Re: dm-multipath: Accept failed paths for multipath maps

[Bart Van Assche <bvanassche@acm.org>]

On 02/19/14 02:14, Mike Snitzer wrote:
> On Thu, Dec 19 2013 at  3:21am -0500,
> Bart Van Assche <bvanassche@acm.org> wrote:
> 
>> On 12/18/13 16:28, Stewart, Sean wrote:
>>> The most severe case is with
>>> InfiniBand, where the LLD may place a device offline, then every single
>>> reload that is trying to add a good path in will fail.  I will qualify
>>> this by saying that I realize it is a problem that the device gets
>>> placed offline in the first place, but this patch would allow it a
>>> chance to continue on. The user still has to take manual steps to fix
>>> the problem in this case, but it seems less disruptive to applications.
>>
>> Are you perhaps referring to the SRP initiator ? The above is correct
>> for old versions of the SRP initiator (< Linux kernel 3.12) but no
>> longer for upstream kernel versions >= 3.12. An effort is ongoing to
>> backport the latest SRP initiator changes into RHEL and SLES.
> 
> It has been a while.  Where do things stand for the RHEL backport of
> these SRP initiator changes?  Are we talking RHEL6 and RHEL7?  Who at
> Red Hat is your contact for this work?
> 
> Regardless of whether some version of Hannes's patch is applied to
> upstream dm-mpath: I'd really like to see this offlining problem that
> forced the need for this dm-mpath change addressed.

Hello Mike,

At https://github.com/bvanassche/ib_srp-backport a version of the SRP
initiator driver can be found that works fine with at least RHEL 6.3,
6.4, 6.5 and SLES 11. I have not yet had a chance to test that driver
against RHEL 7. The SRP initiator driver backport includes all changes
that have been accepted upstream up to and including kernel 3.14-rc3.
That means that both versions of the SRP initiator driver include the
code that changes the SCSI device state from "offline" into "running"
after reconnecting succeeded after a cable pull. The relevant RHEL
bugzilla entries are as follows:
* https://bugzilla.redhat.com/show_bug.cgi?id=1012926
* https://bugzilla.redhat.com/show_bug.cgi?id=1055654

Thanks,

Bart.