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

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Date:   Mon, 18 May 2020 17:21:20 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     Souptick Joarder <jrdr.linux@...il.com>,
        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@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        John Hubbard <jhubbard@...dia.com>
Subject: [PATCH 0/4] mm/gup, drm/i915: refactor gup_fast, convert to pin_user_pages()

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().

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