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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 7A922C3A589 for ; Thu, 15 Aug 2019 16:57:28 +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 4E0DE206C1 for ; Thu, 15 Aug 2019 16:57:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4E0DE206C1 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]:44548 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1hyJ43-00030x-I6 for qemu-devel@archiver.kernel.org; Thu, 15 Aug 2019 12:57:27 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49057) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1hyIvg-0000HI-IE for qemu-devel@nongnu.org; Thu, 15 Aug 2019 12:48:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hyIva-0000m3-8G for qemu-devel@nongnu.org; Thu, 15 Aug 2019 12:48:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45266) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hyIvO-0000hl-Gt; Thu, 15 Aug 2019 12:48:30 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7D568316D8D0; Thu, 15 Aug 2019 16:48:29 +0000 (UTC) Received: from linux.fritz.box (ovpn-117-12.ams2.redhat.com [10.36.117.12]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 24BDE17AAA; Thu, 15 Aug 2019 16:48:22 +0000 (UTC) Date: Thu, 15 Aug 2019 18:48:21 +0200 From: Kevin Wolf To: John Snow Message-ID: <20190815164821.GE7415@linux.fritz.box> References: <20190814100735.24234-1-vsementsov@virtuozzo.com> <20190814100735.24234-3-vsementsov@virtuozzo.com> <3eded188-0161-d494-194c-9d67da644eb1@redhat.com> <20190815104928.GC7415@linux.fritz.box> <9c290e4e-1d3b-bc6e-c6e6-28a0414b866e@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9c290e4e-1d3b-bc6e-c6e6-28a0414b866e@redhat.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Thu, 15 Aug 2019 16:48:29 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 2/2] qapi: deprecate implicit filters 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, Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org, libvir-list@redhat.com, armbru@redhat.com, mreitz@redhat.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 15.08.2019 um 18:07 hat John Snow geschrieben: > > > On 8/15/19 6:49 AM, Kevin Wolf wrote: > > Am 14.08.2019 um 21:27 hat John Snow geschrieben: > >> > >> > >> On 8/14/19 6:07 AM, Vladimir Sementsov-Ogievskiy wrote: > >>> To get rid of implicit filters related workarounds in future let's > >>> deprecate them now. > >>> > >>> Signed-off-by: Vladimir Sementsov-Ogievskiy > >>> --- > >>> qemu-deprecated.texi | 7 +++++++ > >>> qapi/block-core.json | 6 ++++-- > >>> include/block/block_int.h | 10 +++++++++- > >>> blockdev.c | 10 ++++++++++ > >>> 4 files changed, 30 insertions(+), 3 deletions(-) > >>> > >>> diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi > >>> index 2753fafd0b..8222440148 100644 > >>> --- a/qemu-deprecated.texi > >>> +++ b/qemu-deprecated.texi > >>> @@ -183,6 +183,13 @@ the 'wait' field, which is only applicable to sockets in server mode > >>> > >>> Use blockdev-mirror and blockdev-backup instead. > >>> > >>> +@subsection implicit filters (since 4.2) > >>> + > >>> +Mirror and commit jobs inserts filters, which becomes implicit if user > >>> +omitted filter-node-name parameter. So omitting it is deprecated, set it > >>> +always. Note, that drive-mirror don't have this parameter, so it will > >>> +create implicit filter anyway, but drive-mirror is deprecated itself too. > >>> + > >>> @section Human Monitor Protocol (HMP) commands > >>> > >>> @subsection The hub_id parameter of 'hostfwd_add' / 'hostfwd_remove' (since 3.1) > >>> diff --git a/qapi/block-core.json b/qapi/block-core.json > >>> index 4e35526634..0505ac9d8b 100644 > >>> --- a/qapi/block-core.json > >>> +++ b/qapi/block-core.json > >>> @@ -1596,7 +1596,8 @@ > >>> # @filter-node-name: the node name that should be assigned to the > >>> # filter driver that the commit job inserts into the graph > >>> # above @top. If this option is not given, a node name is > >>> -# autogenerated. (Since: 2.9) > >>> +# autogenerated. Omitting this option is deprecated, it will > >>> +# be required in future. (Since: 2.9) > >>> # > >>> # @auto-finalize: When false, this job will wait in a PENDING state after it has > >>> # finished its work, waiting for @block-job-finalize before > >>> @@ -2249,7 +2250,8 @@ > >>> # @filter-node-name: the node name that should be assigned to the > >>> # filter driver that the mirror job inserts into the graph > >>> # above @device. If this option is not given, a node name is > >>> -# autogenerated. (Since: 2.9) > >>> +# autogenerated. Omitting this option is deprecated, it will > >>> +# be required in future. (Since: 2.9) > >>> # > >>> # @copy-mode: when to copy data to the destination; defaults to 'background' > >>> # (Since: 3.0) > >>> diff --git a/include/block/block_int.h b/include/block/block_int.h > >>> index 3aa1e832a8..624da0b4a2 100644 > >>> --- a/include/block/block_int.h > >>> +++ b/include/block/block_int.h > >>> @@ -762,7 +762,15 @@ struct BlockDriverState { > >>> bool sg; /* if true, the device is a /dev/sg* */ > >>> bool probed; /* if true, format was probed rather than specified */ > >>> bool force_share; /* if true, always allow all shared permissions */ > >>> - bool implicit; /* if true, this filter node was automatically inserted */ > >>> + > >>> + /* > >>> + * @implicit field is deprecated, don't set it to true for new filters. > >>> + * If true, this filter node was automatically inserted and user don't > >>> + * know about it and unprepared for any effects of it. So, implicit > >>> + * filters are workarounded and skipped in many places of the block > >>> + * layer code. > >>> + */ > >>> + bool implicit; > >>> > >>> BlockDriver *drv; /* NULL means no media */ > >>> void *opaque; > >>> diff --git a/blockdev.c b/blockdev.c > >>> index 36e9368e01..b3cfaccce1 100644 > >>> --- a/blockdev.c > >>> +++ b/blockdev.c > >>> @@ -3292,6 +3292,11 @@ void qmp_block_commit(bool has_job_id, const char *job_id, const char *device, > >>> BlockdevOnError on_error = BLOCKDEV_ON_ERROR_REPORT; > >>> int job_flags = JOB_DEFAULT; > >>> > >>> + if (!has_filter_node_name) { > >>> + warn_report("Omitting filter-node-name parameter is deprecated, it " > >>> + "will be required in future"); > >>> + } > >>> + > >>> if (!has_speed) { > >>> speed = 0; > >>> } > >>> @@ -3990,6 +3995,11 @@ void qmp_blockdev_mirror(bool has_job_id, const char *job_id, > >>> Error *local_err = NULL; > >>> int ret; > >>> > >>> + if (!has_filter_node_name) { > >>> + warn_report("Omitting filter-node-name parameter is deprecated, it " > >>> + "will be required in future"); > >>> + } > >>> + > >>> bs = qmp_get_root_bs(device, errp); > >>> if (!bs) { > >>> return; > >>> > >> > >> This might be OK to do right away, though. > >> > >> I asked Markus this not too long ago; do we want to amend the QAPI > >> schema specification to allow commands to return with "Warning" strings, > >> or "Deprecated" stings to allow in-band deprecation notices for cases > >> like these? > >> > >> example: > >> > >> { "return": {}, > >> "deprecated": True, > >> "warning": "Omitting filter-node-name parameter is deprecated, it will > >> be required in the future" > >> } > >> > >> There's no "error" key, so this should be recognized as success by > >> compatible clients, but they'll definitely see the extra information. > >> > >> Part of my motivation is to facilitate a more aggressive deprecation of > >> legacy features by ensuring that we are able to rigorously notify users > >> through any means that they need to adjust their scripts. > > > > Who would read this, though? In the best case it ends up deep in a > > libvirt log that nobody will look at because there was no error. In the > > more common case, the debug level is configured so that QMP traffic > > isn't even logged. > > > > Kevin > > > > I believe you are right, but I also can't shake the feeling that this > attitude ensures that we'll never find a way to expose this information > to the end-user. Is this not too defeatist? I think the discussed approach that seemed most likely to me to succeed was adding a command line option that makes QEMU just crash if you use a deprecated feature, and enable that in libvirt test cases (or possibly even any non-release builds, though maybe it's a bit harsh there). > I think deprecation notices in the QMP stream has two benefits: > > 1) Any direct usages via qmp-shell or manual JSON connection are likely > to see this message in development or testing. I feel the usage of QEMU > directly is more likely to increase with time as other stacks seek to > work around libvirt. > > [Whether or not they should is another question, but I believe the > current reality to be that people are trying to.] I don't know about other people, but as a human user, I don't care about deprecation notices. As long as something works, I use it, and once I get an error message back, I'll use something else. If I manually enter drive_mirror and get a warning back, that doesn't tell me that libvirt still does the same thing and needs to be fixed. It just tells me that in the future I might need to change the commands that I use manually. I guess this would still prevent adding new libvirt features that build on deprecated QEMU features because some manual testing will be involved there. But was this ever a problem? > 2) Programmatic deprecation notices can't be presented to a user at all > if we don't send them; at least this way it becomes libvirt's problem > over what to do with them. Perhaps even just in testing and regression > suites libvirt can assert that it sees no deprecation warnings (or > whitelist certain ones it knows about.) > > In the case of libvirt, it's not even necessarily about making sure the > end user sees it, because it isn't even necessarily the user's fault -- > it's libvirt's. This is a sure-fire programmatic way to communicate > compatibility changes to libvirt. If libvirt uses this to make test cases fail, it could work. Kevin