Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261444AbVDTGaz (ORCPT ); Wed, 20 Apr 2005 02:30:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261451AbVDTGac (ORCPT ); Wed, 20 Apr 2005 02:30:32 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:65441 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S261444AbVDTGaR (ORCPT ); Wed, 20 Apr 2005 02:30:17 -0400 Date: Wed, 20 Apr 2005 08:30:10 +0200 From: Jens Axboe To: Tejun Heo Cc: James.Bottomley@steeleye.com, Christoph Hellwig , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH scsi-misc-2.6 01/05] scsi: make blk layer set REQ_SOFTBARRIER when a request is dispatched Message-ID: <20050420063009.GB9371@suse.de> References: <20050419231435.D85F89C0@htj.dyndns.org> <20050419231435.2DEBE102@htj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050419231435.2DEBE102@htj.dyndns.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2019 Lines: 51 On Wed, Apr 20 2005, Tejun Heo wrote: > 01_scsi_blk_make_started_requests_ordered.patch > > Reordering already started requests is without any real > benefit and causes problems if the request has its > driver-specific resources allocated (as in SCSI). This patch > makes elv_next_request() set REQ_SOFTBARRIER automatically > when a request is dispatched. > > As both as and cfq schedulers don't allow passing requeued > requests, the only behavior change is that requests deferred > by prep_fn won't be passed by other requests. This change > shouldn't cause any problem. The only affected driver other > than SCSI is i2o_block. > > Signed-off-by: Tejun Heo > > elevator.c | 8 ++++---- > 1 files changed, 4 insertions(+), 4 deletions(-) > > Index: scsi-reqfn-export/drivers/block/elevator.c > =================================================================== > --- scsi-reqfn-export.orig/drivers/block/elevator.c 2005-04-20 08:13:01.000000000 +0900 > +++ scsi-reqfn-export/drivers/block/elevator.c 2005-04-20 08:13:33.000000000 +0900 > @@ -370,11 +370,11 @@ struct request *elv_next_request(request > > while ((rq = __elv_next_request(q)) != NULL) { > /* > - * just mark as started even if we don't start it, a request > - * that has been delayed should not be passed by new incoming > - * requests > + * just mark as started even if we don't start it. > + * also, as a request that has been delayed should not > + * be passed by new incoming requests, set softbarrier. > */ > - rq->flags |= REQ_STARTED; > + rq->flags |= REQ_STARTED | REQ_SOFTBARRIER; > > if (rq == q->last_merge) > q->last_merge = NULL; Do it on requeue, please - not on the initial spotting of the request. -- 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/