drm/i915: use the new iterator in i915_gem_busy_ioctl v2

This makes the function much simpler since the complex
retry logic is now handled else where.
Signed-off-by: NChristian König <christian.koenig@amd.com>
Acked-by: NDaniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20211116102431.198905-2-christian.koenig@amd.com

drivers/gpu/drm/i915/gem/i915_gem_busy.c

@@ -115,8 +115,8 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
 {
 	struct drm_i915_gem_busy *args = data;
 	struct drm_i915_gem_object *obj;
-	struct dma_resv_list *list;
-	unsigned int seq;
+	struct dma_resv_iter cursor;
+	struct dma_fence *fence;
 	int err;
 
 	err = -ENOENT;
@@ -142,27 +142,20 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
 	 * to report the overall busyness. This is what the wait-ioctl does.
 	 *
 	 */
-retry:
-	seq = raw_read_seqcount(&obj->base.resv->seq);
-
-	/* Translate the exclusive fence to the READ *and* WRITE engine */
-	args->busy = busy_check_writer(dma_resv_excl_fence(obj->base.resv));
-
-	/* Translate shared fences to READ set of engines */
-	list = dma_resv_shared_list(obj->base.resv);
-	if (list) {
-		unsigned int shared_count = list->shared_count, i;
-
-		for (i = 0; i < shared_count; ++i) {
-			struct dma_fence *fence =
-				rcu_dereference(list->shared[i]);
-
+	args->busy = 0;
+	dma_resv_iter_begin(&cursor, obj->base.resv, true);
+	dma_resv_for_each_fence_unlocked(&cursor, fence) {
+		if (dma_resv_iter_is_restarted(&cursor))
+			args->busy = 0;
+
+		if (dma_resv_iter_is_exclusive(&cursor))
+			/* Translate the exclusive fence to the READ *and* WRITE engine */
+			args->busy |= busy_check_writer(fence);
+		else
+			/* Translate shared fences to READ set of engines */
 			args->busy |= busy_check_reader(fence);
-		}
 	}
-
-	if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq))
-		goto retry;
+	dma_resv_iter_end(&cursor);
 
 	err = 0;
 out: