linux-kernel - Re: [PATCH 1/2] libata: get rid of ATA_MAX_QUEUE loop in ata_qc_complete

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Message-ID: <48FFFA15.8060603@kernel.org>
Date:	Thu, 23 Oct 2008 13:14:13 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Jens Axboe <jens.axboe@...cle.com>
CC:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	jeff@...zik.org
Subject: Re: [PATCH 1/2] libata: get rid of ATA_MAX_QUEUE loop in ata_qc_complete_multiple()

Jens Axboe wrote:
> @@ -4811,16 +4811,19 @@ 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;
> +             i += next;
> +             done_mask >>= next;

Shouldn't this be...

        i += next + 1;
        if (i >= ATA_MAX_QUEUE)
                break;

or better...

while (done_mask) {
        struct ata_queued_cmd *qc;
        unsigned int next = __ffs(done_mask);

        tag += next;
        if ((qc = ata_qc_from_tag(ap, tag))) {
                ata_qc_complete(qc);
                nr_done++;
        }
        next++;
        tag += next;
        done_mask >>= next;
}

done_mask is guaranteed to be zero at when tag reaches ATA_MAX_QUEUE.

Thanks.

-- 
tejun
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