vinumdrive geom with an exclusive bit. This should fix the problem
when underlying partitions overlap (i.e. the 'a' partition is at
the same offset as the 'c' partition).
Ideas borrowed from pjd@, quite a bit of testing by
Matthias Schuendehuette <msch@snafu.de>.
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.
