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 <stefa...@linux.vnet.ibm.com> --- 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 339cdc1..f2f4faa 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 + 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 -- 1.7.10.4