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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 B8ED6C04AB6 for ; Tue, 28 May 2019 16:36:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8AA592166E for ; Tue, 28 May 2019 16:36:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726492AbfE1Qga (ORCPT ); Tue, 28 May 2019 12:36:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56190 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726362AbfE1Qg3 (ORCPT ); Tue, 28 May 2019 12:36:29 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9D27630C1328; Tue, 28 May 2019 16:36:24 +0000 (UTC) Received: from [10.10.126.56] (ovpn-126-56.rdu2.redhat.com [10.10.126.56]) by smtp.corp.redhat.com (Postfix) with ESMTP id 549375D6A9; Tue, 28 May 2019 16:36:22 +0000 (UTC) Subject: Re: [PATCH 2/3] nbd: notify userland even if nbd has already disconnected To: Yao Liu , Josef Bacik References: <1558691036-16281-1-git-send-email-yotta.liu@ucloud.cn> <1558691036-16281-2-git-send-email-yotta.liu@ucloud.cn> <20190524130856.zod5agp7hk74pcnr@MacBook-Pro-91.local.dhcp.thefacebook.com> <20190527182323.GB20702@192-168-150-246.7~> Cc: Jens Axboe , linux-block@vger.kernel.org, nbd@other.debian.org, linux-kernel@vger.kernel.org From: Mike Christie Message-ID: <5CED6385.3000802@redhat.com> Date: Tue, 28 May 2019 11:36:21 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20190527182323.GB20702@192-168-150-246.7~> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Tue, 28 May 2019 16:36:29 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 05/27/2019 01:23 PM, Yao Liu wrote: > On Fri, May 24, 2019 at 09:08:58AM -0400, Josef Bacik wrote: >> On Fri, May 24, 2019 at 05:43:55PM +0800, Yao Liu wrote: >>> Some nbd client implementations have a userland's daemon, so we should >>> inform client daemon to clean up and exit. >>> >>> Signed-off-by: Yao Liu >> >> Except the nbd_disconnected() check is for the case that the client told us >> specifically to disconnect, so we don't want to send the notification to >> re-connect because we've already been told we want to tear everything down. >> Nack to this as well. Thanks, >> >> Josef >> > > But in userland, client daemon process and process which send disconnect > command are not same process, so they are not clear to each other, so > client daemon expect driver inform it to exit. > In addition, client daemon will get nbd status with nbd_genl_status interface > after it get notified and it should not re-connect if status connected == 0 > When using the netlink interface you get the NBD_CMD_LINK_DEAD first then the configs_refs goes to zero right? nbd_disconnect_and_put -> sock_shutdown -> nbd_mark_nsock_dead then later we do the final nbd_config_put? Maybe it would be best to add a new netlink event to signal what has happened, because the above nl and stat algorithm seems like a pain. The NBD_CMD_LINK_DEAD will be sent, then userspace has to possibly poll the status to check if this was caused due to nbd_genl_disconnect instead of a downed link due to something like a command timeout, because the refcount may not be down when userspace gets the NL event. Or, I guess the admin/tool process could just send a msg to the daemon process to tell it to do the netlink disconnect request.