From patchwork Fri Jul 14 09:56:37 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Lieven X-Patchwork-Id: 9840409 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id B08D760381 for ; Fri, 14 Jul 2017 09:58:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A1FDB2874F for ; Fri, 14 Jul 2017 09:58:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 957072876E; Fri, 14 Jul 2017 09:58:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id A9F3E2874F for ; Fri, 14 Jul 2017 09:58:27 +0000 (UTC) Received: from localhost ([::1]:36623 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dVxMg-0003hD-Cl for patchwork-qemu-devel@patchwork.kernel.org; Fri, 14 Jul 2017 05:58:26 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38243) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dVxLU-0003fC-Hj for qemu-devel@nongnu.org; Fri, 14 Jul 2017 05:57:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dVxLR-0007zv-GS for qemu-devel@nongnu.org; Fri, 14 Jul 2017 05:57:12 -0400 Received: from mx-v6.kamp.de ([2a02:248:0:51::16]:45011 helo=mx01.kamp.de) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dVxLR-0007yK-73 for qemu-devel@nongnu.org; Fri, 14 Jul 2017 05:57:09 -0400 Received: (qmail 28657 invoked by uid 89); 14 Jul 2017 09:57:04 -0000 Received: from [195.62.97.28] by client-16-kamp (envelope-from , uid 89) with qmail-scanner-2010/03/19-MF (clamdscan: 0.99.2/23562. avast: 1.2.2/17010300. spamassassin: 3.4.1. Clear:RC:1(195.62.97.28):. Processed in 0.242728 secs); 14 Jul 2017 09:57:04 -0000 Received: from smtp.kamp.de (HELO submission.kamp.de) ([195.62.97.28]) by mx01.kamp.de with ESMTPS (DHE-RSA-AES256-GCM-SHA384 encrypted); 14 Jul 2017 09:57:01 -0000 X-GL_Whitelist: yes Received: (qmail 21445 invoked from network); 14 Jul 2017 09:57:00 -0000 Received: from lieven-pc.kamp-intra.net (HELO lieven-pc) (relay@kamp.de@::ffff:172.21.12.60) by submission.kamp.de with ESMTPS (DHE-RSA-AES256-GCM-SHA384 encrypted) ESMTPA; 14 Jul 2017 09:57:00 -0000 Received: by lieven-pc (Postfix, from userid 1000) id 75B59205F9; Fri, 14 Jul 2017 11:57:00 +0200 (CEST) From: Peter Lieven To: qemu-block@nongnu.org Date: Fri, 14 Jul 2017 11:56:37 +0200 Message-Id: <1500026205-15542-2-git-send-email-pl@kamp.de> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1500026205-15542-1-git-send-email-pl@kamp.de> References: <1500026205-15542-1-git-send-email-pl@kamp.de> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2a02:248:0:51::16 Subject: [Qemu-devel] [PATCH V3 1/9] specs/qcow2: add compress format extension X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, Peter Lieven , qemu-devel@nongnu.org, mreitz@redhat.com, den@openvz.org, lersek@redhat.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP Signed-off-by: Peter Lieven --- docs/interop/qcow2.txt | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt index d7fdb1f..c2d3dab 100644 --- a/docs/interop/qcow2.txt +++ b/docs/interop/qcow2.txt @@ -86,7 +86,12 @@ in the description of a field. be written to (unless for regaining consistency). - Bits 2-63: Reserved (set to 0) + Bit 2: Compress format bit. If and only if this bit + is set then the compress format extension + MUST be present and MUST be parsed and checked + for compatibility. + + Bits 3-63: Reserved (set to 0) 80 - 87: compatible_features Bitmask of compatible features. An implementation can @@ -137,6 +142,7 @@ be stored. Each extension has a structure like the following: 0x6803f857 - Feature name table 0x23852875 - Bitmaps extension 0x0537be77 - Full disk encryption header pointer + 0xC03183A3 - Compress format extension other - Unknown header extension, can be safely ignored @@ -311,6 +317,33 @@ The algorithms used for encryption vary depending on the method in the LUKS header, with the physical disk sector as the input tweak. + +== Compress format extension == + +The compress format extension is an optional header extension. It provides +the ability to specify the compress algorithm and compress parameters +that are used for compressed clusters. This new header MUST be present if +the incompatible-feature bit "compress format bit" is set and MUST be absent +otherwise. + +The fields of the compress format extension are: + + Byte 0 - 15: compress_format_name (padded with zeros, but not + necessarily null terminated if it has full length). + Valid compression format names currently are: + + zlib: Standard zlib deflate compression + + 16: compress_level (uint8_t) + + 0 = default compress level (valid for all formats, default) + + Additional valid compression levels for zlib compression: + + All values between 1 and 9. 1 gives best speed, 9 gives best + compression. + + == Host cluster management == qcow2 manages the allocation of host clusters by maintaining a reference count