Re: [Qemu-devel] [PATCH v2 1/6] block: skip implicit nodes in snapshots, blockjobs

[Alberto Garcia]

On Tue 15 Aug 2017 03:50:12 PM CEST, Manos Pitsidianakis wrote:
>>> +static inline BlockDriverState *child_bs(BlockDriverState *bs)
>>> +{
>>> +    BdrvChild *child = QLIST_FIRST(&bs->children);
>>> +    assert(child && !QLIST_NEXT(child, next));
>>> +    return child->bs;
>>> +}
>>
>>This aborts if the bs has a number of children != 1. That's not
>>something that I would expect from a function named like that.
>>
>>Considering that you're only using it in bdrv_get_first_explicit(),
>>why don't you simply move the code there?
>
> It felt useful to have a function that also returns file->bs (we have 
> backing_bs() already) instead of doing backing_bs(bs) ? : file_bs(bs)
>>
>>The other question is of course whether we can rely for the future on
>>the assumption that implicit nodes only have one children.
>
> This is only to get either bs->backing or bs->file (we can't have both
> anyway).

You can have other children (see Quorum for example).

Berto