[linux-lvm] [RFC] Let udev play with snapshots

[Jan Blunck]

On Wed, Oct 11, Alasdair G Kergon wrote:

> We discussed this at OLS and decided that lvm2 would wait
> for udev to finish whatever it wanted to do before writing
> to the cow.  A yet-to-be-specified signalling mechanism would be 
> introduced to achieve this.

Yeah, I forgot to mention that what I propose is what Kay and me came up
with.

It isn't the cow that makes problems here. It is the first LV that we use for
cleaning. AFAIK this is a linear table. IMHO we don't need another signalling
mechanism but a sane way how udev can tell if there every will be a filesystem
in the LV that was just created.

At the moment udev is skipping over all LV with "*snapshot*" or "*error*"
mentioned in the table:

 PROGRAM!="/sbin/dmsetup status -j %M -m %m", GOTO="device_mapper_end"
 RESULT=="|*snapshot*|*error*", GOTO="device_mapper_end"

I think we should extend this by giving udev a way how it could tell if it
should try to do something with the device.