pnfs: encode_layoutcommit

Add a layout driver method to encode the layout type specific
opaque part of layout commit in-line in the xdr stream.

Currently, the pnfs-objects layout driver uses it to encode metadata hints
to the MDS and the blocks layout driver to commit provisionally allocated
extents to the file.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index 1b6b207..3fda971 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -108,6 +108,10 @@
 	void (*encode_layoutreturn) (struct pnfs_layout_hdr *layoutid,
 				     struct xdr_stream *xdr,
 				     const struct nfs4_layoutreturn_args *args);
+
+	void (*encode_layoutcommit) (struct pnfs_layout_hdr *layoutid,
+				     struct xdr_stream *xdr,
+				     const struct nfs4_layoutcommit_args *args);
 };
 
 struct pnfs_layout_hdr {