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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 BACEEC2BA19 for ; Tue, 14 Apr 2020 16:32:44 +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 82D05206E9 for ; Tue, 14 Apr 2020 16:32:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="IGN3S6SI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 82D05206E9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=igalia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:34188 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jOOUN-0008CK-Lk for qemu-devel@archiver.kernel.org; Tue, 14 Apr 2020 12:32:43 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52949) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jOOSf-0006R6-PS for qemu-devel@nongnu.org; Tue, 14 Apr 2020 12:31:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jOOSe-00010y-Kn for qemu-devel@nongnu.org; Tue, 14 Apr 2020 12:30:57 -0400 Received: from fanzine.igalia.com ([178.60.130.6]:51599) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1jOOSd-0000xh-Ov; Tue, 14 Apr 2020 12:30:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Type:MIME-Version:Message-ID:Date:References:In-Reply-To:Subject:Cc:To:From; bh=BVVXGDXpudVw7nOjZv5M0PlmfT18ZPrVoCl7zON5WTs=; b=IGN3S6SIag6kLBHVv21JHa3MPdNPa95C3cFMr/eAAFmMT36D9J0h0jeZoWM2+VCeTIteWtLnoGYXXaAvdAFmNmuUy24TLRsNZqNgmEtg08iWhEJSAckC9tYrzvwi5I6nrSkrL2vMbvPPD7glxCyu4JEShqyP7F1gG4QjJ2U77CpusvNdTDYk7nRRxXxfAAYey3V8wLqNneUukU6fr79f5FDqv4MEKsrZtpmsqDaN32ymWSpPGfJy0WMFnOiPpOxEp3L4rKbEiHzwqmAvJYKYnFMf9Krs1ZdRwp6HlHyHa1Lr57bTcJc4sRJwgJiwnKtRKLwXWuetIhY3grxrWEtSRg==; Received: from maestria.local.igalia.com ([192.168.10.14] helo=mail.igalia.com) by fanzine.igalia.com with esmtps (Cipher TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim) id 1jOOSY-0001YS-1s; Tue, 14 Apr 2020 18:30:50 +0200 Received: from berto by mail.igalia.com with local (Exim) id 1jOOSX-0005pk-No; Tue, 14 Apr 2020 18:30:49 +0200 From: Alberto Garcia To: Vladimir Sementsov-Ogievskiy , Eric Blake , qemu-devel@nongnu.org Subject: Re: [PATCH v4 07/30] qcow2: Document the Extended L2 Entries feature In-Reply-To: <83922517-b5f5-2d4a-6518-c1912942ad27@virtuozzo.com> References: <8c88b96f-c6f5-e06c-73e1-56001089a7ca@redhat.com> <781c734c-e53c-76ae-74de-26d9e827e1a2@virtuozzo.com> <83922517-b5f5-2d4a-6518-c1912942ad27@virtuozzo.com> User-Agent: Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) Date: Tue, 14 Apr 2020 18:30:49 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x (no timestamps) [generic] [fuzzy] X-Received-From: 178.60.130.6 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" , Anton Nefedov , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue 14 Apr 2020 06:19:18 PM CEST, Vladimir Sementsov-Ogievskiy wrote: >>> It still may cache information about zeroed subclusters: gives more >>> detailed block-status. But we should mention somehow external >>> files. Hm. not only for raw external files, but it is documented that >>> cluster can't be unallocated when an external data file is used. >> >> What do you mean by "cluster can't be unallocated" ? > > I mean this sentence from qcow2.txt: > > "The offset may only be 0 with > bit 63 set (indicating a host cluster offset of 0) when an > external data file is used." > > In other words, cluster can't be unallocated with data file in use. I still don't follow... clusters can be unallocated, and when you create a new image they are indeed unallocated. Bit 63 (QCOW_OFLAG_COPIED) is what indicates if a cluster is allocated or not, and you can unmap an allocated cluster with 'write -z -u'. Berto