Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932388AbVKOMAP (ORCPT ); Tue, 15 Nov 2005 07:00:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932386AbVKOMAO (ORCPT ); Tue, 15 Nov 2005 07:00:14 -0500 Received: from ns.virtualhost.dk ([195.184.98.160]:47471 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S932382AbVKOMAM (ORCPT ); Tue, 15 Nov 2005 07:00:12 -0500 Date: Tue, 15 Nov 2005 13:00:16 +0100 From: Jens Axboe To: Jeff Garzik Cc: Tejun Heo , linux-ide@vger.kernel.org, lkml , SCSI Mailing List Subject: Re: [PATCH] libata error handling fixes (ATAPI) Message-ID: <20051115120016.GD7787@suse.de> References: <20051114195717.GA24373@havoc.gtf.org> <20051115074148.GA17459@htj.dyndns.org> <4379AA5B.1060900@pobox.com> <4379B28E.9070708@gmail.com> <4379C062.3010302@pobox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4379C062.3010302@pobox.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1921 Lines: 41 On Tue, Nov 15 2005, Jeff Garzik wrote: > >For departure of libata from SCSI, I was thinking more of another more > >generic block device framework in which libata can live in. And I > >thought that it was reasonable to assume that the framework would supply > >a EH mechanism which supports queue stalling/draining and separate > >thread. So, my EH patches tried to make the same environment for libata > > A big reason why libata uses the SCSI layer is infrastructure like this. > It would certainly be nice to see timeouts and EH at the block layer. > The block layer itself already supports queue stalling/draining. I have a pretty simple plan for this: - Add a timer to struct request. It already has a timeout field for SG_IO originated requests, we could easily utilize this in general. I'm not sure how the querying of timeout would happen so far, it would probably require a q->set_rq_timeout() hook to ask the low level driver to set/return rq->timeout for a given request. - Add a timeout hook to struct request_queue that would get invoked from the timeout handler. Something along the lines of: - Timeout on a request happens. Freeze the queue and use kblockd to take the actual timeout into process context, where we call the queue ->rq_timeout() hook. Unfreeze/reschedule queue operations based on what the ->rq_timeout() hook tells us. That is generic enough to be able to arm the timeout automatically from ->elevator_activate_req_fn() and dearm it when it completes or gets deactivated. It should also be possible to implement the SCSI error handling on top of that. -- 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/