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

[Mike Christie <michaelc cs wisc edu>]

Stefan Bader wrote:
> Some days ago we proposed an extension to the device mapper that allows 
> to specify a timeout after which a given request should return as 
> successful, even if some of the target devices did not react by that 
> time.  As we cannot return a request to the upper layers as long as some 
> io is still running and possibly modifying referenced pages, we also 
> need a way to handle those requests.
> 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 :)

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.