From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [PATCH 3/5] aacraid: update dma mapping Date: Wed, 30 Nov 2005 12:45:27 -0600 Message-ID: <1133376327.3312.43.camel@mulgrave> References: <1133375778.2288.23.camel@markh1.pdx.osdl.net> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from stat9.steeleye.com ([209.192.50.41]:15768 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S1751489AbVK3Spf (ORCPT ); Wed, 30 Nov 2005 13:45:35 -0500 In-Reply-To: <1133375778.2288.23.camel@markh1.pdx.osdl.net> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Mark Haverkamp Cc: linux-scsi , Mark Salyzyn On Wed, 2005-11-30 at 10:36 -0800, Mark Haverkamp wrote: > This patch changes map_single to map_page in compliance with > recommendations made in the IO-Perf howto document to prevent bounce > buffering of DMA requests. Erm, there's a misunderstanding somewhere. You're replacing correct pci_map_single calls with its more difficult to use pci_map_page. This has absolutely zero performance impact and adds the risk that because pci_map_page is more complex to use, someone gets it wrong somewhere. Really, for block devices pci_map_single is the absolutely correct interface. pci_map_page should really only be used by the net stack for packet fragment mapping. James