[PATCH 21/22] nouveau: unlock mmap_sem on all errors from nouveau_range_fault

Christoph Hellwig
2019-07-01T06:21:15Z

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@lst.de>
---
drivers/gpu/drm/nouveau/nouveau_svm.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index e831f4184a17..c0cf7aeaefb3 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -500,8 +500,10 @@ 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, NOUVEAU_RANGE_FAULT_TIMEOUT)) {
/*
@@ -515,15 +517,14 @@ nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range,

ret = hmm_range_fault(range, block);
if (ret <= 0) {
- if (ret == -EBUSY || !ret) {
- /* Same as above, drop mmap_sem to match old API. */
- up_read(&range->vma->vm_mm->mmap_sem);
- ret = -EBUSY;
- } else if (ret == -EAGAIN)
+ if (ret == 0)
ret = -EBUSY;
+ if (ret != -EAGAIN)
+ up_read(&range->vma->vm_mm->mmap_sem);
hmm_range_unregister(range);
return ret;
}
+
return 0;
}

@@ -718,8 +719,8 @@ 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