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[Qemu-devel] [PATCH 04/12] docs: add dirty bit to qcow2 specification
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH 04/12] docs: add dirty bit to qcow2 specification |
Date: |
Mon, 6 Aug 2012 22:44:43 +0200 |
From: Stefan Hajnoczi <address@hidden>
The dirty bit will make it possible to perform lazy refcount updates,
where the image file is not kept consistent all the time. Upon opening
a dirty image file, it is necessary to perform a consistency check and
repair any incorrect refcounts.
Therefore the dirty bit must be an incompatible feature bit. We don't
want old programs accessing a file with stale refcounts.
Signed-off-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
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 87bf785..339cdc1 100644
--- a/docs/specs/qcow2.txt
+++ b/docs/specs/qcow2.txt
@@ -75,7 +75,12 @@ in the description of a field.
Bitmask of incompatible features. An implementation must
fail to open an image if an unknown bit is set.
- Bits 0-63: Reserved (set to 0)
+ Bit 0: Dirty bit. If this bit is set then refcounts
+ may be inconsistent, make sure to scan L1/L2
+ tables to repair refcounts before accessing the
+ image.
+
+ Bits 1-63: Reserved (set to 0)
80 - 87: compatible_features
Bitmask of compatible features. An implementation can
--
1.7.6.5
- [Qemu-devel] [PULL 00/12] Block patches, Kevin Wolf, 2012/08/06
- [Qemu-devel] [PATCH 01/12] ide scsi: Mess with geometry only for hard disk devices, Kevin Wolf, 2012/08/06
- [Qemu-devel] [PATCH 02/12] qapi: generalize documentation of streaming commands, Kevin Wolf, 2012/08/06
- [Qemu-devel] [PATCH 03/12] qemu-iotests: add qed.py image manipulation utility, Kevin Wolf, 2012/08/06
- [Qemu-devel] [PATCH 04/12] docs: add dirty bit to qcow2 specification,
Kevin Wolf <=
- [Qemu-devel] [PATCH 05/12] qcow2: introduce dirty bit, Kevin Wolf, 2012/08/06
- [Qemu-devel] [PATCH 06/12] docs: add lazy refcounts bit to qcow2 specification, Kevin Wolf, 2012/08/06
- [Qemu-devel] [PATCH 07/12] qemu-iotests: ignore qemu-img create lazy_refcounts output, Kevin Wolf, 2012/08/06
- [Qemu-devel] [PATCH 09/12] qemu-io: add "abort" command to simulate program crash, Kevin Wolf, 2012/08/06
- [Qemu-devel] [PATCH 08/12] qcow2: implement lazy refcounts, Kevin Wolf, 2012/08/06
- [Qemu-devel] [PATCH 11/12] qemu-iotests: Be more flexible with image creation options, Kevin Wolf, 2012/08/06
- [Qemu-devel] [PATCH 10/12] qemu-iotests: add 039 qcow2 lazy refcounts test, Kevin Wolf, 2012/08/06