[PATCH 2/2] nvmet: Add port transport active flag

[Sagi Grimberg]

>>> tractive port flag means that nvmet transport is active and ready for
>>> receiving requests from host.
>>> It differ from enabled port state (port with subsystem symbolic link)
>>> which doesn't guarantee this.
>>> The tractive flag is necessary in case the physical ports become down
>>> while nvmet ports are enabled.
>>> In this case the port state remains enabled but tractive flag becomes 
>>> false.
>>>
>>> The tractive flag will help the administrator to monitor the port state
>>> from transport point of view.
>>> The commit also add the ability to activate the port by simply writing
>>> to tractive at the configfs.
>>> e.g.: echo 1 > config/nvmet/ports/1/tractive
>>
>> Why this is a write-able variable? this is a state. I would rename it
>> to be trstate.
> 
> We need a write-able entry to bring-up a listener in case the port/link 
> went down.
> Would you prefer 2 new configfs entries ? trstate (RO) and tractivate 
> (WO) ?

No, I would prefer a trstate which is RO and activation with a subsystem
symlink. We can easily take care of re-activation in the transport.