Comment # 13 on bug 1137390 from Franck Bui

(In reply to Neil Brown from comment #10)
> > # systemctl show mnt.mount | egrep 'RequiredBy|WantedBy'
> > RequiredBy=mnt-tahan.mount mnt-tahan-01_RSH.mount
> 
> So, where are these units coming from..

>From comment #4:

> Submounts, such as,
>
> Safe:/ccsa/tahan/01_RSH 10269457792  777337088 9492120704   8% /mnt/tahan/01_RSH
>
> Are just because in the reality these are different ZFS volumes on the NFSv4 server and have their own exports.

It sounds like they are exported by the server but not referenced by the
client.