iscsi_initiator and tag opening problem

[Matthew Jacob]

>
> it's a CAM thing not PDU/BHS, or at least that is my undertanding.
> myabe it's time to read the RFC again
>

No, what I meant can be seen in the following from iscsi_subr.c:

      /*
       | map tag option, default is UNTAGGED
       */
      switch(csio->tag_action) {
      case MSG_SIMPLE_Q_TAG:     cmd->attr = iSCSI_TASK_SIMPLE;  break;
      case MSG_HEAD_OF_Q_TAG:    cmd->attr = iSCSI_TASK_HOFQ;    break;
      case MSG_ORDERED_Q_TAG:    cmd->attr = iSCSI_TASK_ORDER;   break;
      case MSG_ACA_TASK:         cmd->attr = iSCSI_TASK_ACA;     break;
      }


That is, you're translating from CAM to iSCSI task attributes. Or, rather, 
iSCSI transport related task attributes. The same thing can be seen in the 
isp FibreChannel driver:

                 if (ttype == REQFLAG_OTAG) {
                         ttype = FCP_CMND_TASK_ATTR_ORDERED;
                 } else if (ttype == REQFLAG_HTAG) {
                         ttype = FCP_CMND_TASK_ATTR_HEAD;
                 } else {
                         ttype = FCP_CMND_TASK_ATTR_SIMPLE;
                 }
                 ((ispreqt7_t *)reqp)->req_task_attribute = ttype;

(yes, mine is skipping ACA, oops)

These are attributes of SAM task management. CAM, like any other SCSI 
midlayer, is quite right to attach the specified attribute. Whether the 
underlying transport can faithfully support those attributes is another 
matter.

The RFC has the following:

3.5.1.1.  SCSI-Command

    This request carries the SCSI CDB and all the other SCSI execute
    command procedure call (see [SAM2]) IN arguments such as task
    attributes, Expected Data Transfer Length for one or both transfer
    directions

This would imply that iSCSI is supposed to support task attributes.

Now, it turns out that the linux openiscsi implementation only uses the 
iSCSI_TASK_SIMPLE attribute, so perhaps the simplest fix here is to just 
do that for the FreeBSD initiator driver.