Patchwork [v2,3/7] docs: add lazy refcounts bit to qcow2 specification

login
register
mail settings
Submitter Stefan Hajnoczi
Date July 25, 2012, 12:21 p.m.
Message ID <1343218884-14980-4-git-send-email-stefanha@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/173148/
State New
Headers show

Comments

Stefan Hajnoczi - July 25, 2012, 12:21 p.m.
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(-)
Kevin Wolf - July 26, 2012, 12:57 p.m.
Am 25.07.2012 14:21, schrieb Stefan Hajnoczi:
> 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(-)
> 
> 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

Not sure what was intended here, but the dirty flag isn't set anywhere
yet, so you can't postpone it either. Maybe s/postponing//?

> +                                postponing refcount metadata updates.
> +
> +                    Bits 1-63:  Reserved (set to 0)
>  
>           88 -  95:  autoclear_features
>                      Bitmask of auto-clear features. An implementation may only

Kevin
Stefan Hajnoczi - July 26, 2012, 3:36 p.m.
On Thu, Jul 26, 2012 at 1:57 PM, Kevin Wolf <kwolf@redhat.com> wrote:
> Am 25.07.2012 14:21, schrieb Stefan Hajnoczi:
>> 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(-)
>>
>> 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
>
> Not sure what was intended here, but the dirty flag isn't set anywhere
> yet, so you can't postpone it either. Maybe s/postponing//?

Yes, s/postponing//.

Stefan

Patch

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