[RFC PATCH net-next 08/12] tuntap: tweak on the path of non-xdp case in tun_build_skb()

Jason Wang
2018-05-21T09:05:23Z

If we're sure not to go native XDP, there's no need for several things
like touching preemption counter and rcu stuffs.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/net/tun.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index f6e0f96..ed04291 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1645,10 +1645,12 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
* of xdp_prog above, this should be rare and for simplicity
* we do XDP on skb in case the headroom is not enough.
*/
- if (hdr->gso_type || !xdp_prog)
+ if (hdr->gso_type || !xdp_prog) {
*skb_xdp = 1;
- else
- *skb_xdp = 0;
+ goto build;
+ }
+
+ *skb_xdp = 0;

preempt_disable();
rcu_read_lock();
@@ -1695,6 +1697,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
rcu_read_unlock();
preempt_enable();

+build:
skb = build_skb(buf, buflen);
if (!skb) {
skb = ERR_PTR(-ENOMEM);
--
2.7.4