Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762184AbYGOPce (ORCPT ); Tue, 15 Jul 2008 11:32:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755776AbYGOPbh (ORCPT ); Tue, 15 Jul 2008 11:31:37 -0400 Received: from sh.osrg.net ([192.16.179.4]:53701 "EHLO sh.osrg.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752437AbYGOPbf (ORCPT ); Tue, 15 Jul 2008 11:31:35 -0400 Date: Wed, 16 Jul 2008 00:30:43 +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: <20080715231956A.fujita.tomonori@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20080716003047P.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: 1185 Lines: 24 On Tue, 15 Jul 2008 10:37:58 -0400 (EDT) Mikulas Patocka wrote: > >>> This bug could happen on alpha, parisc, and sparc, which use VMERGE. > >> > >> Parisc doesn't use virtual merge accounting (there is variable for it but > >> it's always 0). > > > > Hmm, really? Looks like PARISC IOMMUs (ccio-dma.c and sba_iomm.c) set > > parisc_vmerge_boundary (CC'ed PARISC mailing list). > > That's right, I looked only at arch and include. > > >> On sparc64 it is broken anyway with or without your patch. > > > > Yeah, we need to modify SPARC64 IOMMU code (I'm not sure that it's > > worth). Right now, the best fix is setting BIO_VMERGE_BOUNDARY to 0. > > 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. -- 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/