> + spin_lock_irq(&q->stats->lock);
> + if (q->poll_stat) {
> + spin_unlock_irq(&q->stats->lock);
> + kfree(poll_stat);
> + return true;
> + }
> + q->poll_stat = poll_stat;
> + spin_unlock_irq(&q->stats->lock);
If we'd use a cmpxchg to install the pointer we could keep the
blk_queue_stats definition private.
