void btrfs_wait_nocow_writers(struct btrfs_block_group *bg)
{
	wait_var_event(&bg->nocow_writers, !atomic_read(&bg->nocow_writers));
}
void btrfs_wait_nocow_writers(struct btrfs_block_group *bg)
{
	wait_var_event(&bg->nocow_writers, !atomic_read(&bg->nocow_writers));
}