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 31 Jul 2015 11:19:12 AM CEST, Wen Congyang wrote:

> +/*
> + * Hot add/remove a BDS's child. So the user can take a child offline when
> + * it is broken and take a new child online
> + */
> +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?

Berto