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    RE: iSCSI abort task - the saga continues



    Hi Julian and Sandeep,
    
    Is section 8.4 still value for Abort task Set, Clear Task Set etc?
    
    Cheers
    
    Matthew
    
    -----Original Message-----
    From: Sandeep Joshi [mailto:sandeepj@research.bell-labs.com]
    Sent: Tuesday, September 04, 2001 1:42 AM
    To: Julian Satran
    Cc: ips@ece.cmu.edu
    Subject: Re: iSCSI abort task - the saga continues
    
    
    
    Julian,
    
    Great..less complexity!
    
    a) I guess this eliminates Sec 8.3 & Sec 8.4 then ?
       Is there a need to eliminate unrelated commands which
       are lower than the cmdSN of the task to be aborted ?
    
      >    For all the tasks covered by the task management response (i.e.,
    with
      >    CmdSN not higher than the task management command CmdSN),
    additional
      >    responses MUST NOT be delivered to the SCSI layer after the task
      >    management response.
    
    b) What is the value in retaining refCmdSN in the PDU now 
       that the same connection is being used for abort task ?
       Even in case of failing connections, the ITT will be used
       by the target to determine if the task to be aborted 
       exists, correct?
    
    -Sandeep
    
    Julian Satran wrote:
    > 
    > Dear colleagues,
    > 
    > Here is a simpler version of the Task Management Request & Response.
    > 
    > Abort task is processed only at target but the initiator issues it only on
    > the same connection (as Santosh Rao once proposed) with the added semantic
    > that if the connection is failing it can be issued on a new connection and
    > it means both abort and change allegiance. Here is the proposed text:
    > 
    > 1.1  Task Management Function Request
    > 
    >    Byte /    0       |       1       |       2       |       3       |
    >       /              |               |               |               |
    >      |7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
    >      +---------------+---------------+---------------+---------------+
    >     0|X|I| x02       |0| Function    | Reserved                      |
    >      +---------------+---------------+---------------+---------------+
    >     4| Reserved                                                      |
    >      +---------------+---------------+---------------+---------------+
    >     8| Logical Unit Number (LUN) or Reserved                         |
    >      +                                                               +
    >    12|                                                               |
    >      +---------------+---------------+---------------+---------------+
    >    16| Initiator Task Tag                                            |
    >      +---------------+---------------+---------------+---------------+
    >    20| Referenced Task Tag or 0xffffffff                             |
    >      +---------------+---------------+---------------+---------------+
    >    24| CmdSN                                                         |
    >      +---------------+---------------+---------------+---------------+
    >    28| ExpStatSN                                        |
    >      +---------------+---------------+---------------+---------------+
    >    32| RefCmdSN or ExpDataSN                                         |
    >      +---------------+---------------+---------------+---------------+
    >    36/ Reserved                                                      /
    >     +/                                                               /
    >      +---------------+---------------+---------------+---------------+
    >    48
    > 
    > 1.1.1     Function
    > 
    >    The Task Management functions provide an initiator with a way to
    >    explicitly control the execution of one or more Tasks (SCSI and iSCSI
    >    tasks). The Task Management functions are (for a more detailed
    >    description of SCSI task management see [SAM2]):
    > 
    >       1    ABORT TASK - aborts the task identified by the Referenced
    >       Task Tag field.
    >       2    ABORT TASK SET - aborts all Tasks issued by this initiator on
    >       the Logical Unit.
    >       3    CLEAR ACA - clears the Auto Contingent Allegiance condition.
    >       4    CLEAR TASK SET - Aborts all Tasks (from all initiators) for the
    >       Logical Unit.
    >       5    LOGICAL UNIT RESET
    >       6    TARGET WARM RESET
    > 7    TARGET COLD RESET
    > 8    TASK RESUME - restart the task identified by the Referenced Task Tag
    > field on this connection
    > 9    TASK REPLAY - replay the task identified by the Referenced Task Tag
    > field on this connection
    > 
    >    For all these functions, if executed, the Task Management Function
    >    Response MUST be returned using the Initiator Task Tag to identify the
    >    operation for which it is responding. All those functions apply to the
    >    referenced tasks regardless if they are proper SCSI tasks or tagged
    >    iSCSI operations.  Task management commands must be executed as if all
    >    the commands having a CmdSN lower or equal to the task management CmdSN
    >    have been received by the target (i.e., have to be executed as if
    >    received for ordered delivery even when marked for immediate delivery).
    >    For all the tasks covered by the task management response (i.e., with
    >    CmdSN not higher than the task management command CmdSN), additional
    >    responses MUST NOT be delivered to the SCSI layer after the task
    >    management response.
    > 
    >    ABORT TAST Task Management Request MUST be issued on the same
    connection
    >    to which the task to be aborted is allegiant at the time the Task
    >    Management Request is issued if the connection is still active (it is
    >    not undergoing an implicit or explicit logout).  If the connection is
    >    being implicitly or explicitly logged out and no other request will be
    >    issued on the failing connection and no other response will be received
    >    on the failing connection then an ABORT TASK Task Management request
    may
    >    be issued on another connection and this Task Management request will
    >    both establish a new allegiance for the command to be aborted and will
    >    abort it (i.e., a task to be aborted will not have to be reinstated,
    >    restarted or replayed and its status if issued but not acknowledged
    will
