linux-kernel - Re: [PATCH 0/4] mm/gup, drm/i915: refactor gup_fast, convert to pin_user

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Date:   Fri, 22 May 2020 17:10:32 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Matthew Auld <matthew.auld@...el.com>,
        intel-gfx@...ts.freedesktop.org,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH 0/4] mm/gup, drm/i915: refactor gup_fast, convert to pin_user_pages()

Hi John,


On Tue, May 19, 2020 at 5:51 AM John Hubbard <jhubbard@...dia.com> wrote:
>
> This needs to go through Andrew's -mm tree, due to adding a new gup.c
> routine. However, I would really love to have some testing from the
> drm/i915 folks, because I haven't been able to run-time test that part
> of it.
>
> Otherwise, though, the series has passed my basic run time testing:
> some LTP tests, some xfs and etx4 non-destructive xfstests, and an
> assortment of other smaller ones: vm selftests, io_uring_register, a
> few more. But that's only on one particular machine. Also, cross-compile
> tests for half a dozen arches all pass.
>
> Details:
>
> In order to convert the drm/i915 driver from get_user_pages() to
> pin_user_pages(), a FOLL_PIN equivalent of __get_user_pages_fast() was
> required. That led to refactoring __get_user_pages_fast(), with the
> following goals:
>
> 1) As above: provide a pin_user_pages*() routine for drm/i915 to call,
>    in place of __get_user_pages_fast(),
>
> 2) Get rid of the gup.c duplicate code for walking page tables with
>    interrupts disabled. This duplicate code is a minor maintenance
>    problem anyway.
>
> 3) Make it easy for an upcoming patch from Souptick, which aims to
>    convert __get_user_pages_fast() to use a gup_flags argument, instead
>    of a bool writeable arg.  Also, if this series looks good, we can
>    ask Souptick to change the name as well, to whatever the consensus
>    is. My initial recommendation is: get_user_pages_fast_only(), to
>    match the new pin_user_pages_only().

Shall I hold my changes till 5.8-rc1 , when this series will appear upstream ?
>
> John Hubbard (4):
>   mm/gup: move __get_user_pages_fast() down a few lines in gup.c
>   mm/gup: refactor and de-duplicate gup_fast() code
>   mm/gup: introduce pin_user_pages_fast_only()
>   drm/i915: convert get_user_pages() --> pin_user_pages()
>
>  drivers/gpu/drm/i915/gem/i915_gem_userptr.c |  22 +--
>  include/linux/mm.h                          |   3 +
>  mm/gup.c                                    | 150 ++++++++++++--------
>  3 files changed, 107 insertions(+), 68 deletions(-)
>
>
> base-commit: 642b151f45dd54809ea00ecd3976a56c1ec9b53d
> --
> 2.26.2
>