From patchwork Mon Aug 6 20:44:45 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 175451 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 3AE672C009D for ; Tue, 7 Aug 2012 06:59:28 +1000 (EST) Received: from localhost ([::1]:33431 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SyUBW-0001fc-Vl for incoming@patchwork.ozlabs.org; Mon, 06 Aug 2012 16:45:54 -0400 Received: from eggs.gnu.org ([208.118.235.92]:60121) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SyUAj-0008Ql-Nv for qemu-devel@nongnu.org; Mon, 06 Aug 2012 16:45:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SyUAi-0004Wi-J0 for qemu-devel@nongnu.org; Mon, 06 Aug 2012 16:45:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42917) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SyUAi-0004VG-BS for qemu-devel@nongnu.org; Mon, 06 Aug 2012 16:45:04 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q76Kj2fG001079 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 6 Aug 2012 16:45:03 -0400 Received: from dhcp-5-188.str.redhat.com (vpn1-7-164.ams2.redhat.com [10.36.7.164]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id q76KiqGG002690; Mon, 6 Aug 2012 16:45:01 -0400 From: Kevin Wolf To: anthony@codemonkey.ws Date: Mon, 6 Aug 2012 22:44:45 +0200 Message-Id: <1344285891-6578-7-git-send-email-kwolf@redhat.com> In-Reply-To: <1344285891-6578-1-git-send-email-kwolf@redhat.com> References: <1344285891-6578-1-git-send-email-kwolf@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 209.132.183.28 Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [Qemu-devel] [PATCH 06/12] 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 From: Stefan Hajnoczi 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 Signed-off-by: Kevin Wolf --- docs/specs/qcow2.txt | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-) diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt index 339cdc1..36a559d 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 + 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