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 B648AC432C0 for ; Wed, 20 Nov 2019 15:20:24 +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 7F48D208C3 for ; Wed, 20 Nov 2019 15:20:24 +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="UQsXtBYk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7F48D208C3 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]:59222 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iXRmJ-0002rJ-NA for qemu-devel@archiver.kernel.org; Wed, 20 Nov 2019 10:20:23 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:32874) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iXRkW-0001zj-O8 for qemu-devel@nongnu.org; Wed, 20 Nov 2019 10:18:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iXRkV-0006VM-PH for qemu-devel@nongnu.org; Wed, 20 Nov 2019 10:18:32 -0500 Received: from fanzine.igalia.com ([178.60.130.6]:39279) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iXRkV-0006Ux-5c; Wed, 20 Nov 2019 10:18:31 -0500 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=c5JGIGSRjaUAHrs3DCxQDhKeZYx0F+iKCX7m0/eHQj8=; b=UQsXtBYk/lG1RhFHPs6m4VUWc3TVZTkmeDvXxRKAch5M05zlnJyLqqz1xSbCAupuyeVNbRELJZxnv906DxyAl9QQCIq0gNccJYScGpMxBJu+iTMoq1mWkayE8ZI58sFvU+UMLnQXPzlwk7dRtwg1d2vHQ3ObOjr0svWMHEv+2K3MsKV8J0ZUHvksx/sr8t4FgrF3iglkOiO2o/cehj/YwoCjoRV9HaYaoUYuwzuNkL6AgbbghxkswGs10wWYAf5Hph39J9yoEB5QXoZUPKmQ+AG94rm5JidJfXyWRa0EJOO5LkKax7DLS6NwthexaZtWtt0Rh6bNyVLGB+PR0mQxvA==; 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 1iXRkR-0005Zp-PE; Wed, 20 Nov 2019 16:18:27 +0100 Received: from berto by mail.igalia.com with local (Exim) id 1iXRkR-00015N-Md; Wed, 20 Nov 2019 16:18:27 +0100 From: Alberto Garcia To: Vladimir Sementsov-Ogievskiy , "qemu-devel\@nongnu.org" Subject: Re: qcow2 preallocation and backing files In-Reply-To: References: <20191120120625.GA25497@igalia.com> User-Agent: Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) Date: Wed, 20 Nov 2019 16:18:27 +0100 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 , "qemu-block@nongnu.org" , Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed 20 Nov 2019 01:27:53 PM CET, Vladimir Semeeausntsov-Ogievskiy wrote: > 3. Also, the latter way is inconsistent with discard. Discarded > regions returns zeroes, not clusters from backing. I think discard and > truncate should behave in the same safe zero way. But then PREALLOC_MODE_OFF implies that the L2 metadata should be preallocated (all clusters should be QCOW2_CLUSTER_ZERO_PLAIN), at least when there is a backing file. Or maybe we just forbid PREALLOC_MODE_OFF during resize if there is a backing file ? Berto