Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932893AbWLSSnM (ORCPT ); Tue, 19 Dec 2006 13:43:12 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932891AbWLSSnM (ORCPT ); Tue, 19 Dec 2006 13:43:12 -0500 Received: from brick.kernel.dk ([62.242.22.158]:16788 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932886AbWLSSnK (ORCPT ); Tue, 19 Dec 2006 13:43:10 -0500 Date: Tue, 19 Dec 2006 19:44:54 +0100 From: Jens Axboe To: Jon Escombe Cc: Arjan van de Ven , Dan Aloni , Linux Kernel List , linux-scsi@vger.kernel.org, Mike Christie , Elias Oltmanns Subject: Re: [PATCH] scsi_execute_async() should add to the tail of the queue Message-ID: <20061219184453.GD5010@kernel.dk> References: <20061219083507.GA20847@localdomain> <1166522613.3365.1198.camel@laptopd505.fenrus.org> <20061219112649.GG5010@kernel.dk> <458830B9.90107@dresco.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <458830B9.90107@dresco.co.uk> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1832 Lines: 43 On Tue, Dec 19 2006, Jon Escombe wrote: > Jens Axboe wrote: > > On Tue, Dec 19 2006, Arjan van de Ven wrote: > >> On Tue, 2006-12-19 at 10:35 +0200, Dan Aloni wrote: > >>> Hello, > >>> > >>> scsi_execute_async() has replaced scsi_do_req() a few versions ago, > >>> but it also incurred a change of behavior. I noticed that over-queuing > >>> a SCSI device using that function causes I/Os to be starved from > >>> low-level queuing for no justified reason. > >>> > >>> I think it makes much more sense to perserve the original behaviour > >>> of scsi_do_req() and add the request to the tail of the queue. > >> Hi, > >> > >> some things should really be added to the head of the queue, like > >> maintenance requests and error handling requests. Are you sure this is > >> the right change? At least I'd expect 2 apis, one for a head and one for > >> a "normal" queueing... > > > > It does sounds broken - head insertion should only be used for careful > > internal commands, not be the default way user issued commands. Looking > > at the current users, the patch makes sense to me. > > > > It's worth noting that the hdaps disk protection patches rely on the > current behaviour to add 'IDLE IMMEDIATE WITH UNLOAD' commands to the > head of the queue.. Another function, or a new parameter for queue > position would be needed to retain this functionality - any preference > for either? The hdaps disk protection should not be using the SCSI internal function, so it should not be an issue. The block layer API exposes both front/back/sort insertion possibilities. -- Jens Axboe - 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/