On Fri, 2021-01-29 at 13:06 -0800, Sagi Grimberg wrote:

quoted

If the -U/--startup option is used, nvme monitor looks for exsiting
nvme controllers on startup, and runs a discovery on the associated
transport address (connection); i.e. tries to connect to a
discovery
subsystem on the same address, retrieve the discovery log pages,
and (if --autoconnect is given) connect all listed controllers.

Oh no no no no... This is a completely wrong assumption to make.
Nothing
suggest that an nvme controller will have a discovery controller on
the
same port.

There is a discovery controller and an NVM controller, the only
connection between the two is that a discovery controller can
refer to an nvme controller (or a different discovery controller).

Information about discovery controllers may be obtained in different
ways, but it absolutely cannot be obtained by any nvme controller.

Now I understand a bit more on the --keep discussion. The monitor
should today get discovery controller endpoints from a conf file
(maybe discovery.conf) and in the future by any other automatic
way, not even looking into the currently connected nvme controllers.

I hear you. I'll drop this in the next version, no problem. 

I didn't expect that probing for a discovery controller was a problem.
IIUC, if we get an fc_udev_device event for a NVMe remote port, we
can't be sure that that remote port offers a discovery controller,
either. We try to connect, and give up if it fails.

Martin



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