net: fix sk_wmem_schedule() and sk_rmem_schedule() errors

If sk->sk_forward_alloc is 150000, and we need to schedule 150001 bytes,
we want to allocate 1 byte more (rounded up to one page),
instead of 150001 :/

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Reviewed-by: NShakeel Butt <shakeelb@google.com>
Acked-by: NSoheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

include/net/sock.h

@@ -1575,19 +1575,23 @@ static inline bool sk_has_account(struct sock *sk)
 
 static inline bool sk_wmem_schedule(struct sock *sk, int size)
 {
+	int delta;
+
 	if (!sk_has_account(sk))
 		return true;
-	return size <= sk->sk_forward_alloc ||
-		__sk_mem_schedule(sk, size, SK_MEM_SEND);
+	delta = size - sk->sk_forward_alloc;
+	return delta <= 0 || __sk_mem_schedule(sk, delta, SK_MEM_SEND);
 }
 
 static inline bool
 sk_rmem_schedule(struct sock *sk, struct sk_buff *skb, int size)
 {
+	int delta;
+
 	if (!sk_has_account(sk))
 		return true;
-	return size <= sk->sk_forward_alloc ||
-		__sk_mem_schedule(sk, size, SK_MEM_RECV) ||
+	delta = size - sk->sk_forward_alloc;
+	return delta <= 0 || __sk_mem_schedule(sk, delta, SK_MEM_RECV) ||
 		skb_pfmemalloc(skb);
 }