Add NFSv3 tree root to mountd

[Rick Macklem]

Alex Burlyga wrote:
> On Apr 23, 2016 04:51, "Rick Macklem" <rmacklem at uoguelph.ca> wrote:
> >
> > Brian Mueller wrote:
> > > Similar to mountd's ability to specify the NFSv4 tree root via the V4:
> line
> > > in the exports file, I would like to add the ability to specify a NFSv3
> tree
> > > root.  The goal to have the same exported path for both the V3 and V4.
> If
> > > you have exports file like the following:
> > >
> > > /foo/bar
> > > V3: /foo/bar
> > > V4: /foo/bar
> > >
> > > NFS clients would mount /foo/bar by running
> > >
> > > mount -t nfs -o ver=3 server:/ /mnt/v3
> > > mount -t nfs -o ver=4 server:/ /mnt/v4
> > >
> > > Without the change, the NFS client would need to specify different
> paths for
> > > v3 and v4
> > >
> > > mount -t nfs -o ver=3 server:/foo/bar /mnt/v3
> > > mount -t nfs -o ver=4 server:/ /mnt/v4
> > >
> > > Feedback appreciated.  If there aren't any objections with
> incorporating this
> > > change into FreeBSD, I will start working on the changes to mountd.
> > >
> > Basically I assume you are planning on using the V3 "/foo/bar" as a
> prefix that
> > is prepended to the path when a Mount RPC request arrives. I, personally,
> don't
> > see a problem with this, assuming that things still work the same when
> the "V3"
> > line isn't in /etc/exports.
> > A couple of comments:
> > - Since NFSv3 doesn't follow server mounts, the results of a V3 mount
> will still
> >   be different than NFSv4 unless there is only one file system under
> "/foo/bar".
> >   --> Maybe adding this will just add to the confusion already present
> w.r.t. the
> >       differences between NFSv3 and NFSv4? (Falsely giving the impression
> that
> >       adding the "V3" line somehow makes them the same?)
> Agreed, also when testing -actual option on netapp filers(maybe that's the
> way to go?) we run into problems with some automounters. Quick look at the
> current freebsd, Linux, and Mac OS X does not reveal any problems, perhaps
> it was some exotic ones like AIX? Also for v3 adding command line option
> that make all exports relative to that path, ala webnfs, would be simpler
> way to go?
> 
> > - In case you haven't looked at it, mountd.c is a beast. You'll have fun
> adding
> >   this change to it.
> Doing command line option or adding another export option I think is
> simpler way.
> 
Yes. I was simply noting that changing mountd.c to add this might be
challenging. You might be able to do it fairly easily by using the handling
of the "V4" line as an example. mountd.c is about as ugly as a C program
gets, at least the part that parses /etc/exports.

One more thing...
You might need to consider if this will apply to the ZFS specific export
stuff. (I know nothing about this except that ZFS generates its own export
file.)

Have fun with it, rick

> >
> > rick
> >
> > > Brian
> > >
> > > Brian Mueller
> > > Panasas Inc.
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