Hi Nicholas,
On Mon, March 10, 2014 6:01 PM, Nicholas A. Bellinger wrote:
> On Fri, 2014-03-07 at 02:04 +0000, Alex Leung wrote:
> > It's not obvious to me why the queue_status() downcall would be made
> > with scsi_status = SAM_STAT_TASK_ABORTED. It would seem to imply that
> > an FCP_RESPONSE with status=40h should be sent on the wire for the
> > associated FCP_CMND. However, since an ABTS was received for the
> > command, no response will be sent for the FCP_CMND itself. Am I
> > reading this correctly?
> >
>
> Yes. It's up to the fabric driver to determine if a ->queue_status being called
> with SAM_STAT_TASK_ABORTED is sent over the wire, or should be
> completed internally.
>
How can the fabric driver distinguish between this case (Abort Task) that
would never send TASK_ABORTED and, say, LUN RESET, that would send
TASK_ABORTED (provided that the TMR came from a different IT Nexus)?
> > core_tmr_handle_tas_abort() has the following 'if' statement before
> > calling transport_send_task_abort():
> >
> > if ((tmr_nacl &&
> > (tmr_nacl == cmd->se_sess->se_node_acl)) || tas)
> > transport_send_task_abort(cmd);
> >
> > It makes sense that if TAS=1, the .queue_status downcall would be made
> > with scsi_status=SAM_STAT_TASK_ABORTED. However, I don't understand
> > the "(tmr_nacl && tmr_nacl == cmd->se_sess->se_node_acl)" part of this
> > statement.
>
> IIRC, this is because TAS only effects nexuses other than the nexus that
> received the LUN_RESET.
>
> > When I configure TAS=0 and send a LUN Reset, the tmr_nacl matches the
> > se_node_acl so the call to transport_send_task_abort() is made
> > regardless of "tas". I would think that if TAS=0, the
> > transport_send_task_abort() call would be skipped. What am I missing?
> >
>
> From SPC-4's description of TAS:
>
> "A task aborted status (TAS) bit set to zero specifies that aborted commands
> shall be terminated by the device server without any response to the
> application client. A TAS bit set to one specifies that commands aborted by
> the actions of an I_T nexus other than the I_T nexus on which the command
> was received shall be completed with TASK ABORTED status (see SAM-4)."
>
> My understanding wrt to TAS has been that it only effects nexuses other
> than the one that received the LUN_RESET.
I agree, that's why I would have expected to only send TASK_ABORTED if TAS=1
and the TMR came from a different IT Nexus. Something like this:
if ((tmr_nacl &&
(tmr_nacl != cmd->se_sess->se_node_acl)) && tas)
transport_send_task_abort(cmd);
Thanks,
Alex
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