From patchwork Mon May 22 18:46:31 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Blake X-Patchwork-Id: 13250948 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 34B03C7EE23 for ; Mon, 22 May 2023 18:47:34 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q1AYQ-0008AY-4N; Mon, 22 May 2023 14:46:46 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q1AYP-00089G-1m for qemu-devel@nongnu.org; Mon, 22 May 2023 14:46:45 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q1AYN-0008JC-3q for qemu-devel@nongnu.org; Mon, 22 May 2023 14:46:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1684781201; 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; bh=9wxyHHmtNJw/tCA3q+lIV5qOOTS+hWiwLY3VPrMUxm8=; b=NMCATKFhp6eYjP4N8kX1kU8183LGuVhkCPJ9sAErAczltKDSIjb5SamB/OGlBMTGPWIZ4i iK2x2XtXO9ELGlogv8xPc42ox0kbtIx3VR2oiKvsdtZ+dhv1yBwtfzY1xlJwWQMJGJsk0j RE/0Hz+LVtKAtb0+mNo6KkaPrrK0X04= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-674-mvw270KPPl-QS2NgDy2C6w-1; Mon, 22 May 2023 14:46:39 -0400 X-MC-Unique: mvw270KPPl-QS2NgDy2C6w-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 3D443185A78B; Mon, 22 May 2023 18:46:39 +0000 (UTC) Received: from green.redhat.com (unknown [10.2.16.46]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9DB39401026; Mon, 22 May 2023 18:46:38 +0000 (UTC) From: Eric Blake To: qemu-devel@nongnu.org Cc: Vladimir Sementsov-Ogievskiy , Kevin Wolf , Hanna Reitz , qemu-block@nongnu.org (open list:qcow2) Subject: [PATCH] qcow2: Explicit mention of padding bytes Date: Mon, 22 May 2023 13:46:31 -0500 Message-Id: <20230522184631.47211-1-eblake@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Although we already covered the need for padding bytes with our changes in commit 3ae3fcfa, commit 66fcbca5 (both v5.0.0) added one byte and relied on the rest of the text for implicitly covering 7 padding bytes. For consistency with other parts of the header (such as the header extension format listing padding from n - m, or the snapshot table entry listing variable padding), we might as well call out the remaining 7 bytes as padding until such time (as any) as they gain another meaning. Signed-off-by: Eric Blake CC: Vladimir Sementsov-Ogievskiy Reviewed-by: Vladimir Sementsov-Ogievskiy --- Spring cleaning my old branches. v3: reviving an old patch; v2 was: https://lists.gnu.org/archive/html/qemu-devel/2020-04/msg00687.html --- docs/interop/qcow2.txt | 1 + 1 file changed, 1 insertion(+) diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt index e7f036c286b..2c4618375ad 100644 --- a/docs/interop/qcow2.txt +++ b/docs/interop/qcow2.txt @@ -226,6 +226,7 @@ version 2. in QEMU. However, clusters with the deflate compression type do not have zlib headers. + 105 - 111: Padding, contents defined below. === Header padding ===