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 31444C4332F for ; Wed, 19 Oct 2022 08:20:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230064AbiJSIUq (ORCPT ); Wed, 19 Oct 2022 04:20:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53840 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230087AbiJSIUn (ORCPT ); Wed, 19 Oct 2022 04:20:43 -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 E0DB47B783 for ; Wed, 19 Oct 2022 01:20:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666167641; 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=HXZBvfNAfi6luas85qTQSWuS6SyKZHjVv+hOV8o6mUU=; b=TcgHbawd5bzvzdVmJm45s1yxcPSVLdVIwosn9hZjpNoWknx0m3fKnnfHD6mrjdxb6RsM9h vNYEKpRdoQMubJUkoTysDEpTeKhvqpJ5DbQty4f5gU1AHpqvTa+di9WJUFb78ZKQ1eieqd iG9yS4NR4FYXITNbHYwOyHdm9CmqCy4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-614-sYYUZg2lMLCIv-hW0rz_jA-1; Wed, 19 Oct 2022 04:20:39 -0400 X-MC-Unique: sYYUZg2lMLCIv-hW0rz_jA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 83E0F8027F5; Wed, 19 Oct 2022 08:20:33 +0000 (UTC) Received: from T590 (ovpn-8-20.pek2.redhat.com [10.72.8.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 91F85414A81C; Wed, 19 Oct 2022 08:20:27 +0000 (UTC) Date: Wed, 19 Oct 2022 16:20:23 +0800 From: Ming Lei To: Christoph Hellwig Cc: axboe@kernel.dk, linux-block@vger.kernel.org Subject: Re: blk_mq_quiesce_queue in del_gendisk Message-ID: References: <20221019073035.GB11606@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221019073035.GB11606@lst.de> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Oct 19, 2022 at 09:30:35AM +0200, Christoph Hellwig wrote: > Based on the per-tagset srcu for quiesce discusion I've been wondering > why we need the queue quiesce around elevator_exit and rq_qos_exit in > del_gendisk. At the point where we call it, we've stopped new fs > I/O submissions, and the queue is frozen. What does the quiesce still > protect against, and if anything can we come up with a cheaper way to > do that? There might be in-progress run queue not finished yet, only rcu can guarantee that. Thanks, Ming