[issue998] Unconfiguring a vn while it is mounted

[Chris Turner]

Stathis Kamperis (via DragonFly issue tracker) wrote:
Stathis Kamperis <ekamperi at gmail.com> added the comment:

On second thoughts, this kind of check should be done in the level of vn(4)
driver itself, under the detach ioctl. 
Agree on this - this bit me many times when I was working on the 
'vnconfig -l' support.. doing this in-kernel makes sense to me -
but perhaps someone might have other ideas..

more on this below

By the way, I've been stumbling through
freebsd's repository and they have deprecated vn(4)/vnconfig(8) in favor of
md/mdconfig. md seems to do the right thing:
. ..
Where do we stand ?

I definately took some looks at all of the various vn-type 
implementations at that time -

personally, I don't like the new freebsd 'md' setup - it seems to muddle 
the different roles of 'memory disk' and 'file disk image' a bit much..
(though of course vnconfig -S kind of negates this argument) - but 
perhaps you're just referring to error handling..

I had planned (before I fell off the planet due to RealLife(TM)) to
migrate openbsd's 'mount_vnd' support over - this to me seems to
be the most useful change in VN support between the various BSDs ..
another useful thing IMHO would be to dynamically select an available vn 
device so that one would not need to be specified..

anyhow.. just some notes from someone who spent some time pondering this..