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 ED89AC433EF for ; Thu, 20 Jan 2022 12:56:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238941AbiATM4Q (ORCPT ); Thu, 20 Jan 2022 07:56:16 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:21961 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236052AbiATM4P (ORCPT ); Thu, 20 Jan 2022 07:56:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1642683375; 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=HnjzfSKHnTIW/FDreC+CYQQVdtBa2Yo1in7OBWnPmf0=; b=EqW21FaptfKYZsDWWj7Zw6RU7trvGdzGuoDHTMJ9MW1opFET3v2LXE8V9NkNpDLy6HXHfO bN6+PIgyhIJEP74Af1j1O9OW0pjuG6u3F6twTzOTyt/k2V3G0FWlCRqa+Oo0znJH3ms/9A v1GlRlIbEVuJwcbD34DDBK4Y6uhBA28= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-539-L3eZGrybOe6NN07JrSBFNg-1; Thu, 20 Jan 2022 07:56:14 -0500 X-MC-Unique: L3eZGrybOe6NN07JrSBFNg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 996668144E1; Thu, 20 Jan 2022 12:56:12 +0000 (UTC) Received: from T590 (ovpn-8-20.pek2.redhat.com [10.72.8.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 01FDB7D72C; Thu, 20 Jan 2022 12:56:07 +0000 (UTC) Date: Thu, 20 Jan 2022 20:56:03 +0800 From: Ming Lei To: Daniel Wagner Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Jens Axboe , Hannes Reinecke Subject: Re: [PATCH 2/2] block: hold queue lock while iterating in diskstats_show Message-ID: References: <20220120105248.117025-1-dwagner@suse.de> <20220120105248.117025-3-dwagner@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220120105248.117025-3-dwagner@suse.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu, Jan 20, 2022 at 11:52:48AM +0100, Daniel Wagner wrote: > The request queues can be freed while we operate on them. Make sure we It shouldn't be freed here. > hold a reference when using blk_mq_queue_tag_busy_iter. > > RIP: blk_mq_queue_tag_busy_iter Any chance to pose the whole stack trace? > Call Trace: > ? blk_mq_hctx_mark_pending > ? diskstats_show > ? blk_mq_hctx_mark_pending > blk_mq_in_flight > diskstats_show > ? klist_next > seq_read > proc_reg_read > vfs_read > ksys_read > do_syscall_64 > entry_SYSCALL_64_after_hwframe > > Signed-off-by: Daniel Wagner > --- > block/genhd.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/block/genhd.c b/block/genhd.c > index c9d4386dd177..0e163055a4e6 100644 > --- a/block/genhd.c > +++ b/block/genhd.c > @@ -1167,10 +1167,13 @@ static int diskstats_show(struct seq_file *seqf, void *v) > if (bdev_is_partition(hd) && !bdev_nr_sectors(hd)) > continue; > part_stat_read_all(hd, &stat); > + if (blk_queue_enter(gp->queue, BLK_MQ_REQ_NOWAIT)) > + continue; The disk device's refcnt is supposed to be grabbed by class device iterator code, so queue shouldn't be released in diskstats_show(). Not mention blk_queue_enter() won't prevent disk from being released... thanks, Ming