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 21CD1C433FE for ; Wed, 10 Nov 2021 09:52:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 012ED61105 for ; Wed, 10 Nov 2021 09:52:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230489AbhKJJzQ (ORCPT ); Wed, 10 Nov 2021 04:55:16 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:27542 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229653AbhKJJzP (ORCPT ); Wed, 10 Nov 2021 04:55:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1636537948; 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=7oqI1vSf7oW8hr4gNp34G0zlAlDGH6S3+qYy9C5RByg=; b=c1jqmqH1HFHlRaVu63sLIMdJaSXy+YfYJmW/lW9CzoH6fpudMK5NJaCuOAG2ImxNfJmvBk tDcNVI/st5nf8goFFzwW1ZnXQNgqUmz2S7RIyznCMxxM/pASnTxJCpmPrRrY2n6I8I7TH1 8SrIDtAVwcOXiVaTFa6QeBCgSQ9wDms= 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-208-pCtNLx6KN3WaiDesogfB7w-1; Wed, 10 Nov 2021 04:52:25 -0500 X-MC-Unique: pCtNLx6KN3WaiDesogfB7w-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 07A50804141; Wed, 10 Nov 2021 09:52:24 +0000 (UTC) Received: from T590 (ovpn-8-19.pek2.redhat.com [10.72.8.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 118E410016F2; Wed, 10 Nov 2021 09:52:20 +0000 (UTC) Date: Wed, 10 Nov 2021 17:52:13 +0800 From: Ming Lei To: Christoph Hellwig Cc: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Nov 10, 2021 at 05:29:26PM +0800, Ming Lei wrote: > On Wed, Nov 10, 2021 at 10:14:07AM +0100, 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? > > freeze can make sure that all requests are done, quiesce can make sure that > dispatch critical area(covered by hctx lock/unlock) is done. Another difference: quiesce usually is used to stop to queue requests to LLD, and driver needs no requets queued any more after the interface returns, freeze can't do that. Thanks, Ming