linux-kernel - [PATCH 4/7] nouveau: unlock mmap_sem on all errors from nouveau_range

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Date:   Wed, 24 Jul 2019 08:52:55 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jérôme Glisse <jglisse@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Ben Skeggs <bskeggs@...hat.com>
Cc:     Ralph Campbell <rcampbell@...dia.com>, linux-mm@...ck.org,
        nouveau@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 4/7] nouveau: unlock mmap_sem on all errors from nouveau_range_fault

Currently nouveau_svm_fault expects nouveau_range_fault to never unlock
mmap_sem, but the latter unlocks it for a random selection of error
codes. Fix this up by always unlocking mmap_sem for non-zero return
values in nouveau_range_fault, and only unlocking it in the caller
for successful returns.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 drivers/gpu/drm/nouveau/nouveau_svm.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index e3097492b4ad..a835cebb6d90 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -495,8 +495,10 @@ nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range)
 	ret = hmm_range_register(range, mirror,
 				 range->start, range->end,
 				 PAGE_SHIFT);
-	if (ret)
+	if (ret) {
+		up_read(&range->vma->vm_mm->mmap_sem);
 		return (int)ret;
+	}
 
 	if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
 		up_read(&range->vma->vm_mm->mmap_sem);
@@ -505,10 +507,9 @@ nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range)
 
 	ret = hmm_range_fault(range, true);
 	if (ret <= 0) {
-		if (ret == -EBUSY || !ret) {
-			up_read(&range->vma->vm_mm->mmap_sem);
+		if (ret == 0)
 			ret = -EBUSY;
-		}
+		up_read(&range->vma->vm_mm->mmap_sem);
 		hmm_range_unregister(range);
 		return ret;
 	}
@@ -706,8 +707,8 @@ nouveau_svm_fault(struct nvif_notify *notify)
 						NULL);
 			svmm->vmm->vmm.object.client->super = false;
 			mutex_unlock(&svmm->mutex);
+			up_read(&svmm->mm->mmap_sem);
 		}
-		up_read(&svmm->mm->mmap_sem);
 
 		/* Cancel any faults in the window whose pages didn't manage
 		 * to keep their valid bit, or stay writeable when required.
-- 
2.20.1