From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alasdair G Kergon Subject: Re: [dm-devel] [RFC] dm-bow working prototype Date: Thu, 25 Oct 2018 01:01:23 +0100 Message-ID: <20181025000123.GB22722@agk-dp.fab.redhat.com> 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 Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: linux-raid.ids 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