On Tue, Dec 06, 2011 at 01:26:05PM +0200, Benny Halevy wrote:
> On 2011-12-06 04:08, J. Bruce Fields wrote:
> > On Sun, Dec 04, 2011 at 02:42:11PM +0200, Benny Halevy wrote:
> >> On 2011-12-04 14:03, tigran.mkrtchyan@xxxxxxx wrote:
> >>> From: Tigran Mkrtchyan <tigran.mkrtchyan@xxxxxxx>
> >>>
> >>>
> >>> Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@xxxxxxx>
> >>> ---
> >>> fs/nfsd/nfs4proc.c | 6 ++++++
> >>> fs/nfsd/nfs4state.c | 26 ++++++++++++++++++++------
> >>> 2 files changed, 26 insertions(+), 6 deletions(-)
> >>>
> >>> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> >>> index fa38336..535aed2 100644
> >>> --- a/fs/nfsd/nfs4proc.c
> >>> +++ b/fs/nfsd/nfs4proc.c
> >>> @@ -400,6 +400,12 @@ nfsd4_open(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> >>> */
> >>> status = nfsd4_process_open2(rqstp, &cstate->current_fh, open);
> >>> WARN_ON(status && open->op_created);
> >>> +
> >>> + if(status)
> >>> + goto out;
> >>> +
> >>> + /* set current state id */
> >>> + memcpy(&cstate->current_stateid, &open->op_stateid, sizeof(stateid_t));
> >
> > That comment is a bit redundant.
> >
> >> Since this should be done for all stateid-returning operations
> >> I think that a cleaner approach could be to mark those as such in
> >> nfsd4_ops by providing a per-op function to return the operation's
> >> stateid. You can then call this method from nfsd4_proc_compound()
> >> after the call to nfsd4_encode_operation() and when status == 0.
> >
> > So the choice is between
> >
> > + memcpy(&cstate->current_stateid, &open->op_stateid,
> > sizeof(stateid_t));
> >
> > and
> >
> > + static void get_open_stateid(stateid_t *s)
> > + {
> > + memcpy(s, open->op_stateid);
> > + }
> > +
> > + [OP_OPEN] = {
> > + ...
> > + .op_get_stateid = get_open_stateid,
> > + ...
> > + }
> >
> > ?
> >
> > I'm not so sure.
>
> The point is to copy the result stateid into the current_stateid
> in a centralized place: nfsd4_proc_compound() and do that for all
> stateid-modifying operations.
>
> >
> > Anyway, thanks Tigran for looking at this.
> >
> > Do we want to guarantee that the client can't expire as long as a
> > compound references the stateid? I think that's the case.
>
> The client can't time out while the 4.1 compound is in progress, see commit d768298.
OK, you're right, and presumably it would be a bug for a compound to use
a session from one client and a stateid from another, so this is taken
care of. (Except--I think we need to check for that case. On a quick
skim I don't see the current code doing that.)
Thanks!
> Are you thinking of explicit expiration of the client?
> We may unhash the client and keep using it while it's referenced
> so that's not a problem. As far as the stateid goes, we're copying the
> value of the stateid, not pointing to any stateid structure. If the
> actual state was destroyed, we will detect that when the current_stateid
> is used by any successive operation and we cannot find the state using
> the stateid.
I *think* the concensus of the working group was that explicit
destruction of a client should wait on in-progress compounds referencing
any of the client's sessions:
http://www.ietf.org/mail-archive/web/nfsv4/current/msg08584.html
So we should probably fix this. But we can fix it at the session level.
So, OK, I can't see any practical objection to doing as Tigran as and
just passing the value of stateid instead of a reference to some object.
Well, except for performance--it seems unfortunate to have to redo the
lookup on each use. As long as there's no impact on the existing cases
(so we're only doing the lookup when a client actually uses the current
stateid), I can live with that until somebody actually demonstrates some
harm.
--b.
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