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=-6.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 276D9C433E3 for ; Tue, 21 Jul 2020 14:29:53 +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 E820920714 for ; Tue, 21 Jul 2020 14:29:52 +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="fEQ4UGhy" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E820920714 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]:50104 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jxtHE-0007w6-5R for qemu-devel@archiver.kernel.org; Tue, 21 Jul 2020 10:29:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33402) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jxtGE-0006fE-Au for qemu-devel@nongnu.org; Tue, 21 Jul 2020 10:28:50 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:44051 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 1jxtGB-0004TS-LC for qemu-devel@nongnu.org; Tue, 21 Jul 2020 10:28:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595341722; 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: in-reply-to:in-reply-to:references:references; bh=k3KfV3j5Vp1n0D93cbzgqvyrEcCNh90Bo6e3qprwoxU=; b=fEQ4UGhyhZ2QrE3ar4MQJjOYndm3B8CJVi9Ois8gRKIV/oAhe+UraMs9+7M0ztjSKRC3gj ayWWaoC3W5AkZpsC0czc8UbAmIs2pqU80vHXoDYcWdseaLdXh6Gsu9XFWCdAoGFbt+uAwK A8NfPuTkLCLneU0Q++vdHvLqwouWWQ0= 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-247-XDGSt-RcNDiWBCvq8O4ETw-1; Tue, 21 Jul 2020 10:28:40 -0400 X-MC-Unique: XDGSt-RcNDiWBCvq8O4ETw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2B0EA1083FA2; Tue, 21 Jul 2020 14:28:39 +0000 (UTC) Received: from linux.fritz.box (ovpn-113-97.ams2.redhat.com [10.36.113.97]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B1ECC5DA30; Tue, 21 Jul 2020 14:28:37 +0000 (UTC) Date: Tue, 21 Jul 2020 16:28:36 +0200 From: Kevin Wolf To: qemu-block@nongnu.org Subject: Re: [PATCH for-5.1 v2 1/2] qcow2: Implement v2 zero writes with discard if possible Message-ID: <20200721142836.GD18481@linux.fritz.box> References: <20200721135520.72355-1-kwolf@redhat.com> <20200721135520.72355-2-kwolf@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200721135520.72355-2-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.81; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/21 10:15:27 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: nsoffer@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 21.07.2020 um 15:55 hat Kevin Wolf geschrieben: > qcow2 version 2 images don't support the zero flag for clusters, so for > write_zeroes requests, we return -ENOTSUP and get explicit zero buffer > writes. If the image doesn't have a backing file, we can do better: Just > discard the respective clusters. > > This is relevant for 'qemu-img convert -O qcow2 -n', where qemu-img has > to assume that the existing target image may contain any data, so it has > to write zeroes. Without this patch, this results in a fully allocated > target image, even if the source image was empty. > > Reported-by: Nir Soffer > Signed-off-by: Kevin Wolf Oops, forgot to apply this from v1: Reviewed-by: Max Reitz The patch is unchanged, so I'll include this when applying. Kevin