From mboxrd@z Thu Jan 1 00:00:00 1970 From: jtk@us.ibm.com (John T. Kohl) Subject: Re: Wrapper fs Code (wrapfs) Date: 07 Aug 2006 16:35:23 -0400 Message-ID: <6coduw708k.fsf@sumu.lexma.ibm.com> References: <20060804060910.70648.qmail@web37515.mail.mud.yahoo.com> <20060804205715.GA18719@filer.fsl.cs.sunysb.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e32.co.us.ibm.com ([32.97.110.150]:37525 "EHLO e32.co.us.ibm.com") by vger.kernel.org with ESMTP id S932343AbWHGUf2 (ORCPT ); Mon, 7 Aug 2006 16:35:28 -0400 Received: from d03relay04.boulder.ibm.com (d03relay04.boulder.ibm.com [9.17.195.106]) by e32.co.us.ibm.com (8.12.11.20060308/8.12.11) with ESMTP id k77KZRox012389 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=FAIL) for ; Mon, 7 Aug 2006 16:35:28 -0400 Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay04.boulder.ibm.com (8.13.6/NCO/VER7.0) with ESMTP id k77KZQVf026894 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 7 Aug 2006 14:35:26 -0600 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id k77KZPv0006767 for ; Mon, 7 Aug 2006 14:35:26 -0600 To: Josef Sipek , linux-fsdevel@vger.kernel.org In-Reply-To: <20060804205715.GA18719@filer.fsl.cs.sunysb.edu> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org >>>>> "Josef" == Josef Sipek writes: Josef> That is an artifact of how the Linux VFS works. When you modify a Josef> file though wrapfs (or any other stackable file system) the Josef> wrapfs code gets called. It then calls the lower file system code Josef> on your behalf. When you modify the lower file directly, ext3 Josef> gets the called, but since Linux has no way for this change to be Josef> announced up the stack, wrapfs happily uses the old, cached Josef> data. If you have ideas about how to solve this, please share Josef> them - right now, there is a lot of work being done to get Josef> Unionfs (ours) and eCryptfs into the vanilla linux kernel. While constructed for a vnode system, the ideas in a set of Ficus-related papers and theses could be helpful here. This is John Heidemann's PhD thesis on the topic (covers necessary VM designs, callbacks, etc.): http://www.isi.edu/people/johnh/PAPERS/Heidemann95e.html -- John Kohl Senior Software Engineer - Rational Software - IBM Software Group Lexington, Massachusetts, USA jtk@us.ibm.com