NFS: Make nfs_updatepage() mark the page as dirty.

This will ensure that we can call set_page_writeback() from within
nfs_writepage(), which is always called with the page lock set.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index d111be6..2e555d4 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -31,6 +31,7 @@
 #define PG_NEED_COMMIT		1
 #define PG_NEED_RESCHED		2
 #define PG_NEED_FLUSH		3
+#define PG_FLUSHING		4
 
 struct nfs_inode;
 struct nfs_page {