dma-buf: use new iterator in dma_resv_copy_fences

This makes the function much simpler since the complex
retry logic is now handled else where.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005113742.1101-5-christian.koenig@amd.com

drivers/dma-buf/dma-resv.c

@@ -432,74 +432,54 @@ EXPORT_SYMBOL(dma_resv_iter_next_unlocked);
  */
 int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
 {
-	struct dma_resv_list *src_list, *dst_list;
-	struct dma_fence *old, *new;
-	unsigned int i;
+	struct dma_resv_iter cursor;
+	struct dma_resv_list *list;
+	struct dma_fence *f, *excl;
 
 	dma_resv_assert_held(dst);
 
-	rcu_read_lock();
-	src_list = dma_resv_shared_list(src);
+	list = NULL;
+	excl = NULL;
 
-retry:
-	if (src_list) {
-		unsigned int shared_count = src_list->shared_count;
+	dma_resv_iter_begin(&cursor, src, true);
+	dma_resv_for_each_fence_unlocked(&cursor, f) {
 
-		rcu_read_unlock();
+		if (dma_resv_iter_is_restarted(&cursor)) {
+			dma_resv_list_free(list);
+			dma_fence_put(excl);
 
-		dst_list = dma_resv_list_alloc(shared_count);
-		if (!dst_list)
-			return -ENOMEM;
+			if (cursor.fences) {
+				unsigned int cnt = cursor.fences->shared_count;
 
-		rcu_read_lock();
-		src_list = dma_resv_shared_list(src);
-		if (!src_list || src_list->shared_count > shared_count) {
-			kfree(dst_list);
-			goto retry;
-		}
-
-		dst_list->shared_count = 0;
-		for (i = 0; i < src_list->shared_count; ++i) {
-			struct dma_fence __rcu **dst;
-			struct dma_fence *fence;
+				list = dma_resv_list_alloc(cnt);
+				if (!list) {
+					dma_resv_iter_end(&cursor);
+					return -ENOMEM;
+				}
 
-			fence = rcu_dereference(src_list->shared[i]);
-			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
-				     &fence->flags))
-				continue;
+				list->shared_count = 0;
 
-			if (!dma_fence_get_rcu(fence)) {
-				dma_resv_list_free(dst_list);
-				src_list = dma_resv_shared_list(src);
-				goto retry;
+			} else {
+				list = NULL;
 			}
-
-			if (dma_fence_is_signaled(fence)) {
-				dma_fence_put(fence);
-				continue;
-			}
-
-			dst = &dst_list->shared[dst_list->shared_count++];
-			rcu_assign_pointer(*dst, fence);
+			excl = NULL;
 		}
-	} else {
-		dst_list = NULL;
-	}
 
-	new = dma_fence_get_rcu_safe(&src->fence_excl);
-	rcu_read_unlock();
-
-	src_list = dma_resv_shared_list(dst);
-	old = dma_resv_excl_fence(dst);
+		dma_fence_get(f);
+		if (dma_resv_iter_is_exclusive(&cursor))
+			excl = f;
+		else
+			RCU_INIT_POINTER(list->shared[list->shared_count++], f);
+	}
+	dma_resv_iter_end(&cursor);
 
 	write_seqcount_begin(&dst->seq);
-	/* write_seqcount_begin provides the necessary memory barrier */
-	RCU_INIT_POINTER(dst->fence_excl, new);
-	RCU_INIT_POINTER(dst->fence, dst_list);
+	excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst));
+	list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst));
 	write_seqcount_end(&dst->seq);
 
-	dma_resv_list_free(src_list);
-	dma_fence_put(old);
+	dma_resv_list_free(list);
+	dma_fence_put(excl);
 
 	return 0;
 }