Re: [Xen-devel] [PATCH 03/10] xen/blkfront: reorg info->io_lock after using blk-mq API

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

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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