reboot-less zfs volmode property refresh?

[Harry Schmalzbauer]

 Hello,

maybe I'm just missing something obvious, but modifying a dataset's
volmode property seems to force me to reboot the host to have any effect.

Test to reproduce (parent dataset hostPsys/bhyveVOL/sys  has volmode set
ot "dev"):

1.) Create new volume with volmode=geom, and write new GPT

zfs create -o volmode=geom -V 10G hostPsys/bhyveVOL/sys/test
gpart create -s gpt /dev/zvol/hostPsys/bhyveVOL/sys/test
gpart show -l /dev/zvol/hostPsys/bhyveVOL/sys/test
=>      40  20971440  zvol/hostPsys/bhyveVOL/sys/test  GPT 
(10G)                           
        40  20971440                                    - free -  (10G)

(works as expected)

2.) Create new volume with volmode=dev, and write new GPT

zfs destroy hostPsys/bhyveVOL/sys/test
zfs create -V 10G hostPsys/bhyveVOL/sys/test
gpart create -s gpt
/dev/zvol/hostPsys/bhyveVOL/sys/test                                             

gpart: arg0 'zvol/hostPsys/bhyveVOL/sys/test': Invalid argument

(fails as expected)

3.) Modify existing volmode=dev dataset and write new GPT

zfs set volmode=geom
hostPsys/bhyveVOL/sys/test                                                     

zfs get volmode
hostPsys/bhyveVOL/sys/test                                                          

NAME                         PROPERTY  VALUE   
SOURCE                                                                                

hostPsys/bhyveVOL/sys/test  volmode   geom     local
gpart create -s gpt
/dev/zvol/hostPsys/bhyveVOL/sys/test                                            

gpart: arg0 'zvol/hostPsys/bhyveVOL/sys/test': Invalid argument

(fails unexpected)

What can I do to let geom(4) know that there's a new device?
And vice versa, changing volmode property from "geom" to "dev" or "none"
doesn't have any effecit either, until reboot.

Thanks,

-harry