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 218B0C433EF for ; Tue, 12 Oct 2021 15:02:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0438E61076 for ; Tue, 12 Oct 2021 15:02:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230195AbhJLPEh (ORCPT ); Tue, 12 Oct 2021 11:04:37 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:29384 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237338AbhJLPEg (ORCPT ); Tue, 12 Oct 2021 11:04:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1634050954; 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=H5n0vZXzpKUr4bdvWBgiF2GxyHPbprOqb+7u3O+dEug=; b=OZXaj8MdraQzsfikS35WDWRJLzHZNmv7WK/bVKyH6/cUTxz4CnP+963Bx85R8bjPLg3jfO YeF7EPP7XfFddM3DxtqEp2ZfHtv1Y6XwHoau7AHYjqDtiN3P32Ct6F7YTDC1wndbGD5hjC o3t9LrLH9OCbKMBPalTkcFXFRIOKj7E= 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-295-jiS4h6U3MFWVJ22ABzKX0Q-1; Tue, 12 Oct 2021 11:02:31 -0400 X-MC-Unique: jiS4h6U3MFWVJ22ABzKX0Q-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 856CF80158D; Tue, 12 Oct 2021 15:02:29 +0000 (UTC) Received: from T590 (ovpn-8-34.pek2.redhat.com [10.72.8.34]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4CCE82B060; Tue, 12 Oct 2021 15:02:24 +0000 (UTC) Date: Tue, 12 Oct 2021 23:01:48 +0800 From: Ming Lei To: Christoph Hellwig Cc: Jens Axboe , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, Chaitanya Kulkarni , Sagi Grimberg , Keith Busch , Bart Van Assche Subject: Re: [PATCH V3 4/6] nvme: paring quiesce/unquiesce Message-ID: References: <20211009034713.1489183-1-ming.lei@redhat.com> <20211009034713.1489183-5-ming.lei@redhat.com> <20211012103620.GB29640@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211012103620.GB29640@lst.de> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, Oct 12, 2021 at 12:36:20PM +0200, Christoph Hellwig wrote: > On Sat, Oct 09, 2021 at 11:47:11AM +0800, Ming Lei wrote: > > The current blk_mq_quiesce_queue() and blk_mq_unquiesce_queue() always > > stops and starts the queue unconditionally. And there can be concurrent > > quiesce/unquiesce coming from different unrelated code paths, so > > unquiesce may come unexpectedly and start queue too early. > > > > Prepare for supporting concurrent quiesce/unquiesce from multiple > > contexts, so that we can address the above issue. > > > > NVMe has very complicated quiesce/unquiesce use pattern, add one atomic > > bit for makeiing sure that blk-mq quiece/unquiesce is always called in > > pair. > > Can you explain the need for these bits a little more? If they are > unbalanced we should probably fix the root cause. > > What issues did you see? There are lots of unbalanced usage in nvme, such as 1) nvme pci: - nvme_dev_disable() can be called more than one times before starting reset, so multiple nvme_stop_queues() vs. single nvme_start_queues(). 2) Forcibly unquiesce queues in nvme_kill_queues() even though queues are never quiesced, and similar usage can be seen in tcp/fc/rdma too Once the quiesce and unquiesce are run from difference context, it becomes not easy to audit if the two is done in pair. Thanks, Ming