From mboxrd@z Thu Jan 1 00:00:00 1970 From: hooanon05@yahoo.co.jp Subject: Re: [fuse-devel] delta filesystem prototype Date: Wed, 04 Mar 2009 01:02:42 +0900 Message-ID: <19966.1236096162@jrobl> References: <9884.1236069117@jrobl> <87r61ec1o7.fsf@frosties.localdomain> <7200.1236085884@jrobl> <1236094078.6988.3.camel@norville.austin.ibm.com> <19642.1236095410@jrobl> <1236095699.6988.6.camel@norville.austin.ibm.com> Cc: Goswin von Brederlow , Miklos Szeredi , linux-fsdevel@vger.kernel.org, fuse-devel@lists.sourceforge.net To: Dave Kleikamp Return-path: Received: from vsmtp01.dti.ne.jp ([202.216.231.136]:46846 "EHLO vsmtp01.dti.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754762AbZCCQC6 (ORCPT ); Tue, 3 Mar 2009 11:02:58 -0500 In-Reply-To: <1236095699.6988.6.camel@norville.austin.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Dave Kleikamp: > No. I was saying the opposite. Nothing that happens to the upper > address space would be visible to the lower address space. The upper > file could read from the lower file system on-demand as pages are > faulted. There is no need to copy everything at once. So you mean, - you have two mmap for a single file - the first mapping is done, it may map the file on the lower rdonly layer - the other mapping modifies the contents - when a page in the first mapping accessed again, the page is read from the upper layer. Right? J. R. Okajima