From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: [PATCH] dc395x: Fix support for highmem Date: Wed, 16 Mar 2005 10:44:50 -0800 Message-ID: <42387EA2.5020106@us.ibm.com> References: <200503160209.j2G29cAf010870@hera.kernel.org> <20050316075839.GC7842@suse.de> <1110986016.5771.3.camel@mulgrave> <20050316160447.GU7842@suse.de> <20050316164806.GO21986@parcelfarce.linux.theplanet.co.uk> <20050316165338.GX7842@suse.de> <20050316170259.GA25056@infradead.org> <20050316170417.GY7842@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Received: from e31.co.us.ibm.com ([32.97.110.129]:31685 "EHLO e31.co.us.ibm.com") by vger.kernel.org with ESMTP id S262747AbVCPSo4 (ORCPT ); Wed, 16 Mar 2005 13:44:56 -0500 Received: from westrelay02.boulder.ibm.com (westrelay02.boulder.ibm.com [9.17.195.11]) by e31.co.us.ibm.com (8.12.10/8.12.9) with ESMTP id j2GIipua397588 for ; Wed, 16 Mar 2005 13:44:52 -0500 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by westrelay02.boulder.ibm.com (8.12.10/NCO/VER6.6) with ESMTP id j2GIipc3236784 for ; Wed, 16 Mar 2005 11:44:51 -0700 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.12.11/8.12.11) with ESMTP id j2GIiotw007791 for ; Wed, 16 Mar 2005 11:44:51 -0700 In-Reply-To: <20050316170417.GY7842@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Jens Axboe Cc: Christoph Hellwig , Matthew Wilcox , James Bottomley , SCSI Mailing List , g.liakhovetski@gmx.de Jens Axboe wrote: > On Wed, Mar 16 2005, Christoph Hellwig wrote: > >>On Wed, Mar 16, 2005 at 05:53:39PM +0100, Jens Axboe wrote: >> >>>The list doesn't really need dma mapping at that point, the problem here >>>is that the driver needs to punt to pio mode because of foo. So calling >>>pci/dma_map_* is pointless, since the CPU will have to do the transfer >>>anyways. What the driver is really looking for at this point, is a way >>>to map the pages in the sglist to a virtual address. >> >>Given that there's quite a few cases of this "problem" it would be nice >>to have common helpers for it. Especially as it's really difficult when >>we allow merging of sg list entries > > > I thought about that when writing the above, but is there really more > than one case for SCSI drivers? If there is, sure lets add the helpers. > But I would consider it a quite rare occurence, I've never seen it > before. > I got lost here. If you are talking about the need to kmap a sglist then software iscsi has it. iscsi-sfnet used to do while (...) kmap() but I fixed that (I think I need to use kmap_atomic though, is that correct or is it just a performance improvement - I am calling kmap from a thread too so). I just added kmap_atomic to open-iscsi and I believe pyx does something similar to the loop above.