dma-buf: warn about containers in dma_resv object

Drivers should not add containers as shared fences to the dma_resv
object, instead each fence should be added individually.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220204100429.2049-5-christian.koenig@amd.com

drivers/dma-buf/dma-resv.c

@@ -256,6 +256,11 @@ void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
 
 	dma_resv_assert_held(obj);
 
+	/* Drivers should not add containers here, instead add each fence
+	 * individually.
+	 */
+	WARN_ON(dma_fence_is_container(fence));
+
 	fobj = dma_resv_shared_list(obj);
 	count = fobj->shared_count;