Re: geom_vol_ffs problems

The attached patch changes the behaviour of geom_vol_ffs so that:

 - It works even if the file system doesn't fill the partition
   completely (it only checks for file system > mediasize).
 - It does not attach to providers it doesn't know how to handle.
 - It does not attach to sunlabel providers if the slice number is 2.
 - It does not attach to bsdlabel providers if the partition type
   isn't FS_BSDFFS.
 - It does not attach to providers that are attached to consumers
   of other types than "DEV".

The last check is to avoid connecting to submirrors, components of a
RAID5, one specific path of a multipathed fibre channel disk, etc.
(Hopefully, there will be a GEOM_FCAL class that implements load
sharing and fault tolerance in multipathed systems?:-) )

The big question is how to make sure geom_vol_ffs doesn't get the
chance to taste (and attach) before, say, geom_mirror does.

What do you think about this approach?


-- 
Per Kristian Hove
Dept. of Mathematical Sciences
Norwegian University of Science and Technology