On 7/3/19 11:45 AM, Christoph Hellwig wrote:
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@xxxxxx>
Reviewed-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
---
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,
You can delete the comment "With the old API the driver must ..."
(not visible in the patch here).
I suggest moving the two assignments:
range->default_flags = 0;
range->pfn_flags_mask = -1UL;
to just above the "again:" where the other range.xxx fields are
initialized in nouveau_svm_fault().
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)) {
/*
You can delete this comment (only the first line is visible here)
since it is about the "old API".
Also, it should return -EBUSY not -EAGAIN since it means there was a
range invalidation collision (similar to hmm_range_fault() if
!range->valid).
@@ -515,15 +517,14 @@ nouveau_range_fault(struct hmm_mirror *mirror, struct hmm_range *range,
ret = hmm_range_fault(range, block);
nouveau_range_fault() is only called with "block = true" so
could eliminate the block parameter and pass true here.
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);
Can ret == -EAGAIN happen if "block = true"?
Generally, I prefer the read_down()/read_up() in the same function
(i.e., nouveau_svm_fault()) but I can see why it should be here
if hmm_range_fault() can return with mmap_sem unlocked.
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);
The "else" case should check for -EBUSY and goto again.
/* Cancel any faults in the window whose pages didn't manage
* to keep their valid bit, or stay writeable when required.
