From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boaz Harrosh Subject: Re: [PATCH] [14/20] Don't disable direct_io for unchecked_isa_dma in st.c Date: Mon, 17 Mar 2008 14:21:02 +0200 Message-ID: <47DE622E.2000909@panasas.com> References: <20080307175414.08C981B41AE@basil.firstfloor.org> <20080314135135.GT17940@kernel.dk> <20080314142412.GA30325@infradead.org> <20080317195459I.tomof@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from bzq-219-195-70.pop.bezeqint.net ([62.219.195.70]:52751 "EHLO bh-buildlin2.bhalevy.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752797AbYCQMWl (ORCPT ); Mon, 17 Mar 2008 08:22:41 -0400 In-Reply-To: <20080317195459I.tomof@acm.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: FUJITA Tomonori Cc: hch@infradead.org, jens.axboe@oracle.com, andi@firstfloor.org, James.Bottomley@HansenPartnership.com, linux-scsi@vger.kernel.org, michaelc@cs.wisc.edu, tomof@acm.org On Mon, Mar 17 2008 at 12:55 +0200, FUJITA Tomonori wrote: > On Fri, 14 Mar 2008 10:24:12 -0400 > Christoph Hellwig wrote: > >> On Fri, Mar 14, 2008 at 02:51:35PM +0100, Jens Axboe wrote: >>> Are you sure? Seems to me that st builds its own list with >>> get_user_pages() for direct io, where will that get bounced? The block >>> layer will only bounce things that are mapped directly, so if st used >>> blk_rq_map_kern() and inserted that request in the queue, we could >>> proceed with killing that check in st. >> Which shouldn't be all too difficult and would be the right thing to >> do. We really need someone to sit down and convert st/osst/sg to use >> the proper block layer helpers. > > I've been working on this (hopefully, I'll submit an updated patchset > this week). > > I think that the main problem was a lack of motivation for these > changes. I bet that nobody reviewed the patchset that Mike posted the > last time. Hopefully, the new patchset will be reviewed and merged. > I have ran and tested these patches for a long time, in my personal workstation (long story). I had no problems with them. Burn CDs and all. > With sg chaining, drain, padding, etc, building a scatterlist is much > complicated than in the past. I believe that we should kill home-made > scatterlist code and convert the users to use the block layer to avoid > potential scatterlist bugs. > -- Definitely, as I remember, Mike's code just prepares BIO's and requests and completely avoids any use of sg-lists. I will be waiting for your patches and will test them here. Thanks Boaz