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


From: Max Reitz
Subject: Re: [Qemu-block] [PATCH v3 13/39] qcow2: Add l2_slice_size field to BDRVQcow2State
Date: Thu, 1 Feb 2018 19:09:09 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2

On 2018-02-01 10:51, Alberto Garcia wrote:
> 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.

So I was missing something, good.

Reviewed-by: Max Reitz <address@hidden>

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