[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PATCH v3 1/7] docs: add dirty bit to qcow2 specification
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH v3 1/7] docs: add dirty bit to qcow2 specification |
Date: |
Fri, 27 Jul 2012 09:05:18 +0100 |
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>
---
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 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
--
1.7.10.4
- [Qemu-devel] [PATCH v3 0/7] qcow2: implement lazy refcounts optimization, Stefan Hajnoczi, 2012/07/27
- [Qemu-devel] [PATCH v3 5/7] qcow2: implement lazy refcounts, Stefan Hajnoczi, 2012/07/27
- [Qemu-devel] [PATCH v3 4/7] qemu-iotests: ignore qemu-img create lazy_refcounts output, Stefan Hajnoczi, 2012/07/27
- [Qemu-devel] [PATCH v3 3/7] docs: add lazy refcounts bit to qcow2 specification, Stefan Hajnoczi, 2012/07/27
- [Qemu-devel] [PATCH v3 2/7] qcow2: introduce dirty bit, Stefan Hajnoczi, 2012/07/27
- [Qemu-devel] [PATCH v3 1/7] docs: add dirty bit to qcow2 specification,
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH v3 7/7] qemu-iotests: add 039 qcow2 lazy refcounts test, Stefan Hajnoczi, 2012/07/27
- [Qemu-devel] [PATCH v3 6/7] qemu-io: add "abort" command to simulate program crash, Stefan Hajnoczi, 2012/07/27