Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757558AbYGPAfZ (ORCPT ); Tue, 15 Jul 2008 20:35:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754239AbYGPAfI (ORCPT ); Tue, 15 Jul 2008 20:35:08 -0400 Received: from sh.osrg.net ([192.16.179.4]:46518 "EHLO sh.osrg.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754050AbYGPAfG (ORCPT ); Tue, 15 Jul 2008 20:35:06 -0400 Date: Wed, 16 Jul 2008 09:34:36 +0900 To: mpatocka@redhat.com Cc: fujita.tomonori@lab.ntt.co.jp, jens.axboe@oracle.com, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, davem@davemloft.net, linux-parisc@vger.kernel.org Subject: Re: [PATCH] block: fix q->max_segment_size checking in blk_recalc_rq_segments about VMERGE From: FUJITA Tomonori In-Reply-To: References: <20080716003047P.fujita.tomonori@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20080716093456J.fujita.tomonori@lab.ntt.co.jp> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1149 Lines: 23 On Tue, 15 Jul 2008 11:46:46 -0400 (EDT) Mikulas Patocka wrote: > >> Even if we fix it now, the question is: how long it will stay fixed? Until > >> someone makes another change to struct device that restricts boundaries on > >> some wacky hardware. > > > > I'm not sure how the boundary restriction of a device can break > > the VMERGE accounting. > > Because block layer code doesn't know anything about the device, pci > access restrictions and so on. Not true, the block layer knows about the device restrictions like DMA boundary. But it's not the point here because the boundary restriction doesn't matter for the VMERGE accounting. An IOMMU just returns an error if it can't allocate an I/O space fit for the device restrictions. Please give me an example how the boundary restriction of a device can break the VMERGE accounting and an IOMMU if you aren't still sure. -- 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/