From: Andreas Dilger Subject: Re: [PATCH 3/4] e2fsprogs: Make mke2fs use undo I/O manager. Date: Wed, 1 Aug 2007 02:14:09 -0500 Message-ID: <20070801071409.GR5469@schatzie.adilger.int> References: <70b3f394cda275d59094d52f60d1ee76492033fc.1185933778.git.aneesh.kumar@linux.vnet.ibm.com> <20070801060439.GP5469@schatzie.adilger.int> <46B024A9.1080000@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: tytso@mit.edu, linux-ext4@vger.kernel.org To: "Aneesh Kumar K.V" Return-path: Received: from mail.clusterfs.com ([74.0.229.162]:56954 "EHLO mail.clusterfs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753610AbXHAHOu (ORCPT ); Wed, 1 Aug 2007 03:14:50 -0400 Content-Disposition: inline In-Reply-To: <46B024A9.1080000@linux.vnet.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Aug 01, 2007 11:44 +0530, Aneesh Kumar K.V wrote: > Andreas Dilger wrote: > >On Aug 01, 2007 07:34 +0530, Aneesh Kumar K.V wrote: > >>When running mke2fs, if a file system is detected > >>on the device, we use Undo I/O manager as the io manager. > >>This helps in reverting the changes made to the filesystem > >>in case we wrongly selected the device. > >> > >>The environment variable MKE2FS_SCRATCH_DIR > >>is used to indicate the directory within which the tdb > >>file need to be created. The file will be named mke2fs-XXXXXX > > > >It might be more useful to have "mke2fs-{dev}-{timestamp}" as > >the filename, so that it is clear where the image came from. > > > > I added it as a FIXME!! in the code. So i was intending to do it. > > + /* FIXME!! Should we generate Unique file name ?? */ > + sprintf(tdb_file, "%s/mke2fs-XXXXXX", tdb_dir); I don't think the "uniqueness" is as important as the fact that having the dev and timestamp makes it easier to know which undo file is related to a particular filesystem. In that regard, the undo file should also contain the filesystem UUID in addition to the mtime to ensure it is being replayed on the same filesystem. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc.