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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 A27B9C433ED for ; Fri, 16 Apr 2021 07:06:57 +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 EB80761029 for ; Fri, 16 Apr 2021 07:06:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB80761029 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]:50886 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lXIZ5-0005DK-Kc for qemu-devel@archiver.kernel.org; Fri, 16 Apr 2021 03:06:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:46270) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lXIXo-0004QM-Fz for qemu-devel@nongnu.org; Fri, 16 Apr 2021 03:05:36 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:51857) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lXIXk-00015z-OS for qemu-devel@nongnu.org; Fri, 16 Apr 2021 03:05:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618556730; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=0xpY8aT8z1FqXD/dZWMpfPgvKLr8bJfiWoTJnE3ZIYQ=; b=LGeJiCFU8GZDZyLkgmPyv65eJ36yBb+D0IpB3xN7CmY7uwyiAYcyUqOhmNqPrjGCoXSJk1 Ro5YBWAtmr+k1vHcp63KFTRPwB+qzV7TApwAPwmlKvvANPtkP2XBZdeJMm94kbG1SUj6jI DJ6PS/Gtr2m/ukU6Gc3cdM7ehpCZICk= 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-568-LBV0OMc7P-eNNY6BNv1d0w-1; Fri, 16 Apr 2021 03:05:28 -0400 X-MC-Unique: LBV0OMc7P-eNNY6BNv1d0w-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id 499B0107ACC7; Fri, 16 Apr 2021 07:05:27 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-113-131.ams2.redhat.com [10.36.113.131]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E3B61437F; Fri, 16 Apr 2021 07:05:25 +0000 (UTC) Subject: Re: about mirror cancel To: Vladimir Sementsov-Ogievskiy , qemu block References: From: Max Reitz Message-ID: <5df8166f-a204-6510-e27a-1b334f0bb3f3@redhat.com> Date: Fri, 16 Apr 2021 09:05:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=mreitz@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, NICE_REPLY_A=-0.001, 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=unavailable 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: Kevin Wolf , "Denis V. Lunev" , qemu-devel Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 15.04.21 20:46, Vladimir Sementsov-Ogievskiy wrote: > Hi all! > > Recently I've implemented fast-cancelling of mirror job: do > bdrv_cancel_in_flight() in mirror_cancel(). > > Now I'm in doubt: is it a correct thing? I heard, that mirror-cancel is > a kind of valid mirror completion.. > > Looking at documentation: > > # Note that if you issue 'block-job-cancel' after 'drive-mirror' has > indicated > # (via the event BLOCK_JOB_READY) that the source and destination are > # synchronized, then the event triggered by this command changes to > # BLOCK_JOB_COMPLETED, to indicate that the mirroring has ended and the > # destination now has a point-in-time copy tied to the time of the > cancellation. > > So, in other words, do we guarantee something to the user, if it calls > mirror-cancel in ready state? Does this abuse exist in libvirt? How is it abuse it if it’s documented? AFAIR it does exist, because libvirt’s blockcopy always uses mirror (with --pivot it’s allowed to complete, without it is cancelled). (And the point of course is that if you want mirror to create a copy without pivoting, you need this behavior, because otherwise the target may be in an inconsistent state.) > ==== > > Note, that if cancelling all in-flight requests on target is wrong on > mirror cancel, we still don't have real bug, as the only implementation > of .bdrv_cancel_in_flight is stopping reconnect waiting in nbd driver. > So, we'll cancel requests only if connection is already lost anyway. > > But that probably means, that correct name of the handler would be > .bdrv_cancel_in_fligth_requests_that_will_most_probably_fail_anyway().. It’s documentation states that it should cancel all in-flight requests, so it’s more likely it just isn’t implemented where it could be. > And it also means, that abuse of mirror-cancel as valid completion is a > bad idea, as we can't distinguish the cases when user calls job-cancel > to have a kind of point-in-time copy, or just to cancel job (and being > not interested in the final state of target). > > So, probably we need an option boolean argument for blockjob-cancel, > like "hard", that will cancel in-flight writes on target node.. There is @force. See commit b76e4458b1eb3c3. Max