udp: introduce __sk_mem_schedule() usage

Keep the accounting schema consistent across different protocols
with __sk_mem_schedule(). Besides, it adjusts a little bit on how
to calculate forward allocated memory compared to before. After
applied this patch, we could avoid receive path scheduling extra
amount of memory.

Link: https://lore.kernel.org/lkml/20230221110344.82818-1-kerneljasonxing@gmail.com/Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230308021153.99777-1-kerneljasonxing@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/udp.c

@@ -1531,10 +1531,21 @@ static void busylock_release(spinlock_t *busy)
 		spin_unlock(busy);
 }
 
+static int udp_rmem_schedule(struct sock *sk, int size)
+{
+	int delta;
+
+	delta = size - sk->sk_forward_alloc;
+	if (delta > 0 && !__sk_mem_schedule(sk, delta, SK_MEM_RECV))
+		return -ENOBUFS;
+
+	return 0;
+}
+
 int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 {
 	struct sk_buff_head *list = &sk->sk_receive_queue;
-	int rmem, delta, amt, err = -ENOMEM;
+	int rmem, err = -ENOMEM;
 	spinlock_t *busy = NULL;
 	int size;
 
@@ -1567,16 +1578,10 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 		goto uncharge_drop;
 
 	spin_lock(&list->lock);
-	if (size >= sk->sk_forward_alloc) {
-		amt = sk_mem_pages(size);
-		delta = amt << PAGE_SHIFT;
-		if (!__sk_mem_raise_allocated(sk, delta, amt, SK_MEM_RECV)) {
-			err = -ENOBUFS;
-			spin_unlock(&list->lock);
-			goto uncharge_drop;
-		}
-
-		sk->sk_forward_alloc += delta;
+	err = udp_rmem_schedule(sk, size);
+	if (err) {
+		spin_unlock(&list->lock);
+		goto uncharge_drop;
 	}
 
 	sk->sk_forward_alloc -= size;