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 6524CCDB474 for ; Tue, 17 Oct 2023 05:54:21 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qsd1Q-000295-2N; Tue, 17 Oct 2023 01:53:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qsd1N-00028Z-Jt for qemu-devel@nongnu.org; Tue, 17 Oct 2023 01:53:38 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qsd1K-0007bz-Sd for qemu-devel@nongnu.org; Tue, 17 Oct 2023 01:53:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1697522014; 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=imrBstr+1OA43oJpWPuDRKVOeZv/CMlFhxjhOeia8wc=; b=dIm2oFilKeJakORGWseAd+TfFm/q5zcHEuDOYH9RpQpnmIBo/UaZ4xa0ECLXHXQbg+y3Vz dvJLiImEkGFm+TKhq7Z2bKBb/OoclK8sua1AVTQSSUbQM9yKXcSkFf2khAAEu9Zy87oMBj Xpwgl5QlEHK1G7w4BoWJOyHkfXxpRJ4= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-483-t3doGZS2OVKDoXCJNnSaAw-1; Tue, 17 Oct 2023 01:53:29 -0400 X-MC-Unique: t3doGZS2OVKDoXCJNnSaAw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 15A66381258B; Tue, 17 Oct 2023 05:53:29 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.56]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C3A39492BEE; Tue, 17 Oct 2023 05:53:28 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id BB7B421E6A1F; Tue, 17 Oct 2023 07:53:27 +0200 (CEST) From: Markus Armbruster To: Juan Quintela Cc: qemu-devel@nongnu.org, Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Fam Zheng , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Eric Blake , libvir-list@redhat.com, Fabiano Rosas , qemu-block@nongnu.org, Peter Xu , Leonardo Bras , "Dr. David Alan Gilbert" , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Stefan Hajnoczi , Thomas Huth , Hailiang Zhang , Paolo Bonzini Subject: Re: [PATCH v4 03/10] migration: migrate 'inc' command option is deprecated. References: <20231013104736.31722-1-quintela@redhat.com> <20231013104736.31722-4-quintela@redhat.com> <8734yehdoc.fsf@pond.sub.org> <87a5sj59ww.fsf@secure.mitica> <87bkcyixwn.fsf@pond.sub.org> <87fs2a3dei.fsf@secure.mitica> Date: Tue, 17 Oct 2023 07:53:27 +0200 In-Reply-To: <87fs2a3dei.fsf@secure.mitica> (Juan Quintela's message of "Mon, 16 Oct 2023 15:28:05 +0200") Message-ID: <87a5sheqw8.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Juan Quintela writes: > Markus Armbruster wrote: >> Juan Quintela writes: >> >>> Markus Armbruster wrote: >>>> Juan Quintela writes: >>> So what I want, I want to remove -i/-b in the next version (9.0?). For >>> the other, I want to remove it, but I don't care if the code is around >>> in "deprecated" state for another couple of years if there are still >>> people that feel that they want it. >>> >>> This is the reason that I put a pointer for -i/-b to >>> @block/@block-incremental. They are "perfect" replacements. >>> >>> I can put here to use blockdev-mirror + NBD, but the replacement is not >>> so direct. >>> >>> Does this make sense? >> >> I see where you're coming from. Now let's change perspective for a >> minute: what's the purpose of deprecating stuff? >> >> We normally deprecate with intent to remove. >> >> We don't remove right away, because we promised to first deprecate for a >> grace period, so users can adjust in an orderly manner. The deprecation >> serves as signal "you need to adjust". The documentation that comes >> with it should help with the adjustment. It's commonly of the form "use >> $alternative instead". The alternative is often a direct replacement, >> but not always. There could even be no replacement at all. We don't >> promise replacements, we promise an orderly process, so users can >> adjust. >> >> Sometimes, we don't have firm plans to remove, but are more like "maybe >> remove when gets in the way". We could soften the "you need to adjust" >> signal in documentation, but I doubt that's a good idea. Regardless, >> the need to help users adjust remains. >> >> Back to your patches. There are two separate interfaces to block >> migration, and both are deprecated at the end of the series: >> >> 1. Migration parameter @block-incremental & friends >> >> Not in the way, content to keep around for longer if it helps users. >> >> The deprecation documentation advises to use block-mirror with NBD >> instead. All good. >> >> 2. QMP migrate parameters @inc and @blk >> >> Firm intent to remove as soon as the grace period expires, because >> it's in the way. >> >> The deprecation documentation advises to use interface 1 instead. >> But that's deprecated, too! >> >> Insufficiently careful readers will miss that the replacement is >> deprecated, and just use it. Risks surprise when the replacement >> goes away, too. >> >> More careful readers will realize that this advises to use something >> we elsewhere advise not to use. Contradiction! Confusion ensues. >> >> On further reflection, these readers might conclude that the >> *combined* advice is to use block-mirror with NBD instead. This is >> correct. >> >> So why not tell them? >> >> Perhaps you'd like to give more nuanced advice, like "you should move >> to block-mirror with NBD, but if that's not practical for you, you >> should at least move to @block-incremental & friends, which will >> likely stick around for longer." That's fine. All I'm asking for is >> to not make things more confusing than they need to be :) >> >> [...] > > Telling this in deprecated.rst is enough? or you want me to put it also > in the error/warn messages and qapi? Let's make all of them point to blockdev-mirror with NBD. If you think mentioning @block-incremental & friends would be useful in some or all places would be useful, go ahead, I don't mind.