Re: [PATCH] scsi_transport_srp: sanitize scsi_target_block/unblock sequences

[Hannes Reinecke <hare@suse.de>]

On 7/28/20 9:50 PM, Laurence Oberman wrote:
> On Tue, 2020-07-28 at 14:43 -0400, Laurence Oberman wrote:
>> On Tue, 2020-07-28 at 15:48 +0200, Hannes Reinecke wrote:
>>> The SCSI midlayer does not allow state transitions from SDEV_BLOCK
>>> to SDEV_BLOCK, so calling scsi_target_block() from
>>> __rport_fast_io_fail()
>>> is wrong as the port is already blocked.
>>> Similarly we don't need to call scsi_target_unblock() afterwards as
>>> the
>>> function has already done this.
>>>
>>> Signed-off-by: Hannes Reinecke <hare@suse.de>
>>> ---
>>>   drivers/scsi/scsi_transport_srp.c | 12 +++++-------
>>>   1 file changed, 5 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/scsi/scsi_transport_srp.c
>>> b/drivers/scsi/scsi_transport_srp.c
>>> index d4d1104fac99..cba1cf6a1c12 100644
>>> --- a/drivers/scsi/scsi_transport_srp.c
>>> +++ b/drivers/scsi/scsi_transport_srp.c
>>> @@ -395,6 +395,10 @@ static void srp_reconnect_work(struct
>>> work_struct *work)
>>>   	}
>>>   }
>>>   
>>> +/*
>>> + * scsi_target_block() must have been called before this function
>>> is
>>> + * called to guarantee that no .queuecommand() calls are in
>>> progress.
>>> + */
>>>   static void __rport_fail_io_fast(struct srp_rport *rport)
>>>   {
>>>   	struct Scsi_Host *shost = rport_to_shost(rport);
>>> @@ -404,11 +408,7 @@ static void __rport_fail_io_fast(struct
>>> srp_rport *rport)
>>>   
>>>   	if (srp_rport_set_state(rport, SRP_RPORT_FAIL_FAST))
>>>   		return;
>>> -	/*
>>> -	 * Call scsi_target_block() to wait for ongoing shost-
>>>> queuecommand()
>>>
>>> -	 * calls before invoking i->f->terminate_rport_io().
>>> -	 */
>>> -	scsi_target_block(rport->dev.parent);
>>> +
>>>   	scsi_target_unblock(rport->dev.parent, SDEV_TRANSPORT_OFFLINE);
>>>   
>>>   	/* Involve the LLD if possible to terminate all I/O on the
>>> rport. */
>>> @@ -570,8 +570,6 @@ int srp_reconnect_rport(struct srp_rport
>>> *rport)
>>>   		 * failure timers if these had not yet been started.
>>>   		 */
>>>   		__rport_fail_io_fast(rport);
>>> -		scsi_target_unblock(&shost->shost_gendev,
>>> -				    SDEV_TRANSPORT_OFFLINE);
>>>   		__srp_start_tl_fail_timers(rport);
>>>   	} else if (rport->state != SRP_RPORT_BLOCKED) {
>>>   		scsi_target_unblock(&shost->shost_gendev,
>>
>> This looks OK to me but I guess its alwasy worked by just ignoring it
>> being called or IU would have seenm issues.
>> I etest that stuff pretty heavily.
>> Reviewed-by: Laurence Oberman <loberman@redhat.com>
>>
> 
> Ouch, my last message saw my bad touch typing creep in. Let me try
> again.
> 
> This looks OK to me but I guess its always worked by just ignoring it
> being called or I would have seen issues already.
> I test that stuff pretty heavily and regularly.
> 
> Reviewed-by: Laurence Oberman <loberman@redhat.com>
> 
> 
Well, we've had a customer running into it.
And they do _heavy_ tests, too.

I haven't said it's a regular occurrence :-)

Cheers,

Hannes
-- 
Dr. Hannes Reinecke            Teamlead Storage & Networking
hare@suse.de                               +49 911 74053 688
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