Re: [PATCH v5 07/31] qcow2: Document the Extended L2 Entries feature

[Alberto Garcia]

On Tue 05 May 2020 09:35:06 PM CEST, Eric Blake wrote:
> On 5/5/20 12:38 PM, Alberto Garcia wrote:
>> Subcluster allocation in qcow2 is implemented by extending the
>> existing L2 table entries and adding additional information to
>> indicate the allocation status of each subcluster.
>> 
>> This patch documents the changes to the qcow2 format and how they
>> affect the calculation of the L2 cache size.
>> 
>> Signed-off-by: Alberto Garcia <address@hidden>
>> Reviewed-by: Max Reitz <address@hidden>
>> ---
>>   docs/interop/qcow2.txt | 68 ++++++++++++++++++++++++++++++++++++++++--
>>   docs/qcow2-cache.txt   | 19 +++++++++++-
>>   2 files changed, 83 insertions(+), 4 deletions(-)
>> 
>
>> @@ -547,7 +557,8 @@ Standard Cluster Descriptor:
>>                       nor is data read from the backing file if the cluster 
>> is
>>                       unallocated.
>>   
>> -                    With version 2, this is always 0.
>> +                    With version 2 or with extended L2 entries (see the next
>> +                    section), this is always 0.
>
> In your cover letter, you said you changed things to tolerate this bit
> being set even with extended L2 entries.  Does this sentence need a
> tweak?

Not a bad idea.


>> +The last 64 bits contain a subcluster allocation bitmap with this format:
>> +
>> +Subcluster Allocation Bitmap (for standard clusters):
>> +
>> +    Bit  0 -  31:   Allocation status (one bit per subcluster)
>
> Why two spaces after '-'?

No reason, I guess I just didn't notice. I'll fix it.

Berto