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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id D15CFC433EF for ; Wed, 13 Apr 2022 15:44:16 +0000 (UTC) Received: from localhost ([::1]:55478 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nefAF-0002mh-I8 for qemu-devel@archiver.kernel.org; Wed, 13 Apr 2022 11:44:15 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:42414) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nef90-0001WM-7L for qemu-devel@nongnu.org; Wed, 13 Apr 2022 11:42:58 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:30319) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nef8x-0001XX-Gb for qemu-devel@nongnu.org; Wed, 13 Apr 2022 11:42:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1649864575; 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=p8crzsj/ks5JVzrilq0k3tC5d9+edaa4ib26eRPGB5k=; b=iAAGcny1OEwVSc7IDRLx171UA5mOwaej4Tg3GyQgxok2ogE70XEKQ1cVskXEJ9MoJGbfN3 /x+hLiDqLhbQMCIUMEnjVCuh859kLoS/3NZv55jze715uT2qXEkaAR9bahk537J1bvPDui rfvI61DVY0NqTmKddiDpXn9Z5bpj9oQ= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-315-rUxffBqiPJqIvPOXmitW0A-1; Wed, 13 Apr 2022 11:42:53 -0400 X-MC-Unique: rUxffBqiPJqIvPOXmitW0A-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 3FD5A1014A61 for ; Wed, 13 Apr 2022 15:42:53 +0000 (UTC) Received: from redhat.com (unknown [10.2.16.138]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E800B2166B4F; Wed, 13 Apr 2022 15:42:52 +0000 (UTC) Date: Wed, 13 Apr 2022 10:42:51 -0500 From: Eric Blake To: Paolo Bonzini Subject: Re: [PATCH for-7.1 4/8] nbd: keep send_mutex/free_sema handling outside nbd_co_do_establish_connection Message-ID: <20220413154251.nk33rcipdvvsuvso@redhat.com> References: <20220412194204.350889-1-pbonzini@redhat.com> <20220412194204.350889-5-pbonzini@redhat.com> MIME-Version: 1.0 In-Reply-To: <20220412194204.350889-5-pbonzini@redhat.com> User-Agent: NeoMutt/20211029-6-a115bf X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.129.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Apr 12, 2022 at 09:42:00PM +0200, Paolo Bonzini wrote: > Elevate s->in_flight early so that other incoming requests will wait > on the CoQueue in nbd_co_send_request; restart them after getting back > from nbd_reconnect_attempt. This could be after the reconnect timer or > nbd_cancel_in_flight have cancelled the attempt, so there is no > need anymore to cancel the requests there. > > nbd_co_send_request now handles both stopping and restarting pending > requests after a successful connection, and there is no need to > hold send_mutex in nbd_co_do_establish_connection. The current setup > is confusing because nbd_co_do_establish_connection is called both with > send_mutex taken and without it. Before the patch it uses free_sema which > (at least in theory...) is protected by send_mutex, after the patch it > does not anymore. > > Signed-off-by: Paolo Bonzini > --- > block/coroutines.h | 4 +-- > block/nbd.c | 66 ++++++++++++++++++++++------------------------ > 2 files changed, 33 insertions(+), 37 deletions(-) > > +++ b/block/nbd.c > @@ -359,25 +354,25 @@ int coroutine_fn nbd_co_do_establish_connection(BlockDriverState *bs, > /* called under s->send_mutex */ > static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s) > { > - assert(nbd_client_connecting(s)); > - assert(s->in_flight == 0); > - > - if (nbd_client_connecting_wait(s) && s->reconnect_delay && > - !s->reconnect_delay_timer) > - { > - /* > - * It's first reconnect attempt after switching to > - * NBD_CLIENT_CONNECTING_WAIT > - */ > - reconnect_delay_timer_init(s, > - qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + > - s->reconnect_delay * NANOSECONDS_PER_SECOND); > - } > + bool blocking = nbd_client_connecting_wait(s); > > /* > * Now we are sure that nobody is accessing the channel, and no one will > * try until we set the state to CONNECTED. > */ > + assert(nbd_client_connecting(s)); > + assert(s->in_flight == 1); > + > + if (blocking && !s->reconnect_delay_timer) { > + /* > + * It's first reconnect attempt after switching to While moving this, we could add the missing article: "It's the first" > + * NBD_CLIENT_CONNECTING_WAIT > + */ > + g_assert(s->reconnect_delay); > + reconnect_delay_timer_init(s, > + qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + > + s->reconnect_delay * NANOSECONDS_PER_SECOND); > + } > > /* Finalize previous connection if any */ > if (s->ioc) { > @@ -388,7 +383,9 @@ static coroutine_fn void nbd_reconnect_attempt(BDRVNBDState *s) > s->ioc = NULL; > } > > - nbd_co_do_establish_connection(s->bs, NULL); > + qemu_co_mutex_unlock(&s->send_mutex); > + nbd_co_do_establish_connection(s->bs, blocking, NULL); > + qemu_co_mutex_lock(&s->send_mutex); > > /* > * The reconnect attempt is done (maybe successfully, maybe not), so > @@ -474,21 +471,21 @@ static int coroutine_fn nbd_co_send_request(BlockDriverState *bs, > qemu_co_mutex_lock(&s->send_mutex); > > while (s->in_flight == MAX_NBD_REQUESTS || > - (!nbd_client_connected(s) && s->in_flight > 0)) > - { > + (!nbd_client_connected(s) && s->in_flight > 0)) { Mixing in a style change here. Not the end of the world. The cosmetics are trivial, and the real change of enlarging the scope of in_flight makes sense to me. Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org