linux-kernel - Re: [RFC PATCH 0/3] restructure memfd code

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Date:   Mon, 20 Nov 2017 11:28:09 +0100
From:   Marc-André Lureau <marcandre.lureau@...il.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     linux-mm@...ck.org, open list <linux-kernel@...r.kernel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        David Herrmann <dh.herrmann@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH 0/3] restructure memfd code

Hi

On Thu, Nov 9, 2017 at 2:41 AM, Mike Kravetz <mike.kravetz@...cle.com> wrote:
> With the addition of memfd hugetlbfs support, we now have the situation
> where memfd depends on TMPFS -or- HUGETLBFS.  Previously, memfd was only
> supported on tmpfs, so it made sense that the code resides in shmem.c.
>
> This patch series moves the memfd code to separate files (memfd.c and
> memfd.h).  It creates a new config option MEMFD_CREATE that is defined
> if either TMPFS or HUGETLBFS is defined.

That looks good to me

>
> In the current code, memfd is only functional if TMPFS is defined.  If
> HUGETLFS is defined and TMPFS is not defined, then memfd functionality
> will not be available for hugetlbfs.  This does not cause BUGs, just a
> potential lack of desired functionality.
>

Indeed

> Another way to approach this issue would be to simply make HUGETLBFS
> depend on TMPFS.
>
> This patch series is built on top of the Marc-André Lureau v3 series
> "memfd: add sealing to hugetlb-backed memory":
> http://lkml.kernel.org/r/20171107122800.25517-1-marcandre.lureau@redhat.com

Are you waiting for this series to be merged before resending as non-rfc?

>
> Mike Kravetz (3):
>   mm: hugetlbfs: move HUGETLBFS_I outside #ifdef CONFIG_HUGETLBFS
>   mm: memfd: split out memfd for use by multiple filesystems
>   mm: memfd: remove memfd code from shmem files and use new memfd files
>
>  fs/Kconfig               |   3 +
>  fs/fcntl.c               |   2 +-
>  include/linux/hugetlb.h  |  27 ++--
>  include/linux/memfd.h    |  16 +++
>  include/linux/shmem_fs.h |  13 --
>  mm/Makefile              |   1 +
>  mm/memfd.c               | 341 +++++++++++++++++++++++++++++++++++++++++++++++
>  mm/shmem.c               | 323 --------------------------------------------
>  8 files changed, 378 insertions(+), 348 deletions(-)
>  create mode 100644 include/linux/memfd.h
>  create mode 100644 mm/memfd.c
>
> --
> 2.13.6
>

Thanks

-- 
Marc-André Lureau