[PATCH 00/29] fs: require filesystems to explicitly opt-in to nfsd export support

[Amir Goldstein]

On Thu, Jan 15, 2026 at 8:14 PM Amir Goldstein <amir73il at gmail.com> wrote:
>
> On Thu, Jan 15, 2026 at 7:32 PM Chuck Lever <cel at kernel.org> wrote:
> >
> >
> >
> > On Thu, Jan 15, 2026, at 1:17 PM, Amir Goldstein wrote:
> > > On Thu, Jan 15, 2026 at 6:48 PM Jeff Layton <jlayton at kernel.org> wrote:
> > >>
> > >> In recent years, a number of filesystems that can't present stable
> > >> filehandles have grown struct export_operations. They've mostly done
> > >> this for local use-cases (enabling open_by_handle_at() and the like).
> > >> Unfortunately, having export_operations is generally sufficient to make
> > >> a filesystem be considered exportable via nfsd, but that requires that
> > >> the server present stable filehandles.
> > >
> > > Where does the term "stable file handles" come from? and what does it mean?
> > > Why not "persistent handles", which is described in NFS and SMB specs?
> > >
> > > Not to mention that EXPORT_OP_PERSISTENT_HANDLES was Acked
> > > by both Christoph and Christian:
> > >
> > > https://lore.kernel.org/linux-fsdevel/20260115-rundgang-leihgabe-12018e93c00c@brauner/
> > >
> > > Am I missing anything?
> >
> > PERSISTENT generally implies that the file handle is saved on
> > persistent storage. This is not true of tmpfs.
>
> That's one way of interpreting "persistent".
> Another way is "continuing to exist or occur over a prolonged period."
> which works well for tmpfs that is mounted for a long time.
>
> But I am confused, because I went looking for where Jeff said that
> you suggested stable file handles and this is what I found that you wrote:
>
> "tmpfs filehandles align quite well with the traditional definition
>  of persistent filehandles. tmpfs filehandles live as long as tmpfs files do,
>  and that is all that is required to be considered "persistent".
>
> >
> > The use of "stable" means that the file handle is stable for
> > the life of the file. This /is/ true of tmpfs.
>
> I can live with STABLE_HANDLES I don't mind as much,
> I understand what it means, but the definition above is invented,
> whereas the term persistent handles is well known and well defined.
>

And also forgot to mention - STABLE HANDLES is very lexicographically
close to STALE HANDLES :-/

Thanks,
Amir.