From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750881AbWGDIBU (ORCPT ); Tue, 4 Jul 2006 04:01:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750872AbWGDIBU (ORCPT ); Tue, 4 Jul 2006 04:01:20 -0400 Received: from outpipe-village-512-1.bc.nu ([81.2.110.250]:40902 "EHLO lxorguk.ukuu.org.uk") by vger.kernel.org with ESMTP id S1750837AbWGDIBT (ORCPT ); Tue, 4 Jul 2006 04:01:19 -0400 Subject: Re: ext4 features (checksums) From: Alan Cox To: Neil Brown Cc: Arjan van de Ven , Tomasz Torcz , Helge Hafting , Thomas Glanzmann , "Theodore Ts'o" , LKML In-Reply-To: <17577.43190.724583.146845@cse.unsw.edu.au> References: <20060701163301.GB24570@cip.informatik.uni-erlangen.de> <20060701170729.GB8763@irc.pl> <20060701174716.GC24570@cip.informatik.uni-erlangen.de> <20060701181702.GC8763@irc.pl> <20060703202219.GA9707@aitel.hist.no> <20060703205523.GA17122@irc.pl> <1151960503.3108.55.camel@laptopd505.fenrus.org> <1151964720.16528.22.camel@localhost.localdomain> <17577.43190.724583.146845@cse.unsw.edu.au> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Tue, 04 Jul 2006 09:17:46 +0100 Message-Id: <1152001067.28597.3.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.6.2 (2.6.2-1.fc5.5) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Ar Maw, 2006-07-04 am 09:31 +1000, ysgrifennodd Neil Brown: > It's been some years that I've felt that most 'logical volume > management' really belongs in the filesystem. > Why have a dm that chops devices up in to segments and assembles them to > look like a big device, only to have that big device chopped up and > presented as files. Seems like double handling to me. Because the interface model is wrong ? Various people have long said the model actually should look rather more like fs to block: handle = alloc_extent(near_handle*, info) write_extent(handle, buffer, offset, length) read_extent(handle, buffer, offset, length) free_extent(handle) (probably with resize_extent) This makes LVM, remapping, checksumming and the like all naturally slip out of the fs but not into the block layer. [Many very good points snipped]