+/*
+ * calculate extra metadata reservation when snapshotting a subvolume
+ * contains orphan files.
+ */
+void btrfs_orphan_pre_snapshot(struct btrfs_trans_handle *trans,
+ struct btrfs_pending_snapshot *pending,
+ u64 *bytes_to_reserve)
+{
+ struct btrfs_root *root;
+ struct btrfs_block_rsv *block_rsv;
+ u64 num_bytes;
+ int index;
+
+ root = pending->root;
+ if (!root->orphan_block_rsv || list_empty(&root->orphan_list))
+ return;
+
+ block_rsv = root->orphan_block_rsv;
+
+ /* orphan block reservation for the snapshot */
+ num_bytes = block_rsv->size;
+
+ /*
+ * after the snapshot is created, COWing tree blocks may use more
+ * space than it frees. So we should make sure there is enough
+ * reserved space.
+ */
+ index = trans->transid & 0x1;
+ if (block_rsv->reserved + block_rsv->freed[index] < block_rsv->size) {
+ num_bytes += block_rsv->size -
+ (block_rsv->reserved + block_rsv->freed[index]);
+ }
+
+ *bytes_to_reserve += num_bytes;
+}
+
+void btrfs_orphan_post_snapshot(struct btrfs_trans_handle *trans,
+ struct btrfs_pending_snapshot *pending)
+{
+ struct btrfs_root *root = pending->root;
+ struct btrfs_root *snap = pending->snap;
+ struct btrfs_block_rsv *block_rsv;
+ u64 num_bytes;
+ int index;
+ int ret;
+
+ if (!root->orphan_block_rsv || list_empty(&root->orphan_list))
+ return;
+
+ /* refill source subvolume's orphan block reservation */
+ block_rsv = root->orphan_block_rsv;
+ index = trans->transid & 0x1;
+ if (block_rsv->reserved + block_rsv->freed[index] < block_rsv->size) {
+ num_bytes = block_rsv->size -
+ (block_rsv->reserved + block_rsv->freed[index]);
+ ret = btrfs_block_rsv_migrate(&pending->block_rsv,
+ root->orphan_block_rsv,
+ num_bytes);
+ BUG_ON(ret);
+ }
+
+ /* setup orphan block reservation for the snapshot */
+ block_rsv = btrfs_alloc_block_rsv(snap);
+ BUG_ON(!block_rsv);
+
+ btrfs_add_durable_block_rsv(root->fs_info, block_rsv);
+ snap->orphan_block_rsv = block_rsv;
+
+ num_bytes = root->orphan_block_rsv->size;
+ ret = btrfs_block_rsv_migrate(&pending->block_rsv,
+ block_rsv, num_bytes);
+ BUG_ON(ret);
+
+#if 0
+ /* insert orphan item for the snapshot */
+ WARN_ON(!root->orphan_item_inserted);
+ ret = btrfs_insert_orphan_item(trans, root->fs_info->tree_root,
+ snap->root_key.objectid);
+ BUG_ON(ret);
+ snap->orphan_item_inserted = 1;
+#endif
+}
+
+enum btrfs_orphan_cleanup_state {
+ ORPHAN_CLEANUP_STARTED = 1,
+ ORPHAN_CLEANUP_DONE = 2,
+};
+
+/*
+ * This is called in transaction commmit time. If there are no orphan
+ * files in the subvolume, it removes orphan item and frees block_rsv
+ * structure.
+ */
+void btrfs_orphan_commit_root(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root)
+{
+ int ret;
+
+ if (!list_empty(&root->orphan_list) ||
+ root->orphan_cleanup_state != ORPHAN_CLEANUP_DONE)
+ return;
+
+ if (root->orphan_item_inserted &&
+ btrfs_root_refs(&root->root_item) > 0) {
+ ret = btrfs_del_orphan_item(trans, root->fs_info->tree_root,
+ root->root_key.objectid);
+ BUG_ON(ret);
+ root->orphan_item_inserted = 0;
+ }
+
+ if (root->orphan_block_rsv) {
+ WARN_ON(root->orphan_block_rsv->size > 0);
+ btrfs_free_block_rsv(root, root->orphan_block_rsv);
+ root->orphan_block_rsv = NULL;
+ }
+}
+