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 EAF41C433FE for ; Thu, 17 Feb 2022 07:45:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230323AbiBQHpY (ORCPT ); Thu, 17 Feb 2022 02:45:24 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:37420 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230237AbiBQHpX (ORCPT ); Thu, 17 Feb 2022 02:45:23 -0500 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3FE2823A1A8; Wed, 16 Feb 2022 23:45:09 -0800 (PST) Received: by verein.lst.de (Postfix, from userid 2407) id BF89F68B05; Thu, 17 Feb 2022 08:45:03 +0100 (CET) Date: Thu, 17 Feb 2022 08:45:02 +0100 From: Christoph Hellwig To: Jens Axboe Cc: Christoph Hellwig , Ming Lei , "Martin K . Petersen" , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org, Laibin Qiu , Ming Lei Subject: Re: [PATCH V2 04/13] block/wbt: fix negative inflight counter when remove scsi device Message-ID: <20220217074502.GA1333@lst.de> References: <20220122111054.1126146-1-ming.lei@redhat.com> <20220122111054.1126146-5-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220122111054.1126146-5-ming.lei@redhat.com> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Jens, can you pick this up for the block-5.17 tree? On Sat, Jan 22, 2022 at 07:10:45PM +0800, Ming Lei wrote: > From: Laibin Qiu > > Now that we disable wbt by set WBT_STATE_OFF_DEFAULT in > wbt_disable_default() when switch elevator to bfq. And when > we remove scsi device, wbt will be enabled by wbt_enable_default. > If it become false positive between wbt_wait() and wbt_track() > when submit write request. > > The following is the scenario that triggered the problem. > > T1 T2 T3 > elevator_switch_mq > bfq_init_queue > wbt_disable_default <= Set > rwb->enable_state (OFF) > Submit_bio > blk_mq_make_request > rq_qos_throttle > <= rwb->enable_state (OFF) > scsi_remove_device > sd_remove > del_gendisk > blk_unregister_queue > elv_unregister_queue > wbt_enable_default > <= Set rwb->enable_state (ON) > q_qos_track > <= rwb->enable_state (ON) > ^^^^^^ this request will mark WBT_TRACKED without inflight add and will > lead to drop rqw->inflight to -1 in wbt_done() which will trigger IO hung. > > Fix this by move wbt_enable_default() from elv_unregister to > bfq_exit_queue(). Only re-enable wbt when bfq exit. > > Fixes: 76a8040817b4b ("blk-wbt: make sure throttle is enabled properly") > > Remove oneline stale comment, and kill one oneshot local variable. > > Signed-off-by: Ming Lei > Reviewed-by: Christoph Hellwig > Link: https://lore.kernel.org/linux-block/20211214133103.551813-1-qiulaibin@huawei.com/ > Signed-off-by: Laibin Qiu > --- > block/bfq-iosched.c | 2 ++ > block/elevator.c | 2 -- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c > index 0c612a911696..36a66e97e3c2 100644 > --- a/block/bfq-iosched.c > +++ b/block/bfq-iosched.c > @@ -7018,6 +7018,8 @@ static void bfq_exit_queue(struct elevator_queue *e) > spin_unlock_irq(&bfqd->lock); > #endif > > + wbt_enable_default(bfqd->queue); > + > kfree(bfqd); > } > > diff --git a/block/elevator.c b/block/elevator.c > index ec98aed39c4f..482df2a350fc 100644 > --- a/block/elevator.c > +++ b/block/elevator.c > @@ -525,8 +525,6 @@ void elv_unregister_queue(struct request_queue *q) > kobject_del(&e->kobj); > > e->registered = 0; > - /* Re-enable throttling in case elevator disabled it */ > - wbt_enable_default(q); > } > } > > -- > 2.31.1 ---end quoted text---