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

[Chuck Lever <chuck.lever@oracle.com>]

On Tue, Jan 23, 2024 at 08:35:07AM +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?

I think that might be an interesting use case. Disabling RDMA, for
example, should kill the RDMA listening endpoints but leave
listening sockets in place.

But for now, our socket listeners are "any". Wondering how net
namespaces play into this.


> 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.

Well, there is that. I guess until we have test coverage for NFSD
administrative interfaces, we should leave well enough alone.


> 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.
> 
> Thanks,
> NeilBrown

-- 
Chuck Lever