Re: [PATCH v2 04/15] IB/srp: Fail I/O fast if target offline

[Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>]

On 07/01/13 11:25, Sebastian Riemer wrote:
> On 28.06.2013 14:49, Bart Van Assche wrote:
>> If reconnecting failed we know that no command completion will
>> be received anymore. Hence let the SCSI error handler fail such
>> commands immediately.
>>
>> Signed-off-by: Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>
>> Cc: Roland Dreier <roland-BHEL68pLQRGGvPXPguhicg@public.gmane.org>
>> Cc: David Dillow <dillowda-1Heg1YXhbW8@public.gmane.org>
>> Cc: Sebastian Riemer <sebastian.riemer-EIkl63zCoXaH+58JC4qpiA@public.gmane.org>
>> Cc: Vu Pham <vu-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
>> ---
>>   drivers/infiniband/ulp/srp/ib_srp.c |    2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
>> index 8c95262..5c91521 100644
>> --- a/drivers/infiniband/ulp/srp/ib_srp.c
>> +++ b/drivers/infiniband/ulp/srp/ib_srp.c
>> @@ -1755,6 +1755,8 @@ static int srp_abort(struct scsi_cmnd *scmnd)
>>   	if (srp_send_tsk_mgmt(target, req->index, scmnd->device->lun,
>>   			      SRP_TSK_ABORT_TASK) == 0)
>>   		ret = SUCCESS;
>> +	else if (target->transport_offline)
>> +		ret = FAST_IO_FAIL;
>>   	else
>>   		ret = FAILED;
>>   	srp_free_req(target, req, scmnd, 0);
>
> I'm also missing the concept for srp_reset_device(). There is a very
> common case that the SCSI error handling and the transport layer error
> handling run in parallel: Congestion.

Can you explain this comment further, and also how this comment relates 
to patch 04/15 ?

> In congestion some LUNs are blocked while others can still transmit. A
> little bit later the QP timeout triggers in the middle of the SCSI error
> handling in srp_abort(), srp_reset_device() or less likely in
> srp_reset_host().

I am aware this can result in concurrent srp_reconnect_rport() calls. 
However, such concurrent calls are serialized via rport->mutex.

Bart.
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html