Re: [PATCH 3/3] dm mpath: add support for using previously attached scsi_dh

[Hannes Reinecke <hare@suse.de>]

On 05/08/2012 04:05 PM, Mike Snitzer wrote:
> On Tue, May 08 2012 at  2:22am -0400,
> Hannes Reinecke<hare@suse.de>  wrote:
>
>> On 05/08/2012 05:19 AM, Mike Snitzer wrote:
>>> Use the previously attached scsi_dh if "default" is provided as the
>>> hardware handler name (the new 'use_default_hw_handler' flag is set in
>>> the multipath structure).
>>>
>>> Leverage scsi_dh_attach's ability to increment the scsi_dh's reference
>>> count if the same scsi_dh name is provided when attaching -- currently
>>> attached scsi_dh name is determined with scsi_dh_attached_handler_name.
>>>
>> Not sure it that's the correct way.
>>
>> Using 'default' as the hardware handler name has the drawback that
>> the original information (ie the original hardware handler name)
>> is lost.
>
> BTW, on this point: How is the original handler's name lost with my
> patches?  I set m->hw_handler_name to the original (aka attached)
> handler's name (as returned scsi_dh_attached_handler_name).
>
> "default" is only used as a key to trigger the use of the attached
> handler (it causes m->use_default_hw_handler to be set).
>
What I meant is that within multipath you can only specify one hardware 
handler. So if it's 'default' and no hardware handler is attached we 
wouldn't know what to look for.

> Was my description or code somehow unclear?  Guess so... otherwise I'd
> not be clarifying this... unfortunately I'm not seeing where I fell
> short.
>
Meanwhile I've sent the patchset, Please check that for details.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)

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