From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dkim1.fusionio.com ([66.114.96.53]:35094 "EHLO dkim1.fusionio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755107Ab3FGOjT (ORCPT ); Fri, 7 Jun 2013 10:39:19 -0400 Received: from mx1.fusionio.com (unknown [10.101.1.160]) by dkim1.fusionio.com (Postfix) with ESMTP id 5335B7C0353 for ; Fri, 7 Jun 2013 08:39:19 -0600 (MDT) Date: Fri, 7 Jun 2013 10:39:16 -0400 From: Josef Bacik To: Stefan Behrens CC: "linux-btrfs@vger.kernel.org" Subject: Re: [PATCH v4 6/8] Btrfs: introduce uuid-tree-gen field Message-ID: <20130607143916.GE29248@localhost.localdomain> References: <49cfd0aca92177345f59f3f700f6d43f8445f405.1370534938.git.sbehrens@giantdisaster.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" In-Reply-To: <49cfd0aca92177345f59f3f700f6d43f8445f405.1370534938.git.sbehrens@giantdisaster.de> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Fri, Jun 07, 2013 at 04:27:51AM -0600, Stefan Behrens wrote: > In order to be able to detect the case that a filesystem is mounted > with an old kernel, add a uuid-tree-gen field like the free space > cache is doing it. It is part of the super block and written with > each commit. Old kernels do not know this field and don't update it. > So to get around the whole crashing before we finish creating the uuid tree maybe set some flag or something that doesn't actually set the super->uuid_tree_generation until _after_ it finishes populating the tree, and then have the scan deal with having a half populated tree. Just an idea, but we have to deal with it some way. Thanks, Josef