net/mptcp: Change some dubious min_t(int, ...) to min()

There are two:
	min_t(int, xxx, mptcp_wnd_end(msk) - msk->snd_nxt);
Both mptcp_wnd_end(msk) and msk->snd_nxt are u64, their difference
(aka the window size) might be limited to 32 bits - but that isn't
knowable from this code.
So checks being added to min_t() detect the potential discard of
significant bits.

Provided the 'avail_size' and return of mptcp_check_allowed_size()
are changed to an unsigned type (size_t matches the type the caller
uses) both min_t() can be changed to min().

Signed-off-by: David Laight <[email protected]>

Author: David Laight

net/mptcp/protocol.c

@@ -1125,8 +1125,8 @@ struct mptcp_sendmsg_info {
 	bool data_lock_held;
 };
 
-static int mptcp_check_allowed_size(const struct mptcp_sock *msk, struct sock *ssk,
-				    u64 data_seq, int avail_size)
+static size_t mptcp_check_allowed_size(const struct mptcp_sock *msk, struct sock *ssk,
+				       u64 data_seq, size_t avail_size)
 {
 	u64 window_end = mptcp_wnd_end(msk);
 	u64 mptcp_snd_wnd;
@@ -1135,7 +1135,7 @@ static int mptcp_check_allowed_size(const struct mptcp_sock *msk, struct sock *s
 		return avail_size;
 
 	mptcp_snd_wnd = window_end - data_seq;
-	avail_size = min_t(unsigned int, mptcp_snd_wnd, avail_size);
+	avail_size = min(mptcp_snd_wnd, avail_size);
 
 	if (unlikely(tcp_sk(ssk)->snd_wnd < mptcp_snd_wnd)) {
 		tcp_sk(ssk)->snd_wnd = min_t(u64, U32_MAX, mptcp_snd_wnd);
@@ -1479,7 +1479,7 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 	if (!ssk || !sk_stream_memory_free(ssk))
 		return NULL;
 
-	burst = min_t(int, MPTCP_SEND_BURST_SIZE, mptcp_wnd_end(msk) - msk->snd_nxt);
+	burst = min(MPTCP_SEND_BURST_SIZE, mptcp_wnd_end(msk) - msk->snd_nxt);
 	wmem = READ_ONCE(ssk->sk_wmem_queued);
 	if (!burst)
 		return ssk;