Re: bin/20767

[Jukka Ruohonen <jruohonen%iki.fi@localhost>]

On Wed, Oct 14, 2009 at 05:15:04AM +0000, Robert Elz wrote:
>    |          - The patch uses kvm(3).
>  
>  where I suspect that adding yet more kmem grovellers, where the
>  direction has been (for good reason) to eliminate them, is not going
>  to meet with much success.

Fair enough. Reducing the use of kmem sounds highly welcome, but I didn't
know that the usage of kvm is discouraged also in this particular scenario.

>  If this data needs to be made available at all the right way to do it
>  (IMO) is to have cgdconfig manage it - just keep a record of what is
>  created and destroyed in a file somewhere (use file locking to avoid
>  race conditions with multiple instances of cgdconfig running in parallel,
>  which isn't likely, but ...).    I'd stick it in /var/run so it gets
>  cleaned automatically on reboot.

If this route is taken, it would perhaps be a good idea to have a common API
that all related tools (ccdconfig, vnconfig, etc.) could possibly use.

>  Or, have cgdconfig write the device name into somewhere in the header
>  of the mounted device, then all you need is to be able to iterate over
>  possible /dev/cgdN's and find which ones are configured (I suspect methods
>  do do that already exist) and upon finding a configured one, extract
>  the name from its data.

How about the use of cgd for swap devices, for an instance?

>  [Aside: I'm not sure the data is really needed ... I use cgd, and I've never
>  encountered the need - on the other hand, if cgd could be made a cloneable
>  type device, so I don't need to pick the N in /dev/cgdN but it can be
>  picked for me, that would be great.]

Agreed.