NFS: Create a common argument structure for reads and writes

Reads and writes have very similar arguments.  This patch combines them
together and documents the few fields used only by write.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index 62db136..461cd8b 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -613,7 +613,7 @@
  *	};
  */
 static void encode_readargs(struct xdr_stream *xdr,
-			    const struct nfs_readargs *args)
+			    const struct nfs_pgio_args *args)
 {
 	u32 offset = args->offset;
 	u32 count = args->count;
@@ -629,7 +629,7 @@
 
 static void nfs2_xdr_enc_readargs(struct rpc_rqst *req,
 				  struct xdr_stream *xdr,
-				  const struct nfs_readargs *args)
+				  const struct nfs_pgio_args *args)
 {
 	encode_readargs(xdr, args);
 	prepare_reply_buffer(req, args->pages, args->pgbase,
@@ -649,7 +649,7 @@
  *	};
  */
 static void encode_writeargs(struct xdr_stream *xdr,
-			     const struct nfs_writeargs *args)
+			     const struct nfs_pgio_args *args)
 {
 	u32 offset = args->offset;
 	u32 count = args->count;
@@ -669,7 +669,7 @@
 
 static void nfs2_xdr_enc_writeargs(struct rpc_rqst *req,
 				   struct xdr_stream *xdr,
-				   const struct nfs_writeargs *args)
+				   const struct nfs_pgio_args *args)
 {
 	encode_writeargs(xdr, args);
 	xdr->buf->flags |= XDRBUF_WRITE;