[dm-devel] multipath and READ_CAPACITY

Christophe Varoqui christophe.varoqui at opensvc.com
Thu Jul 24 09:00:26 UTC 2014

This sanity check is useful because users can set arbitrary getuid scripts,
and thus corrupt data if their getuid callout is bogus.
Now, this getuid callout facility is a lot less publicized ...
I'd apply the patch, no problem on my side.

On Thu, Jul 24, 2014 at 10:46 AM, Hannes Reinecke <hare at suse.de> wrote:

> Hi Christophe,
> I've had a customer issue where someone complained that multipath would
> reject paths if they are in ALUA 'standby'.
> As it turns out, SPC-3 does _not_ require the READ_CAPACITY command to be
> implemented if a target port is in standby.
> Consecutively, linux would register this path with a capacity of '0', and
> multipath would reject the path in ev_add_path().
> Which makes we wonder, do we actually _need_ the check for a matched
> capacity?
> With VPD page 0x83 pretty much standard as of now (and I'm reasonbly sure
> we'll reject any device _not_ providing VPD page 0x83 anyway) we basically
> have to rely on that information.
> IE if the WWID is identical we have assume the devices are identical. So
> it would make sense to just remove the check altogether.
> Thoughts?
> Cheers,
> Hannes
> --
> Dr. Hannes Reinecke                   zSeries & Storage
> hare at suse.de                          +49 911 74053 688
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
> GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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