Re: [nfsv4] can a server replace a read deleg with a write deleg?

[Rick Macklem <[e-mail]>]

On Sun, 4 Jul 2010, Trond Myklebust wrote:

>
> I read RFC3530 as being perfectly clear on this.
>
> In section 9.4 it explicitly states that the client _cannot_ make any
> changes to the contents or attributes of the file if it holds a read
> delegation.
>

Ok, here are 2 paras from page 103:
    When a client has a read open delegation, it may not make any changes
    to the contents or attributes of the file but it is assured that no
    other client may do so.  When a client has a write open delegation,
    it may modify the file data since no other client will be accessing
    the file's data.  The client holding a write delegation may only
    affect file attributes which are intimately connected with the file
    data:  size, time_modify, change.

I see this as saying the read open delegation doesn't allow writing
to the file, but I don't see it saying "the client can't open the
file for writing against the server without first returning the
delegation". (Btw, I have no problem with it saying that, I just
didn't get that from the above para, especially given what it says
in the next para.)

    When a client has an open delegation, it does not send OPENs or
    CLOSEs to the server but updates the appropriate status internally.
-> For a read open delegation, opens that cannot be handled locally
    (opens for write or that deny read access) must be sent to the
    server.

I see "->" simply saying that the open has to be done against the
server. If the read open delegation must be returned for the open
to be done, shouldn't it state that explicitly.

> In section 9.4.4 it states that the server must recall the delegation in
> the event of a conflicting OPEN or READ/WRITE w/ special stateids.
>
If the open for writing is from the same client that holds the read open
delegation, it didn't hit me as a "conflict". I would have thought a
conflicting OPEN would have been one from a different client?

Isn't the english language wonderfully ambiguous?

If others feel the wording is clear, then I have no problem with it.
ie. If the client doesn't return the read open delegation before doing
     an open for writing against the server, the server will CBRECALL it.

rick