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

[Rick Macklem <[e-mail]>]

On Tue, 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?
Seems fine to me.  Right now (without the delstid extension) a client can
hold several open stateids for a file (different open_owner4's) and each of
these has a seqid field that is incremented when additional
Opens/Open_downgrades/Close
are done on that stateid.  The stateid.seqid for other Opens for the same
file are not affected.
Similarly, issuing a delegation for the same file does not affect the
seqid in the
open stateids for the same file.

So, why would issuing a delegation without an open stateid be any different?

> It seems like that would morph the open stateid
> for this openowner without updating the client as to the new stateid.
I'm not sure what you are thinking of here?
The open stateid still refers to a r/o Open and
has nothing to do with the delegation (except they happen to refer to the
same file).

> 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 does a delegreturn, the r/o open still exists for the client
unless/until it does a Close. (It actually could be more optimal for the
client to retain the r/o Open, so that it does not need to re-acquire it
before doing a Delegreturn, I think?)

Now maybe I didn't understand OPEN4_SHARE_ACCESS_WANT_OPEN_XOR_DELEGATION,
but I didn't think it said anything about Opens already issued to the client?

>
> If the client already holds an open stateid, should we ignore
> WANT_OPEN_XOR_DELEGATION?
As I understand it, a server can always ignore the OPEN4_SHARE_WANT_xxx
flags, but I do not see a reason for the server to choose to ignore it
in this case?

Maybe I am missing something and others can clarify it, rick

> --
> Jeff Layton <[e-mail]>
>
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