linux-kernel - [PATCH v1 1/2] nouveau/svm: fix missing folio unlock + put after make_device_exclusive

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Message-ID: <20250124181524.3584236-2-david@redhat.com>
Date: Fri, 24 Jan 2025 19:15:23 +0100
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: dri-devel@...ts.freedesktop.org,
	nouveau@...ts.freedesktop.org,
	David Hildenbrand <david@...hat.com>,
	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>,
	Alistair Popple <apopple@...dia.com>
Subject: [PATCH v1 1/2] nouveau/svm: fix missing folio unlock + put after make_device_exclusive_range()

In case we have to retry the loop, we are missing to unlock+put the
folio. In that case, we will keep failing make_device_exclusive_range()
because we cannot grab the folio lock, and even return from the function
with the folio locked and referenced, effectively never succeeding the
make_device_exclusive_range().

While at it, convert the other unlock+put to use a folio as well.

This was found by code inspection.

Fixes: 8f187163eb89 ("nouveau/svm: implement atomic SVM access")
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 drivers/gpu/drm/nouveau/nouveau_svm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index b4da82ddbb6b2..8ea98f06d39af 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;
@@ -616,12 +617,16 @@ static int nouveau_atomic_range_fault(struct nouveau_svmm *svmm,
 			ret = -EINVAL;
 			goto out;
 		}
+		folio = page_folio(page);
 
 		mutex_lock(&svmm->mutex);
 		if (!mmu_interval_read_retry(&notifier->notifier,
 					     notifier_seq))
 			break;
 		mutex_unlock(&svmm->mutex);
+
+		folio_unlock(folio);
+		folio_put(folio);
 	}
 
 	/* Map the page on the GPU. */
@@ -637,8 +642,8 @@ static int nouveau_atomic_range_fault(struct nouveau_svmm *svmm,
 	ret = nvif_object_ioctl(&svmm->vmm->vmm.object, args, size, NULL);
 	mutex_unlock(&svmm->mutex);
 
-	unlock_page(page);
-	put_page(page);
+	folio_unlock(folio);
+	folio_put(folio);
 
 out:
 	mmu_interval_notifier_remove(&notifier->notifier);
-- 
2.47.1