Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030396AbbKFTGj (ORCPT ); Fri, 6 Nov 2015 14:06:39 -0500 Received: from mail-wm0-f44.google.com ([74.125.82.44]:34146 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030287AbbKFTGi (ORCPT ); Fri, 6 Nov 2015 14:06:38 -0500 Date: Fri, 6 Nov 2015 19:06:34 +0000 From: Sami Tolvanen To: Mikulas Patocka Cc: Milan Broz , device-mapper development , Mandeep Baines , Will Drewry , Kees Cook , Mike Snitzer , linux-kernel@vger.kernel.org, Alasdair Kergon , Mark Salyzyn Subject: Re: [PATCH 0/4] dm verity: add support for error correction Message-ID: <20151106190634.GA2813@google.com> References: <1446688954-29589-1-git-send-email-samitolvanen@google.com> <563B066C.6050202@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1725 Lines: 38 On Fri, Nov 06, 2015 at 12:23:29PM -0500, Mikulas Patocka wrote: > I'm also wondering what is this patch useful for. Disks and flash > controllers have their own error detection and correction I think I addressed this earlier. Some storage devices are able to correct bit flips, but don't have enough redundancy to correct larger errors. Using this patch set we can correct N MiB of consecutive corruption anywhere on the partition with the same amount of storage overhead. > Another point - if the read-only system partition is experiencing some > errors, than the read-write partition will probably have errors too On mobile devices, errors in read-only partitions often lead to bricked devices while errors in the read-write parts might only lead to lost cat photos. There are situations where people would prefer to have a working phone even if it fails to store some of their data. > Do you have some real case where such error corrections > increase longevity of some device? Yes, there have been several cases where read-only partition errors have rendered a device unusable. The sheer volume of mobile devices means that even if a tiny fraction of them suffer from such a problem, it's going to affect a large number of people. > But you can take raid5 in read-only mode, put it on several partitions > protected with dm-verity and you get decent error correction I agree. Unfortunately, we don't currently have the luxury of using raid on mobile devices. Sami -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/