tuntap: simplify error handling in tun_build_skb()

There's no need to duplicate page get logic in each action. So this
patch tries to get page and calculate the offset before processing XDP
actions (except for XDP_DROP), and undo them when meet errors (we
don't care the performance on errors). This will be used for factoring
out XDP logic.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 372caf7..257cf73 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1701,17 +1701,13 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
                        xdp_do_flush_map();
                        if (err)
                                goto err_redirect;
-                       rcu_read_unlock();
-                       local_bh_enable();
-                       return NULL;
+                       goto out;
                case XDP_TX:
                        get_page(alloc_frag->page);
                        alloc_frag->offset += buflen;
                        if (tun_xdp_tx(tun->dev, &xdp) < 0)
                                goto err_redirect;
-                       rcu_read_unlock();
-                       local_bh_enable();
-                       return NULL;
+                       goto out;
                case XDP_PASS:
                        delta = orig_data - xdp.data;
                        len = xdp.data_end - xdp.data;
@@ -1742,7 +1738,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
 
 err_redirect:
        put_page(alloc_frag->page);
-err_xdp:
+out:
        rcu_read_unlock();
        local_bh_enable();
        this_cpu_inc(tun->pcpu_stats->rx_dropped);