Re: [Qemu-devel] [PATCH for-2.5 3/6] Add new block driver interface to add/delete a BDS's child

[Alberto Garcia]

On Fri 07 Aug 2015 03:03:07 AM CEST, Wen Congyang wrote:

>>> +void bdrv_add_child(BlockDriverState *bs, QDict *options, Error **errp)
>>> +{
>>> +
>>> +    if (!bs->drv || !bs->drv->bdrv_add_child) {
>>> +        error_setg(errp, "The BDS %s doesn't support adding a child",
>>> +                   bdrv_get_id_or_node_name(bs));
>>> +        return;
>>> +    }
>>> +
>>> +    bs->drv->bdrv_add_child(bs, options, errp);
>>> +}
>>> +
>>> +void bdrv_del_child(BlockDriverState *bs, BlockDriverState *child_bs,
>>> +                    Error **errp)
>>> +{
>>> +    BdrvChild *child;
>>> +
>>> +    if (!bs->drv || !bs->drv->bdrv_del_child) {
>>> +        error_setg(errp, "The BDS %s doesn't support removing a child",
>>> +                   bdrv_get_id_or_node_name(bs));
>>> +        return;
>>> +    }
>>> +
>>> +    QLIST_FOREACH(child, &bs->children, next) {
>>> +        if (child->bs == child_bs) {
>>> +            break;
>>> +        }
>>> +    }
>>> +
>>> +    if (!child) {
>>> +        error_setg(errp, "The BDS %s is not the BDS %s's child",
>>> +                   bdrv_get_id_or_node_name(child_bs),
>>> +                   bdrv_get_id_or_node_name(bs));
>>> +        return;
>>> +    }
>>> +
>>> +    bs->drv->bdrv_del_child(bs, child_bs, errp);
>>> +}
>> 
>> I see that bdrv_del_child() checks that the child is in bs->children,
>> but who takes care of putting it there in the first place?
>
> The child is opened by the function bdrv_open_image().
> bdrv_open_image()
>     bdrv_open_child()
>         bdrv_attach_child()

I see, it's drv->bdrv_add_child() who takes care of opening the image,
this only provides the BlockdevOptions.

Thanks!

Reviewed-by: Alberto Garcia <address@hidden>

Berto