Patchwork [06/12] docs: add lazy refcounts bit to qcow2 specification

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Submitter Kevin Wolf
Date Aug. 6, 2012, 8:44 p.m.
Message ID <1344285891-6578-7-git-send-email-kwolf@redhat.com>
Download mbox | patch
Permalink /patch/175451/
State New
Headers show

Comments

Kevin Wolf - Aug. 6, 2012, 8:44 p.m.
From: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

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>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 docs/specs/qcow2.txt |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

Patch

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