> +static int blk_iolatency_try_init(char *input)
> +{
> + static DEFINE_MUTEX(init_mutex);
> + struct block_device *bdev;
> + int ret = 0;
> +
> + bdev = blkcg_conf_open_bdev(&input);
> + if (IS_ERR(bdev))
> + return PTR_ERR(bdev);
> +retry:
> ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx);
> + if (ret == -EOPNOTSUPP) {
> + ret = blk_iolatency_try_init(buf);
It's a little sad to do two block device lookups here (even if it
obviously doesn't matter for performance). I wonder if it would
make sense to explicitly support the lazy init pattern
in blkg_conf_prep somehow.
Otherwise I'm all for the lazy init.
