netdev - [PATCH net-next] tcp: move sk_forced_mem

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Message-ID: <20260123111605.4089200-1-edumazet@google.com>
Date: Fri, 23 Jan 2026 11:16:05 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Neal Cardwell <ncardwell@...gle.com>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next] tcp: move sk_forced_mem_schedule() to tcp.c

TCP fast path can (auto)inline this helper, instead
of (auto)inling it from tcp_send_fin().

No change of overall code size, but tcp_sendmsg() is faster.

$ scripts/bloat-o-meter -t vmlinux.old vmlinux.new
add/remove: 0/0 grow/shrink: 1/1 up/down: 141/-140 (1)
Function                                     old     new   delta
tcp_stream_alloc_skb                         216     357    +141
tcp_send_fin                                 688     548    -140
Total: Before=22236729, After=22236730, chg +0.00%

BTW, we might change tcp_send_fin() to use tcp_stream_alloc_skb().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/tcp.c        | 27 +++++++++++++++++++++++++++
 net/ipv4/tcp_output.c | 27 ---------------------------
 2 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 148cdf3cd6233add37ea52e273cb4fb3e75fcbcb..87acd01274601eca799e42b8f895fff4c35cf25a 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -902,6 +902,33 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
 }
 EXPORT_IPV6_MOD(tcp_splice_read);
 
+/* We allow to exceed memory limits for FIN packets to expedite
+ * connection tear down and (memory) recovery.
+ * Otherwise tcp_send_fin() could be tempted to either delay FIN
+ * or even be forced to close flow without any FIN.
+ * In general, we want to allow one skb per socket to avoid hangs
+ * with edge trigger epoll()
+ */
+void sk_forced_mem_schedule(struct sock *sk, int size)
+{
+	int delta, amt;
+
+	delta = size - sk->sk_forward_alloc;
+	if (delta <= 0)
+		return;
+
+	amt = sk_mem_pages(delta);
+	sk_forward_alloc_add(sk, amt << PAGE_SHIFT);
+
+	if (mem_cgroup_sk_enabled(sk))
+		mem_cgroup_sk_charge(sk, amt, gfp_memcg_charge() | __GFP_NOFAIL);
+
+	if (sk->sk_bypass_prot_mem)
+		return;
+
+	sk_memory_allocated_add(sk, amt);
+}
+
 struct sk_buff *tcp_stream_alloc_skb(struct sock *sk, gfp_t gfp,
 				     bool force_schedule)
 {
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 256b669e8d3b4a4d191e61e79784e412aaef8965..597e888af36d8697cd696964077b423e79fdb83e 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3767,33 +3767,6 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
 				     inet_csk(sk)->icsk_rto, true);
 }
 
-/* We allow to exceed memory limits for FIN packets to expedite
- * connection tear down and (memory) recovery.
- * Otherwise tcp_send_fin() could be tempted to either delay FIN
- * or even be forced to close flow without any FIN.
- * In general, we want to allow one skb per socket to avoid hangs
- * with edge trigger epoll()
- */
-void sk_forced_mem_schedule(struct sock *sk, int size)
-{
-	int delta, amt;
-
-	delta = size - sk->sk_forward_alloc;
-	if (delta <= 0)
-		return;
-
-	amt = sk_mem_pages(delta);
-	sk_forward_alloc_add(sk, amt << PAGE_SHIFT);
-
-	if (mem_cgroup_sk_enabled(sk))
-		mem_cgroup_sk_charge(sk, amt, gfp_memcg_charge() | __GFP_NOFAIL);
-
-	if (sk->sk_bypass_prot_mem)
-		return;
-
-	sk_memory_allocated_add(sk, amt);
-}
-
 /* Send a FIN. The caller locks the socket for us.
  * We should try to send a FIN packet really hard, but eventually give up.
  */
-- 
2.52.0.457.g6b5491de43-goog