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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 53B66C35254 for ; Wed, 5 Feb 2020 13:52:55 +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 2010D2082E for ; Wed, 5 Feb 2020 13:52:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hAo6obG9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2010D2082E 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]:47400 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1izL6s-0004d0-8F for qemu-devel@archiver.kernel.org; Wed, 05 Feb 2020 08:52:54 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:52385) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1izL6E-00049T-B7 for qemu-devel@nongnu.org; Wed, 05 Feb 2020 08:52:15 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1izL6C-0001jI-9U for qemu-devel@nongnu.org; Wed, 05 Feb 2020 08:52:13 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:48808 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1izL6C-0001fD-2o for qemu-devel@nongnu.org; Wed, 05 Feb 2020 08:52:12 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580910731; 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=D+bn0gY58nI+S26rHTO5iBso8u7mogSdW8XAPF8jiZs=; b=hAo6obG9DbXV89Vae5RSr5mfKJKXt75YpXEJLKXF6x5jWeHZZkQayWrKCkPIFHwJ+BkS5U iUD74OGM2lk3fUktT5f+EsfNCP830Jrrmk2YG+R24zt+IsD5tdYkExwL7cQI/ugIUpLcIj ZCynEMH7fGd+NCk7i4GhQiOayADiqOY= 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-429-FDeXKmWZOT-Fvh2zD2Gwfg-1; Wed, 05 Feb 2020 08:51:57 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7AFA41007282; Wed, 5 Feb 2020 13:51:56 +0000 (UTC) Received: from [10.3.116.181] (ovpn-116-181.phx2.redhat.com [10.3.116.181]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0483A87B15; Wed, 5 Feb 2020 13:51:55 +0000 (UTC) Subject: Re: [PATCH v2 01/33] block: Add BlockDriver.is_format To: Max Reitz , qemu-block@nongnu.org References: <20200204170848.614480-1-mreitz@redhat.com> <20200204170848.614480-2-mreitz@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: Date: Wed, 5 Feb 2020 07:51:55 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200204170848.614480-2-mreitz@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: FDeXKmWZOT-Fvh2zD2Gwfg-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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 , Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2/4/20 11:08 AM, Max Reitz wrote: > We want to unify child_format and child_file at some point. One of the > important things that set format drivers apart from other drivers is > that they do not expect other format nodes under them (except in the > backing chain). That means we need something on which to distinguish > format drivers from others, and hence this flag. It _is_ possible to set up a format node on top of another; in fact, our testsuite does that in at least iotest 072. I agree that setups like 'qcow2 - qcow2 - file' are uncommon, but the setup 'qcow2 - raw - file' may be useful for extracting a partition of a raw disk when it is known that the partition in that disk itself contains qcow2 data. > > Signed-off-by: Max Reitz > --- > +++ b/include/block/block_int.h > @@ -94,6 +94,13 @@ struct BlockDriver { > * must implement them and return -ENOTSUP. > */ > bool is_filter; > + /* > + * Set to true if the BlockDriver is a format driver. Format nodes > + * generally do not expect their children to be other format nodes > + * (except for backing files), and so format probing is disabled > + * on those children. Aha - nested formats ARE still allowed when you explicitly request it (which is what iotest 72 does) - what you are stating here is that implicit probing of is forbidden for a parent declared as a format driver. That makes more sense. I'm not sure if the commit message needs a tweak, but the patch itself is sane as-is. Reviewed-by: Eric Blake > + */ > + bool is_format; > /* > * Return true if @to_replace can be replaced by a BDS with the > * same data as @bs without it affecting @bs's behavior (that is, > -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org