Re: CLOSE/OPEN race

[Jeff Layton <jlayton@redhat.com>]

On Sat, 2016-11-12 at 06:08 -0500, Benjamin Coddington wrote:
> I've been seeing the following on a modified version of generic/089
> that gets the client stuck sending LOCK with NFS4ERR_OLD_STATEID.
> 
> 1. Client has open stateid A, sends a CLOSE
> 2. Client sends OPEN with same owner
> 3. Client sends another OPEN with same owner
> 4. Client gets a reply to OPEN in 3, stateid is B.2 (stateid B sequence 2)
> 5. Client does LOCK,LOCKU,FREE_STATEID from B.2
> 6. Client gets a reply to CLOSE in 1
> 7. Client gets reply to OPEN in 2, stateid is B.1
> 8. Client sends LOCK with B.1 - OLD_STATEID, now stuck in a loop
> 
> The CLOSE response in 6 causes us to clear NFS_OPEN_STATE, so that the OPEN
> response in 7 is able to update the open_stateid even though it has a lower
> sequence number.
> 
> I think this case could be handled by never updating the open_stateid if the
> stateids match but the sequence number of the new state is less than the
> current open_state.
> 

What kernel is this on?

Yes, that seems wrong. The client should be picking B.2 for the open
stateid to use. I think that decision of whether to take a seqid is made
in nfs_need_update_open_stateid. The logic in there looks correct to me
at first glance though.

-- 
Jeff Layton <jlayton@redhat.com>