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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58840ECAAD8 for ; Tue, 20 Sep 2022 04:02:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229505AbiITECJ (ORCPT ); Tue, 20 Sep 2022 00:02:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43552 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229575AbiITECH (ORCPT ); Tue, 20 Sep 2022 00:02:07 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7BD20328 for ; Mon, 19 Sep 2022 21:02:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1663646524; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=a2Q6u2DGYBJzVi4q2AHZgi4BSpB8IO5nFEbbegWhcS0=; b=aETcI83EN3r4DmysGOn1+sfiNbwygBYyQPWiFvM7eWH0wN1jjYiVnNFlp0bzdd+839ajMM Scj8wiH81fNgldHzZK8Kpl38k/gUWzWmEAa8+gAtEqpOVZNDflKh4FK4Q768EqDT+HKq33 MZoRM6bhXXIJPgZHh1cYA4EwP5VLKgE= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-274-9WVQwIFcPDqyrDTBES0yKg-1; Tue, 20 Sep 2022 00:02:00 -0400 X-MC-Unique: 9WVQwIFcPDqyrDTBES0yKg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 63E6429ABA30; Tue, 20 Sep 2022 04:02:00 +0000 (UTC) Received: from T590 (ovpn-8-20.pek2.redhat.com [10.72.8.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A66621121314; Tue, 20 Sep 2022 04:01:55 +0000 (UTC) Date: Tue, 20 Sep 2022 12:01:50 +0800 From: Ming Lei To: Ziyang Zhang Cc: axboe@kernel.dk, xiaoguang.wang@linux.alibaba.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, joseph.qi@linux.alibaba.com Subject: Re: [PATCH V3 5/7] ublk_drv: consider recovery feature in aborting mechanism Message-ID: References: <20220913041707.197334-1-ZiyangZhang@linux.alibaba.com> <20220913041707.197334-6-ZiyangZhang@linux.alibaba.com> <9a682fac-f022-1f4d-5c2c-e1f0a84746d8@linux.alibaba.com> <64492fad-e14a-c647-b490-cd1f53a475a8@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <64492fad-e14a-c647-b490-cd1f53a475a8@linux.alibaba.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, Sep 20, 2022 at 11:24:12AM +0800, Ziyang Zhang wrote: > On 2022/9/20 11:04, Ming Lei wrote: > > On Tue, Sep 20, 2022 at 09:49:33AM +0800, Ziyang Zhang wrote: > > > > Follows the delta patch against patch 5 for showing the idea: > > > > > > diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c > > index 4409a130d0b6..60c5786c4711 100644 > > --- a/drivers/block/ublk_drv.c > > +++ b/drivers/block/ublk_drv.c > > @@ -656,7 +656,8 @@ static void ublk_complete_rq(struct request *req) > > * Also aborting may not be started yet, keep in mind that one failed > > * request may be issued by block layer again. > > */ > > -static void __ublk_fail_req(struct ublk_io *io, struct request *req) > > +static void __ublk_fail_req(struct ublk_queue *ubq, struct ublk_io *io, > > + struct request *req) > > { > > WARN_ON_ONCE(io->flags & UBLK_IO_FLAG_ACTIVE); > > > > @@ -667,7 +668,10 @@ static void __ublk_fail_req(struct ublk_io *io, struct request *req) > > req->tag, > > io->flags); > > io->flags |= UBLK_IO_FLAG_ABORTED; > > - blk_mq_end_request(req, BLK_STS_IOERR); > > + if (ublk_queue_can_use_recovery_reissue(ubq)) > > + blk_mq_requeue_request(req, false); > > Here is one problem: > We reset io->flags to 0 in ublk_queue_reinit() and it is called before new As we agreed, ublk_queue_reinit() will be moved to ublk_ch_release(), when there isn't any inflight request, which is completed by either ublk server or __ublk_fail_req(). So clearing io->flags isn't related with quisceing device. > ubq_daemon with FETCH_REQ is accepted. ublk_abort_queue() is not protected with > ub_mutex and it is called many times in monitor_work. So same rq may be requeued > multiple times. UBLK_IO_FLAG_ABORTED is set for the slot, so one req is only ended or requeued just once. > > With recovery disabled, there is no such problem since io->flags does not change > until ublk_dev is released. But we have agreed that ublk_queue_reinit() can be moved to release handler of /dev/ublkcN. > > In my patch 5 I only requeue the same rq once. So re-using ublk_abort_queue() is > hard for recovery feature. No, the same rq is just requeued once. Here the point is: 1) reuse previous pattern in ublk_stop_dev(), which is proved as workable reliably 2) avoid to stay in half-working state forever 3) the behind idea is more simpler. Thanks. Ming