From: Andreas Dilger Subject: Re: jbd2 inside a device mapper module Date: Sat, 27 Dec 2008 13:01:27 -0700 Message-ID: <20081227200127.GX5000@webber.adilger.int> References: <20081224211038.GT4127@blitiri.com.ar> <20081224234915.GA23723@mit.edu> <20081225143535.GA4127@blitiri.com.ar> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7BIT Cc: Theodore Tso , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com To: Alberto Bertogli , Alex Zhuravlev Return-path: Received: from sca-es-mail-2.Sun.COM ([192.18.43.133]:46934 "EHLO sca-es-mail-2.sun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753286AbYL0UBq (ORCPT ); Sat, 27 Dec 2008 15:01:46 -0500 In-reply-to: <20081225143535.GA4127@blitiri.com.ar> Content-disposition: inline Sender: linux-ext4-owner@vger.kernel.org List-ID: On Dec 25, 2008 12:35 -0200, Alberto Bertogli wrote: > On Wed, Dec 24, 2008 at 06:49:15PM -0500, Theodore Tso wrote: > > I have no idea why you would need to do manual __breads(). No doubt > > I'm missing some context here. > > I'm writing (just for fun and learning purposes) a device mapper module > that stores checksums on writes and verifies them on reads. The > integrity metadata (currently just the checksum) is interleaved in the > backing device: one sector holding the integrity metadata for the > following 64 data sectors. Alex and I discussed implementing checksums for ext4 using an external device like this, and he might have some more design information for you. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc.