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 X-Spam-Level: X-Spam-Status: No, score=-9.4 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9892FC433DF for ; Wed, 19 Aug 2020 20:46:44 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 5FFF82078D for ; Wed, 19 Aug 2020 20:46:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="INte5ODl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5FFF82078D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51046 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k8Uyo-0004T0-Nm for qemu-devel@archiver.kernel.org; Wed, 19 Aug 2020 16:46:42 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35966) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k8Uxt-0003wR-8z for qemu-devel@nongnu.org; Wed, 19 Aug 2020 16:45:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:26214) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1k8Uxq-0002CE-Ed for qemu-devel@nongnu.org; Wed, 19 Aug 2020 16:45:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597869940; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=uIEo/nusaUA9g8upMurl6etjaA2YhL9fpGKM41gUDNQ=; b=INte5ODlXmedwTnJ7RnGc9ISfU/dIhhwIu3O2DZ+MzoJ9S0jFhx6R2YSnU4AsOWF46Hv2+ NTOcMegLScApD1CS5gBxBLkx949i0kQ8a3iR7cX74/zQJAsGdASAwARQi14Q948ADM/BMp KEdn5m2q1fnXfZtMmLMGl542qIe3d2E= 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-359-vGWkKzAQOSCunEu3pj8S2g-1; Wed, 19 Aug 2020 16:45:38 -0400 X-MC-Unique: vGWkKzAQOSCunEu3pj8S2g-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 53C51839A49; Wed, 19 Aug 2020 20:45:37 +0000 (UTC) Received: from [10.3.112.136] (ovpn-112-136.phx2.redhat.com [10.3.112.136]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F3B7B5D9D5; Wed, 19 Aug 2020 20:45:36 +0000 (UTC) Subject: Re: [RFC PATCH 12/22] nbd/server: Simplify export shutdown To: Kevin Wolf , qemu-block@nongnu.org References: <20200813162935.210070-1-kwolf@redhat.com> <20200813162935.210070-13-kwolf@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: Date: Wed, 19 Aug 2020 15:45:36 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200813162935.210070-13-kwolf@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/19 10:07:28 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=-1, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/13/20 11:29 AM, Kevin Wolf wrote: > Closing export is somewhat convoluted because nbd_export_close() and > nbd_export_put() call each other and the ways they actually end up being > nested is not necessarily obvious. You are in a maze of twisty little passages, all alike. Yes, I've always hated that part of the code; thanks for tackling a cleanup. > > However, it is not really necessary to call nbd_export_close() from > nbd_export_put() when putting the last reference because it only does > three things: > > 1. Close all clients. We're going to refcount 0 and all clients hold a > reference, so we know there is no active client any more. > > 2. Close the user reference (represented by exp->name being non-NULL). > The same argument applies: If the export were still named, we would > still have a reference. > > 3. Freeing exp->description. This is really cleanup work to be done when > the export is finally freed. There is no reason to already clear it > while clients are still in the process of shutting down. > > So after moving the cleanup of exp->description, the code can be > simplified so that only nbd_export_close() calls nbd_export_put(), but > never the other way around. > > Signed-off-by: Kevin Wolf > --- > nbd/server.c | 17 ++++------------- > 1 file changed, 4 insertions(+), 13 deletions(-) > Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org