From nobody Sat Oct 11 10:01:33 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 B76D831CA57 for ; Fri, 19 Sep 2025 15:53:57 +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=1758297239; cv=none; b=NxuYqaCgr1ZGlM8fmIaAH1O5ODQ1V8dhwxqSkfAIHHbbz4Vi145OcGif1Vr4+tfZWxzjTyB69C+c5hFHE8yZ4eHTtDiB06p9AldSl2acejP1FSaJGJhakMPxkG+7If15gOO8CigWbPf59jWrx12xSbPlA1FB6TKpgNEMmGDNyZ0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758297239; c=relaxed/simple; bh=I/pvKuIoRLKrd5FO2JvcUHBy8aiteUrpeS3WW5nnuUk=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=IRfUTFObH+LS0xCLyoMZJxA9Pkp3AqASjLiCD0SMTuX5hee5In8byopj7UmnI7o3vtlQuKeYQ9ORywV8GTR/aIvqx6cF+2KX2dEAK4Qalj17nGXCJzaKzwl/S8Pc13t9soZ/r4GWSeRL8YJhcm3RpRbzPUs0bZtHW0M/N/S8QtE= 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=bu91/Tuk; 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="bu91/Tuk" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758297236; 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=fjb+cIf+fmWWN/Wpl86mlEWkemfac6TNnJd/yK2ZTHc=; b=bu91/TukE8G9Vc4cwOHxLaJ0tLlfW6mS1jBVxzBWTWzXyiKTLNdqkJk+uR7A4HN+4aBnKO XXRb4P6HbU7+VXS/uGbfim5W2AaF7GpGGppXqGXv25jZNAN7SNfEV9vkfJOnSO9WUvwcki njN9ee0sReA7GRz5tjw8Fd+YGEkKpP8= Received: from mx-prod-mc-08.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-473-nC7uaJAmNYmSErJ2wZ7wpw-1; Fri, 19 Sep 2025 11:53:55 -0400 X-MC-Unique: nC7uaJAmNYmSErJ2wZ7wpw-1 X-Mimecast-MFC-AGG-ID: nC7uaJAmNYmSErJ2wZ7wpw_1758297234 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 626661800350 for ; Fri, 19 Sep 2025 15:53:54 +0000 (UTC) Received: from gerbillo.redhat.com (unknown [10.44.32.255]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 862F01800452 for ; Fri, 19 Sep 2025 15:53:53 +0000 (UTC) From: Paolo Abeni To: mptcp@lists.linux.dev Subject: [MPTCP next v3 12/12] mptcp: borrow forward memory from subflow Date: Fri, 19 Sep 2025 17:53:26 +0200 Message-ID: <34ad291e860dfa1bc1c7d5fe3cc5a07820bec571.1758296923.git.pabeni@redhat.com> 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 3.4.1 on 10.30.177.111 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: vI0S_Wpw0ggFsec7J_kQTlvnGEVMirT1ytSauxng8MM_1758297234 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8"; x-default="true" In the MPTCP receive path, we release the subflow allocated fwd memory just to allocate it again shortly after for the msk. That could increases the failures chances, especially during backlog processing, when other actions could consume the just released memory before the msk socket has a chance to do the rcv allocation. Replace the skb_orphan() call with an open-coded variant that explicitly borrows, with a PAGE_SIZE granularity, the fwd memory from the subflow socket instead of releasing it. During backlog processing the borrowed memory is accounted at release_cb time. Signed-off-by: Paolo Abeni Reviewed-by: Geliang Tang Tested-by: Geliang Tang --- v1 -> v2: - rebased - explain why skb_orphan is removed --- net/mptcp/protocol.c | 27 +++++++++++++++++++++------ net/mptcp/protocol.h | 1 + 2 files changed, 22 insertions(+), 6 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 2a025c0c4ca0c..7db5adb43d41b 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -338,11 +338,12 @@ static void mptcp_data_queue_ofo(struct mptcp_sock *m= sk, struct sk_buff *skb) mptcp_rcvbuf_grow(sk); } =20 -static void mptcp_init_skb(struct sock *ssk, - struct sk_buff *skb, int offset, int copy_len) +static int mptcp_init_skb(struct sock *ssk, + struct sk_buff *skb, int offset, int copy_len) { const struct mptcp_subflow_context *subflow =3D mptcp_subflow_ctx(ssk); bool has_rxtstamp =3D TCP_SKB_CB(skb)->has_rxtstamp; + int borrowed; =20 /* the skb map_seq accounts for the skb offset: * mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq @@ -358,6 +359,15 @@ static void mptcp_init_skb(struct sock *ssk, =20 skb_ext_reset(skb); skb_dst_drop(skb); + + /* "borrow" the fwd memory from the subflow, instead of reclaiming it */ + skb->destructor =3D NULL; + skb->sk =3D NULL; + atomic_sub(skb->truesize, &ssk->sk_rmem_alloc); + borrowed =3D ssk->sk_forward_alloc - sk_unused_reserved_mem(ssk); + borrowed &=3D ~(PAGE_SIZE - 1); + sk_forward_alloc_add(ssk, skb->truesize - borrowed); + return borrowed; } =20 static void __mptcp_add_backlog(struct sock *sk, struct sock *ssk, @@ -717,14 +727,17 @@ static bool __mptcp_move_skbs_from_subflow(struct mpt= cp_sock *msk, =20 if (offset < skb->len) { size_t len =3D skb->len - offset; + int bmem; =20 - mptcp_init_skb(ssk, skb, offset, len); - skb_orphan(skb); + bmem =3D mptcp_init_skb(ssk, skb, offset, len); =20 - if (own_msk) + if (own_msk) { + sk_forward_alloc_add(sk, bmem); ret |=3D __mptcp_move_skb(sk, skb); - else + } else { + msk->borrowed_fwd_mem +=3D bmem; __mptcp_add_backlog(sk, ssk, skb); + } seq +=3D len; =20 if (unlikely(map_remaining < len)) { @@ -3514,6 +3527,8 @@ static void mptcp_release_cb(struct sock *sk) if (__test_and_clear_bit(MPTCP_SYNC_SNDBUF, &msk->cb_flags)) __mptcp_sync_sndbuf(sk); } + sk_forward_alloc_add(sk, msk->borrowed_fwd_mem); + msk->borrowed_fwd_mem =3D 0; } =20 /* MP_JOIN client subflow must wait for 4th ack before sending any data: diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index a295ce11774ea..ff87dd9a0da5a 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -298,6 +298,7 @@ struct mptcp_sock { u32 last_data_sent; u32 last_data_recv; u32 last_ack_recv; + int borrowed_fwd_mem; unsigned long timer_ival; u32 token; unsigned long flags; --=20 2.51.0