From nobody Mon Feb 9 21:36:49 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=virtuozzo.com ARC-Seal: i=1; a=rsa-sha256; t=1576498759; cv=none; d=zohomail.com; s=zohoarc; b=D2G/+UJHjwfBbHMI7m+wv8k7JwoGTV5NucGCl0w7faSqNVj8TPTGGjWJOgHsCrK51tAlS+8KsG4N1nhuo4VXuouLPWzfU/F8PYqh3Nec1tbKM4VzrLs5KJ6NoE22YIctPl0ltSOO7pvi9GvefDnnGm2pou9DJqARMPUZN3yx9Ms= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1576498759; h=Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:Message-ID:References:Sender:Subject:To; bh=sQAWK0brmVWLa3B/U1oSId2nhxKOYgvP4XOD7mSUii8=; b=fnZwWGWD/I+qIyS193VgrT/H/zSfAUJ2yt2FiGjHmCZajPnk1XIjX1Y3CPxcqLmiTaZUnU4nMIhMmv9Idma/fzQbN4f8gtO2wxVC65hg3v9+eyGcgBbaeYH+tUf2tLtCN93o4+3xtNx7k8pP5p6saR/iWGep+MFdJIrxmpNxrCg= ARC-Authentication-Results: i=1; mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 157649875902465.72408289231191; Mon, 16 Dec 2019 04:19:19 -0800 (PST) Received: from localhost ([::1]:52596 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1igpLJ-00020k-Fv for importer@patchew.org; Mon, 16 Dec 2019 07:19:17 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:49370) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1igpJp-0000Wi-Hb for qemu-devel@nongnu.org; Mon, 16 Dec 2019 07:17:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1igpJn-0001rp-TL for qemu-devel@nongnu.org; Mon, 16 Dec 2019 07:17:45 -0500 Received: from relay.sw.ru ([185.231.240.75]:33562) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1igpJn-0001r9-M5; Mon, 16 Dec 2019 07:17:43 -0500 Received: from vovaso.qa.sw.ru ([10.94.3.0] helo=kvm.qa.sw.ru) by relay.sw.ru with esmtp (Exim 4.92.3) (envelope-from ) id 1igpJe-00033D-Gr; Mon, 16 Dec 2019 15:17:34 +0300 From: Vladimir Sementsov-Ogievskiy To: qemu-devel@nongnu.org Subject: [PATCH v9 2/2] docs: qcow2: introduce compression type feature Date: Mon, 16 Dec 2019 15:17:33 +0300 Message-Id: <20191216121733.63562-3-vsementsov@virtuozzo.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20191216121733.63562-1-vsementsov@virtuozzo.com> References: <20191216121733.63562-1-vsementsov@virtuozzo.com> 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, qemu-block@nongnu.org, armbru@redhat.com, mreitz@redhat.com, dplotnikov@virtuozzo.com, den@openvz.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" 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 | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt index d92c827763..77146b5169 100644 --- a/docs/interop/qcow2.txt +++ b/docs/interop/qcow2.txt @@ -109,6 +109,11 @@ the next fields through header_length. An External Data File Name header extensio= n may be present if this bit is set. =20 + Bit 3: Compression type bit. If this bit is set, + non-default compression is used for compre= ssed + clusters. compression_type field must be + present and not zero. + Bits 3-63: Reserved (set to 0) =20 80 - 87: compatible_features @@ -188,7 +193,16 @@ present*, if not altered by specific incompatible bit. *. Field is not present when header_length is less or equal to field's off= set. Also, all additional fields are not present for version 2. =20 - < ... No additional fields in the header currently ... > + 104: compression_type + Defines the compression method used for compressed clu= sters. + A single compression type is applied to all compressed= image + clusters. + If incompatible compression type bit is set: the field= must + be present and non-zero (which means non-zlib compress= ion type) + If incompatible compression type bit is unset: the fie= ld + may not exist or it must be zero (which means zlib). + Available compression type values: + 0: zlib =20 Header padding =20 --=20 2.18.0