From nobody Wed Sep 17 18:14:33 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 973B52F7AA6 for ; Tue, 16 Sep 2025 16:27:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758040071; cv=none; b=t+tTYtOcShIoyvBhirQvp5bDivPYJ1MCitv93kbLNG0DwFYOrKTtuF2ZPtBkjqHgA2HRFmmg3Mui5W4yjSHZFTtrneSpL7tjZbeIqXkxSPzfUgTHBcVXBVUGWb+wpNLzeKCDB3i3HXjCs6i89cMI2jquq220680EF2vZLkFpaxE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758040071; c=relaxed/simple; bh=vlTAfd2YF5vOaQohY0F6PvXTTCfn58beu7u8KzirW9s=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=JM23McdMTlbyyxppb40+oD7Iqt/knEuv/lKG5emWOEWw1iwRdiIYdhsO4Hznwds3h3IGJHmZBbHRVYYufpKJp7N+gfwTEOKgkLilPskBJHSkbzWj+b1P8DZvmUZdRrOO4CffDBGOVRP7FYgz/6IzgzbT//tDWHQbKopKjjL1aU8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=FDdFD21U; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FDdFD21U" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758040068; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hrsxKyYgpVFXf9TFixAIDt7teXpvh2As8MNaCoOdS6s=; b=FDdFD21UXBbQysR5PBEnCUU4KTFetf+DtyZH8Eyuw5u3WJjcEG+LB29yZqAUomhEk6IVNO V/RcbQT8Rtr+5unsCmymnVWYKLLuUJYhAgYbUczZPYIFohLRUlrnRaFzN8vsW6+acgJdSQ FqURSI1W/qCDIXnzkm+ojqswj9rSlKk= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-211-yOBPHOg7P-SskSu8OuQdBg-1; Tue, 16 Sep 2025 12:27:44 -0400 X-MC-Unique: yOBPHOg7P-SskSu8OuQdBg-1 X-Mimecast-MFC-AGG-ID: yOBPHOg7P-SskSu8OuQdBg_1758040062 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 093031800299 for ; Tue, 16 Sep 2025 16:27:42 +0000 (UTC) Received: from gerbillo.redhat.com (unknown [10.44.32.160]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 2C6C419560B8 for ; Tue, 16 Sep 2025 16:27:40 +0000 (UTC) From: Paolo Abeni To: mptcp@lists.linux.dev Subject: [MPTCP next 10/12] mptcp: prevernt __mptcp_move_skbs() interferring with the fastpath Date: Tue, 16 Sep 2025 18:27:20 +0200 Message-ID: In-Reply-To: References: Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 2x6yNHOPbGlxGG7XIRi_wA_rkCPxrWpXfR6kRofiQ4o_1758040062 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8"; x-default="true" skbs will be left waiting in the subflow only in exceptional cases, we want to avoid messing with the fast path by unintentionally processing in __mptcp_move_skbs() packets landed into the subflows after the last check. Use a separate flag to mark delayed skbs and only process subflow with such flag set. Also add new mibs to track the exceptional events. Signed-off-by: Paolo Abeni --- net/mptcp/mib.c | 2 ++ net/mptcp/mib.h | 4 ++++ net/mptcp/protocol.c | 40 ++++++++++++---------------------------- net/mptcp/protocol.h | 1 + 4 files changed, 19 insertions(+), 28 deletions(-) diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c index cf879c188ca26..7af9d35cde884 100644 --- a/net/mptcp/mib.c +++ b/net/mptcp/mib.c @@ -85,6 +85,8 @@ static const struct snmp_mib mptcp_snmp_list[] =3D { SNMP_MIB_ITEM("DssFallback", MPTCP_MIB_DSSFALLBACK), SNMP_MIB_ITEM("SimultConnectFallback", MPTCP_MIB_SIMULTCONNFALLBACK), SNMP_MIB_ITEM("FallbackFailed", MPTCP_MIB_FALLBACKFAILED), + SNMP_MIB_ITEM("RcvDelayed", MPTCP_MIB_RCVDELAYED), + SNMP_MIB_ITEM("DelayedProcess", MPTCP_MIB_DELAYED_PROCESS), SNMP_MIB_SENTINEL }; =20 diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h