Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756242AbXJ3X2e (ORCPT ); Tue, 30 Oct 2007 19:28:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751904AbXJ3X20 (ORCPT ); Tue, 30 Oct 2007 19:28:26 -0400 Received: from mx1.redhat.com ([66.187.233.31]:39458 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751377AbXJ3X2Z (ORCPT ); Tue, 30 Oct 2007 19:28:25 -0400 Date: Tue, 30 Oct 2007 23:26:17 +0000 From: Alasdair G Kergon To: Vasily Averin Cc: Andrew Morton , dm-devel@redhat.com, linux-kernel@vger.kernel.org, devel@openvz.org, stable@kernel.org, Jens Axboe , Milan Broz Subject: Re: [dm-devel] Re: dm: bounce_pfn limit added Message-ID: <20071030232617.GJ10006@agk.fab.redhat.com> Mail-Followup-To: Vasily Averin , Andrew Morton , dm-devel@redhat.com, linux-kernel@vger.kernel.org, devel@openvz.org, stable@kernel.org, Jens Axboe , Milan Broz References: <47257E4B.4080904@sw.ru> <20071030131138.3ba59731.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071030131138.3ba59731.akpm@linux-foundation.org> User-Agent: Mutt/1.4.1i Organization: Red Hat UK Ltd. Registered in England and Wales, number 03798903. Registered Office: Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE. Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1277 Lines: 26 On Tue, Oct 30, 2007 at 01:11:38PM -0700, Andrew Morton wrote: > On Mon, 29 Oct 2007 09:31:39 +0300 > Vasily Averin wrote: > > Device mapper uses its own bounce_pfn that may differ from one on underlying > > device. In that way dm can build incorrect requests that contain sg elements > > greater than underlying device is able to handle. > > This is the cause of slab corruption in i2o layer, occurred on i386 arch when > > very long direct IO requests are addressed to dm-over-i2o device. Interesting. When this patch was originally proposed a couple of years ago, we did this instead: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=daef265f1590cf3e6de989d074041a280c82d58b;hp=00d6da9b4d6707b808481372537adb0fb38f99b3 ) DM doesn't need to bounce bio's on its own, but the block layer defaults ) to that in blk_queue_make_request(). The lower level drivers should ) bounce ios themselves, that is what they need to do if not layered below ) dm anyways. Alasdair -- agk@redhat.com - 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/