On 05.02.20 16:24, Eric Blake wrote:
> On 2/4/20 11:08 AM, Max Reitz wrote:
>> This enum will supplement BdrvChildClass when it comes to what role (or
>> combination of roles) a child takes for its parent.
>>
>> Because empty enums are not allowed, let us just start with it filled.
>>
>> Signed-off-by: Max Reitz <mre...@redhat.com>
>> ---
>> include/block/block.h | 27 +++++++++++++++++++++++++++
>> 1 file changed, 27 insertions(+)
>>
>> diff --git a/include/block/block.h b/include/block/block.h
>> index 38963ef203..0f7e8caa5b 100644
>> --- a/include/block/block.h
>> +++ b/include/block/block.h
>> @@ -279,6 +279,33 @@ enum {
>> DEFAULT_PERM_UNCHANGED = BLK_PERM_ALL &
>> ~DEFAULT_PERM_PASSTHROUGH,
>> };
>> +typedef enum BdrvChildRole {
>> + /* Child stores data */
>> + BDRV_CHILD_DATA = (1 << 0),
>> +
>> + /* Child stores metadata */
>> + BDRV_CHILD_METADATA = (1 << 1),
>> +
>> + /* Filtered child */
>> + BDRV_CHILD_FILTERED = (1 << 2),
>
> I'm not sure this comment does justice for what the flag represents, but
> am not sure of what longer comment to put in its place.You’re right. I thought I could just rely on our .is_filter documentation (at least after https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg01721.html), but that doesn’t really apply here. For example, this series makes raw (without further parameters) have a CHILD_FILTERED child, without raw being a filter itself. So there should indeed be some definition here. Maybe: A child to which the parent forwards all reads and writes. Therefore, this child presents exactly the same visible data as the parent. Would that work? Max
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