Re: [PATCH v6 3/3] NFSD: add write_ports to netlink command

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2024-01-23 at 08:35 +1100, NeilBrown wrote:
> On Tue, 23 Jan 2024, Jeff Layton wrote:
> > On Sat, 2024-01-20 at 18:33 +0100, Lorenzo Bianconi wrote:
> > > Introduce write_ports netlink command. For listener-set, userspace is
> > > expected to provide a NFS listeners list it wants to enable (all the
> > > other ports will be closed).
> > > 
> > 
> > Ditto here. This is a change to a declarative interface, which I think
> > is a better way to handle this, but we should be aware of the change.
> 
> I agree it is better, and thanks for highlighting the change.
> 
> > > +	/* 2- remove stale listeners */
> > 
> > 
> > The old portlist interface was weird, in that it was only additive. You
> > couldn't use it to close a listening socket (AFAICT). We may be able to
> > support that now with this interface, but we'll need to test that case
> > carefully.
> 
> Do we ever want/need to remove listening sockets?
> Normal practice when making any changes is to stop and restart where
> "stop" removes all sockets, unexports all filesystems, disables all
> versions.
> I don't exactly object to supporting fine-grained changes, but I suspect
> anything that is not used by normal service start will hardly ever be
> used in practice, so will not be tested.
> 
> So if it is easiest to support reverting previous configuration (as it
> probably is for version setting), then do so.  But if there is any
> complexity (as maybe there is with listening sockets), then don't
> add complexity that won't be used.
> 


I completely agree here. It's probably simplest to just prevent this for
now unless and until there is some need for it.
-- 
Jeff Layton <jlayton@kernel.org>