drm/i915: use the new iterator in i915_request_await_object v2

Simplifying the code a bit.

v2: add missing rcu_read_lock()/rcu_read_unlock()
v3: use dma_resv_for_each_fence instead

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005113742.1101-20-christian.koenig@amd.com

drivers/gpu/drm/i915/i915_request.c

@@ -1509,38 +1509,14 @@ i915_request_await_object(struct i915_request *to,
 			  struct drm_i915_gem_object *obj,
 			  bool write)
 {
-	struct dma_fence *excl;
+	struct dma_resv_iter cursor;
+	struct dma_fence *fence;
 	int ret = 0;
 
-	if (write) {
-		struct dma_fence **shared;
-		unsigned int count, i;
-
-		ret = dma_resv_get_fences(obj->base.resv, &excl, &count,
-					  &shared);
+	dma_resv_for_each_fence(&cursor, obj->base.resv, write, fence) {
+		ret = i915_request_await_dma_fence(to, fence);
 		if (ret)
-			return ret;
-
-		for (i = 0; i < count; i++) {
-			ret = i915_request_await_dma_fence(to, shared[i]);
-			if (ret)
-				break;
-
-			dma_fence_put(shared[i]);
-		}
-
-		for (; i < count; i++)
-			dma_fence_put(shared[i]);
-		kfree(shared);
-	} else {
-		excl = dma_resv_get_excl_unlocked(obj->base.resv);
-	}
-
-	if (excl) {
-		if (ret == 0)
-			ret = i915_request_await_dma_fence(to, excl);
-
-		dma_fence_put(excl);
+			break;
 	}
 
 	return ret;