linux-kernel - Re: [PATCH 2/2] iscsi: set session to FREE state after unbind session in remove session

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Date:   Fri, 15 Apr 2022 10:17:40 -0500
From:   Mike Christie <michael.christie@...cle.com>
To:     Wenchao Hao <haowenchao@...wei.com>, Lee Duncan <lduncan@...e.com>,
        Chris Leech <cleech@...hat.com>,
        "James E . J . Bottomley" <jejb@...ux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        open-iscsi@...glegroups.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     linfeilong@...wei.com
Subject: Re: [PATCH 2/2] iscsi: set session to FREE state after unbind session
 in remove session

On 4/15/22 4:40 AM, Wenchao Hao wrote:
> On 2022/4/14 23:30, Mike Christie wrote:
>> On 4/13/22 8:49 PM, Wenchao Hao wrote:
>>> __iscsi_unbind_session() set session state to ISCSI_SESSION_UNBOUND, which
>>> would overwrite the ISCSI_SESSION_FREE state.
>>>
>>> Signed-off-by: Wenchao Hao <haowenchao@...wei.com>
>>> ---
>>>  drivers/scsi/scsi_transport_iscsi.c | 26 ++++++++++++++++----------
>>>  1 file changed, 16 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
>>> index 97a9fee02efa..d8dd9279cea8 100644
>>> --- a/drivers/scsi/scsi_transport_iscsi.c
>>> +++ b/drivers/scsi/scsi_transport_iscsi.c
>>> @@ -2173,6 +2173,22 @@ void iscsi_remove_session(struct iscsi_cls_session *session)
>>>  	if (!cancel_work_sync(&session->block_work))
>>>  		cancel_delayed_work_sync(&session->recovery_work);
>>>  	cancel_work_sync(&session->unblock_work);
>>> +
>>> +	scsi_target_unblock(&session->dev, SDEV_TRANSPORT_OFFLINE);
>>> +	/*
>>> +	 * qla4xxx can perform it's own scans when it runs in kernel only
>>> +	 * mode. Make sure to flush those scans.
>>> +	 */
>>> +	flush_work(&session->scan_work);
>>> +
>>> +	/*
>>> +	 * flush running unbind operations
>>> +	 * if unbind work did not queued, call __iscsi_unbind_session
>>> +	 * directly to perform target remove
>>
>> We probably don't need the flush_work test because we are going to
>> normally call __iscsi_unbind_session.
>>
> 
> I think we still need calling flush_work here. The introduce of flush_work

Above I was saying we don't need to *test* if it returned true/false.
Just always flush and then call __iscsi_unbind_session like we did
originally below. The check you added in __iscsi_unbind_session in the
first patch will detect if it's been called or not.


> is to make sure sysfs objects are removed in an correct order. There is a
> very low probability that __iscsi_unbind_session() triggered by queue_work()
> has not been finished, and iscsi_remove_session() is called. So we need
> flush_work() to make sure __iscsi_unbind_session() has done if it has been
> activated by queue_work().
> 
>> If the unbind work had already run, which is the normal case, then
>> flush_work returns false and we end up calling __iscsi_unbind_session
>> like before. That function then checks if the target is really unbound.
>> So the extra check doesn't normally buy us anything with your patches
>> because in patch 1 you fixed it so __iscsi_unbind_session doesn't send
>> the extra event.
>>
>>
>>> +	 */
>>> +	if (!flush_work(&session->unbind_work))
>>> +		__iscsi_unbind_session(&session->unbind_work);
>>> +
>>>  	/*
>>>  	 * If we are blocked let commands flow again. The lld or iscsi
>>>  	 * layer should set up the queuecommand to fail commands.
>>> @@ -2183,16 +2199,6 @@ void iscsi_remove_session(struct iscsi_cls_session *session)
>>>  	session->state = ISCSI_SESSION_FREE;
>>>  	spin_unlock_irqrestore(&session->lock, flags);
>>>  
>>> -	scsi_target_unblock(&session->dev, SDEV_TRANSPORT_OFFLINE);
>>> -	/*
>>> -	 * qla4xxx can perform it's own scans when it runs in kernel only
>>> -	 * mode. Make sure to flush those scans.
>>> -	 */
>>> -	flush_work(&session->scan_work);
>>> -	/* flush running unbind operations */
>>> -	flush_work(&session->unbind_work);
>>> -	__iscsi_unbind_session(&session->unbind_work);
>>> -
>>>  	/* hw iscsi may not have removed all connections from session */
>>>  	err = device_for_each_child(&session->dev, NULL,
>>>  				    iscsi_iter_destroy_conn_fn);
>>
>> .
>