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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 BD6A0C433C1 for ; Tue, 23 Mar 2021 13:46:57 +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 0CE4C6198C for ; Tue, 23 Mar 2021 13:46:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0CE4C6198C 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]:56752 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lOhN1-00065G-Sk for qemu-devel@archiver.kernel.org; Tue, 23 Mar 2021 09:46:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33918) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lOhLj-00054O-KP for qemu-devel@nongnu.org; Tue, 23 Mar 2021 09:45:35 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:32989) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lOhLg-0000Vf-Kr for qemu-devel@nongnu.org; Tue, 23 Mar 2021 09:45:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616507131; 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=5AxyvAGf/nIuQg2dYxK/nV3ZsQWnzRs36zOrss3GqEg=; b=h2R+DGlLug5pREk+3IPodOGcGMuc9/u6TE9KbCmfSmxEshlTCNozd8leKHYlUndYFqOrAb YHVyXEMTrRKwgNoKPFZpMD7gWD8F2b5QAh9mcOvImGI2GcyuZEjwFp7p2Ku0MexcKn6tTF 3NTD7IGgyj7FxIADR0ZMLU7VnXyM/N8= 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-169-uredp_DrO2uu0Ei86sTbCg-1; Tue, 23 Mar 2021 09:45:24 -0400 X-MC-Unique: uredp_DrO2uu0Ei86sTbCg-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 D84AE180FCDB; Tue, 23 Mar 2021 13:45:07 +0000 (UTC) Received: from localhost (ovpn-114-89.ams2.redhat.com [10.36.114.89]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5591710023AF; Tue, 23 Mar 2021 13:45:07 +0000 (UTC) Date: Tue, 23 Mar 2021 13:45:06 +0000 From: Stefan Hajnoczi To: Vivek Goyal Subject: Re: [Virtio-fs] [External] Re: [RFC PATCH 0/9] Support for Virtio-fs daemon crash reconnection Message-ID: References: <20201215162119.27360-1-zhangjiachen.jaycee@bytedance.com> <20210322201326.GH446288@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210322201326.GH446288@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="wuS6R2OceLl3Kyfx" Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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 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: vrothber@redhat.com, "Daniel P. Berrange" , "Michael S . Tsirkin" , dwalsh@redhat.com, QEMU , virtio-fs@redhat.com, Xie Yongji , Jiachen Zhang , =?iso-8859-1?Q?Marc-Andr=E9?= Lureau Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --wuS6R2OceLl3Kyfx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Mar 22, 2021 at 04:13:26PM -0400, Vivek Goyal wrote: > On Mon, Mar 22, 2021 at 11:00:52AM +0000, Stefan Hajnoczi wrote: > > On Wed, Mar 17, 2021 at 08:32:31PM +0800, Jiachen Zhang wrote: > > > On Wed, Mar 17, 2021 at 6:05 PM Stefan Hajnoczi = wrote: > > > > On Fri, Dec 18, 2020 at 05:39:34PM +0800, Jiachen Zhang wrote: > > > I agreed with you that a virtiofsd must be launched by a software lik= e > > > systemd. So we are planning to define more generic persist/restore > > > interfaces (callbacks). Then anyone can implement their own persist/r= estore > > > callbacks to store states to proper places. And I think in the next > > > version we will implement default callbacks for the interfaces. Inste= ad of > > > vhost-user messages, systemd's sd_notify(3) will be the default metho= d for > > > storing fds, and several tmpfs files can be the default place to stor= e the > > > shm regions. > >=20 > > Okay, great! > >=20 > > I was thinking about how to make the crash recovery mechanism reusable > > as a C library or Rust crate. The mechanism is a combination of: > > 1. sd_listen_fds(3) for restoring the fds on restart. > > 2. sd_notify(3) for storing the fds. > > 3. memfd or tmpfs for storing state (could be mmapped). > >=20 > > I'm not sure if there is enough common behavior to create a reusable AP= I > > or if this is quite application-specific. >=20 > I am wondering what will happen for use cases where virtiofsd is running > inside a container (with no systemd inside containers). >=20 > Do container managers offer systemd like services to save and restore > state. It appears so, at least for Podman where sd_notify is explicitly mentioned: https://www.redhat.com/sysadmin/improved-systemd-podman As mentioned in this email thread, the socket activation and sd_notify(3) interface can also be implemented by non-systemd software. Anyone running a custom container runtime or orchestration software could add these interfaces (they are reasonably simple and the protocols are documented in the systemd documentation). 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