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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 94F36CA9EA0 for ; Fri, 18 Oct 2019 09:50:43 +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 6F75E222BD for ; Fri, 18 Oct 2019 09:50:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6F75E222BD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=virtuozzo.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:37252 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iLOuA-00013o-Id for qemu-devel@archiver.kernel.org; Fri, 18 Oct 2019 05:50:42 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49167) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iLOrf-0006iE-4g for qemu-devel@nongnu.org; Fri, 18 Oct 2019 05:48:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iLOrd-0005ZV-Tt for qemu-devel@nongnu.org; Fri, 18 Oct 2019 05:48:07 -0400 Received: from relay.sw.ru ([185.231.240.75]:42976) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iLOra-0005Wc-TH; Fri, 18 Oct 2019 05:48:03 -0400 Received: from [10.94.3.0] (helo=kvm.qa.sw.ru) by relay.sw.ru with esmtp (Exim 4.92.2) (envelope-from ) id 1iLOrY-0004Ah-BZ; Fri, 18 Oct 2019 12:48:00 +0300 From: Vladimir Sementsov-Ogievskiy To: qemu-block@nongnu.org Subject: [PATCH v8 3/3] docs: qcow2: introduce compression type feature Date: Fri, 18 Oct 2019 12:47:58 +0300 Message-Id: <20191018094758.7124-4-vsementsov@virtuozzo.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20191018094758.7124-1-vsementsov@virtuozzo.com> References: <20191018094758.7124-1-vsementsov@virtuozzo.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 185.231.240.75 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: kwolf@redhat.com, vsementsov@virtuozzo.com, armbru@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, dplotnikov@virtuozzo.com, den@openvz.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" The patch add new additional field to qcow2 header: compression_type, which specifies compression type. If field is absent or zero, default compression type is set: ZLIB, which corresponds to current behavior. New compression type (ZSTD) is to be added in further commit. Suggested-by: Denis Plotnikov Signed-off-by: Vladimir Sementsov-Ogievskiy --- docs/interop/qcow2.txt | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt index b971e59b1a..4eabd81363 100644 --- a/docs/interop/qcow2.txt +++ b/docs/interop/qcow2.txt @@ -109,6 +109,12 @@ least next five fields, up to the @header_length field. An External Data File Name header extension may be present if this bit is set. + Bit 3: Compression type bit. If this bit is set, + non-default compression is used for compressed + clusters. In this case, @header_length must + be at least 105 and @compression_type field + must be non-zero. + Bits 3-63: Reserved (set to 0) 80 - 87: compatible_features @@ -183,7 +189,18 @@ It's allowed for the header end to cut some field in the middle (in this case the field is considered as absent), but in this case the part of the field which is covered by @header_length must be zeroed. - < ... No additional fields in the header currently ... > + 104: compression_type + Defines the compression method used for compressed clusters. + A single compression type is applied to all compressed image + clusters. + If incompatible compression type bit is set: the field must + exist (i.e. @header_length >= 105) and must be non-zero ( + which means non-zlib compression type) + If incompatible compression type bit is unset: the field + may not exist (if @header_length < 105) or it must be zero + (which means zlib). + Available compression type values: + 0: zlib Header padding If @header_length is larger than 104, software SHOULD make it a -- 2.21.0