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

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Message-ID: <48fd75b9-696e-402c-95bd-55f2f0e24dfc@redhat.com>
Date: Tue, 11 Feb 2025 09:33:54 +0100
From: David Hildenbrand <david@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>
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 11.02.25 06:00, Andrew Morton wrote:
> 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

Ah! Because I was carrying on the same branch SVM fixes [1] that are
getting surprisingly little attention so far.

The following sorts it out for now:

 From 337c68bf24af59f36477be11ea6ef7c7ce9aa8ae Mon Sep 17 00:00:00 2001
From: David Hildenbrand <david@...hat.com>
Date: Tue, 11 Feb 2025 09:33:04 +0100
Subject: [PATCH] merge

Signed-off-by: David Hildenbrand <david@...hat.com>
---
  drivers/gpu/drm/nouveau/nouveau_svm.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index 39e3740980bb7..1fed638b9eba8 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -590,6 +590,7 @@ static int nouveau_atomic_range_fault(struct nouveau_svmm *svmm,
  	unsigned long timeout =
  		jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
  	struct mm_struct *mm = svmm->notifier.mm;
+	struct folio *folio;
  	struct page *page;
  	unsigned long start = args->p.addr;
  	unsigned long notifier_seq;
-- 
2.48.1

I'll resend [1] once this stuff here landed.

Let me know if you want a full resend of this series, thanks.

[1] https://lkml.kernel.org/r/20250124181524.3584236-1-david@redhat.com

-- 
Cheers,

David / dhildenb