udp: add udp_drops_inc() helper

Generic sk_drops_inc() reads sk->sk_drop_counters.
We know the precise location for UDP sockets.

Move sk_drop_counters out of sock_read_rxtx
so that sock_write_rxtx starts at a cache line boundary.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250916160951.541279-9-edumazet@google.com
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

5 files changed, 15 insertions, 11 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 867dc44140d4..82bcdb7d7e67 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -451,7 +451,6 @@ struct sock {
 #ifdef CONFIG_XFRM
 	struct xfrm_policy __rcu *sk_policy[2];
 #endif
-	struct numa_drop_counters *sk_drop_counters;
 	__cacheline_group_end(sock_read_rxtx);
 
 	__cacheline_group_begin(sock_write_rxtx);
@@ -568,6 +567,7 @@ struct sock {
 #ifdef CONFIG_BPF_SYSCALL
 	struct bpf_local_storage __rcu	*sk_bpf_storage;
 #endif
+	struct numa_drop_counters *sk_drop_counters;
 	struct rcu_head		sk_rcu;
 	netns_tracker		ns_tracker;
 	struct xarray		sk_user_frags;
diff --git a/include/net/udp.h b/include/net/udp.h
index 93b159f30e88..a08822e294b0 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -295,6 +295,11 @@ static inline void udp_lib_init_sock(struct sock *sk)
 	set_bit(SOCK_CUSTOM_SOCKOPT, &sk->sk_socket->flags);
 }
 
+static inline void udp_drops_inc(struct sock *sk)
+{
+	numa_drop_add(&udp_sk(sk)->drop_counters, 1);
+}
+
 /* hash routines shared between UDPv4/6 and UDP-Litev4/6 */
 static inline int udp_lib_hash(struct sock *sk)
 {
diff --git a/net/core/sock.c b/net/core/sock.c
index 1f8ef4d8bcd9..21742da19e45 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -4444,7 +4444,6 @@ static int __init sock_struct_check(void)
 #ifdef CONFIG_MEMCG
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_rxtx, sk_memcg);
 #endif
-	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_read_rxtx, sk_drop_counters);
 
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_rxtx, sk_lock);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct sock, sock_write_rxtx, sk_reserved_mem);
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 658ae8782799..25143f932447 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1790,7 +1790,7 @@ uncharge_drop:
 	atomic_sub(skb->truesize, &sk->sk_rmem_alloc);
 
 drop:
-	sk_drops_inc(sk);
+	udp_drops_inc(sk);
 	busylock_release(busy);
 	return err;
 }
@@ -1855,7 +1855,7 @@ static struct sk_buff *__first_packet_length(struct sock *sk,
 					IS_UDPLITE(sk));
 			__UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS,
 					IS_UDPLITE(sk));
-			sk_drops_inc(sk);
+			udp_drops_inc(sk);
 			__skb_unlink(skb, rcvq);
 			*total += skb->truesize;
 			kfree_skb_reason(skb, SKB_DROP_REASON_UDP_CSUM);
@@ -2011,7 +2011,7 @@ try_again:
 
 		__UDP_INC_STATS(net, UDP_MIB_CSUMERRORS, is_udplite);
 		__UDP_INC_STATS(net, UDP_MIB_INERRORS, is_udplite);
-		sk_drops_inc(sk);
+		udp_drops_inc(sk);
 		kfree_skb_reason(skb, SKB_DROP_REASON_UDP_CSUM);
 		goto try_again;
 	}
@@ -2081,7 +2081,7 @@ try_again:
 
 	if (unlikely(err)) {
 		if (!peeking) {
-			sk_drops_inc(sk);
+			udp_drops_inc(sk);
 			UDP_INC_STATS(sock_net(sk),
 				      UDP_MIB_INERRORS, is_udplite);
 		}
@@ -2452,7 +2452,7 @@ csum_error:
 	__UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
 drop:
 	__UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
-	sk_drops_inc(sk);
+	udp_drops_inc(sk);
 	sk_skb_reason_drop(sk, skb, drop_reason);
 	return -1;
 }
@@ -2537,7 +2537,7 @@ start_lookup:
 		nskb = skb_clone(skb, GFP_ATOMIC);
 
 		if (unlikely(!nskb)) {
-			sk_drops_inc(sk);
+			udp_drops_inc(sk);
 			__UDP_INC_STATS(net, UDP_MIB_RCVBUFERRORS,
 					IS_UDPLITE(sk));
 			__UDP_INC_STATS(net, UDP_MIB_INERRORS,
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index e87d0ef861f8..9f4d340d1e3a 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -524,7 +524,7 @@ try_again:
 	}
 	if (unlikely(err)) {
 		if (!peeking) {
-			sk_drops_inc(sk);
+			udp_drops_inc(sk);
 			SNMP_INC_STATS(mib, UDP_MIB_INERRORS);
 		}
 		kfree_skb(skb);
@@ -908,7 +908,7 @@ csum_error:
 	__UDP6_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
 drop:
 	__UDP6_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
-	sk_drops_inc(sk);
+	udp_drops_inc(sk);
 	sk_skb_reason_drop(sk, skb, drop_reason);
 	return -1;
 }
@@ -1013,7 +1013,7 @@ start_lookup:
 		}
 		nskb = skb_clone(skb, GFP_ATOMIC);
 		if (unlikely(!nskb)) {
-			sk_drops_inc(sk);
+			udp_drops_inc(sk);
 			__UDP6_INC_STATS(net, UDP_MIB_RCVBUFERRORS,
 					 IS_UDPLITE(sk));
 			__UDP6_INC_STATS(net, UDP_MIB_INERRORS,