Re: [PATCH v2][RFC] scsi_transport_fc: Implement I_T nexus reset

[Hannes Reinecke <hare@suse.de>]

On 12/11/2012 01:46 PM, Martin Peschke wrote:
> Hello Hannes,
>
>> fc_eh_it_nexus_loss_handler() is invoked as the
>> eh_target_reset_handler() callback and the
>> eh_bus_reset_handler() is removed.
>
> lpfc_target_reset_handler(), which is replaced by your patch, used to
> issue a TARGET_RESET task management function over FCP in the
> eh_target_reset_handler() callback. What's wrong with that?
>
Nothing per se.
Only that the TARGET_RESET TMF has been removed from SAM-3/FCP-3 
onwards, so there might not be any functionality behind it.
But drivers can supply the functionality via ->eh_it_nexus_loss 
callback.

I didn't want to touch the existing eh_target_reset_handler myself
as I'm not familiar with the firmware specifics.
That is being left as an exercise to the reader :-)

The main point here is that we're emulating REMOVE I_T NEXUS by 
setting the port state to BLOCKED and invoke dev_loss_tmo.
This will prevent any further I/O to be send down.
With the original handler the port state wasn't modified,
which led to excessive recovery times when no RSCN was received.

And yes, I had several bug reports now where the HBA did not receive 
RSCNs, either due to a switch malfunction or due to an error injection.

Cheers,

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