Re: [PATCHv7 0/3][Resend] Display EVPD pages in sysfs

[Hannes Reinecke <hare@suse.de>]

On 03/05/2014 09:23 AM, Bart Van Assche wrote:
> On 03/05/14 09:00, Hannes Reinecke wrote:
>> On 03/02/2014 09:53 AM, Bart Van Assche wrote:
>>> A general comment about this patch series: I think the cached copies of
>>> these pages should be refreshed at least after an INQUIRY DATA HAS
>>> CHANGED unit attention code has been received. Some SCSI target
>>> implementations allow to change this data after a LUN has been created.
>>
>> Yes, eventually. But this needs to be handled in a general context,
>> as (potentially) even the inquiry string itself has been invalidated
>> after receiving such an event.
>> So we should be doing a rescan of the scsi device upon receiving
>> such an event. But this is a general problem, not one particular to
>> this patchset.
> 
> Sorry but since the ALUA patch series is based on this patch series I'm
> afraid that the ALUA patch series introduces a regression that seems
> unacceptable to me. SCSI target implementations like LIO allow to remove
> and re-add a LUN after initial discovery of a SCSI host. My concern here
> is that the caching introduced by this patch series and which is used in
> the ALUA patch series will cause INQUIRY data not to be updated after it
> has been changed at the target side. Today the scsi_dh_alua handler
> processes such INQUIRY data changes fine. Does this make sense to you ?
> 
Currently, the SCSI stack itself is not well-equipped to handle
these kind of setups anyway.
(The only known working solution is to remove the device _entirely_
and have the HBA rescan the LUN).
So while you are right I'm still preferring to keep those two issues
separate.

James, any preferences here?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@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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