[PATCH net-next V2 05/11] tuntap: tweak on the path of skb XDP case in tun_build_skb()
From: Jason Wang <jasowang@redhat.com>
Date: 2018-09-12 03:17:50
Also in:
kvm, lkml
Subsystem:
networking drivers, the rest, tun/tap driver · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds, Willem de Bruijn, Jason Wang
If we're sure not to go native XDP, there's no need for several things like bh and rcu stuffs. So this patch introduces a helper to build skb and hold page refcnt. When we found we will go through skb path, build skb directly. Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/net/tun.c | 39 ++++++++++++++++++++++++--------------- 1 file changed, 24 insertions(+), 15 deletions(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 257cf7342d54..946c6148ed75 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c@@ -1635,6 +1635,23 @@ static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile, return true; } +static struct sk_buff *__tun_build_skb(struct page_frag *alloc_frag, char *buf, + int buflen, int len, int pad, int delta) +{ + struct sk_buff *skb = build_skb(buf, buflen); + + if (!skb) + return ERR_PTR(-ENOMEM); + + skb_reserve(skb, pad - delta); + skb_put(skb, len); + + get_page(alloc_frag->page); + alloc_frag->offset += buflen; + + return skb; +} + static struct sk_buff *tun_build_skb(struct tun_struct *tun, struct tun_file *tfile, struct iov_iter *from,
@@ -1642,7 +1659,6 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun, int len, int *skb_xdp) { struct page_frag *alloc_frag = ¤t->task_frag; - struct sk_buff *skb; struct bpf_prog *xdp_prog; int buflen = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); unsigned int delta = 0;
@@ -1672,10 +1688,12 @@ 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; + return __tun_build_skb(alloc_frag, buf, buflen, len, pad, delta); + } + + *skb_xdp = 0; local_bh_disable(); rcu_read_lock();
@@ -1719,22 +1737,13 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun, trace_xdp_exception(tun->dev, xdp_prog, act); /* fall through */ case XDP_DROP: - goto err_xdp; + goto out; } } rcu_read_unlock(); local_bh_enable(); - skb = build_skb(buf, buflen); - if (!skb) - return ERR_PTR(-ENOMEM); - - skb_reserve(skb, pad - delta); - skb_put(skb, len); - get_page(alloc_frag->page); - alloc_frag->offset += buflen; - - return skb; + return __tun_build_skb(alloc_frag, buf, buflen, len, pad, delta); err_redirect: put_page(alloc_frag->page);
--
2.17.1