NFS: Clean up - simplify the switch to read/write-through-MDS

Use nfs_pageio_reset_read_mds and nfs_pageio_reset_write_mds instead of
completely reinitialising the struct nfs_pageio_descriptor.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 93c7329..38e5508 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -1075,7 +1075,7 @@
 					   GFP_KERNEL);
 	/* If no lseg, fall back to read through mds */
 	if (pgio->pg_lseg == NULL)
-		nfs_pageio_init_read_mds(pgio, pgio->pg_inode);
+		nfs_pageio_reset_read_mds(pgio);
 
 }
 EXPORT_SYMBOL_GPL(pnfs_generic_pg_init_read);
@@ -1093,7 +1093,7 @@
 					   GFP_NOFS);
 	/* If no lseg, fall back to write through mds */
 	if (pgio->pg_lseg == NULL)
-		nfs_pageio_init_write_mds(pgio, pgio->pg_inode, pgio->pg_ioflags);
+		nfs_pageio_reset_write_mds(pgio);
 }
 EXPORT_SYMBOL_GPL(pnfs_generic_pg_init_write);