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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 D0DF7C433DF for ; Wed, 27 May 2020 13:28:05 +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 9D2FF20899 for ; Wed, 27 May 2020 13:28:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RJHUf0Y3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D2FF20899 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]:36566 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jdw6G-0000b7-T3 for qemu-devel@archiver.kernel.org; Wed, 27 May 2020 09:28:04 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59580) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jdw5j-00005D-LK for qemu-devel@nongnu.org; Wed, 27 May 2020 09:27:31 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:29791 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jdw5i-0005Qd-GL for qemu-devel@nongnu.org; Wed, 27 May 2020 09:27:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590586049; 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=eBlHYRr+2Dh8pEH404jcIq99PLQqY8QrTlAXqVTDhS8=; b=RJHUf0Y39xZrlTlXLqy8w19FlcJHJ5A/HApu7mNlYploDq2cjfX7hqJQh6aEXH1kPxdFYj UbjZAA+fclv3phdZB34eGx0COpHH+LkOjIuOvHRiy/BVeS9st7+rOBP51ek86xD8xdy5Gp 9BratT4AhnixYiiu666JNbbEFp0hZl8= 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-77-zVGhS5a3MQCqtzRdiYPJ-Q-1; Wed, 27 May 2020 09:27:25 -0400 X-MC-Unique: zVGhS5a3MQCqtzRdiYPJ-Q-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AAB3B460; Wed, 27 May 2020 13:27:23 +0000 (UTC) Received: from [10.3.112.88] (ovpn-112-88.phx2.redhat.com [10.3.112.88]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0427A60C84; Wed, 27 May 2020 13:27:21 +0000 (UTC) Subject: Re: [PATCH v7 14/32] qcow2: Add QCow2SubclusterType and qcow2_get_subcluster_type() To: Alberto Garcia , qemu-devel@nongnu.org References: <961e6f3e3af13a25c666859b391b7ed147873d8b.1590429901.git.berto@igalia.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: Date: Wed, 27 May 2020 08:27:21 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/27 00:45:05 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN 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 , Derek Su , Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/27/20 4:51 AM, Alberto Garcia wrote: > On Tue 26 May 2020 10:32:08 PM CEST, Eric Blake wrote: >>> +/* The subcluster X [0..31] is allocated */ >>> +#define QCOW_OFLAG_SUB_ALLOC(X) (1ULL << (X)) >>> +/* The subcluster X [0..31] reads as zeroes */ >>> +#define QCOW_OFLAG_SUB_ZERO(X) (QCOW_OFLAG_SUB_ALLOC(X) << 32) >>> +/* Subclusters [X, Y) (0 <= X <= Y <= 32) are allocated */ >> >> As you are now using a half-open range, should this be: >> (0 <= X < Y <= 32) > > I changed the macros because I wanted to allow cases where X == Y. > > The reason is the new qcow2_get_subcluster_range_type() function: > > case QCOW2_SUBCLUSTER_NORMAL: > val = l2_bitmap | QCOW_OFLAG_SUB_ALLOC_RANGE(0, sc_from); > return cto32(val) - sc_from; > > If sc_from is 0 then the result of the macro is also 0, and 'val' equals > the lower 32 bits (allocation status bits) of the L2 bitmap, as > expected. > >>> +#define QCOW_OFLAG_SUB_ALLOC_RANGE(X, Y) \ >>> + (QCOW_OFLAG_SUB_ALLOC(Y) - QCOW_OFLAG_SUB_ALLOC(X)) >> >> with <= instead of <, then it is impossible to distinguish between >> QCOW_OFLAG_SUB_ALLOC_RANGE(0,0) and QCOW_OFLAG_SUB_ALLOC_RANGE(31,31) >> which both resolve to 0. > > Exactly, there is no difference and there should not be. Okay, then with that explanation, I agree that the comment is correct as written. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org