nfs: merge nfs_pgio_data into _header

struct nfs_pgio_data only exists as a member of nfs_pgio_header, but is
passed around everywhere, because there used to be multiple _data structs
per _header. Many of these functions then use the _data to find a pointer
to the _header.  This patch cleans this up by merging the nfs_pgio_data
structure into nfs_pgio_header and passing nfs_pgio_header around instead.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Weston Andros Adamson <dros@primarydata.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 4359265..d0fae7b 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -64,10 +64,11 @@
 	const fmode_t rw_mode;
 	struct nfs_pgio_header *(*rw_alloc_header)(void);
 	void (*rw_free_header)(struct nfs_pgio_header *);
-	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 *,
+	void (*rw_release)(struct nfs_pgio_header *);
+	int  (*rw_done)(struct rpc_task *, struct nfs_pgio_header *,
+			struct inode *);
+	void (*rw_result)(struct rpc_task *, struct nfs_pgio_header *);
+	void (*rw_initiate)(struct nfs_pgio_header *, struct rpc_message *,
 			    struct rpc_task_setup *, int);
 };