From mboxrd@z Thu Jan 1 00:00:00 1970 From: Amir Goldstein Subject: Next3 on-disk format change request Date: Tue, 22 Jun 2010 13:30:54 +0300 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: Andreas Dilger , Ext4 Developers List To: Theodore Tso Return-path: Received: from mail-bw0-f46.google.com ([209.85.214.46]:56896 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754010Ab0FVKa5 (ORCPT ); Tue, 22 Jun 2010 06:30:57 -0400 Received: by bwz7 with SMTP id 7so1331406bwz.19 for ; Tue, 22 Jun 2010 03:30:55 -0700 (PDT) Sender: linux-ext4-owner@vger.kernel.org List-ID: Hi Ted, As you may have read, Next3 release 1.0.11 automatically migrates to new on-disk format. (see http://next3.sf.net) Also, I would like to ask you again to promote Next3/Ext4 merge as a topic on LSF, if you think it is an appropriate topic. My on-disk format change request is to re-assign a ro_compat feature for IS_SNAPSHOT (currently in s_flags). The reason for this request is the following scenario, which was posted on next3-users list: "If I use dd to restore a full snapshot image to another volume, can I mount it as Next3?" The answer to this question is that read-only mount is ok, but for read-write mount, fsck needs to be run first to fix the free blocks counters. The restored image is identified with the IS_SNAPSHOT flag. If it was a ro_compat feature, it would prevent users from mistakingly mounting it read-write before the fix. Also, 'tune2fs -O ^is_snapshot' could be used to fix the counters, without running full fsck. Please assign me a constant for the feature if you agree, Thanks, Amir.