RE: Scsi Error handling query

[Kashyap Desai <kashyap.desai@avagotech.com>]

> -----Original Message-----
> From: Hannes Reinecke [mailto:hare@suse.de]
> Sent: Friday, March 27, 2015 9:32 PM
> To: Kashyap Desai; linux-scsi@vger.kernel.org
> Subject: Re: Scsi Error handling query
>
> 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.

Thanks Hannes.!  OK so idea was to have single TMF for "Task set abort."   I
am not sure how to frame my  next question.. But what if Linux SCSI layer
traverse each IO of one particular target and issue individual Task abort?
Don’t we call that as "task set aborts" ?  How LLD Driver should interface
for "task set aborts" as single TMF ? My understanding is "Task set abort"
will be internally converted to single Task abort either by SCSI layer or
HBA FW.

> 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
> GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284
> (AG
> Nürnberg)
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