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 9A050C41513 for ; Thu, 17 Aug 2023 17:19:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353904AbjHQRSe (ORCPT ); Thu, 17 Aug 2023 13:18:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60612 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353922AbjHQRSJ (ORCPT ); Thu, 17 Aug 2023 13:18:09 -0400 Received: from out-31.mta1.migadu.com (out-31.mta1.migadu.com [IPv6:2001:41d0:203:375::1f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 654ED10C8 for ; Thu, 17 Aug 2023 10:18:07 -0700 (PDT) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1692292685; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oP35WFkAGM1mqUKfAAOZno6K6eolQgOYmd9Fifhu4bc=; b=nQo8ZaFh4yp+bsrYRq0hie4ebKHaQlZGU0ayDy4fw+UT2srPnsKGHaDOxfutrxnFSty3xy owB27Rv6A0jVF2M8vERdix/hdktvDxtiYnQsOySRG8TRjycni0KqVonZceBF5+CL8Cc8U1 b1FIdi7T6aopaNAnKoLgJqqxdTDkLxw= Date: Fri, 18 Aug 2023 01:17:38 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v2] blk-mq: release scheduler resource when request complete Content-Language: en-US To: Bart Van Assche , axboe@kernel.dk, hch@lst.de Cc: oe-lkp@lists.linux.dev, lkp@intel.com, Chuck Lever , linux-block@vger.kernel.org, cel@kernel.org, linux-kernel@vger.kernel.org, kernel test robot References: <202308172100.8ce4b853-oliver.sang@intel.com> <317715dc-f6e4-1847-5b78-b2d8184b446a@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Chengming Zhou In-Reply-To: <317715dc-f6e4-1847-5b78-b2d8184b446a@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/8/17 23:29, Chengming Zhou wrote: > On 2023/8/17 22:50, Bart Van Assche wrote: >> On 8/17/23 07:41, kernel test robot wrote: >>> [  222.622837][ T2216] statistics for priority 1: i 276 m 0 d 276 c 278 >>> [ 222.629307][ T2216] WARNING: CPU: 0 PID: 2216 at block/mq-deadline.c:680 dd_exit_sched (block/mq-deadline.c:680 (discriminator 3)) >> >> The above information shows that dd_inserted_request() has been called >> 276 times and also that dd_finish_request() has been called 278 times. > > Thanks much for your help. > > This patch indeed introduced a regression, postflush requests will be completed > twice, so here dd_finish_request() is more than dd_inserted_request(). > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index a8c63bef8ff1..7cd47ffc04ce 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -686,8 +686,10 @@ static void blk_mq_finish_request(struct request *rq) > { > struct request_queue *q = rq->q; > > - if (rq->rq_flags & RQF_USE_SCHED) > + if (rq->rq_flags & RQF_USE_SCHED) { > q->elevator->type->ops.finish_request(rq); > + rq->rq_flags &= ~RQF_USE_SCHED; > + } > } > I just tried to run LKP and xfstests, firstly failed to run LKP on my server which seems to miss some dependencies. Then I ran xfstests successfully. But xfstests generic/704 always pass and no WARN in dmesg. (I don't know why, maybe my server settings are some different from the test robot.) So I try to reproduce it manually. Steps: ``` echo mq-deadline > /sys/block/sdb/queue/scheduler mkfs.ext4 /dev/sdb mount /dev/sdb /fs/sdb cd /fs/sdb stress-ng --symlink 4 --timeout 60 echo none > /sys/block/sdb/queue/scheduler ``` This way the WARNING in mq-deadline can be reproduced easily. Then retest with the diff, mq-deadline WARNING still happened... So there are still other requests which have RQF_USE_SCHED flag completed without being inserted into elevator. Will use some tracing and look again. Thanks. > > Clear RQF_USE_SCHED flag here should fix this problem, which should be ok > since finish_request() is the last callback, this flag isn't needed anymore. > > Jens, should I send this diff as another patch or resend updated v3? > > Thanks. > >> Calling dd_finish_request() more than once per request breaks the code >> for priority handling since that code checks how many requests are >> pending per priority level by subtracting the number of completion calls >> from the number of insertion calls (see also dd_queued()). I think the >> above output indicates that this patch introduced a regression. >> >> Bart. >>