[PATCH 1/9] dma-buf: add dma_fence_was_initialized function v2

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Some driver use fence->ops to test if a fence was initialized or not.
The problem is that this utilizes internal behavior of the dma_fence
implementation.

So better abstract that into a function.

v2: use a flag instead of testing fence->ops, rename the function, move
    to the beginning of the patch set.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/dma-buf/dma-fence.c             |  2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_job.c | 13 +++++++------
 drivers/gpu/drm/qxl/qxl_release.c       |  2 +-
 include/linux/dma-fence.h               | 15 +++++++++++++++
 4 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 21c5c30b4f34..c9a036b0d592 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -1054,7 +1054,7 @@ __dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
 	fence->lock = lock;
 	fence->context = context;
 	fence->seqno = seqno;
-	fence->flags = flags;
+	fence->flags = flags | BIT(DMA_FENCE_FLAG_INITIALIZED_BIT);
 	fence->error = 0;
 
 	trace_dma_fence_init(fence);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
index 0a0dcbf0798d..d1e74d0050c7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
@@ -278,9 +278,10 @@ void amdgpu_job_free_resources(struct amdgpu_job *job)
 	unsigned i;
 
 	/* Check if any fences were initialized */
-	if (job->base.s_fence && job->base.s_fence->finished.ops)
+	if (job->base.s_fence &&
+	    dma_fence_was_initialized(&job->base.s_fence->finished))
 		f = &job->base.s_fence->finished;
-	else if (job->hw_fence && job->hw_fence->base.ops)
+	else if (dma_fence_was_initialized(&job->hw_fence->base))
 		f = &job->hw_fence->base;
 	else
 		f = NULL;
@@ -297,11 +298,11 @@ static void amdgpu_job_free_cb(struct drm_sched_job *s_job)
 
 	amdgpu_sync_free(&job->explicit_sync);
 
-	if (job->hw_fence->base.ops)
+	if (dma_fence_was_initialized(&job->hw_fence->base))
 		dma_fence_put(&job->hw_fence->base);
 	else
 		kfree(job->hw_fence);
-	if (job->hw_vm_fence->base.ops)
+	if (dma_fence_was_initialized(&job->hw_vm_fence->base))
 		dma_fence_put(&job->hw_vm_fence->base);
 	else
 		kfree(job->hw_vm_fence);
@@ -335,11 +336,11 @@ void amdgpu_job_free(struct amdgpu_job *job)
 	if (job->gang_submit != &job->base.s_fence->scheduled)
 		dma_fence_put(job->gang_submit);
 
-	if (job->hw_fence->base.ops)
+	if (dma_fence_was_initialized(&job->hw_fence->base))
 		dma_fence_put(&job->hw_fence->base);
 	else
 		kfree(job->hw_fence);
-	if (job->hw_vm_fence->base.ops)
+	if (dma_fence_was_initialized(&job->hw_vm_fence->base))
 		dma_fence_put(&job->hw_vm_fence->base);
 	else
 		kfree(job->hw_vm_fence);
diff --git a/drivers/gpu/drm/qxl/qxl_release.c b/drivers/gpu/drm/qxl/qxl_release.c
index 7b3c9a6016db..06b0b2aa7953 100644
--- a/drivers/gpu/drm/qxl/qxl_release.c
+++ b/drivers/gpu/drm/qxl/qxl_release.c
@@ -146,7 +146,7 @@ qxl_release_free(struct qxl_device *qdev,
 	idr_remove(&qdev->release_idr, release->id);
 	spin_unlock(&qdev->release_idr_lock);
 
-	if (release->base.ops) {
+	if (dma_fence_was_initialized(&release->base)) {
 		WARN_ON(list_empty(&release->bos));
 		qxl_release_free_list(release);
 
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index d4c92fd35092..9c4d25289239 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -48,6 +48,7 @@ struct seq_file;
  * atomic ops (bit_*), so taking the spinlock will not be needed most
  * of the time.
  *
+ * DMA_FENCE_FLAG_INITIALIZED_BIT - fence was initialized
  * DMA_FENCE_FLAG_SIGNALED_BIT - fence is already signaled
  * DMA_FENCE_FLAG_TIMESTAMP_BIT - timestamp recorded for fence signaling
  * DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT - enable_signaling might have been called
@@ -98,6 +99,7 @@ struct dma_fence {
 };
 
 enum dma_fence_flag_bits {
+	DMA_FENCE_FLAG_INITIALIZED_BIT,
 	DMA_FENCE_FLAG_SEQNO64_BIT,
 	DMA_FENCE_FLAG_SIGNALED_BIT,
 	DMA_FENCE_FLAG_TIMESTAMP_BIT,
@@ -263,6 +265,19 @@ void dma_fence_release(struct kref *kref);
 void dma_fence_free(struct dma_fence *fence);
 void dma_fence_describe(struct dma_fence *fence, struct seq_file *seq);
 
+/**
+ * dma_fence_was_initialized - test if fence was initialized
+ * @fence: fence to test
+ *
+ * Return: True if fence was ever initialized, false otherwise. Works correctly
+ * only when memory backing the fence structure is zero initialized on
+ * allocation.
+ */
+static inline bool dma_fence_was_initialized(struct dma_fence *fence)
+{
+	return fence && test_bit(DMA_FENCE_FLAG_INITIALIZED_BIT, &fence->flags);
+}
+
 /**
  * dma_fence_put - decreases refcount of the fence
  * @fence: fence to reduce refcount of
-- 
2.43.0