linux-kernel - Re: [PATCH v3] xen-blkfront: dynamic configuration of per-vbd resources

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Date:	Wed, 27 Jul 2016 12:59:49 +0200
From:	Roger Pau Monné <roger.pau@...rix.com>
To:	Bob Liu <bob.liu@...cle.com>
CC:	<linux-kernel@...r.kernel.org>, <xen-devel@...ts.xenproject.org>,
	<konrad.wilk@...cle.com>
Subject: Re: [PATCH v3] xen-blkfront: dynamic configuration of per-vbd
 resources

On Wed, Jul 27, 2016 at 11:21:25AM +0800, Bob Liu wrote:
[...]
> +static ssize_t dynamic_reconfig_device(struct blkfront_info *info, ssize_t count)
> +{
> +	/*
> +	 * Prevent new requests even to software request queue.
> +	 */
> +	blk_mq_freeze_queue(info->rq);
> +
> +	/*
> +	 * Guarantee no uncompleted reqs.
> +	 */

I'm also wondering, why do you need to guarantee that there are no 
uncompleted requests? The resume procedure is going to call blkif_recover 
that will take care of requeuing any unfinished requests that are on the 
ring.

> +	if (part_in_flight(&info->gd->part0) || info->reconfiguring) {
> +		blk_mq_unfreeze_queue(info->rq);
> +		pr_err("Dev:%s busy, please retry later.\n", dev_name(&info->xbdev->dev));
> +		return -EBUSY;
> +	}

Roger.