Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758234AbYGNV2N (ORCPT ); Mon, 14 Jul 2008 17:28:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756383AbYGNV16 (ORCPT ); Mon, 14 Jul 2008 17:27:58 -0400 Received: from mx1.redhat.com ([66.187.233.31]:54539 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753325AbYGNV15 (ORCPT ); Mon, 14 Jul 2008 17:27:57 -0400 Date: Mon, 14 Jul 2008 17:26:38 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@devserv.devel.redhat.com To: FUJITA Tomonori cc: davem@davemloft.net, andi@firstfloor.org, sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, jens.axboe@oracle.com Subject: Re: [SUGGESTION]: drop virtual merge accounting in I/O requests In-Reply-To: <20080715024424R.fujita.tomonori@lab.ntt.co.jp> Message-ID: References: <20080713.174119.71992292.davem@davemloft.net> <20080714111917S.fujita.tomonori@lab.ntt.co.jp> <20080713.202035.172246136.davem@davemloft.net> <20080715024424R.fujita.tomonori@lab.ntt.co.jp> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1419 Lines: 40 On Tue, 15 Jul 2008, FUJITA Tomonori wrote: > On Sun, 13 Jul 2008 20:20:35 -0700 (PDT) > David Miller wrote: > >> From: FUJITA Tomonori >> Date: Mon, 14 Jul 2008 11:19:02 +0900 >> >>> Now IOMMUs don't ignore the max_segment_size. We hit this problem. >> >> It seems simply that max_segment_size needs to propagate >> down into the block layer VMERGE code so that it can >> act accordingly. > > Yeah, I think so. I'll take care of that. > > But I think that even with the fix, SPARC64 IOMMU still hits the > problem. > > With the VMERGE accounting enabled, > > - an IOMMU must merge segments that the block layer expects the IOMMU > to merge. > > - an IOMMU must return an error if it can't merge such segments. > > But the current SPARC64 IOMMU code doesn't return an error if it can't > merge such segments (as POWER's IOMMU does, as you know). BTW. what should the block device driver do when it receives a mapping error? (if it aborts the request and it was write request, there will be data corruption). Is it even legal to return IOMMU error in case where no real hardware error or overflow happened? Mikulas -- 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/