Re: iSCSI target: Handling in-flight requests during ctld shutdown

On 12/31/21 1:27 PM, Alexander Motin wrote:
> On 31.12.2021 13:41, John Baldwin wrote:
>> On 12/30/21 3:06 PM, Alexander Motin wrote:
>>> No.  cfiscsi_datamove_out() called before the new flag is set would
>>> still try to send R2T over the dying connection to be aborted by the
>>> cfiscsi_session_terminate_tasks() few milliseconds later.
>>> cfiscsi_data_wait_abort() would only be needed if
>>> cfiscsi_session_terminate_tasks() has already passed through the data
>>> waiters list and waiting for the last tasks completion.
>>
>> So I think what I was missing is that I had assumed in the race case
>> that the task was not visible when the NEXUS_I_T_RESET ran, but I think
>> from re-reading now that the task has to have been in the lun's OOA
>> queue as we don't permit queueing more tasks due to LUN_RESERVED being
>> cleared, so I think that means that even in the race case the task
>> has been aborted.  Perhaps then the code in cfiscsi_datamove_out can
>> just check CTL_FLAG_ABORT instead of cs_terminating?  That would
>> function similar to your proposed new flag I think assuming it is correct
>> that the task for any I/O being passed to cfiscsi_datamove_out concurrent
>> with cfiscsi_session_terminate_tasks must have been "visible" on the OAA
>> queue and thus aborted by the handler?
> 
> It was looking like a good idea for few seconds, since you right that
> almost all commands should be visible via OAA queues and so should be
> aborted by cfiscsi_session_terminate_tasks() at that point.  But there
> are few exceptions of commands that can be executed without LUNs
> present, see CTL_CMD_FLAG_OK_ON_NO_LUN.  All 3 of them are
> CTL_FLAG_DATA_IN, so should not appear in cfiscsi_datamove_out(), but I
> am still not sure it is very good, even though it may probably work.

So my remaining question I guess is if I add a new 'cs->cs_terminating_tasks'
or the like, how does cfiscsi_datamove_out ensure that no response is sent?
The only thing I've seen so far is this code in cfiscsi_scsi_command_done:

	/*
	 * Do not return status for aborted commands.
	 * There are exceptions, but none supported by CTL yet.
	 */
	if (((io->io_hdr.flags & CTL_FLAG_ABORT) &&
	     (io->io_hdr.flags & CTL_FLAG_ABORT_STATUS) == 0) ||
	    (io->io_hdr.flags & CTL_FLAG_STATUS_SENT)) {
		ctl_free_io(io);
		icl_pdu_free(request);
		return;
	}

Would you prefer checking cs_terminating_tasks in this function as well to
avoid sending the peudo-aborted responses instead of forcing CTL_FLAG_ABORT
on?

-- 
John Baldwin