[dm-devel] Re: Missing end_io in path selector interface

[Alasdair G Kergon]

On Mon, Nov 08, 2004 at 02:15:36PM +0100, Stefan Bader wrote:
> you removed the hook for end_io from the path selector interface. 
> Unfortunately I need this
> hook for round-robing path selector. This selector needs to be called for 
> every started and
> finished I/O for bookkeeping. This is also a reason that this selector 
> should be called every
> time I/O is maped and not only for every n'th I/O.
> Could you please put the end_io hook back into the interface?

Maybe - but what sort of bookkeeping?
i.e. What information does your PS want at endio time?
  [mpio->pgpath plus a success/failure flag?]
How does this interact with what hw_handler is doing?
The PS already gets called the first time there's a failure (fail_path).
Is there a better interface?
If this is purely statistical, would the functionality fit better elsewhere
(e.g. counters in the core)?

Alasdair
-- 
agk at redhat.com