From patchwork Wed Jul 25 12:21:20 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 173148 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 5735D2C009B for ; Wed, 25 Jul 2012 22:33:12 +1000 (EST) Received: from localhost ([::1]:57289 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Su0m6-0006EA-Bu for incoming@patchwork.ozlabs.org; Wed, 25 Jul 2012 08:33:10 -0400 Received: from eggs.gnu.org ([208.118.235.92]:45981) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Su0ly-0006Dt-Rg for qemu-devel@nongnu.org; Wed, 25 Jul 2012 08:33:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Su0lx-0001pV-IA for qemu-devel@nongnu.org; Wed, 25 Jul 2012 08:33:02 -0400 Received: from e06smtp14.uk.ibm.com ([195.75.94.110]:58628) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Su0lx-0001pA-9k for qemu-devel@nongnu.org; Wed, 25 Jul 2012 08:33:01 -0400 Received: from /spool/local by e06smtp14.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 25 Jul 2012 13:32:54 +0100 Received: from d06nrmr1806.portsmouth.uk.ibm.com (9.149.39.193) by e06smtp14.uk.ibm.com (192.168.101.144) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Wed, 25 Jul 2012 13:32:23 +0100 Received: from d06av05.portsmouth.uk.ibm.com (d06av05.portsmouth.uk.ibm.com [9.149.37.229]) by d06nrmr1806.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q6PCLbDc2601008 for ; Wed, 25 Jul 2012 13:21:37 +0100 Received: from d06av05.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av05.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q6PCLaKW011466 for ; Wed, 25 Jul 2012 06:21:36 -0600 Received: from localhost (sig-9-145-198-37.de.ibm.com [9.145.198.37]) by d06av05.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id q6PCLZa2011429; Wed, 25 Jul 2012 06:21:36 -0600 From: Stefan Hajnoczi To: Date: Wed, 25 Jul 2012 13:21:20 +0100 Message-Id: <1343218884-14980-4-git-send-email-stefanha@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1343218884-14980-1-git-send-email-stefanha@linux.vnet.ibm.com> References: <1343218884-14980-1-git-send-email-stefanha@linux.vnet.ibm.com> x-cbid: 12072512-1948-0000-0000-0000027EA61A X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 195.75.94.110 Cc: Kevin Wolf , Khoa Huynh , Anthony Liguori , Stefan Hajnoczi Subject: [Qemu-devel] [PATCH v2 3/7] docs: add lazy refcounts bit to 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 The lazy refcounts bit indicates that this image can take advantage of the dirty bit and that refcount updates can be postponed. Signed-off-by: Stefan Hajnoczi --- docs/specs/qcow2.txt | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt index 339cdc1..f2f4faa 100644 --- a/docs/specs/qcow2.txt +++ b/docs/specs/qcow2.txt @@ -86,7 +86,12 @@ in the description of a field. Bitmask of compatible features. An implementation can safely ignore any unknown bits that are set. - Bits 0-63: Reserved (set to 0) + Bit 0: Lazy refcounts bit. If this bit is set then + lazy refcount updates can be used. This means + postponing marking the image file dirty and + postponing refcount metadata updates. + + Bits 1-63: Reserved (set to 0) 88 - 95: autoclear_features Bitmask of auto-clear features. An implementation may only