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

[Mike Christie <michaelc@cs.wisc.edu>]

On 12/07/2012 08:51 AM, Hannes Reinecke wrote:
> 'Bus reset' is not really applicable to FibreChannel, as
> the concept of a bus doesn't apply. Hence all FC LLDD
> simulate a 'bus reset' by sending a target reset to each
> attached remote port, causing error handling to spill
> over to unaffected devices.
> 
> This patch implements a 'I_T nexus reset' handler,
> which attempts to reset the I_T nexus to the remote
> port. This way only the affected remote ports are
> reset; other ports are left untouched.

Is the I_T nexus reset we are doing in this patch supposed to be the
same one defined in SAM? Was the I_T nexus reset TMF added to SAM at the
same time the target reset one was removed? In SAM 4 and 5 there is no
target reset anymore is there?

I think we should just kill the bus reset use from the FC drivers. Add a
new I_T nexus reset callout to the scsi_host_template or to the
scsi_transport_template. Then have scsi-ml call just either target reset
eh callout or I_T nexus eh reset callout depending on what the target
supports.

To figure out what the target supports could we do a REPORTED SUPPORTED
TASK MANAGEMENT FUNCTION command. If the target supports that command
and reports that the target supports the I_T nexus reset TMF then call
that eh callback, else drop down to older target reset eh callback.

It seems that if we do I_T nexus reset we do not need to also do a
target reset do we?



> @@ -3266,8 +3271,8 @@ fc_timeout_fail_rport_io(struct work_struct *work)
>  	if (rport->port_state != FC_PORTSTATE_BLOCKED)
>  		return;
>  
> -	rport->flags |= FC_RPORT_FAST_FAIL_TIMEDOUT;
>  	fc_terminate_rport_io(rport);
> +	rport->flags |= FC_RPORT_FAST_FAIL_TIMEDOUT;
>  }
>  

What was the reason for moving this? For the eh case in this patch was
it causing IO to be failed with DID_TRANSPORT_FAILFAST when we wanted it
failed with some other error.