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=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 37D9DC63777 for ; Fri, 27 Nov 2020 10:07:51 +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 8920D221F7 for ; Fri, 27 Nov 2020 10:07:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="KqdUidqy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8920D221F7 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]:42152 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kiafN-0004wP-1O for qemu-devel@archiver.kernel.org; Fri, 27 Nov 2020 05:07:49 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:51290) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kiaeO-0004Q6-Tp for qemu-devel@nongnu.org; Fri, 27 Nov 2020 05:06:48 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:37287) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kiaeK-0002fG-Ne for qemu-devel@nongnu.org; Fri, 27 Nov 2020 05:06:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606471603; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type; bh=OeiOePxDH8XgJODFzYqYQRc7X41EcvLOnxyuX1Qlquc=; b=KqdUidqyYFukhM9uT61+lVNdc6oL57fjEHNSKXXwryWMsS1K7s2dYTURKJJvG7HFERqdrD WpPEt+Yept7TvqsETtuh8wC/R3rbF9qkesV02rWHWRJzvT3yxe+L6Fa+KhEELFl2QvFYP8 P7xoLioF5MJcJRPbklc9mDG23eAwv9I= 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-394-g5yzwLwrPwGWYX4iBj57zA-1; Fri, 27 Nov 2020 05:06:39 -0500 X-MC-Unique: g5yzwLwrPwGWYX4iBj57zA-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 84CEE18C89DA; Fri, 27 Nov 2020 10:06:38 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-112-103.ams2.redhat.com [10.36.112.103]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 55FC76085D; Fri, 27 Nov 2020 10:06:38 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id E197F113864E; Fri, 27 Nov 2020 11:06:36 +0100 (CET) From: Markus Armbruster To: Kevin Wolf , Max Reitz , Denis Plotnikov , qemu-devel@nongnu.org, qemu-block@nongnu.org Subject: ImageInfo oddities regarding compression Date: Fri, 27 Nov 2020 11:06:36 +0100 Message-ID: <87r1ofru4z.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=63.128.21.124; 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=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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" ImageInfo has an optional member @compressed: ## # @ImageInfo: [...] # @compressed: true if the image is compressed (Since 1.7) Doc bug: neglects to specify the default. I guess it's false. The only user appears to be vmdk_get_extent_info(). Goes back to v1.7.0's commits f4c129a38a vmdk: Implment bdrv_get_specific_info cbe82d7fb3 qapi: Add optional field 'compressed' to ImageInfo ImageInfo also has an optional member @format-specific. Doc bug: neglects to specify when it's present. I assume it's always present when member @format has a value that has a non-empty variant in @format-specific's type ImageInfoSpecific. Format qcow2's variant is ImageInfoSpecificQCow2. It has a mandatory member @compression-type. ## # @Qcow2CompressionType: # # Compression type used in qcow2 image file # # @zlib: zlib compression, see # @zstd: zstd compression, see # # Since: 5.1 ## { 'enum': 'Qcow2CompressionType', 'data': [ 'zlib', { 'name': 'zstd', 'if': 'defined(CONFIG_ZSTD)' } ] } Apparently, you can't have a qcow2 image without compression. Correct? Can you imagine a use case for "without compression"? I fell down this (thankfully shallow) rabbit hole because we also have { 'enum': 'MultiFDCompression', 'data': [ 'none', 'zlib', { 'name': 'zstd', 'if': 'defined(CONFIG_ZSTD)' } ] } I wonder whether we could merge them into a common type.