Re: [pnfs] [PATCH] nfsd: use nfs client rpc callback program

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

On Wed, 2008-09-24 at 12:35 -0400, J. Bruce Fields wrote:
> On Thu, Sep 18, 2008 at 02:24:39PM -0500, Benny Halevy wrote:
> > From: Benny Halevy <bhalevy@panasas.com>
> > 
> > since commit ff7d9756b501744540be65e172d27ee321d86103
> > "nfsd: use static memory for callback program and stats"
> > do_probe_callback uses a static callback program
> > (NFS4_CALLBACK) rather than the one set in clp->cl_callback.cb_prog
> > as passed in by the client in setclientid (4.0)
> > or create_session (4.1).
> > 
> > This patches allows allocating cb_program (and cb_stats) dynamically
> > and setting a free_rpc_program function pointer to be
> > called when the rpc_clnt structure is destroyed.
> 
> So that means we handle two cases:
> 
> 	- free_rpc_program = NULL: We assume the program and stats are
> 	  in static memory (or module memory--which might be a problem
> 	  if we shut down the server and remove the nfsd module in quick
> 	  succession.  I assume there's a similar (probably very
> 	  hard-to-hit) bug on the client too, but haven't looked
> 	  carefully.).
> 	- free_rpc_program != NULL: We assume this rpc_client is the
> 	  last user of the program.
> 
> It seems a little ad hoc, but I can't see why it wouldn't solve the
> problem.
> 
> I'd want Trond's ack.

Well the current implementation is certainly broken. Look at what
happens if I clone the rpc_clnt...

  Trond