From patchwork Fri Jan 31 17:44:22 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 11360349 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9449492A for ; Fri, 31 Jan 2020 17:52:07 +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 6AB17206D5 for ; Fri, 31 Jan 2020 17:52:07 +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="IWikJnzq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6AB17206D5 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+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:57312 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ixaSc-0006O6-JX for patchwork-qemu-devel@patchwork.kernel.org; Fri, 31 Jan 2020 12:52:06 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:41361) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ixaLb-0002jY-J7 for qemu-devel@nongnu.org; Fri, 31 Jan 2020 12:44:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ixaLa-0004Qn-4j for qemu-devel@nongnu.org; Fri, 31 Jan 2020 12:44:51 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:30298 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 1ixaLZ-0004Pu-Tk for qemu-devel@nongnu.org; Fri, 31 Jan 2020 12:44:50 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580492689; 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=xOcmGmzDjNdL53A3beBj1FGQfubPjec9rtjHXJju37M=; b=IWikJnzqsG+PrVikzolD7EmPP7BaERKKlqNdTedYJmXv/EGhWh6rPdXVfdcuIibzmgd0oI XI2Wxw7+UgzQeVBqvOHGAI+S8MEbO1sWlcUghX/W33Y0Fjx16aeiOEBNZscD/rs6AfPX8v 4RFskVnF7hph0BD/2V687ZOg12UJYok= 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-377-Jn7vHhgnNgidW9bvBLtCZQ-1; Fri, 31 Jan 2020 12:44:42 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 25436800D54; Fri, 31 Jan 2020 17:44:41 +0000 (UTC) Received: from blue.redhat.com (ovpn-116-181.phx2.redhat.com [10.3.116.181]) by smtp.corp.redhat.com (Postfix) with ESMTP id A95887FB60; Fri, 31 Jan 2020 17:44:40 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Subject: [PATCH 03/17] qcow2: Avoid feature name extension on small cluster size Date: Fri, 31 Jan 2020 11:44:22 -0600 Message-Id: <20200131174436.2961874-4-eblake@redhat.com> In-Reply-To: <20200131174436.2961874-1-eblake@redhat.com> References: <20200131174436.2961874-1-eblake@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: Jn7vHhgnNgidW9bvBLtCZQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com 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: david.edmondson@oracle.com, Kevin Wolf , qemu-block@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" As the feature name table can be quite large (over 9k if all 64 bits of all three feature fields have names; a mere 8 features leaves only 8 bytes for a backing file name in a 512-byte cluster), it is unwise to emit this optional header in images with small cluster sizes. Update iotest 036 to skip running on small cluster sizes; meanwhile, note that iotest 061 never passed on alternative cluster sizes (however, I limited this patch to tests with output affected by adding feature names, rather than auditing for other tests that are not robust to alternative cluster sizes). Signed-off-by: Eric Blake Reviewed-by: Vladimir Sementsov-Ogievskiy Reviewed-by: Alberto Garcia --- block/qcow2.c | 11 +++++++++-- tests/qemu-iotests/036 | 6 ++++-- tests/qemu-iotests/061 | 6 ++++-- 3 files changed, 17 insertions(+), 6 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index d3e7709ac2b4..6ea06dbdf48a 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2819,8 +2819,15 @@ int qcow2_update_header(BlockDriverState *bs) buflen -= ret; } - /* Feature table */ - if (s->qcow_version >= 3) { + /* + * Feature table. A mere 8 feature names occupies 392 bytes, and + * when coupled with the v3 minimum header of 104 bytes plus the + * 8-byte end-of-extension marker, that would leave only 8 bytes + * for a backing file name in an image with 512-byte clusters. + * Thus, we choose to omit this header for cluster sizes 4k and + * smaller. + */ + if (s->qcow_version >= 3 && s->cluster_size > 4096) { static const Qcow2Feature features[] = { { .type = QCOW2_FEAT_TYPE_INCOMPATIBLE, diff --git a/tests/qemu-iotests/036 b/tests/qemu-iotests/036 index 512598421c20..cf522de7a1aa 100755 --- a/tests/qemu-iotests/036 +++ b/tests/qemu-iotests/036 @@ -44,8 +44,10 @@ trap "_cleanup; exit \$status" 0 1 2 3 15 _supported_fmt qcow2 _supported_proto file # Only qcow2v3 and later supports feature bits; -# qcow2.py does not support external data files -_unsupported_imgopts 'compat=0.10' data_file +# qcow2.py does not support external data files; +# this test requires a cluster size large enough for the feature table +_unsupported_imgopts 'compat=0.10' data_file \ + 'cluster_size=\(512\|1024\|2048\|4096\)' echo echo === Image with unknown incompatible feature bit === diff --git a/tests/qemu-iotests/061 b/tests/qemu-iotests/061 index 36b040491fef..ce285d308408 100755 --- a/tests/qemu-iotests/061 +++ b/tests/qemu-iotests/061 @@ -44,8 +44,10 @@ _supported_os Linux # Conversion between different compat versions can only really work # with refcount_bits=16; # we have explicit tests for data_file here, but the whole test does -# not work with it -_unsupported_imgopts 'refcount_bits=\([^1]\|.\([^6]\|$\)\)' data_file +# not work with it; +# we have explicit tests for various cluster sizes, the remaining tests +# require the default 64k cluster +_unsupported_imgopts 'refcount_bits=\([^1]\|.\([^6]\|$\)\)' data_file cluster_size echo echo "=== Testing version downgrade with zero expansion ==="