[nfsv4] Re: OPEN_XOR_DELEGATION when there is existing OPEN stateid

[Rick Macklem <[e-mail]>]

On Wed, Oct 2, 2024 at 9:16 AM Thomas Haynes <[e-mail]> wrote:
>
>
>
> > On Oct 2, 2024, at 5:51 AM, Jeff Layton <[e-mail]> wrote:
> >
> > On Tue, 2024-10-01 at 22:24 -0700, Thomas Haynes wrote:
> >>
> >>> On Oct 1, 2024, at 6:11 AM, Jeff Layton <[e-mail]> wrote:
> >>>
> >>> Another delstid question. Consider the following situation. All opens
> >>> have WANT_OPEN_XOR_DELEGATION set:
> >>>
> >>> 1/ Client opens a file r/o. Server doesn't assign a delegation, so an
> >>> open stateid (with seq=1) is returned.
> >>>
> >>> 2/ Client opens the file again for r/w. Server assigns a delegation and
> >>> skips updating the OPEN stateid's seqid and sending the result back to
> >>> the client.
> >>>
> >>> Is that wrong behavior? It seems like that would morph the open stateid
> >>> for this openowner without updating the client as to the new stateid.
> >>> The delegation does cover it in that case, but it seems less than
> >>> optimal if the client ends up returning that delegation later.
> >>>
> >>> If the client already holds an open stateid, should we ignore
> >>> WANT_OPEN_XOR_DELEGATION?
> >>> --
> >>> Jeff Layton <[e-mail]>
> >>
> >>
> >> It seems to me we can’t break the upgrade, so we have to honor the WANT_OPEN_XOR_DELEGATION by returning an upgraded open stateid.
> >>
> >> I.e., if the client already has an open stateid and presents an WANT_OPEN_XOR_DELEGATION, then cannot return just a delegation. Either we just upgrade the existing open stateid or we upgrade it and also return the delegation.
> >>
> >> Likewise, if we had already returned a delegation stateid, we should just return a delegation stateid.
> >>
> >> Feel free to argue with me ….
> >
> > No, that makes sense I think.
> >
> > Would it be OK to just ignore WANT_OPEN_XOR_DELEGATION in this case,
> > and return both an updated open stateid and the delegation stateid?
> > That's probably the more desirable outcome (regardless of the "XOR" in
> > the name).
> > --
> > Jeff Layton <[e-mail]>
>
>
> It is a hint, none of the language states it MUST return one or the other.
The only bother is that you have to provide a reason for ignoring it.
Having said that, I doubt clients care what the reason is and I'll
note that a client is being "dumb" if it uses the
OPEN4_SHARE_ACCESS_WANT_OPEN_XOR_DELEGATION flag
in this case.

rick

>
> So yes, it is okay.
>
> Let me see if I can still add this text.
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