From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030435AbWGUBia (ORCPT ); Thu, 20 Jul 2006 21:38:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030434AbWGUBia (ORCPT ); Thu, 20 Jul 2006 21:38:30 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:20066 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S1030431AbWGUBi3 (ORCPT ); Thu, 20 Jul 2006 21:38:29 -0400 Date: Fri, 21 Jul 2006 03:38:23 +0200 From: Jens Axboe To: Jeff Garzik Cc: James Bottomley , Ed Lin , "linux-scsi@vger.kernel.org" , hch , linux-kernel , akpm , promise_linux Subject: Re: [PATCH] Promise 'stex' driver Message-ID: <20060721013822.GA25504@suse.de> References: <44BFF539.4000700@garzik.org> <1153439728.4754.19.camel@mulgrave> <44C01CD7.4030308@garzik.org> <20060721010724.GB24176@suse.de> <44C02D1E.4090206@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <44C02D1E.4090206@garzik.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 20 2006, Jeff Garzik wrote: > Jens Axboe wrote: > >On Thu, Jul 20 2006, Jeff Garzik wrote: > >>James Bottomley wrote: > >>>On Thu, 2006-07-20 at 17:27 -0400, Jeff Garzik wrote: > >>>>Since _no individual SCSI driver_ uses the block layer > >>>>tagging, it is likely that some instability and core kernel > >>>>development > >>>>will occur, in order to make that work. > >>>That's not quite true: 53c700 and tmscsim both use it ... I could with > >>>the usage were wider, but at least 53c700 has pretty regular and > >>>constant usage ... enough I think to validate the block tag code (it's > >>>been using it for the last three years). > >>Not for the case being discussed in this thread, adapter-wide tags. > > > >That just means the map is shared, otherwise there should be little if > >any difference. > > > >>AFAICS, no file in include/scsi/* or drivers/scsi/* ever calls > >>blk_queue_init_tags() with a non-NULL third arg. > > > >grpe again, it's in scsi_tcq.h. > > What tree are you looking at? > > There is only one user in the entire tree, and NULL is hardcoded as the > third arg. This is 2.6.18-rc2: Sorry, missed your non-NULL statement, I thought you meant in generel. As long as you get the locking right for the map access, there's really nothing that seperates shared vs non-shared tag mappings. So I don't think it's a big deal. If we don't encourage new drivers to use the block layer tagging, we might as well not bother with it. -- Jens Axboe