Re: [pnfs] [PATCH 0/2] fix nfsd stateid encoding

J. Bruce Fields
2008-08-11T16:27:49Z

On Mon, Aug 11, 2008 at 07:11:40PM +0300, Benny Halevy wrote:
> On Aug. 11, 2008, 18:58 +0300, "J. Bruce Fields" <bfields@fieldses.org> wrote:
> > On Mon, Aug 11, 2008 at 05:09:36PM +0300, Benny Halevy wrote:
> >> Bruce, in a couple locations the nfsd needs to encode the stateid.seqid
> >> as a uint32_t rather than as opaque.
> >
> > Agreed, thanks.
> >
> > Though I have a hard time figuring out whether this has any impact in
> > practice. Presumably the only change on the wire is that we'll get the
> > endianness of the stateid4.seqid right? But that field is mostly opaque
> > to the client anyway; 3530 says
> >
> > The server is required to increment the seqid field
> > monotonically at each transition of the stateid. This is
> > important since the client will inspect the seqid in OPEN
> > stateids to determine the order of OPEN processing done by the
> > server.
> >
> > but doesn't say why this is important. I'm sure this has been brought
> > up on the ietf list before, but can't recall whether someone came up
> > with a justification for the importance of this.
> >
> > Anyway, so I figure these should be queued up for the next (2.6.28)
> > merge window. Thanks!
>
> Actually, I think this breaks delegreturn.
> Since we decode the stateid.si_generation correctly, it will get swabbed
> in delegreturn on little-endian servers. This will cause
> nfs4_preprocess_stateid_op/check_stateid_generation as called by
> nfsd4_delegreturn to fail. And eventually, unhash_delegation
> wouldn't be called.

Yipes. If delegations have always been broken and we haven't noticed,
then there's a more serious problem here--we should at least look into
why pynfs isn't catching that.

Oh, I see: si_generation is always zero for delegation stateid's!

> Hence, I think these patches are appropriate for 2.6.27 and
> even to older stable releases.

So unless I've missed something, I think this still looks more like a
style/consistency question?

--b.

>
> Benny
>
> >
> > --b.
> >
> >> Patch #1 fixes that for cb_recall.
> >> Patch #2 fixes the deleg stateid returned by open.
> >>
> >> The patches should apply to linux-2.6/master
> >> commit 796aadeb1b2db9b5d463946766c5bbfd7717158c
> >>
> >> Benny
> > _______________________________________________
> > pNFS mailing list
> > pNFS@linux-nfs.org
> > http://linux-nfs.org/cgi-bin/mailman/listinfo/pnfs
>