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

[Vladimir Sementsov-Ogievskiy]

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

  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 <address@hidden>

-- 
Best regards,
Vladimir