iSCSI: draft 7: Abort Task and RefCmdSN

["Elliott, Robert" <Robert.Elliott@compaq.com>]

The Task Management [function] Command PDU includes two fields
currently only used by the ABORT TASK function:

2.5.2 Referenced Task Tag  
  Initiator Task Tag of the task to be aborted - for abort task 
 
2.5.3 RefCmdSN [Referenced command sequence number]
  For abort-task the task CmdSN to enable task removal. If RefCmdSN is 
  is lower that ExpCmdSN or higher than MaxCmdSN the target will ignore 
  RefCmdSN.

Both fields identify the task to be aborted.  The Referenced Task
Tag field sits at the SCSI level and matches the SAM-2 function
call description (SAM-2 revision 18):
6.2 ABORT TASK
  Function call:
    Service Response = ABORT TASK (IN (I_T_L_Q Nexus) )

The RefCmdSN field sits at the iSCSI level.

I suggest removing one of these fields.  Having two ways to
specify the same thing just raises the question of what to do
when the values don't agree.  If that happens, should the 
target:
send back a Reject PDU
abort both tasks
abort the task indicated by the Referenced Task Tag
abort the task indicated by the RefCmdSN
abort one of the tasks but also report an error
do any of the above

Since task management functions in general may rely on the
SCSI tag (although Abort Task is the only current user of it), 
I suggest keeping that flag and dropping the iSCSI field.

--
Robert.Elliott@compaq.com
Compaq Computer Server Storage