netdev - [PATCH net-next v3 12/15] virtio

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Date:   Sun, 23 Apr 2023 18:57:33 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     netdev@...r.kernel.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        virtualization@...ts.linux-foundation.org, bpf@...r.kernel.org
Subject: [PATCH net-next v3 12/15] virtio_net: small: optimize code

Avoid the problem that some variables(headroom and so on) will repeat
the calculation when process xdp.

Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
---
 drivers/net/virtio_net.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 5bc3dca0f60c..601c0e7fc32b 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1031,11 +1031,10 @@ static struct sk_buff *receive_small(struct net_device *dev,
 	struct sk_buff *skb;
 	struct bpf_prog *xdp_prog;
 	unsigned int xdp_headroom = (unsigned long)ctx;
-	unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
-	unsigned int headroom = vi->hdr_len + header_offset;
-	unsigned int buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
-			      SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 	struct page *page = virt_to_head_page(buf);
+	unsigned int header_offset;
+	unsigned int headroom;
+	unsigned int buflen;
 
 	len -= vi->hdr_len;
 	stats->bytes += len;
@@ -1063,6 +1062,11 @@ static struct sk_buff *receive_small(struct net_device *dev,
 	rcu_read_unlock();
 
 skip_xdp:
+	header_offset = VIRTNET_RX_PAD + xdp_headroom;
+	headroom = vi->hdr_len + header_offset;
+	buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
+		SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+
 	skb = build_skb(buf, buflen);
 	if (!skb)
 		goto err;
-- 
2.32.0.3.g01195cf9f