struct btrfs_root *root,
struct btrfs_path *path, u64 objectid,
u64 bytenr, int mod);
+u64 btrfs_file_extent_length(struct btrfs_path *path);
int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_ordered_sum *sums);