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

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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>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2018-09-12 11:17:03 +08:00 committed by David S. Miller
parent f7053b6ccb
commit ac1f1f6c5a
1 changed files with 24 additions and 15 deletions
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39
drivers/net/tun.c
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@ -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;
@ -1672,10 +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);