[dm-devel] [PATCH] improve atomicity of device creation

[Alasdair G Kergon]

On Tue, Dec 11, 2007 at 07:25:32PM +0100, Kay Sievers wrote:
> Should we create an additional new iocl to request the device node
> creation, or add that call to an existing one?

Currently we get an ADD from alloc_dev -> add_disk -> register_disk.
But the device is not usable until the dm resume ioctl, so ideally that
one should be ignored, and it's the CHANGE issued by dm resume that udev
should act upon.  (That's not essential though - the /dev node can be
created in response to the ADD, but nothing in udev userspace should
attempt to open it until after the CHANGE is received.)

> Could it be that we want to pass more properties to the event, which are
> added as environment keys?
 
Don't think so - we'll be handing full control of ownership/permissions
over to udev.

Alasdair
-- 
agk at redhat.com