[dm-devel] [RFC] New interface for dm-io to handle timed requests

[Stefan Bader]

dm-devel-bounces at redhat.com wrote on 14.03.2006 21:15:10:

> Stefan Bader wrote:
> > The ideal solution would be to have an interface in the block layer 
that 
> > allows us to cancel any submitted requests. But since such a change 
will 
> > take quite a lot discussions and work, we want to emulate such a 
> > behavior in the dm core for now.
> > 
> 
> The scsi people and some block people have been talking about moving 
> more error handling functionality into the block layer for a while and 
> it is slowing moving that way. It could probably be done faster if 
> people did not concentrate on one subsystem :)
> 

It is not that much about error handling. More about policy. If the
subsystem decides that io took enough time or maybe it just doesn't
want to go on (could be a force umount...) it would be nice to be
able to stop lower level drivers from doing error recovery. Thus
the idea of stopping a submitted request.

The changes to the core now shall fake this as long as there isn't
such a functionality in the kernel with an interface that can handle
this.

> Maybe you should post to lkml and linux-scsi and get some responses from 

> them before adding it to dm core. If a post already went out to those 
> list my fault for missing it.
> 
No it didn't. I guess lkml is a good point. I am not sure about 
linux-scsi.
As it is not related specifically to scsi...

Stefan Bader

SW Linux on zSeries Development & Services
Stefan.Bader at de.ibm.com
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