Re: Scsi Error handling query

[Hannes Reinecke <hare@suse.de>]

On 03/26/2015 07:43 PM, Kashyap Desai wrote:
>> -----Original Message-----
>> From: Hannes Reinecke [mailto:hare@suse.de]
>> Sent: Thursday, March 26, 2015 9:28 PM
>> To: Kashyap Desai; linux-scsi@vger.kernel.org
>> Subject: Re: Scsi Error handling query
>>
>> On 03/26/2015 02:38 PM, Kashyap Desai wrote:
>>> Hi Hannes,
>>>
>>> I was going through one of the slide posted at below link.
>>>
>>> http://events.linuxfoundation.org/sites/events/files/slides/SCSI-EH.pd
>>> f
>>>
>>> Slide #59 has below data. I was trying to correlate with latest
>>> upstream code, but do not understand few things. Does Linux handle
>>> blocking I/O to the device and target before it actually start legacy EH
>> recovery ?
>>
>> Yes. This is handled by 'scsi_eh_scmd_add()', which adds the command to
>> the
>> internal 'eh_entry' list and starts recovery once all remaining
>> outstanding
>> commands are completed.
> 
> Thanks Hannes..! Scsi_eh_scmd_add() move shost state to recovery, so it
> means  blocking further IO to the Host and not really a limited to
> Device/Target for which command was timed out. Right ?
> I understood that, new improvement of scsi error handling will allow IOs to
> the other Devices attached to the host except the IO belongs to specific
> target.
> 
> Also, one more thing to clarify... In presentation, term "task set aborts"
> was used. Does this mean task set abort is handled as traversing complete
> list of timed out command and sending individual TASK ABORT ?
> 
No. The idea was to send 'task set aborts' as a single TMF.
However, I'm not sure if I'll be going ahead with that one; once
we've issued a 'transport reset the commands will be cone anyway.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		               zSeries & Storage
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
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