memory types that can be used from 4.11
>   ioctl_userfaultfd.2: describe memory types that can be used from 4.11
>   ioctl_userfaultfd.2: update UFFDIO_API description
>   userfaultfd.2: add Linux container migration use-case to NOTES
>   usefaultfd.2: add brief description of "non-cooperative" mode
> 
>  man2/ioctl_userfaultfd.2 | 46 ++++++++++++++++++++++++++++++++++++++--------
>  man2/userfaultfd.2       | 25 ++++++++++++++++++++++---
>  2 files changed, 60 insertions(+), 11 deletions(-)
> 


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