From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8AD64C47404 for ; Mon, 7 Oct 2019 15:05:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 67CCA21479 for ; Mon, 7 Oct 2019 15:05:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728031AbfJGPFx (ORCPT ); Mon, 7 Oct 2019 11:05:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:16475 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728014AbfJGPFx (ORCPT ); Mon, 7 Oct 2019 11:05:53 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4B6703082132; Mon, 7 Oct 2019 15:05:53 +0000 (UTC) Received: from ming.t460p (ovpn-8-21.pek2.redhat.com [10.72.8.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D2B815C1D4; Mon, 7 Oct 2019 15:05:39 +0000 (UTC) Date: Mon, 7 Oct 2019 23:05:35 +0800 From: Ming Lei To: Hannes Reinecke Cc: Jens Axboe , linux-block@vger.kernel.org, John Garry , Bart Van Assche , Hannes Reinecke , Christoph Hellwig , Thomas Gleixner , Keith Busch Subject: Re: [PATCH V2 RESEND 4/5] blk-mq: re-submit IO in case that hctx is dead Message-ID: <20191007150534.GC1668@ming.t460p> References: <20191006024516.19996-1-ming.lei@redhat.com> <20191006024516.19996-5-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Mon, 07 Oct 2019 15:05:53 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Oct 07, 2019 at 08:27:38AM +0200, Hannes Reinecke wrote: > On 10/6/19 4:45 AM, Ming Lei wrote: > > When all CPUs in one hctx are offline, we shouldn't run this hw queue > > for completing request any more. > > > > So steal bios from the request, and resubmit them, and finally free > > the request in blk_mq_hctx_notify_dead(). > > > > Cc: Bart Van Assche > > Cc: Hannes Reinecke > > Cc: Christoph Hellwig > > Cc: Thomas Gleixner > > Cc: Keith Busch > > Signed-off-by: Ming Lei > > --- > > block/blk-mq.c | 48 +++++++++++++++++++++++++++++++++++++++++------- > > 1 file changed, 41 insertions(+), 7 deletions(-) > > > > diff --git a/block/blk-mq.c b/block/blk-mq.c > > index d991c122abf2..0b35fdbd1f17 100644 > > --- a/block/blk-mq.c > > +++ b/block/blk-mq.c > > @@ -2280,10 +2280,30 @@ static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node) > > return 0; > > } > > > > +static void blk_mq_resubmit_io(struct request *rq) > > +{ > > + struct bio_list list; > > + struct bio *bio; > > + > > + bio_list_init(&list); > > + blk_steal_bios(&list, rq); > > + > > + while (true) { > > + bio = bio_list_pop(&list); > > + if (!bio) > > + break; > > + > > + generic_make_request(bio); > > + } > > + > > + blk_mq_cleanup_rq(rq); > > + blk_mq_end_request(rq, 0); > > +} > > + > Hmm. Not sure if this is a good idea. > Shouldn't we call 'blk_mq_end_request()' before calling > generic_make_request()? > otherwise the cloned request might be completed before original one, > which looks a bit dodgy to me; and might lead to quite a recursion if we > have several dead cpus to content with ... Good catch, we should have freed the old empty request before calling generic_make_request(), will fix it in V3. Thanks, Ming