Re: dm_ioctl: Only send a change uevent when a resume ioctl changes the device.

[Dave Wysochanski <dwysocha@redhat.com>]

On Tue, 2010-01-26 at 16:12 -0500, Mike Snitzer wrote:
> > > > 
> > > 
> > > Nice simplification Mike, as discussed on IRC.
> > > 
> > > Ack.
> > > 
> > 
> > Actually, the more I think about it I am not sure about sending the
> > uevent in the case where dm_resume() fails.  Seems like we should send
> > it since the map could have changed - depends on whether we went through
> > that 'if (new_map)' block.
> 
> Pretty sure we resolved this.  As we discussed (just after you sent this
> last reply); for the benefit of others:
> 
> <dave> so the change uevent here really means "resume was successful"
> <mike> yes
> <dave> wait - if we suspend it, but resume fails, shouldn't we still
> send the event?
> <mike> in that case the device will be left suspended; in terms of udev
> that's not a "change"
> <mike> device is wedged (suspended)
> <mike> telling udev about it could just stack up other processes trying
> to issue IO to it
> <mike> but to be honest I don't know what the purist definition of what
> a "change" uevent is; I'm just treating it as telling some blackbox that
> DM device has changed and is functional
> <dave> that does make sense
> 

Yes, I should have stopped with my original Ack!