linux-kernel - [PATCH net-next 02/14] mptcp: factor-out cgroup data inherit helper

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Message-Id: <20251121-net-next-mptcp-memcg-backlog-imp-v1-2-1f34b6c1e0b1@kernel.org>
Date: Fri, 21 Nov 2025 18:02:01 +0100
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>, 
 Kuniyuki Iwashima <kuniyu@...gle.com>, Paolo Abeni <pabeni@...hat.com>, 
 Willem de Bruijn <willemb@...gle.com>, 
 "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
 Simon Horman <horms@...nel.org>, David Ahern <dsahern@...nel.org>, 
 Mat Martineau <martineau@...nel.org>, Geliang Tang <geliang@...nel.org>, 
 Peter Krystad <peter.krystad@...ux.intel.com>, 
 Florian Westphal <fw@...len.de>, Christoph Paasch <cpaasch@...le.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 mptcp@...ts.linux.dev, Davide Caratti <dcaratti@...hat.com>, 
 "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
Subject: [PATCH net-next 02/14] mptcp: factor-out cgroup data inherit
 helper

From: Paolo Abeni <pabeni@...hat.com>

MPTCP will soon need the same functionality for passive sockets,
factor them out in a common helper. No functional change intended.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Reviewed-by: Geliang Tang <geliang@...nel.org>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
 net/mptcp/protocol.h |  2 ++
 net/mptcp/subflow.c  | 20 ++++++++++++--------
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index a23780ff670f..6d9de13c1f9c 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -707,6 +707,8 @@ mptcp_subflow_delegated_next(struct mptcp_delegated_action *delegated)
 	return ret;
 }

+void __mptcp_inherit_cgrp_data(struct sock *sk, struct sock *ssk);
+
 int mptcp_is_enabled(const struct net *net);
 unsigned int mptcp_get_add_addr_timeout(const struct net *net);
 int mptcp_is_checksum_enabled(const struct net *net);
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index ddd0fc6fcf45..d98d151392d2 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -1712,21 +1712,25 @@ int __mptcp_subflow_connect(struct sock *sk, const struct mptcp_pm_local *local,
 	return err;
 }

-static void mptcp_attach_cgroup(struct sock *parent, struct sock *child)
+void __mptcp_inherit_cgrp_data(struct sock *sk, struct sock *ssk)
 {
 #ifdef CONFIG_SOCK_CGROUP_DATA
-	struct sock_cgroup_data *parent_skcd = &parent->sk_cgrp_data,
-				*child_skcd = &child->sk_cgrp_data;
+	struct sock_cgroup_data *sk_cd = &sk->sk_cgrp_data,
+				*ssk_cd = &ssk->sk_cgrp_data;

 	/* only the additional subflows created by kworkers have to be modified */
-	if (cgroup_id(sock_cgroup_ptr(parent_skcd)) !=
-	    cgroup_id(sock_cgroup_ptr(child_skcd))) {
-		cgroup_sk_free(child_skcd);
-		*child_skcd = *parent_skcd;
-		cgroup_sk_clone(child_skcd);
+	if (cgroup_id(sock_cgroup_ptr(sk_cd)) !=
+	    cgroup_id(sock_cgroup_ptr(ssk_cd))) {
+		cgroup_sk_free(ssk_cd);
+		*ssk_cd = *sk_cd;
+		cgroup_sk_clone(sk_cd);
 	}
 #endif /* CONFIG_SOCK_CGROUP_DATA */
+}

+static void mptcp_attach_cgroup(struct sock *parent, struct sock *child)
+{
+	__mptcp_inherit_cgrp_data(parent, child);
 	if (mem_cgroup_sockets_enabled)
 		mem_cgroup_sk_inherit(parent, child);
 }

-- 
2.51.0