From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp208.alice.it ([82.57.200.104]:51862 "EHLO smtp208.alice.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753214Ab2GJRz2 (ORCPT ); Tue, 10 Jul 2012 13:55:28 -0400 Message-ID: <4FFC6C89.6030303@libero.it> Date: Tue, 10 Jul 2012 19:55:21 +0200 From: Goffredo Baroncelli Reply-To: kreijack@inwind.it MIME-Version: 1.0 To: Arnd Hannemann CC: Christian Robert , linux-btrfs@vger.kernel.org Subject: Re: 3.5.0-rc6: btrfs and LVM snapshots -> wrong devicename in /proc/mounts References: <4FFB59BF.1050104@arndnet.de> <4FFBA1C8.9020502@polymtl.ca> <4FFBED3C.3000302@arndnet.de> In-Reply-To: <4FFBED3C.3000302@arndnet.de> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 07/10/2012 10:52 AM, Arnd Hannemann wrote: > Hi, > > Am 10.07.2012 05:30, schrieb Christian Robert: >> I agree with you, but you should never mount a snapshot of a btrfs filesystem at the same time the original is, >> because both the original and the snapshot had same "device fsid 5c3e8ca2-da56-4ade-9fef-103a6a8a70c2" I think that the kernel should be smarter in this regard. At kernel level, as golden rule it should be not possible to add a duplicate fsid if the previous one is mounted. "btrfs dev scan" MUST return an error in this case. This in any case is an error. Today it seems that if a device with the same fsid is already registered, the new one overwrites the old one (or almost the name is overwritten). This could be acceptable if the filesystem is unmounted. I think that it is a serious error otherwise. >> >> the kernel will tkink twice and fold back to the same device. > > If that is correct the bug is that the kernel lets me mount the same device fsid on different devices twice. > >> >> btrsf does not behave like other filesystems, you can't snapshot a btrfs filesystem >> and hope to mount the snapshot somewhere else. > >> snapsoot also duplicate lots of things internally that have no sence in a snapshot (like raid level, single or multiple devies ...) > > I see. However, I expect a "simple" btrfs to just work or fail gracefully. > > Best regards, > Arnd > > -- > 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 > . >