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Subject[PATCH net-next 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>
---
Depends on:

"[PATCH net v2] net: Use WARN_ON_ONCE() in {tcp,udp}_read_skb()"
https://lore.kernel.org/all/20220913184016.16095-1-yepeilin.cs@gmail.com/

Thanks,
Peilin Ye

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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