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Thu, 24 Sep 2026 15:24:04 +0800 (CST) Received: from whupemk100010.china.huawei.com (unknown [7.152.184.41]) by mail.maildlp.com (Postfix) with ESMTPS id 83D4940565; Thu, 24 Sep 2026 15:36:10 +0800 (CST) Received: from octopus.huawei.com (10.67.174.191) by whupemk100010.china.huawei.com (7.152.184.41) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Thu, 24 Sep 2026 15:36:08 +0800 From: Cai Xinchen To: , , , , , , , , , , , , , , , , , , , , CC: , , , , , , , , Subject: [PATCH RFC -next 3/5] mptcp: sync memcg budget and drop backlog page compensation Date: Thu, 24 Sep 2026 16:02:17 +0800 Message-ID: <20260924080219.1036588-4-caixinchen1@huawei.com> X-Mailer: git-send-email 2.18.0.huawei.25 In-Reply-To: <20260924080219.1036588-1-caixinchen1@huawei.com> References: <20260924080219.1036588-1-caixinchen1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.67.174.191] X-ClientProxiedBy: kwepems500001.china.huawei.com (7.221.188.70) To whupemk100010.china.huawei.com (7.152.184.41) X-Rspam-User: X-Stat-Signature: cattejwxhd161cttgixdsatp5wrqmuan X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: DE2E5140002 X-HE-Tag: 1790235374-379391 X-HE-Meta: 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 Ne2m76+d axtIMboooZIy4VXmk364+e8Y/qLAuJsd89+kUf6NPtqUX5p+8ap80s3Mkz3CvaYu0eNzwNzkS9Dn3LTndtvhDFQ5C8gbUhYBa3tGVxsEL1AVUiIaBUhGmWKYEn7OuxodOOWJruXv+3LrGvx5m+Lnc+oj1WNFB82jAZwQ/jf4MhZDSTMpeRJvctTCrxz8qcXcjV3LDIvu63Af/0npqinZOYh1ABH9j9fy78E9luBG8kZMJgfqlCNiDFpn+lnCIjEHY9UlG6sjyatCBBMXc1SoFrU8/GNu6umbOqX0ob22rSKpYzbysgXpBYfCvi3r5xGfpQ+St Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Sync the memcg budget tracker at the MPTCP budget writes: mptcp_init_sock() (per-net rcvbuf default), mptcp_rcvbuf_grow(), __mptcp_sync_sndbuf(), __mptcp_subflow_set_rcvbuf() and mptcp_set_rcvlowat() (both on the msk and on each subflow). __mptcp_inherit_memcg() moves a subflow to the msk's memcg: refund the budget the subflow still holds in the old memcg with sk_memcg_budget_release() before the switch; the new memcg side re-charges it through __sk_charge(). With budgets charged upfront, the pages an MPTCP socket spooled into its backlog before being accepted are covered by the full budget that __sk_charge() charges at accept time, so the old per-page compensation in mptcp_graft_subflows() (fed by mptcp_sock->backlog_unaccounted) would now double-charge. Remove the counter, its accumulation in __mptcp_add_backlog() and the compensation charge. Assisted-by: opencode:glm-5.3 Signed-off-by: Cai Xinchen --- net/mptcp/protocol.c | 42 ++++++------------------------------------ net/mptcp/protocol.h | 2 +- net/mptcp/sockopt.c | 3 +++ net/mptcp/subflow.c | 5 +++++ 4 files changed, 15 insertions(+), 37 deletions(-) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 0098e2830931..3c8b885d8298 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -238,6 +238,7 @@ static bool mptcp_rcvbuf_grow(struct sock *sk, u32 newval) rcvbuf = min_t(u32, mptcp_space_from_win(sk, rcvwin), cap); if (rcvbuf > sk->sk_rcvbuf) { WRITE_ONCE(sk->sk_rcvbuf, rcvbuf); + sk_memcg_budget_sync(sk, gfp_memcg_charge()); return true; } return false; @@ -791,12 +792,6 @@ static void __mptcp_add_backlog(struct sock *sk, account: WRITE_ONCE(msk->backlog_len, msk->backlog_len + delta); - - /* Possibly not accept()ed yet, keep track of memory not CG - * accounted, mptcp_graft_subflows() will handle it. - */ - if (!mem_cgroup_from_sk(ssk)) - msk->backlog_unaccounted += delta; } static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk, @@ -2315,12 +2310,6 @@ static bool mptcp_can_spool_backlog(struct sock *sk, struct list_head *skbs) { struct mptcp_sock *msk = mptcp_sk(sk); - /* After CG initialization, subflows should never add skb before - * gaining the CG themself. - */ - DEBUG_NET_WARN_ON_ONCE(msk->backlog_unaccounted && sk->sk_socket && - mem_cgroup_from_sk(sk)); - if (list_empty(&msk->backlog_list)) return false; @@ -3252,6 +3241,10 @@ static int mptcp_init_sock(struct sock *sk) sk_sockets_allocated_inc(sk); sk->sk_rcvbuf = READ_ONCE(net->ipv4.sysctl_tcp_rmem[1]); sk->sk_sndbuf = READ_ONCE(net->ipv4.sysctl_tcp_wmem[1]); + /* The default buffers grew from the generic sock_init_data() + * values: charge the difference to the memcg. + */ + sk_memcg_budget_sync(sk, gfp_memcg_charge()); sk->sk_write_space = sk_stream_write_space; return 0; @@ -4329,10 +4322,7 @@ static void mptcp_graft_subflows(struct sock *sk) LIST_HEAD(join_list); /* Subflows joining after __inet_accept() will get the - * mem CG properly initialized at mptcp_finish_join() time, - * but subflows pending in join_list need explicit - * initialization before flushing `backlog_unaccounted` - * or MPTCP can later unexpectedly observe unaccounted memory. + * mem CG properly initialized at mptcp_finish_join() time. */ mptcp_data_lock(sk); list_splice_init(&msk->join_list, &join_list); @@ -4361,26 +4351,6 @@ static void mptcp_graft_subflows(struct sock *sk) unlock: release_sock(ssk); } - - if (mem_cgroup_sk_enabled(sk)) { - gfp_t gfp = GFP_KERNEL | __GFP_NOFAIL; - int amt; - - /* Account the backlog memory; prior accept() is aware of - * fwd and rmem only. - */ - mptcp_data_lock(sk); - amt = sk_mem_pages(sk->sk_forward_alloc + - msk->backlog_unaccounted + - atomic_read(&sk->sk_rmem_alloc)) - - sk_mem_pages(sk->sk_forward_alloc + - atomic_read(&sk->sk_rmem_alloc)); - msk->backlog_unaccounted = 0; - mptcp_data_unlock(sk); - - if (amt) - mem_cgroup_sk_charge(sk, amt, gfp); - } } static int mptcp_stream_accept(struct socket *sock, struct socket *newsock, diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 2b4c27426477..aa34be38cf14 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -377,7 +377,6 @@ struct mptcp_sock { struct list_head backlog_list; /* protected by the data lock */ u32 backlog_len; - u32 backlog_unaccounted; }; #define mptcp_data_lock(sk) spin_lock_bh(&(sk)->sk_lock.slock) @@ -1040,6 +1039,7 @@ static inline void __mptcp_sync_sndbuf(struct sock *sk) /* the msk max wmem limit is * tcp wmem[2] */ WRITE_ONCE(sk->sk_sndbuf, new_sndbuf); + sk_memcg_budget_sync(sk, gfp_memcg_charge()); mptcp_write_space(sk); } diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c index fcf6feb2a9eb..05d9dafa8c07 100644 --- a/net/mptcp/sockopt.c +++ b/net/mptcp/sockopt.c @@ -70,6 +70,7 @@ static int mptcp_get_int_option(struct mptcp_sock *msk, sockptr_t optval, static void __mptcp_subflow_set_rcvbuf(struct sock *ssk, int val) { WRITE_ONCE(ssk->sk_rcvbuf, val); + sk_memcg_budget_sync(ssk, gfp_memcg_charge()); tcp_set_rcvbuf(ssk, val); } @@ -1656,12 +1657,14 @@ int mptcp_set_rcvlowat(struct sock *sk, int val) /* propagate the rcvbuf changes to all the subflows */ WRITE_ONCE(sk->sk_rcvbuf, space); + sk_memcg_budget_sync(sk, gfp_memcg_charge()); mptcp_for_each_subflow(mptcp_sk(sk), subflow) { struct sock *ssk = mptcp_subflow_tcp_sock(subflow); bool slow; slow = lock_sock_fast(ssk); WRITE_ONCE(ssk->sk_rcvbuf, space); + sk_memcg_budget_sync(ssk, gfp_memcg_charge()); WRITE_ONCE(tcp_sk(ssk)->window_clamp, val); unlock_sock_fast(ssk, slow); } diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 01db7edce18a..817a98b5f40f 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1731,6 +1731,11 @@ void __mptcp_inherit_memcg(struct sock *sk, struct sock *ssk, gfp_t gfp) if (!mem_cgroup_sockets_enabled || !sk->sk_socket) return; + /* The subflow's budget charge went to its previous memcg: return + * it before the memcg association moves to the msk's one, the + * __sk_charge() below re-charges the budget there. + */ + sk_memcg_budget_release(ssk); mem_cgroup_sk_inherit(sk, ssk); __sk_charge(ssk, gfp); } -- 2.18.0.huawei.25