[dm-devel] [multipath] event-nr does not increment

christophe varoqui christophe.varoqui at free.fr
Fri Jul 9 22:48:18 UTC 2004

Where are we on the subjet below ?
I see the mv-path-code-to-ps.patch from Mike is still in the latest udm
patchset ...


On ven, 2004-06-11 at 21:24, Mike Christie wrote:
> Kevin Corry wrote:
> > On Friday 11 June 2004 12:23 pm, Kevin Corry wrote:
> > 
> >>On Friday 11 June 2004 07:09, christophe.varoqui at free.fr wrote:
> >>
> >>>Hello,
> >>>
> >>>please consider the following log, illustrating the bug that hits
> >>>lk2.6.7+
> >>
> >>I've been playing with the dm-mirror code this week and I know for certain
> >>that I've seen the event-nr increment correctly when the mirrors finish
> >>syncing. So the core event counting code should be working fine.
> >>
> >>Mike, did one of your recent patches possibly change the event counting in
> >>dm-multipath? I'll take a look once I get to work this morning.
> > 
> > 
> > In the "mv-path-code-to-ps" patch (originally posted to dm-devel on May 25), 
> > the fail_path() routine is removed from dm-mpath.c. This routine called 
> > schedule_work(&m->trigger_event) (which eventually leads to a call to 
> > dm_table_event()). However, this schedule_work() call was not added anywhere 
> > else in the code, so it looks like dm-multipath is no longer triggering an 
> > event after a path-failure.
> > 
> That's right. I messed up.
> The problem is that the path-selector was supposed to be where vendors 
> add their code. As a result - as it is in udm today - it will eventually 
> need to get detailed error values to decide if they want to fail the 
> path. This is not possible today as SCSI cannot pass sense data up to 
> DM, and it is not possible today for SCSI to accurately decode the 
> vendor specific sense into a generic block layer error value.
> Also putting the vendor specifics in the selector has problems wrt each 
> vendor having to duplicate the path-selection algorithm.
> As both problems are not solved, and even my current patch set that was 
> posted the other day solves the latter problem but is still a work in 
> progress, I do not know if it is worth it to keep my patches in udm. <- 
> I cc'd Alasdair for this.

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