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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29AE6C433F5 for ; Wed, 10 Nov 2021 10:46:16 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E68E761168 for ; Wed, 10 Nov 2021 10:46:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org E68E761168 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=eqCttD3Xd5hwRL+t63xG9x7gvxrIP+8WdXxav6/uzGQ=; b=qor03XPMd0ZnDlpluWR8UihvUl 7o5++tmIS+RK9aV/IZM4CeZYw5Tt5iWxykQ91iUkPgo05j1UtpLVn2LWg+iZBfhaoUZ/g5ov1AOeP UDYqMkeblc6+NjQIhBvYyHVXzVwaMSG7jR9CYfN7UPvYWFd/oH9pRko7Q8+zIOx4i5VZqdI66agl8 7A8PWPKSxglttfaq74V/8JfOxYlsVCvPSJLruZPrOdgiycdI+gdaqDMFx1+z84mqtzJxpwsm0Kwjf FgMf6g556Hp1PENm5F+VEdh0KbX+mOv6pIZtlLJC3okcENUZVhyTRvNH4j47OvQt3czTqLbit/W0R q7ThsZ3Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mkl7L-005Aix-J3; Wed, 10 Nov 2021 10:46:11 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mkl7J-005Ag3-0W for linux-nvme@lists.infradead.org; Wed, 10 Nov 2021 10:46:10 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1636541165; 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=eqCttD3Xd5hwRL+t63xG9x7gvxrIP+8WdXxav6/uzGQ=; b=dNV+lAx9O58dlRi9AD1xRLmeVlv8dTnK8pwDwNqGaQtJsa92PGnHjN319firljtGddy4Bz OUdy6hqXC2xJvf4c9ozUsXZpJTH/C3HV20EFkMyIMguGFr3XStY+yZ1q4kIBQrPP5aHL0M Pi/gjLbTl8JZi40ID1gynhGc3VEhP/M= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-247-7ug1M-ffNG6h2smBDU4Y7Q-1; Wed, 10 Nov 2021 05:46:02 -0500 X-MC-Unique: 7ug1M-ffNG6h2smBDU4Y7Q-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DD6CE871803; Wed, 10 Nov 2021 10:46:00 +0000 (UTC) Received: from T590 (ovpn-8-19.pek2.redhat.com [10.72.8.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 34E4410074E0; Wed, 10 Nov 2021 10:45:56 +0000 (UTC) Date: Wed, 10 Nov 2021 18:45:52 +0800 From: Ming Lei To: Hannes Reinecke Cc: Christoph Hellwig , Jens Axboe , linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, linux-nvme@lists.infradead.org Subject: Re: sorting out the freeze / quiesce mess Message-ID: References: <20211110091407.GA8396@lst.de> <477f3098-39be-ad07-e2fb-3ef3309c4dce@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <477f3098-39be-ad07-e2fb-3ef3309c4dce@suse.de> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211110_024609_174964_9AEAA320 X-CRM114-Status: GOOD ( 21.21 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Wed, Nov 10, 2021 at 11:22:05AM +0100, Hannes Reinecke wrote: > On 11/10/21 10:14 AM, Christoph Hellwig wrote: > > Hi Jens and Ming, > > > > I've been looking into properly supporting queue freezing for bio based > > drivers (that is only release q_usage_counter on bio completion for them). > > And the deeper I look into the code the more I'm confused by us having > > the blk_mq_quiesce* interface in addition to blk_freeze_queue. What > > is a good reason to do a quiesce separately from a freeze? > > > IIRC the 'quiesce' interface was an abstraction from the SCSI 'quiesce' > operation, where we had to stop all I/O except for TMFs and scanning. > And 'freeze' was designed fro stopping all I/O. > > But I'm not sure if that ever was the distinction, or if it still > applies today. > > And yeah, I've been wondering myself. > > Probably we should just kill the 'quiesce' stuff and see where we end up :-) In case of EH, no queued requests can be completed, however driver still needs to stop queue and reset hardware, then how can you use freeze to stop queue? See nvme_dev_disable(). Freeze can stop to allocate new request and drain all queued requests, but it can't prevent IO from being queued to LLD. On the contrary, blk_mq_freeze_queue_wait() requires LLD to handle IO for moving on, otherwise it will wait forever. Thanks, Ming