From nobody Thu Nov 27 13:59:26 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC8913451A3; Fri, 21 Nov 2025 17:02:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763744559; cv=none; b=D+dyM4f4420+ozdtjPaK8aZG4A0LUtSg3Pa4HJrIXtCg1mj97tGrSz+CtWlxqaze3bDxOJvybqnto4z+5a5gqKjiwW6NsmPJCRXHAT/hB5/PtlLv7gxRtpyp0UCmyJnMcUL9vEbM+PJNQNds4TGftEKGYQJrTt5T61/AmsAdOqg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763744559; c=relaxed/simple; bh=jQ0UDB4U29x/KlnOx2L558m9xp5Y4bGvMVx4QgXsvAY=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=X3PGst/2kjkSZ8KzeyN0a5i70U0VQiJtzX9Rnja/EtTNOay9UbI/j8ufr6RCSg7LxQl0abuBCAvXX1Op4uc/GufKu9ZIXja8LHbbdu2jEnQfBFGHMFbw1lLVW+PvyCqlEPXC99W861TkzLIGCnNsrK8+SyS71S52l4LTjdvjMB8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ilEO6GAI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ilEO6GAI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 895B0C4CEF1; Fri, 21 Nov 2025 17:02:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763744558; bh=jQ0UDB4U29x/KlnOx2L558m9xp5Y4bGvMVx4QgXsvAY=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=ilEO6GAIQEmvi73CO+PkIZFQJQVe0bSLd+kKfmOnlWX2iZL87CqdFE+GZVWihWM8d gXnDXPKmJKj5bLUvMJsneqO52HhCRT9E/+XM0BzdW1qJIiznpcshFrE0KKkcPi8tye 2Qpymrjrfg34+SIwF1b3ZNkysGT0TDdQmDPRWiJoc8TSec4QmNmlmVap419R8tKw4V GfP1ubAx9A7sFa2kCcl3RciRw47kxo0y2zQ0FkM77nE3A7kZKcPZXAuiAI7zOrFM+1 yK9kaJVddyIyw4LTzqp17Og5b5TT040P88fGIPEmOCTYFmOmyM/+vrsBD6KR52Py+a 1D+un71sEVX1A== From: "Matthieu Baerts (NGI0)" Date: Fri, 21 Nov 2025 18:02:02 +0100 Subject: [PATCH net-next 03/14] mptcp: grafting MPJ subflow earlier Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251121-net-next-mptcp-memcg-backlog-imp-v1-3-1f34b6c1e0b1@kernel.org> References: <20251121-net-next-mptcp-memcg-backlog-imp-v1-0-1f34b6c1e0b1@kernel.org> In-Reply-To: <20251121-net-next-mptcp-memcg-backlog-imp-v1-0-1f34b6c1e0b1@kernel.org> To: Eric Dumazet , Kuniyuki Iwashima , Paolo Abeni , Willem de Bruijn , "David S. Miller" , Jakub Kicinski , Simon Horman , David Ahern , Mat Martineau , Geliang Tang , Peter Krystad , Florian Westphal , Christoph Paasch Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, mptcp@lists.linux.dev, Davide Caratti , "Matthieu Baerts (NGI0)" X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=2932; i=matttbe@kernel.org; h=from:subject:message-id; bh=TzG7leIFSjvo22mwXd7Xqen2NE60+AKXWYBJRpqRFhM=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGDIVZgsnx991bsrfwRHTa9TEnH1z7h9DpjkBfY8286umR nQcM9vYUcrCIMbFICumyCLdFpk/83kVb4mXnwXMHFYmkCEMXJwCMJFTkxkZLkY0c/LkvL721P3S p0+P10nz5tfkrdo/my1+FcOWI+K32Bn+Gf7iTGx767X9cc5NvYzjb7c8rLmqruO+eP+sDQpWjxd YcQIA X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 From: Paolo Abeni Later patches need to ensure that all MPJ subflows are grafted to the msk socket before accept() completion. Currently the grafting happens under the msk socket lock: potentially at msk release_cb time which make satisfying the above condition a bit tricky. Move the MPJ subflow grafting earlier, under the msk data lock, so that we can use such lock as a synchronization point. Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/protocol.c | 30 +++++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 75bb1199bed9..2104ab1eda1d 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -895,12 +895,6 @@ static bool __mptcp_finish_join(struct mptcp_sock *msk= , struct sock *ssk) mptcp_subflow_joined(msk, ssk); spin_unlock_bh(&msk->fallback_lock); =20 - /* attach to msk socket only after we are sure we will deal with it - * at close time - */ - if (sk->sk_socket && !ssk->sk_socket) - mptcp_sock_graft(ssk, sk->sk_socket); - mptcp_subflow_ctx(ssk)->subflow_id =3D msk->subflow_id++; mptcp_sockopt_sync_locked(msk, ssk); mptcp_stop_tout_timer(sk); @@ -3647,6 +3641,20 @@ void mptcp_sock_graft(struct sock *sk, struct socket= *parent) write_unlock_bh(&sk->sk_callback_lock); } =20 +/* Can be called without holding the msk socket lock; use the callback lock + * to avoid {READ_,WRITE_}ONCE annotations on sk_socket. + */ +static void mptcp_sock_check_graft(struct sock *sk, struct sock *ssk) +{ + struct socket *sock; + + write_lock_bh(&sk->sk_callback_lock); + sock =3D sk->sk_socket; + write_unlock_bh(&sk->sk_callback_lock); + if (sock) + mptcp_sock_graft(ssk, sock); +} + bool mptcp_finish_join(struct sock *ssk) { struct mptcp_subflow_context *subflow =3D mptcp_subflow_ctx(ssk); @@ -3662,7 +3670,9 @@ bool mptcp_finish_join(struct sock *ssk) return false; } =20 - /* active subflow, already present inside the conn_list */ + /* Active subflow, already present inside the conn_list; is grafted + * either by __mptcp_subflow_connect() or accept. + */ if (!list_empty(&subflow->node)) { spin_lock_bh(&msk->fallback_lock); if (!msk->allow_subflows) { @@ -3689,11 +3699,17 @@ bool mptcp_finish_join(struct sock *ssk) if (ret) { sock_hold(ssk); list_add_tail(&subflow->node, &msk->conn_list); + mptcp_sock_check_graft(parent, ssk); } } else { sock_hold(ssk); list_add_tail(&subflow->node, &msk->join_list); __set_bit(MPTCP_FLUSH_JOIN_LIST, &msk->cb_flags); + + /* In case of later failures, __mptcp_flush_join_list() will + * properly orphan the ssk via mptcp_close_ssk(). + */ + mptcp_sock_check_graft(parent, ssk); } mptcp_data_unlock(parent); =20 --=20 2.51.0