Weird mout output

[Jov]

Mount output my root partition mount info as this,which is wired:
stage/vm/centos7 at zrep_000007_split/dev/da0s1a on / (ufs, local, journaled
soft-updates)

This should be:
/dev/da0s1a on /.....

more info:
cat /etc/fstab
/dev/da0s1a     /       ufs     rw      1

zfs mount
stage/pgdata                    /pgdata
stage                           /stage
stage/vm                        /stage/vm
stage/work_space
/stage/work_spacestage/vm/smartos
/stage/vm/smartosstage/vm/centos7
/stage/vm/centos7stage/vm/ubuntu16               /stage/vm/ubuntu16
stage/vm/omnios                 /stage/vm/omnios

uname -a
FreeBSD xx 11.0-RC2 FreeBSD 11.0-RC2 #0 r304729: Wed Aug 24 06:59:03 UTC
2016     root at releng2.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  amd64

$ mount
stage/vm/centos7 at zrep_000007_split/dev/da0s1a on / (ufs, local, journaled
soft-updates)
devfs on /dev (devfs, local, multilabel)
stage/pgdata on /pgdata (zfs, local, noatime, nfsv4acls)
stage on /stage (zfs, local, noatime, nfsv4acls)
stage/vm on /stage/vm (zfs, local, noatime, nfsv4acls)
stage/work_space on /stage/work_space (zfs, local, noatime, nfsv4acls)
stage/vm/smartos on /stage/vm/smartos (zfs, local, noatime, nfsv4acls)
stage/vm/centos7 on /stage/vm/centos7 (zfs, local, noatime, nfsv4acls)
stage/vm/ubuntu16 on /stage/vm/ubuntu16 (zfs, local, noatime, nfsv4acls)
stage/vm/omnios on /stage/vm/omnios (zfs, local, noatime, nfsv4acls)
/dev/md0 on /mnt (cd9660, local, read-only)