Re: [PATCH RFC] nfsd: serialize layout stateid morphing operations

[Christoph Hellwig <hch@lst.de>]

On Thu, Dec 03, 2015 at 05:08:50PM -0500, J. Bruce Fields wrote:
> OK, so if I understand right, the current code is letting the rpc state
> machine drive the whole thing, and your proposal is that the rpc task
> lasts until the client either responds NFS4ERR_NOMATCHING_LAYOUT or we
> just run out of time.  (NOMATCHING_LAYOUT being the one response that
> isn't either "try again" or "OK I'll get to it soon").

Yes (except fatal errors would end the rpc state machine).

> I understand why that would work, and that handling anything other than
> the NOMATCHING_LAYOUT case is a lower priority for now, but this
> approach worries me.
> 
> Is there a reason we can't do as in the delegation case, and track the
> revocation timeout separately from the callback rpc?

There is no reason not to do it, except for the significant effort
to implement it a well as a synthetic test case to actually reproduce
the behavior we want to handle.