From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id A49E47D082 for ; Thu, 25 Oct 2018 00:01:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726546AbeJYIbk (ORCPT ); Thu, 25 Oct 2018 04:31:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36334 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726497AbeJYIbk (ORCPT ); Thu, 25 Oct 2018 04:31:40 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1D33AC05090A; Thu, 25 Oct 2018 00:01:29 +0000 (UTC) Received: from agk-dp.fab.redhat.com (agk-dp.fab.redhat.com [10.33.15.10]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 274775D75D; Thu, 25 Oct 2018 00:01:25 +0000 (UTC) Received: from agk by agk-dp.fab.redhat.com with local (Exim 4.69) (envelope-from ) id 1gFT5X-00067Y-Qf; Thu, 25 Oct 2018 01:01:23 +0100 Date: Thu, 25 Oct 2018 01:01:23 +0100 From: Alasdair G Kergon To: Paul Lawrence Cc: Mikulas Patocka , Alasdair Kergon , Mike Snitzer , linux-doc@vger.kernel.org, kernel-team@android.com, Jonathan Corbet , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, dm-devel@redhat.com, Shaohua Li Subject: Re: [dm-devel] [RFC] dm-bow working prototype Message-ID: <20181025000123.GB22722@agk-dp.fab.redhat.com> Mail-Followup-To: Paul Lawrence , Mikulas Patocka , Alasdair Kergon , Mike Snitzer , linux-doc@vger.kernel.org, kernel-team@android.com, Jonathan Corbet , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, dm-devel@redhat.com, Shaohua Li References: <20181023212358.60292-1-paullawrence@google.com> <20181023221819.GB17552@agk-dp.fab.redhat.com> <296148c2-f2d9-5818-ea76-d71a0d6f5cd4@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Red Hat UK Ltd. Registered in England and Wales, number 03798903. Registered Office: Peninsular House, 30-36 Monument Street, 4th Floor, London, England, EC3R 8NB. User-Agent: Mutt/1.5.18 (2008-05-17) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Thu, 25 Oct 2018 00:01:29 +0000 (UTC) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Wed, Oct 24, 2018 at 03:24:29PM -0400, Mikulas Patocka wrote: > What about allocating a big file, using the FIEMAP ioctl to find the For reference, dmfilemapd in the lvm2 tree (in daemons/) uses FIEMAP (in libdm/libdm-stats.c) for monitoring I/O by file. > If you decide that rollback is no longer needed, you just unload the > snapshot target and delete the big file. If you decide that you want to > rollback, you can use the snapshot merge functionality (or you can write a > userspace utility that does offline merge). There's some old code from Mark McLoughlin for userspace snapshot merging here: https://people.gnome.org/~markmc/code/merge-dm-snapshot.c Alasdair