NFSv4: Truncating file opens should also sync O_DIRECT writes

We don't just want to sync out buffered writes, but also O_DIRECT ones.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index b01ccf3..b638eb6 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -512,6 +512,7 @@
  * Try to write back everything synchronously (but check the
  * return value!)
  */
+extern int nfs_sync_inode(struct inode *inode);
 extern int nfs_wb_all(struct inode *inode);
 extern int nfs_wb_page(struct inode *inode, struct page* page);
 extern int nfs_wb_page_cancel(struct inode *inode, struct page* page);