Re: [Qemu-devel] [PATCH v5 05/42] block: Add chain helper functions

[Vladimir Sementsov-Ogievskiy]

13.06.2019 15:33, Max Reitz wrote:
> On 13.06.19 14:26, Vladimir Sementsov-Ogievskiy wrote:
>> 13.06.2019 1:09, Max Reitz wrote:
>>> Add some helper functions for skipping filters in a chain of block
>>> nodes.
>>>
>>> Signed-off-by: Max Reitz <address@hidden>
>>> ---
>>>    include/block/block_int.h |  3 +++
>>>    block.c                   | 55 +++++++++++++++++++++++++++++++++++++++
>>>    2 files changed, 58 insertions(+)
>>>
>>> diff --git a/include/block/block_int.h b/include/block/block_int.h
>>> index 7ce71623f8..875a33f255 100644
>>> --- a/include/block/block_int.h
>>> +++ b/include/block/block_int.h
>>> @@ -1264,6 +1264,9 @@ BdrvChild *bdrv_filtered_child(BlockDriverState *bs);
>>>    BdrvChild *bdrv_metadata_child(BlockDriverState *bs);
>>>    BdrvChild *bdrv_storage_child(BlockDriverState *bs);
>>>    BdrvChild *bdrv_primary_child(BlockDriverState *bs);
>>> +BlockDriverState *bdrv_skip_implicit_filters(BlockDriverState *bs);
>>> +BlockDriverState *bdrv_skip_rw_filters(BlockDriverState *bs);
>>> +BlockDriverState *bdrv_backing_chain_next(BlockDriverState *bs);
>>>    
>>>    static inline BlockDriverState *child_bs(BdrvChild *child)
>>>    {
>>> diff --git a/block.c b/block.c
>>> index 724d8889a6..be18130944 100644
>>> --- a/block.c
>>> +++ b/block.c
>>> @@ -6494,3 +6494,58 @@ BdrvChild *bdrv_primary_child(BlockDriverState *bs)
>>>    {
>>>        return bdrv_filtered_rw_child(bs) ?: bs->file;
>>>    }
>>> +
>>> +static BlockDriverState *bdrv_skip_filters(BlockDriverState *bs,
>>> +                                           bool stop_on_explicit_filter)
>>> +{
>>> +    BdrvChild *filtered;
>>> +
>>> +    if (!bs) {
>>> +        return NULL;
>>> +    }
>>> +
>>> +    while (!(stop_on_explicit_filter && !bs->implicit)) {
>>> +        filtered = bdrv_filtered_rw_child(bs);
>>> +        if (!filtered) {
>>> +            break;
>>> +        }
>>> +        bs = filtered->bs;
>>> +    }
>>> +    /*
>>> +     * Note that this treats nodes with bs->drv == NULL
>>
>> as well as filters without filtered_rw child
> 
> A filter always must have a filtered_rw child, though.  So I don’t quite
> understand what you mean here...
> 
> Max
> 
>>    as not being
>>> +     * R/W filters (bs->drv == NULL should be replaced by something
>>> +     * else anyway).
>>> +     * The advantage of this behavior is that this function will thus
>>> +     * always return a non-NULL value (given a non-NULL @bs).
>>
>> and this is the advantage of what I've written, not about bs->drv.

I mean, that advantage seems unrelated to the reason about bs->drv == NULL,
as even with bs->drv == NULL we can go to bs->backing or bs->file..

But I don't  really care, my r-b stays here anyway

>>
>>> +     */
>>> +
>>> +    return bs;
>>> +}
>>> +
>>> +/*
>>> + * Return the first BDS that has not been added implicitly or that
>>> + * does not have an RW-filtered child down the chain starting from @bs
>>> + * (including @bs itself).
>>> + */
>>> +BlockDriverState *bdrv_skip_implicit_filters(BlockDriverState *bs)
>>> +{
>>> +    return bdrv_skip_filters(bs, true);
>>> +}
>>> +
>>> +/*
>>> + * Return the first BDS that does not have an RW-filtered child down
>>> + * the chain starting from @bs (including @bs itself).
>>> + */
>>> +BlockDriverState *bdrv_skip_rw_filters(BlockDriverState *bs)
>>> +{
>>> +    return bdrv_skip_filters(bs, false);
>>> +}
>>> +
>>> +/*
>>> + * For a backing chain, return the first non-filter backing image of
>>> + * the first non-filter image.
>>> + */
>>> +BlockDriverState *bdrv_backing_chain_next(BlockDriverState *bs)
>>> +{
>>> +    return 
>>> bdrv_skip_rw_filters(bdrv_filtered_cow_bs(bdrv_skip_rw_filters(bs)));
>>> +}
>>>
>>
>>
>> Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
>>
> 
> 


-- 
Best regards,
Vladimir