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

Christoph Hellwig
2026-01-21T10:00:33Z

On Tue, Jan 20, 2026 at 07:50:32AM -0500, Jeff Layton wrote:
> > > and it DOES provide stable filehandles.
> >
>
> Across reboot? Not really.
>
> It's quite possible that we may end up with the same "id" numbers in
> cgroupfs on a new incarnation of the filesystem after a reboot. The
> files in there are not the same ones as the ones before, but their
> filehandles may match because kernfs doesn't factor in an i_generation
> number.
>
> Could we fix it by adding a random i_generation value or something?
> Possibly, but there really isn't a good use-case that I can see for
> allowing cgroupfs to be exported via nfsd. Best to disallow it until
> someone comes up with one.

Yeah. And I'm pretty sure everyone here will push back hard on any
such use case.