On 11.02.25 06:00, Andrew Morton wrote:

On Mon, 10 Feb 2025 20:37:45 +0100 David Hildenbrand [off-list ref] wrote:

quoted

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 <redacted>
Date: Tue, 11 Feb 2025 09:33:04 +0100
Subject: [PATCH] merge

Signed-off-by: David Hildenbrand <redacted>
---
  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