Re: sharing protocol defintions between client and server?

[Christoph Hellwig <hch@infradead.org>]

On Thu, Nov 14, 2013 at 10:05:46AM -0500, J. Bruce Fields wrote:
> On Wed, Nov 13, 2013 at 08:21:16AM -0800, Christoph Hellwig wrote:
> > >From a lot of the recent work it seems like there's basically no
> > sharing of protocol definitions between the Linux NFS client and
> > server, which seems fairly annoying to me.
> 
> What are you thinking of exactly?
> 
> I suspect that there could be more sharing.

To make it easy I'll just quote from the SEEK patches.

client:

+struct nfs42_seek_args {
+	struct nfs4_sequence_args	seq_args;
+
+	struct nfs_fh			*sa_fh;
+	nfs4_stateid			*sa_stateid;
+	u64				sa_offset;
+	u32				sa_what;
+};
+
+struct nfs42_seek_res {
+	struct nfs4_sequence_res	seq_res;
+	unsigned int			status;
+
+	u32	sr_eof;
+	u32	sr_whence;
+	u64	sr_offset;
+	u64	sr_length;
+	u32	sr_allocated;
+};
+#endif

server:

+struct nfsd4_seek {
+	/* request */
+	stateid_t	seek_stateid;
+	loff_t		seek_offset;
+	u32		seek_whence;
+
+	/* response */
+	u64		seek_pos;
+	u32		seek_eof;
+	u64		seek_length;
+	u32		seek_allocated;
+};

note that a lot of server operations also seem to have separate
args and result substrutures.  In general I'd love to have one
structure for the actual on-the wire operation in a header, and then
client and server could build in-memory versions around them.

Of course just generating those from the XDR would be even better.

Maybe I'll play around with doing a krpcgen that we can initially
just use for producing the structures, for which it should be
pretty clear benefit.  If we're lucky we might be to also move
some marshalling/unmarshalling over to it later.