From patchwork Wed Oct 17 16:00:10 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: =?utf-8?q?Beno=C3=AEt_Canet?= X-Patchwork-Id: 192087 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 411532C0097 for ; Thu, 18 Oct 2012 03:19:39 +1100 (EST) Received: from localhost ([::1]:60351 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TOWLJ-0001d1-0e for incoming@patchwork.ozlabs.org; Wed, 17 Oct 2012 12:19:37 -0400 Received: from eggs.gnu.org ([208.118.235.92]:50804) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TOW3O-0003SU-Fl for qemu-devel@nongnu.org; Wed, 17 Oct 2012 12:01:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TOW38-0002q9-HP for qemu-devel@nongnu.org; Wed, 17 Oct 2012 12:01:00 -0400 Received: from nodalink.pck.nerim.net ([62.212.105.220]:48752 helo=paradis.irqsave.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TOW37-0002lt-Go for qemu-devel@nongnu.org; Wed, 17 Oct 2012 12:00:50 -0400 Received: by paradis.irqsave.net (Postfix, from userid 1002) id 4FEFE874304; Wed, 17 Oct 2012 18:06:06 +0200 (CEST) Received: from localhost.localdomain (unknown [192.168.77.1]) by paradis.irqsave.net (Postfix) with ESMTP id 069E88742EC; Wed, 17 Oct 2012 18:05:56 +0200 (CEST) From: =?UTF-8?q?Beno=C3=AEt=20Canet?= To: qemu-devel@nongnu.org Date: Wed, 17 Oct 2012 18:00:10 +0200 Message-Id: <1350489629-1838-2-git-send-email-benoit@irqsave.net> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1350489629-1838-1-git-send-email-benoit@irqsave.net> References: <1350489629-1838-1-git-send-email-benoit@irqsave.net> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 62.212.105.220 Cc: kwolf@redhat.com, =?UTF-8?q?Beno=C3=AEt=20Canet?= , stefanha@redhat.com Subject: [Qemu-devel] [RFC V2 01/20] qcow2: Add deduplication to the qcow2 specification. X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org --- docs/specs/qcow2.txt | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt index 36a559d..013a16b 100644 --- a/docs/specs/qcow2.txt +++ b/docs/specs/qcow2.txt @@ -80,7 +80,10 @@ in the description of a field. tables to repair refcounts before accessing the image. - Bits 1-63: Reserved (set to 0) + Bit 1: Deduplication bit. If this bit is set then + deduplication is used on this image. + + Bits 2-63: Reserved (set to 0) 80 - 87: compatible_features Bitmask of compatible features. An implementation can @@ -116,6 +119,7 @@ be stored. Each extension has a structure like the following: 0x00000000 - End of the header extension area 0xE2792ACA - Backing file format name 0x6803f857 - Feature name table + 0xCD8E819B - Deduplication other - Unknown header extension, can be safely ignored @@ -159,6 +163,16 @@ the header extension data. Each entry look like this: terminated if it has full length) +== Deduplication == + +The deduplication extension contains the offset and size of the deduplication +table. + + Byte 0 - 7: Offset + + 8 - 11: Size + + == Host cluster management == qcow2 manages the allocation of host clusters by maintaining a reference count