nvme: batch completions and do them outside of the queue lock

[Keith Busch]

On Wed, May 16, 2018 at 05:39:02PM -0600, Jens Axboe wrote:
>  static int __nvme_poll(struct nvme_queue *nvmeq, unsigned int tag)
>  {
> -	struct nvme_completion cqe;
> -	int found = 0, consumed = 0;
> +	u16 start, end;
>  
>  	if (!nvme_cqe_valid(nvmeq, nvmeq->cq_head, nvmeq->cq_phase))
>  		return 0;
>  
>  	spin_lock_irq(&nvmeq->q_lock);
> -	while (nvme_read_cqe(nvmeq, &cqe)) {
> -		nvme_handle_cqe(nvmeq, &cqe);
> -		consumed++;
> -
> -		if (tag == cqe.command_id) {
> -			found = 1;
> -			break;
> -		}
> -       }
> -
> -	if (consumed)
> -		nvme_ring_cq_doorbell(nvmeq);
> -	spin_unlock_irq(&nvmeq->q_lock);
> +	nvme_process_cq(nvmeq, &start, &end);
> +	spin_unlock(&nvmeq->q_lock);

You'll need to use the spin_unlock_irq() here, otherwise looks good.