From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261777AbVF0Uvo (ORCPT ); Mon, 27 Jun 2005 16:51:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261775AbVF0UvB (ORCPT ); Mon, 27 Jun 2005 16:51:01 -0400 Received: from rwcrmhc11.comcast.net ([204.127.198.35]:61363 "EHLO rwcrmhc11.comcast.net") by vger.kernel.org with ESMTP id S261689AbVF0UrZ (ORCPT ); Mon, 27 Jun 2005 16:47:25 -0400 Message-ID: <42C065D5.30805@namesys.com> Date: Mon, 27 Jun 2005 13:47:17 -0700 From: Hans Reiser User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.5) Gecko/20041217 X-Accept-Language: en-us, en MIME-Version: 1.0 To: "Theodore Ts'o" CC: Steve Lord , Markus T?rnqvist , Horst von Brand , David Masover , Alan Cox , Jeff Garzik , Christoph Hellwig , Andrew Morton , Linux Kernel Mailing List , ReiserFS List , vitaly@thebsh.namesys.com, Chris Mason Subject: Re: reiser4 plugins References: <42BB7B32.4010100@slaphack.com> <200506240334.j5O3YowB008100@laptop11.inf.utfsm.cl> <20050627092138.GD11013@nysv.org> <20050627124255.GB6280@thunk.org> <42C0578F.7030608@namesys.com> <42C05F16.5000804@xfs.org> <20050627202841.GA27805@thunk.org> In-Reply-To: <20050627202841.GA27805@thunk.org> X-Enigmail-Version: 0.90.1.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Theodore Ts'o wrote: >On Mon, Jun 27, 2005 at 03:18:30PM -0500, Steve Lord wrote: > > >>I presume Ted is referring to problems guaranteeing the integrity of >>the journal at recovery time. I am coming into this without all the >>available context, so I may be barking up the wrong tree.... In >>particular, I am not sure how journaling whole blocks protects >>you from this. >> >> > >Actually, I was talking about the problem what happens when power >fails while DMA'ing to the disk, and memory, which is more sensitive >to voltage drops than the rest of the system, starts sending garbage >to the bus, which the disk then faithfully writes to the inode table. > >As I recall, you were the one who told me about this problem, and how >it was fixed in Irix by using a powerfail interrupt to abort DMA >transfers, as well as giving me a program which tests for this >condition (basically it writes known test pattern to the disk, and >then you do an unclean shutdown, and you look to see if garbage is >written to the disk instead of one of the known test patterns). If it >wasn't you, it must have been Jim Mostek --- but I could have sworn it >was you..... > > - Ted > > > > Maybe a more positive approach would be to say, hey, I got this program from the XFS guys that tests for DMA problems on power failure, maybe all the Linux filesystem developers should give it a try? Shall we try that style of interaction? Ted, if this corruption hits an ext3 directory structure, and that corrupted directory structure commits, what happens? With ReiserFS (Chris please comment here) it would have to corrupt the directory in the journal, return successful IO, then after that point not corrupt the commit block and have enough power to write the commit block. How is that different for XFS or ext3? Hans