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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, 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 69765C2D0A8 for ; Mon, 28 Sep 2020 14:36:10 +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 D8F8B2075A for ; Mon, 28 Sep 2020 14:36:09 +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="Iwa72SCD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D8F8B2075A 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]:56692 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kMuG9-0006HL-0R for qemu-devel@archiver.kernel.org; Mon, 28 Sep 2020 10:36:09 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:55598) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kMuDf-00052R-1P for qemu-devel@nongnu.org; Mon, 28 Sep 2020 10:33:35 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:30956) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kMuDc-0004vb-Qc for qemu-devel@nongnu.org; Mon, 28 Sep 2020 10:33:34 -0400 Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1601303610; 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=W7fK/NQPPePoj8L/gqsYMkyYNYN5zy779blewpwgWb8=; b=Iwa72SCDu2iYEK8mVzK3COQQllnG2pxO5OYzC53prSczbXVmD/y/ZUMW0nDKqA2PUp+qYV KzGm2a2qLcZ4Gc5QeodkesBD0RHOxUfzrPX5TdVDy4x3RQAuvb2vyqrnhQPen5DsH99NGT Vd38fiJKNqsy47YqupZVE2w5hJCv33c= 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-526-wPVAIw2tOwCpqLwvU_mJww-1; Mon, 28 Sep 2020 10:33:28 -0400 X-MC-Unique: wPVAIw2tOwCpqLwvU_mJww-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 49E4880572E; Mon, 28 Sep 2020 14:33:26 +0000 (UTC) Received: from [10.3.112.208] (ovpn-112-208.phx2.redhat.com [10.3.112.208]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B9D055C1BB; Mon, 28 Sep 2020 14:33:22 +0000 (UTC) Subject: Re: [PATCH 2/3] nbd: Add new qemu:allocation-depth metacontext To: "Richard W.M. Jones" References: <20200925203249.155705-1-eblake@redhat.com> <20200925203249.155705-3-eblake@redhat.com> <20200926073308.GV3888@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: Date: Mon, 28 Sep 2020 09:33:22 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200926073308.GV3888@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/28 03:47:08 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.687, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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: Kevin Wolf , pkrempa@redhat.com, qemu-block@nongnu.org, Markus Armbruster , qemu-devel@nongnu.org, Max Reitz , vsementsov@virtuozzo.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/26/20 2:33 AM, Richard W.M. Jones wrote: > On Fri, Sep 25, 2020 at 03:32:48PM -0500, Eric Blake wrote: >> +The second is related to exposing the source of various extents within >> +the image, with a single context named: >> + >> + qemu:allocation-depth >> + >> +In the allocation depth context, bits 0 and 1 form a tri-state value: >> + >> + bits 0-1 clear: NBD_STATE_DEPTH_UNALLOC, means the extent is unallocated >> + bit 0 set: NBD_STATE_DEPTH_LOCAL, the extent is allocated in this image >> + bit 1 set: NBD_STATE_DEPTH_BACKING, the extent is inherited from a >> + backing layer > >>>From the cover description I imagined it would show the actual depth, ie: > > top -> backing -> backing -> backing > depth: 1 2 3 .... (0 = unallocated) > > I wonder if that is possible? (Perhaps there's something I don't > understand here.) The real reason I don't want to do a straight depth number is that 'qemu-img map' combined with x-dirty-bitmap is still a very convenient way to get at bits 0 and 1 (even if it requires decoding). But if we plumb in a way for bdrv_get_status to return depth counts (rather than reimplementing the depth count ourselves), I would have no problem with returning a struct: bits 31-4: the depth of the chain bits 3-2: reserved (to make reading hex values easier...) bits 1-0: tri-state of unalloc, local, or backing where it would look like: 0x0000 -> unallocated 0x0011 -> depth 1, local 0x0022 -> depth 2, from the first backing layer 0x0032 -> depth 3, from the second backing layer 0x0042 ... -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org