Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752458AbaFDQJU (ORCPT ); Wed, 4 Jun 2014 12:09:20 -0400 Received: from mail-pd0-f172.google.com ([209.85.192.172]:53736 "EHLO mail-pd0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751376AbaFDQJT (ORCPT ); Wed, 4 Jun 2014 12:09:19 -0400 Message-ID: <538F44AD.4090906@kernel.dk> Date: Wed, 04 Jun 2014 10:09:17 -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> In-Reply-To: Content-Type: text/plain; charset=UTF-8 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 10:00 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. -- 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/