    >    be reissued). For the ABORT TASK task management request the target
    MUST
    >    NOT deliver additional responses after the task management response.
    >    Whether the initiator should deliver or not task responses while a TASK
    >    ABORT is executing but before delivering the task management response
    is
    >    a matter of implementation.
    > 
    >    For the LOGICAL UNIT RESET function, the target MUST behave as dictated
    >    by the Logical Unit Reset function in [SAM2].
    > 
    >    The TARGET RESET function (WARM and COLD) implementation is OPTIONAL
    and
    >    when implemented should act as described below.  Target Reset MAY be
    >    also subject to SCSI access controls for the requesting initiator.
    When
    >    not implemented or when authorization fails at target, Target Reset
    >    functions should end as if the function was executed successfully and
    >    the response qualifier will detail what was executed.
    > 
    >    For the TARGET WARM RESET and TARGET COLD RESET functions, the target
    >    cancels all pending operations and are both equivalent to the Target
    >    Reset function specified by [SAM2].  They can both affect many other
    >    initiators.
    > 
    >    In addition, for the TARGET COLD RESET the target then MUST terminate
    >    all of its TCP connections to all initiators (all sessions are
    >    terminated).
    > 
    >    For the TASK RESUME and TASK REPLAY the target should resume executing
    >    the referenced task respectively replay it completely. TASK REPLAY MUST
    >    be received by the target ONLY after the status for the command was
    >    issued. TASK RESUME MUST be received by the target ONLY after the
    >    connection on which the command was previously executing has been
    >    successfully logged-out.
    >    TASK RESUME and TASK REPLAY MUST be issued as immediate commands.
    > 
    > 1.1.2     LUN
    > 
    >    This field is required for functions addressing a specific LU (ABORT
    >    TASK, CLEAR TASK SET, ABORT TASK SET, CLEAR ACA, LOGICAL UNIT RESET)
    and
    >    is reserved in all others.
    > 
    > 1.1.3     Referenced Task Tag
    > 
    >    Initiator Task Tag of the task to be aborted, restarted or replayed
    > 
    > 1.1.4     RefCmdSN or ExpDataSN
    > 
    >    For ABORT TASK the task CmdSN to enable task removal. If RefCmdSN does
    >    not match the CmdSN of the command to be aborted at the target
    >    The abort action MUST not be performed and the response MUST be
    function
    >    rejected.
    > 
    >    If the function is task resume establishing a new connection allegiance
    >    for a previously issued command, this field will contain the next
    >    consecutive input DataSN number expected by the initiator (no gaps) for
    >    the referenced command in a previous execution.
    > 
    > 1.2  Task Management Function Response
    > 
    >    Byte /    0       |       1       |       2       |       3       |
    >       /              |               |               |               |
    >      |7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
    >      +---------------+---------------+---------------+---------------+
    >     0|1|1| 0x22      |1| Reserved                                    |
    >      +---------------+---------------+---------------+---------------+
    >     4/ Reserved                                                      /
    >      /                                                               /
    >      +---------------+---------------+---------------+---------------+
    >    16| Initiator Task Tag                                            |
    >      +---------------+---------------+---------------+---------------+
    >    20| Referenced Task Tag or 0xffffffff                             |
    >      +---------------+---------------+---------------+---------------+
    >    24| StatSN                                                        |
    >      +---------------+---------------+---------------+---------------+
    >    28| ExpCmdSN                                                      |
    >      +---------------+---------------+---------------+---------------+
    >    32| MaxCmdSN                                                      |
    >      +---------------+---------------+---------------+---------------+
    >    36| Response      | Qualifier     | Reserved                      |
    >      +---------------+---------------+---------------+---------------+
    >    40/ Reserved                                                      /
    >     +/                                                               /
    >      +---------------+---------------+---------------+---------------+
    >    48
    > 
    >    For the functions ABORT TASK, ABORT TASK SET, CLEAR ACA, CLEAR TASK
    SET,
    >    LOGICAL UNIT RESET, TARGET WARM RESET, the target performs the
    requested
    >    Task Management function and sends a Task Management Response back to
    >    the initiator. The target provides a Response, which may take on the
    >    following values:
    > 
    >            0 - Function Complete
    >            1 - Task specified in the Referenced Task Tag field was not in
    >            task set
    >            2 - LUN does not exist
    >            3 - Task running on a connection that was not logged-out
    >            4 - Task failover not supported
    >            5 - Task in progress
    >            6 - Task replay not supported
    >       255   Function Rejected
    > 
    >    All other values are reserved.
    > 
    >    The Qualifier field provides additional information about the Response.
    > 
    >    For a Response of "Function Complete" the valid Qualifiers are:
    > 
    >       0 - Function Executed
    >       1 - Not Authorized
    > 
    >    For the TARGET COLD RESET and TARGET WARM RESET functions, the target
    >    cancels all pending operations.  For the TARGET COLD RESET function the
    >    target MUST then close all of its TCP connections to all initiators
    >    (terminates all sessions).
    > 
    >    The mapping of the response code into a SCSI service response code, if
    >    needed, is outside the scope of this document.
    > 
    > 1.2.1     Referenced Task Tag
    > 
    >    Initiator Task Tag of the task not found used in conjunction with
    >    responses referring to a specific task. It MUST be set to 0xffffffff in
    >    other cases.
    > 
    >    Comments?
    > 
    >    Julo
    


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