drm: use new iterator in drm_gem_fence_array_add_implicit v3

Simplifying the code a bit.

v2: add missing rcu_read_lock()/unlock()
v3: switch to locked version

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005113742.1101-24-christian.koenig@amd.com

drivers/gpu/drm/drm_gem.c

@@ -1340,31 +1340,15 @@ int drm_gem_fence_array_add_implicit(struct xarray *fence_array,
 				     struct drm_gem_object *obj,
 				     bool write)
 {
-	int ret;
-	struct dma_fence **fences;
-	unsigned int i, fence_count;
+	struct dma_resv_iter cursor;
+	struct dma_fence *fence;
+	int ret = 0;
 
-	if (!write) {
-		struct dma_fence *fence =
-			dma_resv_get_excl_unlocked(obj->resv);
-
-		return drm_gem_fence_array_add(fence_array, fence);
-	}
-
-	ret = dma_resv_get_fences(obj->resv, NULL,
-						&fence_count, &fences);
-	if (ret || !fence_count)
-		return ret;
-
-	for (i = 0; i < fence_count; i++) {
-		ret = drm_gem_fence_array_add(fence_array, fences[i]);
+	dma_resv_for_each_fence(&cursor, obj->resv, write, fence) {
+		ret = drm_gem_fence_array_add(fence_array, fence);
 		if (ret)
 			break;
 	}
-
-	for (; i < fence_count; i++)
-		dma_fence_put(fences[i]);
-	kfree(fences);
 	return ret;
 }
 EXPORT_SYMBOL(drm_gem_fence_array_add_implicit);