RE: iSCSI: draft 7: Abort Task and RefCmdSN

["Julian Satran" <Julian_Satran@il.ibm.com>]

Alex,

That is correct but has no relevance if you want to abbort one specific
task.

Julo

"Nicolson, Alex" <Alex.Nicolson@emulex.com> on 06-08-2001 21:16:28

Please respond to <Alex.Nicolson@emulex.com>

To:   Julian Satran/Haifa/IBM@IBMIL, <ips@ece.cmu.edu>
cc:
Subject:  RE: iSCSI: draft 7: Abort Task and RefCmdSN



Julo,

I must be misunderstanding something. I thought that Task Management
commands were to be executed as if they had arrived in sequence based on
their CmdSN.

        "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)."

Why wouldn't that be the case with Abort Task?

Alex.Nicolson@emulex.com


> -----Original Message-----
> From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf Of
> Julian Satran
> Sent: Sunday, August 05, 2001 2:37 PM
> To: ips@ece.cmu.edu
> Subject: Re: iSCSI: draft 7: Abort Task and RefCmdSN
>
>
> Robert,
>
> This is related to the fact that the abort command can arrive before the
> command to be aborted if sent on a different connection (or the
> command has
> been dropped due to some error). As such RefCmdSN indicates where the
> command would have been in the command queue.  If they don't agree the
> target should not abbort. And the main criteria for finding a task is the
> Initiator Task Tag.
> I've changed the wording to:
>
> 1.1.1     RefCmdSN
>
>    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.
>
> Julo
>
>
>
> "Elliott, Robert" <Robert.Elliott@compaq.com>@ece.cmu.edu on 05-08-2001
> 20:36:10
>
> Please respond to "Elliott, Robert" <Robert.Elliott@compaq.com>
>
> Sent by:  owner-ips@ece.cmu.edu
>
>
> To:   "'ips@ece.cmu.edu'" <ips@ece.cmu.edu>
> cc:
> Subject:  iSCSI: draft 7: Abort Task and RefCmdSN
>
>
>
> 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
>
>
>