Antw: [EXT] Re: [PATCH v6] scsi:iscsi: Fix multiple iscsi session unbind event sent to userspace

[Ulrich Windl]

>>> "'Wenchao Hao' via open-iscsi" <open-iscsi@xxxxxxxxxxxxxxxx> schrieb am
21.11.2022 um 15:17 in Nachricht
<89692b2b-90f7-e8e8-fa77-f14dbe996b72@xxxxxxxxxx>:
> On 2022/11/9 11:47, Mike Christie wrote:
>> On 11/7/22 7:44 PM, Wenchao Hao wrote:
>>> I found an issue that kernel would send ISCSI_KEVENT_UNBIND_SESSION
>>> for multiple times which should be fixed.
>>>  
>>> +static char *iscsi_session_target_state_names[] = {
>>> +	"UNBOUND",
>>> +	"ALLOCATED",
>>> +	"SCANNED",
>>> +	"UNBINDING",
>>> +};
>> 
>> I think maybe Lee meant you to do something like:
>> 
>> static int iscsi_target_state_to_name[] = {
>> 	[ISCSI_SESSION_TARGET_UNBOUND] = "UNBOUND",
>> 	[ISCSI_SESSION_TARGET_ALLOCATED] = "ALLOCATED",
>> 	.....
>> 
>> 
> 
> Define array as following and remove previous helper function:
> 
> static char *iscsi_session_target_state_name[] = {
>        [ISCSI_SESSION_TARGET_UNBOUND]   = "UNBOUND",
>        [ISCSI_SESSION_TARGET_ALLOCATED] = "ALLOCATED",
>        [ISCSI_SESSION_TARGET_SCANNED]   = "SCANNED",
>        [ISCSI_SESSION_TARGET_UNBINDING] = "UNBINDING",
> };
> 
> Reference the array directly:

Actually I think with a modern optimizing compiler there should be little difference in the code created.

> 
> static ssize_t
> show_priv_session_target_state(struct device *dev, struct device_attribute 
> *attr,
>                        char *buf)
> {
>        struct iscsi_cls_session *session = iscsi_dev_to_session(dev->parent);
>        return sysfs_emit(buf, "%s\n",
>                        
> iscsi_session_target_state_name[session->target_state]);
> }
> 
>>> +	spin_lock_irqsave(&session->lock, flags);
>>> +	if (session->target_state == ISCSI_SESSION_TARGET_ALLOCATED) {
>>> +		spin_unlock_irqrestore(&session->lock, flags);
>>> +		if (session->ida_used)
>>> +			ida_free(&iscsi_sess_ida, session->target_id);
>>> +		ISCSI_DBG_TRANS_SESSION(session, "Donot unbind sesison: allocated\n");
>> 
>> Could you change the error message to "Skipping target unbinding: Session 
> not yet scanned.\n"
>> 
>>> +		goto unbind_session_exit;
>>> +	}
>> 
>> Just add a newline/return here.
> 
> Actually we should skip unbind this session if call into 
> __iscsi_unbind_session() with target state
> is ALLOCATED. So I removed the check, and check only one condition in 
> __iscsi_unbind_session(): if the
> target state is SCANNED.
> 
>> 
>> I think you want to move both state checks to after the we take the host 
> lock and
>> session lock after the line above. You don't have to take the lock multiple 
> times
>> and we can drop the target_id == ISCSI_MAX_TARGET since it would then rely 
> on the
>> state checks (I left out the ISCSI_DBG_TRANS_SESSION because I'm lazy):
>> 
>> 	bool remove_target = false;
>> .....
>> 
>> 
> I think it's not necessary to add a flag remove_target, here is my changes 
> for function __iscsi_unbind_session:
> 
> @@ -1966,23 +1977,28 @@ static void __iscsi_unbind_session(struct 
> work_struct *work)
>         /* Prevent new scans and make sure scanning is not in progress */
>         mutex_lock(&ihost->mutex);
>         spin_lock_irqsave(&session->lock, flags);
> -       if (session->target_id == ISCSI_MAX_TARGET) {
> +       if (session->target_state != ISCSI_SESSION_TARGET_SCANNED) {
>                 spin_unlock_irqrestore(&session->lock, flags);
>                 mutex_unlock(&ihost->mutex);
> -               goto unbind_session_exit;
> +               ISCSI_DBG_TRANS_SESSION(session, "Skipping target unbinding: 
> Session is %s.\n",
> +                                       
> iscsi_session_target_state_name[session->target_state]);
> +               return;
>         }
> -
>         target_id = session->target_id;
>         session->target_id = ISCSI_MAX_TARGET;
> +       session->target_state = ISCSI_SESSION_TARGET_UNBINDING;
>         spin_unlock_irqrestore(&session->lock, flags);
>         mutex_unlock(&ihost->mutex);
>  
>         scsi_remove_target(&session->dev);
>  
> +       spin_lock_irqsave(&session->lock, flags);
> +       session->target_state = ISCSI_SESSION_TARGET_UNBOUND;
> +       spin_unlock_irqrestore(&session->lock, flags);
> +
>         if (session->ida_used)
>                 ida_free(&iscsi_sess_ida, target_id);
>  
> -unbind_session_exit:
>         iscsi_session_event(session, ISCSI_KEVENT_UNBIND_SESSION);
>         ISCSI_DBG_TRANS_SESSION(session, "Completed target removal\n");
>  }
> 
> And the function looks like following after change:
> 
> static void __iscsi_unbind_session(struct work_struct *work)
> {
> 	struct iscsi_cls_session *session =
> 			container_of(work, struct iscsi_cls_session,
> 				     unbind_work);
> 	struct Scsi_Host *shost = iscsi_session_to_shost(session);
> 	struct iscsi_cls_host *ihost = shost->shost_data;
> 	unsigned long flags;
> 	unsigned int target_id;
> 
> 	ISCSI_DBG_TRANS_SESSION(session, "Unbinding session\n");
> 
> 	/* Prevent new scans and make sure scanning is not in progress */
> 	mutex_lock(&ihost->mutex);
> 	spin_lock_irqsave(&session->lock, flags);
> 	if (session->target_state != ISCSI_SESSION_TARGET_SCANNED) {
> 		spin_unlock_irqrestore(&session->lock, flags);
> 		mutex_unlock(&ihost->mutex);
> 		ISCSI_DBG_TRANS_SESSION(session, "Skipping target unbinding: Session is 
> %s.\n",
> 					iscsi_session_target_state_name[session->target_state]);
> 		return;
> 	}
> 	target_id = session->target_id;
> 	session->target_id = ISCSI_MAX_TARGET;
> 	session->target_state = ISCSI_SESSION_TARGET_UNBINDING;
> 	spin_unlock_irqrestore(&session->lock, flags);
> 	mutex_unlock(&ihost->mutex);
> 
> 	scsi_remove_target(&session->dev);
> 
> 	spin_lock_irqsave(&session->lock, flags);
> 	session->target_state = ISCSI_SESSION_TARGET_UNBOUND;
> 	spin_unlock_irqrestore(&session->lock, flags);
> 
> 	if (session->ida_used)
> 		ida_free(&iscsi_sess_ida, target_id);
> 
> 	iscsi_session_event(session, ISCSI_KEVENT_UNBIND_SESSION);
> 	ISCSI_DBG_TRANS_SESSION(session, "Completed target removal\n");
> }
> 
> 
> 
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