linux-kernel - Re: [PATCH v2 03/17] mm/rmap: convert make_device_exclusive_range() to make_device

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Message-Id: <20250210210001.5dc68b38eb1bfa44d0fd78f6@linux-foundation.org>
Date: Mon, 10 Feb 2025 21:00:01 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linux-mm@...ck.org,
 nouveau@...ts.freedesktop.org, linux-trace-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, damon@...ts.linux.dev, Jérôme Glisse <jglisse@...hat.com>, Jonathan Corbet
 <corbet@....net>, Alex Shi <alexs@...nel.org>, Yanteng Si
 <si.yanteng@...ux.dev>, Karol Herbst <kherbst@...hat.com>, Lyude Paul
 <lyude@...hat.com>, Danilo Krummrich <dakr@...nel.org>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Masami Hiramatsu
 <mhiramat@...nel.org>, Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra
 <peterz@...radead.org>, SeongJae Park <sj@...nel.org>, "Liam R. Howlett"
 <Liam.Howlett@...cle.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>, Pasha
 Tatashin <pasha.tatashin@...een.com>, Peter Xu <peterx@...hat.com>,
 Alistair Popple <apopple@...dia.com>, Jason Gunthorpe <jgg@...dia.com>,
 Simona Vetter <simona.vetter@...ll.ch>
Subject: Re: [PATCH v2 03/17] mm/rmap: convert make_device_exclusive_range()
 to make_device_exclusive()

On Mon, 10 Feb 2025 20:37:45 +0100 David Hildenbrand <david@...hat.com> wrote:

> The single "real" user in the tree of make_device_exclusive_range() always
> requests making only a single address exclusive. The current implementation
> is hard to fix for properly supporting anonymous THP / large folios and
> for avoiding messing with rmap walks in weird ways.
> 
> So let's always process a single address/page and return folio + page to
> minimize page -> folio lookups. This is a preparation for further
> changes.
> 
> Reject any non-anonymous or hugetlb folios early, directly after GUP.
> 
> While at it, extend the documentation of make_device_exclusive() to
> clarify some things.

x86_64 allmodconfig:

drivers/gpu/drm/nouveau/nouveau_svm.c: In function 'nouveau_atomic_range_fault':
drivers/gpu/drm/nouveau/nouveau_svm.c:612:68: error: 'folio' undeclared (first use in this function)
  612 |                 page = make_device_exclusive(mm, start, drm->dev, &folio);
      |                                                                    ^~~~~
drivers/gpu/drm/nouveau/nouveau_svm.c:612:68: note: each undeclared identifier is reported only once for each function it appears in