From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ea0-f178.google.com ([209.85.215.178]:55709 "EHLO mail-ea0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751279Ab3BJN10 (ORCPT ); Sun, 10 Feb 2013 08:27:26 -0500 Received: by mail-ea0-f178.google.com with SMTP id a14so2328834eaa.23 for ; Sun, 10 Feb 2013 05:27:25 -0800 (PST) Message-ID: <5117A071.8060607@gmail.com> Date: Sun, 10 Feb 2013 14:28:17 +0100 From: Goffredo Baroncelli Reply-To: kreijack@inwind.it MIME-Version: 1.0 To: =?UTF-8?B?UGlvdHIgUGF3xYJvdw==?= CC: Linux Btrfs Subject: Re: btrfs and LVM snapshots (Re: kernel BUG at fs/btrfs/extent-tree.c:1772) References: <55e4fbbdada4ee37bdccac2537683d83.squirrel@lampka.siedziba.pl> <20130204165825.GC2275@localhost.localdomain> <20130205135147.GD2275@localhost.localdomain> <5116EAA1.1030901@siedziba.pl> In-Reply-To: <5116EAA1.1030901@siedziba.pl> Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 02/10/2013 01:32 AM, Piotr Pawłow wrote: > Hello, >> Yeah you can't mount images, we clear out the chunk tree so >> nothing works. Let me know if you run into any problems in the >> future. Thanks, > > That's surprising, I haven't seen it mentioned anywhere. > > With any other filesystem I could use an LVM snapshot to save the > original state, but with a multi-device btrfs it would be very > risky. Origin and snapshot volumes could easily get mixed up by > kernel and tools. > > I tried that in qemu, and I've seen btrfs happily mount 1 origin and > 1 snapshot device as a single FS. And then I've seen it mount both > origin devices, even though one of them had old content. Naturally > it complained a lot about bad checksums. I can confirm that, even with a single-device btrfs filesystem. However I am curious why you want to use the lvm snapshot capability instead of the btrfs one. > > Is there any way to avoid such mix-ups? To somehow mark devices so > that btrfs would know these devices belong together? Btrfs assume that every device has an "unique" uuid. However when a device is snapshotted it uuid is copied too, so it is not unique any more. This is the reason of the btrfs confusing. > Regards -- To unsubscribe from this list: send the line "unsubscribe > linux-btrfs" in the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- gpg @keyserver.linux.it: Goffredo Baroncelli (kreijackATinwind.it> Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5 ss