The fcntl tests only ever held locks in the guest's own process, where FreeBSD's lf_blocks never reports a conflict, so the host lock path that answers F_GETLK was not exercised. A forked process now holds a read lock, a write lock and a write lock to the end of the file through the host. F_GETLK with F_UNLCK reports only the write locks, F_RDLCK the same and F_WRLCK the read lock, each with the owner's pid and SEEK_SET; F_SETLK over the read lock fails with EAGAIN, and nothing is reported once the owner exits.