Re: [Qemu-devel] [PATCH v3 13/39] qcow2: Add l2_slice_size field to BDRVQcow2State

[Alberto Garcia]

On Wed 31 Jan 2018 08:48:08 PM CET, Max Reitz wrote:
> On 2018-01-26 15:59, Alberto Garcia wrote:
>> The BDRVQcow2State structure contains an l2_size field, which stores
>> the number of 64-bit entries in an L2 table.
>> 
>> For efficiency reasons we want to be able to load slices instead of
>> full L2 tables, so we need to know how many entries an L2 slice can
>> hold.
>> 
>> An L2 slice is the portion of an L2 table that is loaded by the qcow2
>> cache. At the moment that cache can only load complete tables,
>> therefore an L2 slice has the same size as an L2 table (one cluster)
>> and l2_size == l2_slice_size.
>> 
>> Later we'll allow smaller slices, but until then we have to use this
>> new l2_slice_size field to make the rest of the code ready for that.
>> 
>> Signed-off-by: Alberto Garcia <address@hidden>
>> Reviewed-by: Eric Blake <address@hidden>
>> ---
>>  block/qcow2.c | 3 +++
>>  block/qcow2.h | 1 +
>>  2 files changed, 4 insertions(+)
>
> Am I missing something or does this patch miss setting l2_slice_size
> in qcow2_do_open()?

qcow2_do_open() calls qcow2_update_options() which is what reads
l2-cache-entry-size and sets s->l2_slice_size.

Berto