Re: [nfsv4] RFC: Is Open/Claim_Delegate_Prev done before/after Reclaim_complete?

On Thu, Apr 4, 2024 at 7:23 PM Rick Macklem <rick.macklem@gmail.com> wrote:

> Hi,
>
> I am in the process of implementing Open/Claim_Delegate_Prev and have run
> into a question I cannot seem to answer from reading RFC8881.
>

Let me see if I can make this clearer in rfc5661bis-04.  Fingers croosed.

>
> There is this snippet:
>    enum open_claim_type4 {
>            /*
>             * Not a reclaim.
>             */
>            CLAIM_NULL              = 0,
>
>            CLAIM_PREVIOUS          = 1,
>            CLAIM_DELEGATE_CUR      = 2,
>            CLAIM_DELEGATE_PREV     = 3,
>
>            /*
>             * Not a reclaim.
>             *
>             * Like CLAIM_NULL, but object identified
>             * by the current filehandle.
>             */
>            CLAIM_FH                = 4, /* new to v4.1 */
> The comments in the above seem to "hint" that CLAIM_DELEGATE_PREV is a
> reclaim type operation.
> If that is the case, I'd assume it/should be performed by the client
> before it does a
> Reclaim_Complete?
>

I think that's right.

>
> Then there is this snippet:
>    For OPEN requests that reach the server during the grace period, the
>    server returns an error of NFS4ERR_GRACE.  The following claim types
>    are exceptions:
>
>    *  OPEN requests specifying the claim type CLAIM_PREVIOUS are devoted
>       to reclaiming opens after a server restart and are typically only
>       valid during the grace period.
>
>    *  OPEN requests specifying the claim types CLAIM_DELEGATE_CUR and
>       CLAIM_DELEG_CUR_FH are valid both during and after the grace
>       period.  Since the granting of the delegation that they are
>       subordinate to assures that there is no conflict with locks to be
>       reclaimed by other clients, the server need not return
>       NFS4ERR_GRACE when these are received during the grace period.
> This clearly states that CLAIM_DELEGATE_PREV cannot be performed
> during the server's grace period.
>
>
It seems to me that this is an oversight.

> The above two statements are not necessarily contradictory but it does seem
> that, if the server is in its grace period, the Reclaim_Complete needs to
> be
> done before any Open/Claim_Delegate_Prev, since Reclaim_Complete tells
> the server when to end its grace period.
>

Yes.

> Note that, usually, a client would not be rebooting when a server is in its
> grace period, but that could happen.
>

Yes it can.  It wouldn't matter if you said "MUST NOT" or "IST STRENG
VERBOTEN".

>
> Bottom line...
> Should a client perform Open/Claim_Delegate_Prev before or after
> Reclaim_Complete?
>

Before.

> And, if the answer is "after", how does the server know when a client
> is done recovering opens/delegations via Open/Claim_Delegate_Prev?
>
> That's why "after" is not a good answer.

> Thanks for any help with this, rick
>
> Thanks for bringing this up.

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