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 <[email protected]>
---
 drivers/gpu/drm/nouveau/nouveau_svm.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c 
b/drivers/gpu/drm/nouveau/nouveau_svm.c
index 5dd83a46578f..5de2d54b9782 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -494,8 +494,10 @@ 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);
@@ -504,11 +506,9 @@ 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);
-                       ret = -EBUSY;
-               } else if (ret == -EAGAIN)
+               if (ret == 0)
                        ret = -EBUSY;
+               up_read(&range->vma->vm_mm->mmap_sem);
                hmm_range_unregister(range);
                return ret;
        }
@@ -706,8 +706,8 @@ 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

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