Re: [PATCH] cifs: Allow nfsd over cifs

["J. Bruce Fields" <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>]

On Tue, Mar 01, 2011 at 02:38:27PM -0600, Steve French wrote:
> On Tue, Mar 1, 2011 at 2:34 PM, J. Bruce Fields <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org> wrote:
> > On Tue, Mar 01, 2011 at 02:11:32PM -0600, Steve French wrote:
> >> I vaguely remember that the same problem can occur with nfsd on a
> >> local file system
> >
> > Not true; as I've said, exportable local filesystems know how to look up
> > a file on disk by filehandle.
> >
> >> and that nfs clients have to be able to recover from
> >> ESTALE (e.g. lookup/delete/create/lookup would fail with ESTALE
> >> otherwise).
> >
> > It is true, however, that there are some *other* cases when a server can
> > return ESTALE.  In those cases (such as the one Peter Staubach discusses
> > in more detail at http://lwn.net/Articles/272684/) there may be some
> > recovery that a client might reasonably attempt.
> >
> > Alas, no client can be expected to recover from ESTALE errors on an
> > opened file--those will just be passed on to the application.
> 
> If this is v4 (only) wouldn't we always have an open->dentry in cache?

That's correct, but only as long as the server is running.  We need
reboot recovery to work as well.

Also:

	- NFSv4 uptake is still rather small as far as I know, so the v3
	  behavior is important
	- We don't currently have any way to export cifs as v4 only.

--b.