Re: [PATCH 0/4] mm/gup, drm/i915: refactor gup_fast, convert to pin_user_pages()

From: Souptick Joarder <jrdr.linux@gmail.com>
To: John Hubbard <jhubbard@nvidia.com>
Cc: dri-devel <dri-devel@lists.freedesktop.org>,
	Tvrtko Ursulin <tvrtko.ursulin@intel.com>,
	David Airlie <airlied@linux.ie>,
	intel-gfx@lists.freedesktop.org,
	LKML <linux-kernel@vger.kernel.org>,
	Chris Wilson <chris@chris-wilson.co.uk>,
	Linux-MM <linux-mm@kvack.org>,
	Matthew Wilcox <willy@infradead.org>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Matthew Auld <matthew.auld@intel.com>
Subject: Re: [PATCH 0/4] mm/gup, drm/i915: refactor gup_fast, convert to pin_user_pages()
Date: Fri, 22 May 2020 17:10:32 +0530	[thread overview]
Message-ID: <CAFqt6zZTZrB=LiGQpcOtZfnr7-CL4tkLHz8eXFvxwCTcfKy4sQ@mail.gmail.com> (raw)
In-Reply-To: <20200519002124.2025955-1-jhubbard@nvidia.com>

Hi John,

On Tue, May 19, 2020 at 5:51 AM John Hubbard <jhubbard@nvidia.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
>
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