Re: [PATCH v3 1/2] dma-buf: Split out dma fence array create into alloc and arm functions

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Am 23.08.24 um 06:54 schrieb Matthew Brost:
Useful to preallocate dma fence array and then arm in path of reclaim or
a dma fence.

Exactly that was rejected before because it allows to create circle dependencies.

You would need a really really good argument why that is necessary.

Regards,
Christian.


Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
---
  drivers/dma-buf/dma-fence-array.c | 81 ++++++++++++++++++++++---------
  include/linux/dma-fence-array.h   |  7 +++
  2 files changed, 66 insertions(+), 22 deletions(-)

diff --git a/drivers/dma-buf/dma-fence-array.c b/drivers/dma-buf/dma-fence-array.c
index c74ac197d5fe..b03e0a87a5cd 100644
--- a/drivers/dma-buf/dma-fence-array.c
+++ b/drivers/dma-buf/dma-fence-array.c
@@ -144,36 +144,38 @@ const struct dma_fence_ops dma_fence_array_ops = {
  EXPORT_SYMBOL(dma_fence_array_ops);
/**
- * dma_fence_array_create - Create a custom fence array
+ * dma_fence_array_alloc - Allocate a custom fence array
+ * @num_fences:		[in]	number of fences to add in the array
+ *
+ * Return dma fence array on success, NULL on failure
+ */
+struct dma_fence_array *dma_fence_array_alloc(int num_fences)
+{
+	struct dma_fence_array *array;
+
+	return kzalloc(struct_size(array, callbacks, num_fences), GFP_KERNEL);
+}
+EXPORT_SYMBOL(dma_fence_array_alloc);
+
+/**
+ * dma_fence_array_arm - Arm a custom fence array
+ * @array:		[in]	dma fence array to arm
   * @num_fences:		[in]	number of fences to add in the array
   * @fences:		[in]	array containing the fences
   * @context:		[in]	fence context to use
   * @seqno:		[in]	sequence number to use
   * @signal_on_any:	[in]	signal on any fence in the array
   *
- * Allocate a dma_fence_array object and initialize the base fence with
- * dma_fence_init().
- * In case of error it returns NULL.
- *
- * The caller should allocate the fences array with num_fences size
- * and fill it with the fences it wants to add to the object. Ownership of this
- * array is taken and dma_fence_put() is used on each fence on release.
- *
- * If @signal_on_any is true the fence array signals if any fence in the array
- * signals, otherwise it signals when all fences in the array signal.
+ * Implementation of @dma_fence_array_create without allocation. Useful to arm a
+ * preallocated dma fence fence in the path of reclaim or dma fence signaling.
   */
-struct dma_fence_array *dma_fence_array_create(int num_fences,
-					       struct dma_fence **fences,
-					       u64 context, unsigned seqno,
-					       bool signal_on_any)
+void dma_fence_array_arm(struct dma_fence_array *array,
+			 int num_fences,
+			 struct dma_fence **fences,
+			 u64 context, unsigned seqno,
+			 bool signal_on_any)
  {
-	struct dma_fence_array *array;
-
-	WARN_ON(!num_fences || !fences);
-
-	array = kzalloc(struct_size(array, callbacks, num_fences), GFP_KERNEL);
-	if (!array)
-		return NULL;
+	WARN_ON(!array || !num_fences || !fences);
array->num_fences = num_fences; @@ -200,6 +202,41 @@ struct dma_fence_array *dma_fence_array_create(int num_fences,
  	 */
  	while (num_fences--)
  		WARN_ON(dma_fence_is_container(fences[num_fences]));
+}
+EXPORT_SYMBOL(dma_fence_array_arm);
+
+/**
+ * dma_fence_array_create - Create a custom fence array
+ * @num_fences:		[in]	number of fences to add in the array
+ * @fences:		[in]	array containing the fences
+ * @context:		[in]	fence context to use
+ * @seqno:		[in]	sequence number to use
+ * @signal_on_any:	[in]	signal on any fence in the array
+ *
+ * Allocate a dma_fence_array object and initialize the base fence with
+ * dma_fence_init().
+ * In case of error it returns NULL.
+ *
+ * The caller should allocate the fences array with num_fences size
+ * and fill it with the fences it wants to add to the object. Ownership of this
+ * array is taken and dma_fence_put() is used on each fence on release.
+ *
+ * If @signal_on_any is true the fence array signals if any fence in the array
+ * signals, otherwise it signals when all fences in the array signal.
+ */
+struct dma_fence_array *dma_fence_array_create(int num_fences,
+					       struct dma_fence **fences,
+					       u64 context, unsigned seqno,
+					       bool signal_on_any)
+{
+	struct dma_fence_array *array;
+
+	array = dma_fence_array_alloc(num_fences);
+	if (!array)
+		return NULL;
+
+	dma_fence_array_arm(array, num_fences, fences,
+			    context, seqno, signal_on_any);
return array;
  }
diff --git a/include/linux/dma-fence-array.h b/include/linux/dma-fence-array.h
index 29c5650c1038..3466ffc4b803 100644
--- a/include/linux/dma-fence-array.h
+++ b/include/linux/dma-fence-array.h
@@ -79,6 +79,13 @@ to_dma_fence_array(struct dma_fence *fence)
  	for (index = 0, fence = dma_fence_array_first(head); fence;	\
  	     ++(index), fence = dma_fence_array_next(head, index))
+struct dma_fence_array *dma_fence_array_alloc(int num_fences);
+void dma_fence_array_arm(struct dma_fence_array *array,
+			 int num_fences,
+			 struct dma_fence **fences,
+			 u64 context, unsigned seqno,
+			 bool signal_on_any);
+
  struct dma_fence_array *dma_fence_array_create(int num_fences,
  					       struct dma_fence **fences,
  					       u64 context, unsigned seqno,




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