From: "Aneesh Kumar K.V" Subject: Re: [PATCH 2/4] e2fsprogs: Add undoe2fs Date: Wed, 01 Aug 2007 11:46:25 +0530 Message-ID: <46B02539.5020505@linux.vnet.ibm.com> References: <47f96570519d76b8d59f92b729a0a48c4a1b68d8.1185933778.git.aneesh.kumar@linux.vnet.ibm.com> <20070801060211.GO5469@schatzie.adilger.int> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: tytso@mit.edu, linux-ext4@vger.kernel.org To: Andreas Dilger Return-path: Received: from ausmtp06.au.ibm.com ([202.81.18.155]:59846 "EHLO ausmtp06.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754304AbXHAGSW (ORCPT ); Wed, 1 Aug 2007 02:18:22 -0400 Received: from d23relay01.au.ibm.com (d23relay01.au.ibm.com [202.81.18.232]) by ausmtp06.au.ibm.com (8.13.8/8.13.8) with ESMTP id l716KmCe5406872 for ; Wed, 1 Aug 2007 16:20:48 +1000 Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.250.237]) by d23relay01.au.ibm.com (8.13.8/8.13.8/NCO v8.4) with ESMTP id l716Fkfb210978 for ; Wed, 1 Aug 2007 16:15:46 +1000 Received: from d23av04.au.ibm.com (loopback [127.0.0.1]) by d23av04.au.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id l716GXvh030618 for ; Wed, 1 Aug 2007 16:16:33 +1000 In-Reply-To: <20070801060211.GO5469@schatzie.adilger.int> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Andreas Dilger wrote: > On Aug 01, 2007 07:34 +0530, Aneesh Kumar K.V wrote: >> undoe2fs can be used to replay the transaction saved >> in the transaction file using undo I/O Manager > > This should save the mtime of the superblock, and only do the undo > step if the filesystem hasn't changed. Otherwise it could seriously > corrupt the filesystem. I am not sure i understand this. The Undo I/O manager tracks all the write happening to the file system and copy the original content of the blocks to the tdb file. Undoe2fs simply copies these blocks back to the file system. So That way if you look at undoe2fs it doesn't have any knowledge of the file system at all. Can you let me know a use case where this will fail. -aneesh