NFS41/flexfiles: zero out DS write wcc

commit 54204010 upstream.

We do not want to update inode attributes with DS values.
Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/nfs/flexfilelayout/flexfilelayout.c

@@ -1039,6 +1039,8 @@ static int ff_layout_write_done_cb(struct rpc_task *task,
 	    hdr->res.verf->committed == NFS_DATA_SYNC)
 		ff_layout_set_layoutcommit(hdr);
 
+	/* zero out fattr since we don't care DS attr at all */
+	hdr->fattr.valid = 0;
 	if (task->tk_status >= 0)
 		nfs_writeback_update_inode(hdr);