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SubjectRe: [PATCH 03/10] xen/blkfront: reorg info->io_lock after using blk-mq API
On Sun, Feb 15, 2015 at 04:18:58PM +0800, Bob Liu wrote:
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index 3589436..5a90a51 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -614,25 +614,28 @@ static int blk_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
> blk_mq_start_request(qd->rq);
> spin_lock_irq(&info->io_lock);
> if (RING_FULL(&info->ring)) {
> + spin_unlock_irq(&info->io_lock);
> blk_mq_stop_hw_queue(hctx);
> ret = BLK_MQ_RQ_QUEUE_BUSY;
> goto out;
> }
>
> if (blkif_request_flush_invalid(qd->rq, info)) {
> + spin_unlock_irq(&info->io_lock);
> ret = BLK_MQ_RQ_QUEUE_ERROR;
> goto out;
> }
>
> if (blkif_queue_request(qd->rq)) {
> + spin_unlock_irq(&info->io_lock);
> blk_mq_stop_hw_queue(hctx);
> ret = BLK_MQ_RQ_QUEUE_BUSY;
> goto out;
> }
>
> flush_requests(info);
> -out:
> spin_unlock_irq(&info->io_lock);
> +out:
> return ret;
> }

I'd rather write the function something like:

spin_lock_irq(&info->io_lock);
if (RING_FULL(&info->ring))
goto out_busy;
if (blkif_request_flush_invalid(qd->rq, info))
goto out_error;

if (blkif_queue_request(qd->rq))
goto out_busy;

flush_requests(info);
spin_unlock_irq(&info->io_lock);
return BLK_MQ_RQ_QUEUE_OK;
out_error:
spin_unlock_irq(&info->io_lock);
return BLK_MQ_RQ_QUEUE_ERROR;
out_busy:
spin_unlock_irq(&info->io_lock);
blk_mq_stop_hw_queue(hctx);
return BLK_MQ_RQ_QUEUE_BUSY;
}

Also this really should be merged into the first patch.


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