Re: [PATCH 1/2] scsi: iscsi: introduce session UNBOUND state to avoid multiple unbind event

[Wenchao Hao]

On 2022/4/14 23:22, Mike Christie wrote:
> On 4/13/22 8:49 PM, Wenchao Hao wrote:
>> Fix the issue of kernel send multiple ISCSI_KEVENT_UNBIND_SESSION event.
>> If session is in UNBOUND state, do not perform unbind operations anymore,
>> else unbind session and set session to UNBOUND state.
>>
> 
> I don't think we want this to be a state because you can have a session
> with no target or it could be partially deleted and it could be in the
> logged in or failed state. If scsi-ml is sending SYNC_CACHEs as part of
> the target/device removal operation, and we lose the session then we could
> go through recovery and the state will go from failed to logged in, and
> your new unbound state will have been overwritten.
> 
> I think it might be better to have a new sysfs file, target_state, for
> this where you could have values like scanning, bound, unbinding, and
> unbound, or just a sysfs file, target_bound, that is bool.
> 

Thanks for your review, I would modify and send another patch.

>> Reference:https://github.com/open-iscsi/open-iscsi/issues/338
>>
> 
> You should add a description of the problem in the commit, because that
> link might be gone one day.
> 
> 
>> Signed-off-by: Wenchao Hao <haowenchao@xxxxxxxxxx>
>> ---
>>  drivers/scsi/scsi_transport_iscsi.c | 19 +++++++++++++++++--
>>  include/scsi/scsi_transport_iscsi.h |  1 +
>>  2 files changed, 18 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
>> index 27951ea05dd4..97a9fee02efa 100644
>> --- a/drivers/scsi/scsi_transport_iscsi.c
>> +++ b/drivers/scsi/scsi_transport_iscsi.c
>> @@ -1656,6 +1656,7 @@ static struct {
>>  	{ ISCSI_SESSION_LOGGED_IN,	"LOGGED_IN" },
>>  	{ ISCSI_SESSION_FAILED,		"FAILED" },
>>  	{ ISCSI_SESSION_FREE,		"FREE" },
>> +	{ ISCSI_SESSION_UNBOUND,	"UNBOUND" },
>>  };
>>  
>>  static const char *iscsi_session_state_name(int state)
>> @@ -1686,6 +1687,9 @@ int iscsi_session_chkready(struct iscsi_cls_session *session)
>>  	case ISCSI_SESSION_FREE:
>>  		err = DID_TRANSPORT_FAILFAST << 16;
>>  		break;
>> +	case ISCSI_SESSION_UNBOUND:
>> +		err = DID_NO_CONNECT << 16;
>> +		break;
>>  	default:
>>  		err = DID_NO_CONNECT << 16;
>>  		break;
>> @@ -1838,7 +1842,8 @@ int iscsi_block_scsi_eh(struct scsi_cmnd *cmd)
>>  
>>  	spin_lock_irqsave(&session->lock, flags);
>>  	while (session->state != ISCSI_SESSION_LOGGED_IN) {
>> -		if (session->state == ISCSI_SESSION_FREE) {
>> +		if ((session->state == ISCSI_SESSION_FREE) ||
>> +		    (session->state == ISCSI_SESSION_UNBOUND)) {
>>  			ret = FAST_IO_FAIL;
>>  			break;
>>  		}
>> @@ -1869,6 +1874,7 @@ static void session_recovery_timedout(struct work_struct *work)
>>  		break;
>>  	case ISCSI_SESSION_LOGGED_IN:
>>  	case ISCSI_SESSION_FREE:
>> +	case ISCSI_SESSION_UNBOUND:
>>  		/* we raced with the unblock's flush */
>>  		spin_unlock_irqrestore(&session->lock, flags);
>>  		return;
>> @@ -1957,6 +1963,14 @@ static void __iscsi_unbind_session(struct work_struct *work)
>>  	unsigned long flags;
>>  	unsigned int target_id;
>>  
>> +	spin_lock_irqsave(&session->lock, flags);
>> +	if (session->state == ISCSI_SESSION_UNBOUND) {
>> +		spin_unlock_irqrestore(&session->lock, flags);
>> +		return;
>> +	}
>> +	session->state = ISCSI_SESSION_UNBOUND;
>> +	spin_unlock_irqrestore(&session->lock, flags);
>> +
>>  	ISCSI_DBG_TRANS_SESSION(session, "Unbinding session\n");
>>  
>>  	/* Prevent new scans and make sure scanning is not in progress */
>> @@ -4329,7 +4343,8 @@ store_priv_session_##field(struct device *dev,				\
>>  	struct iscsi_cls_session *session =				\
>>  		iscsi_dev_to_session(dev->parent);			\
>>  	if ((session->state == ISCSI_SESSION_FREE) ||			\
>> -	    (session->state == ISCSI_SESSION_FAILED))			\
>> +	    (session->state == ISCSI_SESSION_FAILED) ||			\
>> +	    (session->state == ISCSI_SESSION_UNBOUND))			\
>>  		return -EBUSY;						\
>>  	if (strncmp(buf, "off", 3) == 0) {				\
>>  		session->field = -1;					\
>> diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h
>> index 38e4a67f5922..80149643cbcd 100644
>> --- a/include/scsi/scsi_transport_iscsi.h
>> +++ b/include/scsi/scsi_transport_iscsi.h
>> @@ -232,6 +232,7 @@ enum {
>>  	ISCSI_SESSION_LOGGED_IN,
>>  	ISCSI_SESSION_FAILED,
>>  	ISCSI_SESSION_FREE,
>> +	ISCSI_SESSION_UNBOUND,
>>  };
>>  
>>  #define ISCSI_MAX_TARGET -1
> 
> .