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[Qemu-devel] [RFC 3/7] docs: add lazy refcounts bit to qcow2 specificati

From: Stefan Hajnoczi
Subject: [Qemu-devel] [RFC 3/7] docs: add lazy refcounts bit to qcow2 specification
Date: Fri, 22 Jun 2012 16:08:42 +0100

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 <address@hidden>
 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

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