linux-kernel - Re: [PATCH v2 2/4] vhost: Drop variable last_avail_idx in vhost_get_vq

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Date: Mon, 29 Apr 2024 14:45:48 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Gavin Shan <gshan@...hat.com>
Cc: virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org,
	jasowang@...hat.com, shan.gavin@...il.com
Subject: Re: [PATCH v2 2/4] vhost: Drop variable last_avail_idx in
 vhost_get_vq_desc()

On Mon, Apr 29, 2024 at 08:13:58PM +1000, Gavin Shan wrote:
> The local variable @last_avail_idx is equivalent to vq->last_avail_idx.
> So the code can be simplified a bit by dropping the local variable
> @last_avail_idx.
> 
> No functional change intended.
> 
> Signed-off-by: Gavin Shan <gshan@...hat.com>
> ---
>  drivers/vhost/vhost.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 7aa623117aab..b278c0333a66 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -2524,7 +2524,6 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
>  {
>  	struct vring_desc desc;
>  	unsigned int i, head, found = 0;
> -	u16 last_avail_idx = vq->last_avail_idx;
>  	__virtio16 ring_head;
>  	int ret, access;
>  
> @@ -2539,10 +2538,10 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
>  
>  	/* Grab the next descriptor number they're advertising, and increment
>  	 * the index we've seen. */
> -	if (unlikely(vhost_get_avail_head(vq, &ring_head, last_avail_idx))) {
> +	if (unlikely(vhost_get_avail_head(vq, &ring_head, vq->last_avail_idx))) {
>  		vq_err(vq, "Failed to read head: idx %d address %p\n",
> -		       last_avail_idx,
> -		       &vq->avail->ring[last_avail_idx % vq->num]);
> +		       vq->last_avail_idx,
> +		       &vq->avail->ring[vq->last_avail_idx % vq->num]);
>  		return -EFAULT;
>  	}

I don't see the big advantage and the line is long now.

>  
> -- 
> 2.44.0