From patchwork Fri Jun 22 15:08:42 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 166640 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 C309CB6FA7 for ; Sat, 23 Jun 2012 01:10:53 +1000 (EST) Received: from localhost ([::1]:43209 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Si5Vb-0001KH-J6 for incoming@patchwork.ozlabs.org; Fri, 22 Jun 2012 11:10:51 -0400 Received: from eggs.gnu.org ([208.118.235.92]:54364) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Si5UJ-0006S2-27 for qemu-devel@nongnu.org; Fri, 22 Jun 2012 11:09:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Si5UC-0007v4-Vg for qemu-devel@nongnu.org; Fri, 22 Jun 2012 11:09:30 -0400 Received: from e06smtp15.uk.ibm.com ([195.75.94.111]:58802) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Si5UC-0007ul-NM for qemu-devel@nongnu.org; Fri, 22 Jun 2012 11:09:24 -0400 Received: from /spool/local by e06smtp15.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 22 Jun 2012 16:09:20 +0100 Received: from d06nrmr1307.portsmouth.uk.ibm.com (9.149.38.129) by e06smtp15.uk.ibm.com (192.168.101.145) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Fri, 22 Jun 2012 16:08:56 +0100 Received: from d06av08.portsmouth.uk.ibm.com (d06av08.portsmouth.uk.ibm.com [9.149.37.249]) by d06nrmr1307.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q5MF8tgH2203686 for ; Fri, 22 Jun 2012 16:08:55 +0100 Received: from d06av08.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av08.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q5MF8thm020762 for ; Fri, 22 Jun 2012 09:08:55 -0600 Received: from localhost (stefanha-thinkpad.manchester-maybrook.uk.ibm.com [9.174.219.145]) by d06av08.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id q5MF8t8u020755; Fri, 22 Jun 2012 09:08:55 -0600 From: Stefan Hajnoczi To: Kevin Wolf Date: Fri, 22 Jun 2012 16:08:42 +0100 Message-Id: <1340377726-5896-4-git-send-email-stefanha@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.10 In-Reply-To: <1340377726-5896-1-git-send-email-stefanha@linux.vnet.ibm.com> References: <1340377726-5896-1-git-send-email-stefanha@linux.vnet.ibm.com> x-cbid: 12062215-0342-0000-0000-000002134BE5 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 195.75.94.111 Cc: qemu-devel@nongnu.org, Stefan Hajnoczi Subject: [Qemu-devel] [RFC 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 | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt index 3a789ce..8b2c0eb 100644 --- a/docs/specs/qcow2.txt +++ b/docs/specs/qcow2.txt @@ -85,7 +85,11 @@ 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