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

[Max Reitz]

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 <mre...@redhat.com>
>> ---
>>   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.
> 
>> +     */
>> +
>> +    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 <vsement...@virtuozzo.com>
> 

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