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    Subject[PATCH net-next RESEND 1/2] udp: Refactor udp_read_skb()
    Date
    From: Peilin Ye <peilin.ye@bytedance.com>

    Delete the unnecessary while loop in udp_read_skb() for readability.
    Additionally, since recv_actor() cannot return a value greater than
    skb->len (see sk_psock_verdict_recv()), remove the redundant check.

    Suggested-by: Cong Wang <cong.wang@bytedance.com>
    Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
    ---
    net/ipv4/udp.c | 46 +++++++++++++++++-----------------------------
    1 file changed, 17 insertions(+), 29 deletions(-)

    diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
    index 560d9eadeaa5..d63118ce5900 100644
    --- a/net/ipv4/udp.c
    +++ b/net/ipv4/udp.c
    @@ -1801,41 +1801,29 @@ EXPORT_SYMBOL(__skb_recv_udp);

    int udp_read_skb(struct sock *sk, skb_read_actor_t recv_actor)
    {
    - int copied = 0;
    -
    - while (1) {
    - struct sk_buff *skb;
    - int err, used;
    -
    - skb = skb_recv_udp(sk, MSG_DONTWAIT, &err);
    - if (!skb)
    - return err;
    + struct sk_buff *skb;
    + int err, copied;

    - if (udp_lib_checksum_complete(skb)) {
    - __UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS,
    - IS_UDPLITE(sk));
    - __UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS,
    - IS_UDPLITE(sk));
    - atomic_inc(&sk->sk_drops);
    - kfree_skb(skb);
    - continue;
    - }
    +try_again:
    + skb = skb_recv_udp(sk, MSG_DONTWAIT, &err);
    + if (!skb)
    + return err;

    - WARN_ON_ONCE(!skb_set_owner_sk_safe(skb, sk));
    - used = recv_actor(sk, skb);
    - if (used <= 0) {
    - if (!copied)
    - copied = used;
    - kfree_skb(skb);
    - break;
    - } else if (used <= skb->len) {
    - copied += used;
    - }
    + if (udp_lib_checksum_complete(skb)) {
    + int is_udplite = IS_UDPLITE(sk);
    + struct net *net = sock_net(sk);

    + __UDP_INC_STATS(net, UDP_MIB_CSUMERRORS, is_udplite);
    + __UDP_INC_STATS(net, UDP_MIB_INERRORS, is_udplite);
    + atomic_inc(&sk->sk_drops);
    kfree_skb(skb);
    - break;
    + goto try_again;
    }

    + WARN_ON_ONCE(!skb_set_owner_sk_safe(skb, sk));
    + copied = recv_actor(sk, skb);
    + kfree_skb(skb);
    +
    return copied;
    }
    EXPORT_SYMBOL(udp_read_skb);
    --
    2.20.1
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