From: Alasdair G Kergon Subject: Re: [dm-devel] Ext4 and xfs problems in dm-thin on allocation and discard Date: Tue, 19 Jun 2012 17:03:01 +0100 Message-ID: <20120619160300.GF14208@agk-dp.fab.redhat.com> References: <4FDF9EBE.2030809@shiftmail.org> <20120619141933.GC10637@thunk.org> <20120619144316.GD14208@agk-dp.fab.redhat.com> <20120619152856.GB7225@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: =?utf-8?B?THVrw6HFoQ==?= Czerner , linux-ext4@vger.kernel.org, xfs@oss.sgi.com, Spelic To: device-mapper development Return-path: Received: from mx1.redhat.com ([209.132.183.28]:36674 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751792Ab2FSQDK (ORCPT ); Tue, 19 Jun 2012 12:03:10 -0400 Content-Disposition: inline In-Reply-To: <20120619152856.GB7225@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Jun 19, 2012 at 11:28:56AM -0400, Mike Snitzer wrote: > That is an lvm2 BZ but there is further kernel work needed. In principle, userspace should already be able to handle the replumbing I think. (But when we work through the details of an online import, perhaps we'll want some further kernel change for atomicity/speed reasons? In particular we need to be able to do the last part of the metadata merge quickly.) Roughly: 1. rejig the lvm metadata for the new configuration [lvm] - appends the "whole LV" data to the pool's data 2. Generate metadata for the appended data and append this to the metadata area [dmpd] 3. suspend all the affected devices [lvm] 4. link the already-prepared metadata into the existing metadata [dmpd] 5. resume all the devices (now using the new extended pool) Alasdair