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/fs/nfs/inode.c b/fs/nfs/inode.c
index 60f9076..f1fc0e4 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -133,11 +133,12 @@
 	nfs_clear_inode(inode);
 }
 
-static int nfs_sync_inode(struct inode *inode)
+int nfs_sync_inode(struct inode *inode)
 {
 	nfs_inode_dio_wait(inode);
 	return nfs_wb_all(inode);
 }
+EXPORT_SYMBOL_GPL(nfs_sync_inode);
 
 /**
  * nfs_sync_mapping - helper to flush all mmapped dirty data to disk