XFS_RTRMAP_BLOCK_LEN
blocklen -= XFS_RTRMAP_BLOCK_LEN;
size_t sz = XFS_RTRMAP_BLOCK_LEN;
((char *)block + XFS_RTRMAP_BLOCK_LEN +
((char *)block + XFS_RTRMAP_BLOCK_LEN +
((char *)block + XFS_RTRMAP_BLOCK_LEN +
((char *)block + XFS_RTRMAP_BLOCK_LEN +