Re: [PATCH] libata: get rid of ATA_MAX_QUEUE loop in ata_qc_complete_multiple()

[Tejun Heo <htejun@gmail.com>]

Hello, Jens.

Jens Axboe wrote:
> @@ -5039,16 +5039,19 @@ int ata_qc_complete_multiple(struct ata_port *ap, u32 qc_active)
>  		return -EINVAL;
>  	}
>  
> -	for (i = 0; i < ATA_MAX_QUEUE; i++) {
> +	while (done_mask) {
>  		struct ata_queued_cmd *qc;
> +		unsigned int next = __ffs(done_mask);
>  
> -		if (!(done_mask & (1 << i)))
> -			continue;
> -
> -		if ((qc = ata_qc_from_tag(ap, i))) {
> +		qc = ata_qc_from_tag(ap, i + next);
> +		if (qc) {
>  			ata_qc_complete(qc);
>  			nr_done++;
>  		}
> +		if (++next >= ATA_MAX_QUEUE)
> +			break;

Given that __ffs doesn't care how far the first bit is on most archs
(even the generic one), I think it would be simpler and more efficient
to simply do done_mask &= ~(1 << i) and loop without adding to index
and shifting.

Thanks.

-- 
tejun