From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752880AbXCaLCM (ORCPT ); Sat, 31 Mar 2007 07:02:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752881AbXCaLCM (ORCPT ); Sat, 31 Mar 2007 07:02:12 -0400 Received: from e31.co.us.ibm.com ([32.97.110.149]:34416 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752879AbXCaLCL (ORCPT ); Sat, 31 Mar 2007 07:02:11 -0400 Date: Sat, 31 Mar 2007 16:39:35 +0530 From: Bharata B Rao To: Jan Engelhardt Cc: linux-kernel@vger.kernel.org, jblunck@suse.de Subject: Re: Heads up on VFS based union mount Message-ID: <20070331110935.GA5831@in.ibm.com> Reply-To: bharata@linux.vnet.ibm.com References: <20070330100854.GD16104@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 30, 2007 at 09:04:16PM +0200, Jan Engelhardt wrote: > > On Mar 30 2007 15:38, Bharata B Rao wrote: > > > >In union mount approach we maintain this stacking information in the > >dentry structure. When a filesytem is union mounted on a mountpoint, > >the dentry of the mount root would hold a reference to the mountpoint > >dentry as an overlaid dentry and these two dentries together form a > >union stack. Any subsequent readdir operation on this union mounted > >dentry would work on the overlaid dentry also thereby providing the > >merged view of the two filesystems. > > What about whiteouts? (I cannot remember whether Jan Blunk's paper > mentioned it at all.) We do have whiteout support. And as I mentioned earlier, the underlying filesystem needs to support the new 'whiteout' filetype. As of now it is supported for ext2, ext3 and ramfs. Regards, Bharata.