[dm-devel] mechanism for multipath to pass information to hardware handler

[Chandra Seetharaman]

Yes, Mike Christie and I were aware of this and it was one of the issue
we were trying to resolve before we pushed scsi_dh interface upstream.
(It is little complicated as we need the parameters to be set per
vendor-product tuple).

The original code I ported to scsi_dh interface was from Ed Goggin(who
was working for EMC then). IIRC, he was also aware of this issue.

When we pushed scsi_dh interface, we did get few of the EMC folks (on
Cc) to review/test the code and they did, and this issue was not seen as
a problem. 

We wanted to get back to that issue sometime later, got busy with other
things, and it disappeared from my list of things-to-do as the
regression was not seen as an issue (till now :)... I will get back to
it.

chandra

On Fri, 2009-06-26 at 14:10 -0500, James Bottomley wrote:
> On Wed, 2009-06-24 at 13:14 -0400, Eddie Williams wrote:
> > I notice in scsi_dh_emc.c that there is a comment:
> > 
> > TODO: need some interface so we can set trespass values
> > 
> > I don't see where any such interface has been developed or even any
> > discussion on the different mailing lists to create such an interface.
> > Did I miss something?
> > 
> > As it stands now there is no way that I can see to have the emc hardware
> > handler support the "honor trespass" feature short of recompiling the
> > module forcing the flag to be set.  This leaves a feature that worked in
> > earlier versions of multipath not working now.
> 
> OK so as I understand it that means that the line
> 
> hardware handler "1 emc 0 1"
> 
> now fails to function correctly because dm-emc no longer exists.  That
> makes this a functionality regression from 2.6.26 because of this
> commit:
> 
> 
> commit cb520223d7f22c5386aff27a5856a66e2c32aaac
> Author: Chandra Seetharaman <sekharan at us.ibm.com>
> Date:   Thu May 1 14:50:34 2008 -0700
> 
>     [SCSI] scsi_dh: Remove hardware handlers from dm
>     
>     This patch removes the 3 hardware handlers that currently exist
>     under dm as the functionality is moved to SCSI layer in the earlier
>     patches.
> 
> Because we haven't actually moved all the functionality.
> 
> James
> 
> 
>