+struct btrfs_trans_handle *btrfs_start_transaction_fallback_global_rsv(
+ struct btrfs_root *root,
+ unsigned int num_items,
+ int min_factor)
+{
+ struct btrfs_trans_handle *trans;
+ u64 num_bytes;
+ int ret;
+
+ trans = btrfs_start_transaction(root, num_items);
+ if (!IS_ERR(trans) || PTR_ERR(trans) != -ENOSPC)
+ return trans;
+
+ trans = btrfs_start_transaction(root, 0);
+ if (IS_ERR(trans))
+ return trans;
+
+ num_bytes = btrfs_calc_trans_metadata_size(root, num_items);
+ ret = btrfs_cond_migrate_bytes(root->fs_info,
+ &root->fs_info->trans_block_rsv,
+ num_bytes,
+ min_factor);
+ if (ret) {
+ btrfs_end_transaction(trans, root);
+ return ERR_PTR(ret);
+ }
+
+ trans->block_rsv = &root->fs_info->trans_block_rsv;
+ trans->bytes_reserved = num_bytes;
+
+ return trans;
+}