Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754216AbaFDQ0Y (ORCPT ); Wed, 4 Jun 2014 12:26:24 -0400 Received: from mail-ve0-f181.google.com ([209.85.128.181]:48852 "EHLO mail-ve0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754199AbaFDQ0Q (ORCPT ); Wed, 4 Jun 2014 12:26:16 -0400 MIME-Version: 1.0 In-Reply-To: <538F44AD.4090906@kernel.dk> 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> Date: Thu, 5 Jun 2014 00:26:15 +0800 Message-ID: Subject: Re: [patch]blk-mq: blk_mq_tag_to_rq should handle flush request From: Ming Lei To: Jens Axboe Cc: Christoph Hellwig , Shaohua Li , Linux Kernel Mailing List Content-Type: multipart/mixed; boundary=bcaec51ba27b63502c04fb0516b9 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --bcaec51ba27b63502c04fb0516b9 Content-Type: text/plain; charset=UTF-8 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. Thanks, -- Ming Lei --bcaec51ba27b63502c04fb0516b9 Content-Type: text/x-patch; charset=US-ASCII; name="clear_flush_rq_tag.patch" Content-Disposition: attachment; filename="clear_flush_rq_tag.patch" Content-Transfer-Encoding: base64 X-Attachment-Id: f_hw0ukfp80 ZGlmZiAtLWdpdCBhL2Jsb2NrL2Jsay1mbHVzaC5jIGIvYmxvY2svYmxrLWZsdXNoLmMKaW5kZXgg ZmY4N2M2Ni4uOGZmZWU0YiAxMDA2NDQKLS0tIGEvYmxvY2svYmxrLWZsdXNoLmMKKysrIGIvYmxv Y2svYmxrLWZsdXNoLmMKQEAgLTIyNSw3ICsyMjUsNyBAQCBzdGF0aWMgdm9pZCBmbHVzaF9lbmRf aW8oc3RydWN0IHJlcXVlc3QgKmZsdXNoX3JxLCBpbnQgZXJyb3IpCiAKIAlpZiAocS0+bXFfb3Bz KSB7CiAJCXNwaW5fbG9ja19pcnFzYXZlKCZxLT5tcV9mbHVzaF9sb2NrLCBmbGFncyk7Ci0JCXEt PmZsdXNoX3JxLT5jbWRfZmxhZ3MgPSAwOworCQlxLT5mbHVzaF9ycS0+dGFnID0gLTE7CiAJfQog CiAJcnVubmluZyA9ICZxLT5mbHVzaF9xdWV1ZVtxLT5mbHVzaF9ydW5uaW5nX2lkeF07Cg== --bcaec51ba27b63502c04fb0516b9-- -- 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/