Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753410AbaFDQ2o (ORCPT ); Wed, 4 Jun 2014 12:28:44 -0400 Received: from mail-pd0-f176.google.com ([209.85.192.176]:50754 "EHLO mail-pd0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751948AbaFDQ2n (ORCPT ); Wed, 4 Jun 2014 12:28:43 -0400 Message-ID: <538F4938.7040309@kernel.dk> Date: Wed, 04 Jun 2014 10:28:40 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Ming Lei CC: Christoph Hellwig , Shaohua Li , Linux Kernel Mailing List Subject: Re: [patch]blk-mq: blk_mq_tag_to_rq should handle flush request References: <20140509120733.GA27918@kernel.org> <20140509150018.GA26215@infradead.org> <20140510040023.GA13788@kernel.org> <5388912F.7010609@kernel.dk> <20140604111133.GA7826@infradead.org> <538F2A11.4060800@kernel.dk> <20140604142012.GA20056@infradead.org> <538F331F.60101@kernel.dk> <20140604145803.GA7826@infradead.org> <538F34FB.7050003@kernel.dk> <20140604153159.GA27096@infradead.org> <538F3FB5.2020102@kernel.dk> <538F44AD.4090906@kernel.dk> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/04/2014 10:26 AM, Ming Lei wrote: > On Thu, Jun 5, 2014 at 12:09 AM, Jens Axboe wrote: >> On 06/04/2014 10:00 AM, Ming Lei wrote: >>> On Wed, Jun 4, 2014 at 11:48 PM, Jens Axboe wrote: >>>> On 06/04/2014 09:43 AM, Ming Lei wrote: >>>>> On Wed, Jun 4, 2014 at 11:31 PM, Christoph Hellwig wrote: >>>>>> On Wed, Jun 04, 2014 at 09:02:19AM -0600, Jens Axboe wrote: >>>>>>>> scsi_mq_find_tag only gets the scsi host, which may have multiple >>>>>>>> queues. When called from scsi_find_tag we actually have a scsi device, >>>>>>>> so that's not an issue, but when called from scsi_host_find_tag the >>>>>>>> driver only provides the host. >>>>>>> >>>>>>> Only solution I see right now is to have the flush_rq in the shared >>>>>>> tags, but that would potentially be a regression for multiple >>>>>>> devices and heavy flush uses cases. I'll see if I can come up with >>>>>>> something better, or maybe Shaohua has an idea. >>>>>> >>>>>> What about something like the following (untest, uncompiled, maybe >>>>>> pseudo-code): >>>>>> >>>>>> struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag) >>>>>> { >>>>>> struct request *rq = tags->rqs[tag]; >>>>>> >>>>>> if ((rq->cmd_flags & REQ_FLUSH_SEQ) && rq->q->flush_rq->tag == tag) >>>>>> return rq->q->flush_rq; >>>>>> return rq; >>>>>> } >>>>> >>>>> Looks we thought it together, :-) >>>>> >>>>> Also maybe the flush_rq->tag need to be cleared in flush_end_io(). >>>> >>>> It clears the command flag, so that should be enough. >>> >>> Only the flush_rq's command flag is cleared, and its parent request >>> flag isn't cleared. >> >> Good point. Care to send in a patch? We can just clear it to -1U, at >> least in blk-mq that's defined as an invalid tag. > > Attachment patch should be enough. Yep, looks fine. Care to send as a proper patch, then I will include it? -- 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/