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[v3,3/7] docs: add lazy refcounts bit to qcow2 specification

Message ID 1343376324-19458-4-git-send-email-stefanha@linux.vnet.ibm.com
State New
Headers show

Commit Message

Stefan Hajnoczi July 27, 2012, 8:05 a.m. UTC
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 <stefanha@linux.vnet.ibm.com>
 docs/specs/qcow2.txt |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
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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