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 17:40:20 +0800
From:   Wenchao Hao <haowenchao@...wei.com>
To:     Mike Christie <michael.christie@...cle.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>, Wenchao Hao <haowenchao@...wei.com>
CC:     <linfeilong@...wei.com>
Subject: Re: [PATCH 2/2] iscsi: set session to FREE state after unbind session
 in remove session

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
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);
> 
> .