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

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.

-- 
Alexander Motin