From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 9 Sep 2001 19:57:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 9 Sep 2001 19:56:57 -0400 Received: from humbolt.nl.linux.org ([131.211.28.48]:47880 "EHLO humbolt.nl.linux.org") by vger.kernel.org with ESMTP id ; Sun, 9 Sep 2001 19:56:43 -0400 Content-Type: text/plain; charset=US-ASCII From: Daniel Phillips To: Alan Cox , torvalds@transmeta.com (Linus Torvalds) Subject: Re: linux-2.4.10-pre5 Date: Mon, 10 Sep 2001 02:04:19 +0200 X-Mailer: KMail [version 1.3.1] Cc: adilger@turbolabs.com (Andreas Dilger), andrea@suse.de (Andrea Arcangeli), linux-kernel@vger.kernel.org (Kernel Mailing List) In-Reply-To: In-Reply-To: MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Message-Id: <20010909235703Z16150-26183+678@humbolt.nl.linux.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On September 10, 2001 01:54 am, Alan Cox wrote: > How do you plan to handle the situation where we have multiple instances > of the same 4K disk block each of which contains 1K of data in the > start of the page copy and 3K of zeroes. > > This isnt idle speculation - thing about BSD UFS fragments. This is handled the same way ReiserFS handles tail merging now - by instantiating multiple pages in the respective inode mappings with copies of the respective parts of the shared block, which stays in the physical block cashe (aka buffer cache). The dirty work is done by xxx_get_block. -- Daniel