Commit ac1f1f6c authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

tuntap: tweak on the path of skb XDP case in tun_build_skb() 



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: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f7053b6c

drivers/net/tun.c

+24 −15
Original line number Diff line number Diff line
@@ -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 = &current->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;
@@ -1672,9 +1688,11 @@ 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

		return __tun_build_skb(alloc_frag, buf, buflen, len, pad, delta);

	}



	*skb_xdp = 0;



	local_bh_disable();
@@ -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);

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