not active GEOM providers, it will result in a kernel panic.
If the GEOM provider or disk goes away before the volume
configuration data gets written to the disk, it will result
in another kernel panic.
o Make sure that the drives specified for volume creation
are active GEOM providers.
o When writing out volume configuration data to associated drives,
make sure that the GEOM provider is active, otherwise continue
to the next drive in the volume.
Approved by: le, bmilekic (mentor)
allocated ressouces should be ultimately freed in gv_destroy_geom()
(when unloading the module and not earlier), but I need to look at this
more closely.
