netdev - Re: [PATCH net-next v5 07/15] virtio-net: standalone virtnet_aloc

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Date:   Wed, 16 Jun 2021 10:45:40 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org,
        "dust . li" <dust.li@...ux.alibaba.com>
Subject: Re: [PATCH net-next v5 07/15] virtio-net: standalone
 virtnet_aloc_frag function


在 2021/6/10 下午4:22, Xuan Zhuo 写道:
> This logic is used by small and merge when adding buf, and the
> subsequent patch will also use this logic, so it is separated as an
> independent function.
>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>


Acked-by: Jason Wang <jasiowang@...hat.com>


> ---
>   drivers/net/virtio_net.c | 29 ++++++++++++++++++++---------
>   1 file changed, 20 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index d791543a8dd8..3fd87bf2b2ad 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -264,6 +264,22 @@ static struct xdp_frame *ptr_to_xdp(void *ptr)
>   	return (struct xdp_frame *)((unsigned long)ptr & ~VIRTIO_XDP_FLAG);
>   }
>   
> +static char *virtnet_alloc_frag(struct receive_queue *rq, unsigned int len,
> +				int gfp)
> +{
> +	struct page_frag *alloc_frag = &rq->alloc_frag;
> +	char *buf;
> +
> +	if (unlikely(!skb_page_frag_refill(len, alloc_frag, gfp)))
> +		return NULL;
> +
> +	buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
> +	get_page(alloc_frag->page);
> +	alloc_frag->offset += len;
> +
> +	return buf;
> +}
> +
>   static void __free_old_xmit(struct send_queue *sq, bool in_napi,
>   			    struct virtnet_sq_stats *stats)
>   {
> @@ -1190,7 +1206,6 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
>   static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
>   			     gfp_t gfp)
>   {
> -	struct page_frag *alloc_frag = &rq->alloc_frag;
>   	char *buf;
>   	unsigned int xdp_headroom = virtnet_get_headroom(vi);
>   	void *ctx = (void *)(unsigned long)xdp_headroom;
> @@ -1199,12 +1214,10 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
>   
>   	len = SKB_DATA_ALIGN(len) +
>   	      SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> -	if (unlikely(!skb_page_frag_refill(len, alloc_frag, gfp)))
> +	buf = virtnet_alloc_frag(rq, len, gfp);
> +	if (unlikely(!buf))
>   		return -ENOMEM;
>   
> -	buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
> -	get_page(alloc_frag->page);
> -	alloc_frag->offset += len;
>   	sg_init_one(rq->sg, buf + VIRTNET_RX_PAD + xdp_headroom,
>   		    vi->hdr_len + GOOD_PACKET_LEN);
>   	err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
> @@ -1295,13 +1308,11 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
>   	 * disabled GSO for XDP, it won't be a big issue.
>   	 */
>   	len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room);
> -	if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp)))
> +	buf = virtnet_alloc_frag(rq, len + room, gfp);
> +	if (unlikely(!buf))
>   		return -ENOMEM;
>   
> -	buf = (char *)page_address(alloc_frag->page) + alloc_frag->offset;
>   	buf += headroom; /* advance address leaving hole at front of pkt */
> -	get_page(alloc_frag->page);
> -	alloc_frag->offset += len + room;
>   	hole = alloc_frag->size - alloc_frag->offset;
>   	if (hole < len + room) {
>   		/* To avoid internal fragmentation, if there is very likely not