linux-kernel - Re: [PATCH] virtio_ring: remove unnecessary to

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Message-ID: <4366e621c74e46bfa642d6802187ad44@inspur.com>
Date:   Wed, 28 Sep 2022 02:26:16 +0000
From:   Bo Liu (刘波)-浪潮信息 <liubo03@...pur.com>
To:     "mst@...hat.com" <mst@...hat.com>
CC:     "jasowang@...hat.com" <jasowang@...hat.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] virtio_ring: remove unnecessary to_vvq() call

>On Mon, Sep 26, 2022 at 05:11:30AM -0400, Bo Liu wrote:
>> It passes '_vq' to vring_free(), which still calls to_vvq() to get
>> 'vq', let's directly pass 'vq'. It can avoid unnecessary call of
>> to_vvq() in hot path.
>>
>> Signed-off-by: Bo Liu <liubo03@...pur.com>
>
>What is the point of this change?
>
>__vring_new_virtqueue returns struct virtqueue *, so vring_free matches
that.
>No?
>

Hi
In function vring_free(), to_vvq() js unnecessary, we can directly pass
struct vring_virtqueue * to avoid this and remove the unnecessary code.

>> ---
>>  drivers/virtio/virtio_ring.c | 12 +++++-------
>>  1 file changed, 5 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/virtio/virtio_ring.c
>> b/drivers/virtio/virtio_ring.c index 8974c34b40fd..d6d77bf58802 100644
>> --- a/drivers/virtio/virtio_ring.c
>> +++ b/drivers/virtio/virtio_ring.c
>> @@ -221,7 +221,7 @@ static struct virtqueue
>*__vring_new_virtqueue(unsigned int index,
>>  					       void (*callback)(struct
virtqueue *),
>>  					       const char *name);
>>  static struct vring_desc_extra *vring_alloc_desc_extra(unsigned int
>> num); -static void vring_free(struct virtqueue *_vq);
>> +static void vring_free(struct vring_virtqueue *vq);
>>
>>  /*
>>   * Helpers.
>> @@ -1140,7 +1140,7 @@ static int virtqueue_resize_split(struct virtqueue
>*_vq, u32 num)
>>  	if (err)
>>  		goto err_state_extra;
>>
>> -	vring_free(&vq->vq);
>> +	vring_free(vq);
>>
>>  	virtqueue_vring_init_split(&vring_split, vq);
>>
>> @@ -2059,7 +2059,7 @@ static int virtqueue_resize_packed(struct virtqueue
>*_vq, u32 num)
>>  	if (err)
>>  		goto err_state_extra;
>>
>> -	vring_free(&vq->vq);
>> +	vring_free(vq);
>>
>>  	virtqueue_vring_init_packed(&vring_packed, !!vq->vq.callback);
>>
>> @@ -2649,10 +2649,8 @@ struct virtqueue *vring_new_virtqueue(unsigned
>> int index,  }  EXPORT_SYMBOL_GPL(vring_new_virtqueue);
>>
>> -static void vring_free(struct virtqueue *_vq)
>> +static void vring_free(struct vring_virtqueue *vq)
>>  {
>> -	struct vring_virtqueue *vq = to_vvq(_vq);
>> -
>>  	if (vq->we_own_ring) {
>>  		if (vq->packed_ring) {
>>  			vring_free_queue(vq->vq.vdev,
>> @@ -2693,7 +2691,7 @@ void vring_del_virtqueue(struct virtqueue *_vq)
>>  	list_del(&_vq->list);
>>  	spin_unlock(&vq->vq.vdev->vqs_list_lock);
>>
>> -	vring_free(_vq);
>> +	vring_free(vq);
>>
>>  	kfree(vq);
>>  }
>> --
>> 2.27.0


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