From: Theodore Tso Subject: Re: Mentor for a GSoC application wanted (Online ext2/3 filesystem checker) Date: Fri, 18 Apr 2008 21:29:52 -0400 Message-ID: <20080419012952.GE25797@mit.edu> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, linux-fsdev@vger.kernel.org, Rik van Riel To: Alexey Zaytsev Return-path: Received: from BISCAYNE-ONE-STATION.MIT.EDU ([18.7.7.80]:65049 "EHLO biscayne-one-station.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751224AbYDSBbF (ORCPT ); Fri, 18 Apr 2008 21:31:05 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Apr 18, 2008 at 06:20:14PM +0400, Alexey Zaytsev wrote: > Hello, guys. > > It seems like the Linux-fountation was not able to find a mentor for > my project. If somebody is willing to mentor this project through the > Google Summer of Code, please contact Rik and me now, as little > time is left. > > A link to the application: > http://rom.etherboot.org/share/xl0/gsoc2008/application-linux-foundation.txt Hi Alexey, I really don't think your project is likely to be successful given the 3 month timeframe of a GSoC. At least not without a mentor spending vast amounts of time educating you about how things works within ext2 and e2fsck. Even given some broad hints about problems that you need to address, you still have not addressed how you will solve fundamental race conditions resulting from trying to read the multiple blocks scattered all over the disk which comprise allocation bitmap blocks while allocations might be taking place, for example. Your approach of monitoring writes to the buffer cache for metadata writes is completely busted; suppose the kernel modifies block #12345 in the filesystem; how do you know what that means? Could that be an indirect block? If so, to which inode does it belong? If all you are doing is monitoring metadata blocks, you would have no idea! The fact that it apparently didn't even occur to you that this might be a show-stopping problem scares the heck out of me. It leads me to believe that this project is very likely to fail, and/or will require vast amounts of time from the mentor. Unfortunately, the former is something that I just don't have this summer. Regards, - Ted