Re: [PATCH 1/3] Send KOBJ_ADD event after dm resume ioctl.

[Hannes Reinecke <hare@suse.de>]

Peter Rajnoha wrote:
> On 03/19/2010 10:24 AM, Kay Sievers wrote:
>> No, that's what "change" is for, and we already have these "change"
>> events for dm. Udev does not care if the device is ready or not, it
>> synchronizes /sys and /dev, and that works just fine with "change"
>> events.
> 
> CHANGE events, not quite... We can't even rely on these.
> 
> Just to mention, there's also a CHANGE event generated when
> read-only flag is set for a device (this is not managed by
> device-mapper of course). This one is generated even before
> the actual CHANGE event that is generated when DM device is
> ready to be used.
> 
As mentioned earlier, CHANGE events do not carry any
information about _what_ has changed.
The udev rules / programs are expected to check for
this themselves. So from that point of view yes, you
cannot simply wait for 'the' CHANGE event as you
might get more than one.

I guess most of this discussion could be solved if
the CHANGE events would be modify to attach some
enviroment variables indicating the nature of the change.

EG adding 'DM_STATE=LIVE' or whatever is appropriate
here.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
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