NFS: Create an read_pageio_init() function

pNFS needs to select a read function based on the layout driver
currently in use, so I let each NFS version decide how to best handle
initializing reads.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index 4d62b77..e00b8b3 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -1354,6 +1354,7 @@
 struct nfs_client;
 struct rpc_timeout;
 struct nfs_client_initdata;
+struct nfs_pageio_descriptor;
 
 /*
  * RPC procedure vector for NFSv2/NFSv3 demuxing
@@ -1407,6 +1408,8 @@
 	int	(*set_capabilities)(struct nfs_server *, struct nfs_fh *);
 	int	(*decode_dirent)(struct xdr_stream *, struct nfs_entry *, int);
 	void	(*read_setup)   (struct nfs_read_data *, struct rpc_message *);
+	void	(*read_pageio_init)(struct nfs_pageio_descriptor *, struct inode *,
+				    const struct nfs_pgio_completion_ops *);
 	void	(*read_rpc_prepare)(struct rpc_task *, struct nfs_read_data *);
 	int	(*read_done)  (struct rpc_task *, struct nfs_read_data *);
 	void	(*write_setup)  (struct nfs_write_data *, struct rpc_message *);