Re: [PATCH] nfsd: don't break lease while servicing a COMMIT call (try #2)

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Thu, 2010-03-25 at 13:47 -0400, J. Bruce Fields wrote: 
> On Mon, Mar 22, 2010 at 04:33:40PM -0400, Jeff Layton wrote:
> > It looks like nfs_inode_return_delegation always calls nfs_msync_inode
> > on any valid delegation before returning it, regardless of the
> > delegation type.
> > 
> > RFC 3530 says this:
> > 
> >    If the client is granted a read delegation, it is assured that no
> >    other client has the ability to write to the file for the duration of
> >    the delegation.  If the client is granted a write delegation, the
> >    client is assured that no other client has read or write access to
> >    the file.
> > 
> > That doesn't seem to imply that we must flush writes before returning
> > either type of delegation. OTOH, maybe it makes sense to treat those as
> > cache consistency points since a delegreturn sort of implies that
> > another client wants to use the file.
> > 
> > I'm not quite sure how to interpret the spec here...
> 
> If there's that call could cause the client to wait for an actual write
> to succeed before returning the delegation, then something's wrong.

We're certainly expected to write back data before returning a write
delegation (see Section 9.4.4 of RFC 3530).

For the case of a read delegation, then the spec is silent because it
contains no discussion of the case where a server grants both an open
for write and a read delegation. If you want a normative statement on
what clients should do for that case, then I suggest a discussion on the
IETF list with a view to getting it into RFC3530-bis.

Trond