linux-kernel - [PATCH net-next 06/15] mptcp: Change some dubious min

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Message-Id: <20260203-net-next-mptcp-misc-feat-6-20-v1-6-31ec8bfc56d1@kernel.org>
Date: Tue, 03 Feb 2026 19:41:22 +0100
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: Mat Martineau <martineau@...nel.org>, Geliang Tang <geliang@...nel.org>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>, Shuah Khan <shuah@...nel.org>
Cc: netdev@...r.kernel.org, mptcp@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 "Matthieu Baerts (NGI0)" <matttbe@...nel.org>, 
 David Laight <david.laight.linux@...il.com>
Subject: [PATCH net-next 06/15] mptcp: Change some dubious min_t(int, ...)
 to min()

From: David Laight <david.laight.linux@...il.com>

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 <david.laight.linux@...il.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
[ wrapped too long lines when declaring mptcp_check_allowed_size() ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
 net/mptcp/protocol.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 197ee169c0bc..e0b4745bbaa9 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1160,8 +1160,9 @@ 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;
@@ -1170,7 +1171,7 @@ 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);
@@ -1514,7 +1515,7 @@ 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;

-- 
2.51.0