lfs_fcntl_markv
#define LFCNBMAPV _FCNRW_FSPRIV('L', 16, struct lfs_fcntl_markv)
#define LFCNMARKV _FCNRW_FSPRIV('L', 17, struct lfs_fcntl_markv)
struct lfs_fcntl_markv blkvp;
blkvp = *(struct lfs_fcntl_markv *)ap->a_data;