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



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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