xfs_dir2_data_off_t
xfs_dir2_data_off_t offset; /* start of freespace */
xfs_dir2_data_off_t length; /* length of freespace */
xfs_dir2_data_off_t tag; /* starting offset of us */
xfs_dir2_data_off_t length; /* total free length */
xfs_dir2_data_off_t tag; /* starting offset of us */