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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 98056C38A2A for ; Thu, 7 May 2020 14:11:08 +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 5F6A92084D for ; Thu, 7 May 2020 14:11:08 +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="SyK5JDB8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F6A92084D 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]:37240 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jWhEw-0005BW-JO for qemu-devel@archiver.kernel.org; Thu, 07 May 2020 10:11:06 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39382) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jWhEF-0004es-Lx for qemu-devel@nongnu.org; Thu, 07 May 2020 10:10:23 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:44019 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 1jWhEE-0006j3-Mx for qemu-devel@nongnu.org; Thu, 07 May 2020 10:10:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588860622; 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=kLeUgkfEnYXyc0+xOjy2ggt6iNIC/XE3g08n7nwzmYI=; b=SyK5JDB8yBJ+qm/Mxol9hgvv3OB4qfz+ksSyVFe4XSEg53kXT6gNhiLyL14Wttk2busDbk EIcfqTKfo3VJ9rQdfwMzt7knrvuvuqi1NmUKZtRN3YsgC2O5JkksOy5zRXOozw0agbsupA 2glJUzPqv+5T3njOFKI/mWNYDndIEM0= 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-285-CLcqMTNNMseOFLoZPKQ_0g-1; Thu, 07 May 2020 10:10:18 -0400 X-MC-Unique: CLcqMTNNMseOFLoZPKQ_0g-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 BE290474; Thu, 7 May 2020 14:10:16 +0000 (UTC) Received: from [10.3.114.73] (ovpn-114-73.phx2.redhat.com [10.3.114.73]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 998E15D9C5; Thu, 7 May 2020 14:10:12 +0000 (UTC) Subject: Re: [PATCH v2 3/9] block/vdi: return ZERO block-status when appropriate To: Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org References: <20200507084800.20596-1-vsementsov@virtuozzo.com> <20200507084800.20596-4-vsementsov@virtuozzo.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <91b67c7b-68b1-2663-8abb-e6b2392b0611@redhat.com> Date: Thu, 7 May 2020 09:10:12 -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: <20200507084800.20596-4-vsementsov@virtuozzo.com> Content-Language: en-US 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=windows-1252; 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 = 2020/05/07 00:55:34 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_H3=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: fam@euphon.net, kwolf@redhat.com, ronniesahlberg@gmail.com, sw@weilnetz.de, pl@kamp.de, qemu-devel@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, pbonzini@redhat.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/7/20 3:47 AM, Vladimir Sementsov-Ogievskiy wrote: > In case of !VDI_IS_ALLOCATED[], we do zero out the corresponding chunk > of qiov. So, this should be reported as ZERO. > > Note that this changes visible output of "qemu-img map --output=json" > and "qemu-io -c map" commands. For qemu-img map, the change is obvious: > we just mark as zero what is really zero. For qemu-io it's less > obvious: what was unallocated now is allocated. > > There is an inconsistency in understanding of unallocated regions in > Qemu: backing-supporting format-drivers return 0 block-status to report > go-to-backing logic for this area. Some protocol-drivers (iscsi) return > 0 to report fs-unallocated-non-zero status (i.e., don't occupy space on > disk, read result is undefined). > > BDRV_BLOCK_ALLOCATED is defined as something more close to > go-to-backing logic. Still it is calculated as ZERO | DATA, so 0 from > iscsi is treated as unallocated. It doesn't influence backing-chain > behavior, as iscsi can't have backing file. But it does influence > "qemu-io -c map". > > We should solve this inconsistency at some future point. Now, let's > just make backing-not-supporting format drivers (vdi at this patch and > vpc with the following) to behave more like backing-supporting drivers > and not report 0 block-status. More over, returning ZERO status is > absolutely valid thing, and again, corresponds to how the other > format-drivers (backing-supporting) work. > > After block-status update, it never reports 0, so setting > unallocated_blocks_are_zero doesn't make sense (as the only user of it > is bdrv_co_block_status and it checks unallocated_blocks_are_zero only > for unallocated areas). Drop it. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > block/vdi.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > Yes, much better commit message, showing why the code change is correct. Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org