NFS: Create a common initiate_pgio() function

Most of this code is the same for both the read and write paths, so
combine everything and use the rw_ops when necessary.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index 01aa29c..c6a587f 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -59,6 +59,8 @@
 	void (*rw_release)(struct nfs_pgio_data *);
 	int  (*rw_done)(struct rpc_task *, struct nfs_pgio_data *, struct inode *);
 	void (*rw_result)(struct rpc_task *, struct nfs_pgio_data *);
+	void (*rw_initiate)(struct nfs_pgio_data *, struct rpc_message *,
+			    struct rpc_task_setup *, int);
 };
 
 struct nfs_pageio_descriptor {