index 309bac6fea325..f6d0eaea463e5 100644 --- a/net/mptcp/mib.h +++ b/net/mptcp/mib.h @@ -88,6 +88,10 @@ enum linux_mptcp_mib_field { MPTCP_MIB_DSSFALLBACK, /* Bad or missing DSS */ MPTCP_MIB_SIMULTCONNFALLBACK, /* Simultaneous connect */ MPTCP_MIB_FALLBACKFAILED, /* Can't fallback due to msk status */ + MPTCP_MIB_RCVDELAYED, /* Data move from subflow is delayed due to msk + * receive buffer full + */ + MPTCP_MIB_DELAYED_PROCESS, /* Delayed data moved in slowpath */ __MPTCP_MIB_MAX }; =20 diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 9c3baed948d1d..f211a939daf39 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -665,13 +665,17 @@ static bool __mptcp_move_skbs_from_subflow(struct mpt= cp_sock *msk, tp =3D tcp_sk(ssk); do { int mem =3D own_msk ? sk_rmem_alloc_get(sk) : sk->sk_backlog.len; + bool over_limit =3D mem > READ_ONCE(sk->sk_rcvbuf); u32 map_remaining, offset; u32 seq =3D tp->copied_seq; struct sk_buff *skb; bool fin; =20 - if (mem > READ_ONCE(sk->sk_rcvbuf)) + WRITE_ONCE(subflow->data_delayed, over_limit); + if (subflow->data_delayed) { + MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RCVDELAYED); break; + } =20 /* try to move as much data as available */ map_remaining =3D subflow->map_data_len - @@ -2081,32 +2085,13 @@ static void mptcp_rcv_space_adjust(struct mptcp_soc= k *msk, int copied) msk->rcvq_space.time =3D mstamp; } =20 -static struct mptcp_subflow_context * -__mptcp_first_ready_from(struct mptcp_sock *msk, - struct mptcp_subflow_context *subflow) -{ - struct mptcp_subflow_context *start_subflow =3D subflow; - - while (!READ_ONCE(subflow->data_avail)) { - subflow =3D mptcp_next_subflow(msk, subflow); - if (subflow =3D=3D start_subflow) - return NULL; - } - return subflow; -} - static bool __mptcp_move_skbs(struct sock *sk) { struct mptcp_subflow_context *subflow; struct mptcp_sock *msk =3D mptcp_sk(sk); bool ret =3D false; =20 - if (list_empty(&msk->conn_list)) - return false; - - subflow =3D list_first_entry(&msk->conn_list, - struct mptcp_subflow_context, node); - for (;;) { + mptcp_for_each_subflow(msk, subflow) { struct sock *ssk; bool slowpath; =20 @@ -2117,23 +2102,22 @@ static bool __mptcp_move_skbs(struct sock *sk) if (sk_rmem_alloc_get(sk) > sk->sk_rcvbuf) break; =20 - subflow =3D __mptcp_first_ready_from(msk, subflow); - if (!subflow) - break; + if (!subflow->data_delayed) + continue; =20 ssk =3D mptcp_subflow_tcp_sock(subflow); slowpath =3D lock_sock_fast(ssk); - ret =3D __mptcp_move_skbs_from_subflow(msk, ssk, true) || ret; + ret |=3D __mptcp_move_skbs_from_subflow(msk, ssk, true); if (unlikely(ssk->sk_err)) __mptcp_error_report(sk); unlock_sock_fast(ssk, slowpath); - - subflow =3D mptcp_next_subflow(msk, subflow); } =20 __mptcp_ofo_queue(msk); - if (ret) + if (ret) { + MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DELAYED_PROCESS); mptcp_check_data_fin((struct sock *)msk); + } return ret; } =20 diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index a6e775d6412e5..2905e4b250070 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -559,6 +559,7 @@ struct mptcp_subflow_context { u8 reset_transient:1; u8 reset_reason:4; u8 stale_count; + bool data_delayed; =20 u32 subflow_id; =20 --=20 2.51.0