From 7439d687b79cbbd971c6a170be9aefda4a564be4 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Fri, 27 Nov 2020 11:10:26 +0100 Subject: [PATCH] mptcp: avoid a few atomic ops in the rx path Extending the data_lock scope in mptcp_incoming_option we can use that to protect both snd_una and wnd_end. In the typical case, we will have a single atomic op instead of 2 Acked-by: Florian Westphal Signed-off-by: Paolo Abeni Reviewed-by: Mat Martineau Signed-off-by: Jakub Kicinski --- net/mptcp/mptcp_diag.c | 2 +- net/mptcp/options.c | 33 +++++++++++++-------------------- net/mptcp/protocol.c | 34 ++++++++++++++++------------------ net/mptcp/protocol.h | 8 ++++---- 4 files changed, 34 insertions(+), 43 deletions(-) diff --git a/net/mptcp/mptcp_diag.c b/net/mptcp/mptcp_diag.c index 5f390a97f556..b70ae4ba3000 100644 --- a/net/mptcp/mptcp_diag.c +++ b/net/mptcp/mptcp_diag.c @@ -140,7 +140,7 @@ static void mptcp_diag_get_info(struct sock *sk, struct inet_diag_msg *r, info->mptcpi_flags = flags; info->mptcpi_token = READ_ONCE(msk->token); info->mptcpi_write_seq = READ_ONCE(msk->write_seq); - info->mptcpi_snd_una = atomic64_read(&msk->snd_una); + info->mptcpi_snd_una = READ_ONCE(msk->snd_una); info->mptcpi_rcv_nxt = READ_ONCE(msk->ack_seq); unlock_sock_fast(sk, slow); } diff --git a/net/mptcp/options.c b/net/mptcp/options.c index 8a59b3e44599..3986454a0340 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -833,15 +833,17 @@ static void ack_update_msk(struct mptcp_sock *msk, const struct sock *ssk, struct mptcp_options_received *mp_opt) { - u64 new_snd_una, snd_una, old_snd_una = atomic64_read(&msk->snd_una); - u64 new_wnd_end, wnd_end, old_wnd_end = atomic64_read(&msk->wnd_end); - u64 snd_nxt = READ_ONCE(msk->snd_nxt); + u64 new_wnd_end, new_snd_una, snd_nxt = READ_ONCE(msk->snd_nxt); struct sock *sk = (struct sock *)msk; + u64 old_snd_una; + + mptcp_data_lock(sk); /* avoid ack expansion on update conflict, to reduce the risk of * wrongly expanding to a future ack sequence number, which is way * more dangerous than missing an ack */ + old_snd_una = msk->snd_una; new_snd_una = expand_ack(old_snd_una, mp_opt->data_ack, mp_opt->ack64); /* ACK for data not even sent yet? Ignore. */ @@ -850,26 +852,17 @@ static void ack_update_msk(struct mptcp_sock *msk, new_wnd_end = new_snd_una + tcp_sk(ssk)->snd_wnd; - while (after64(new_wnd_end, old_wnd_end)) { - wnd_end = old_wnd_end; - old_wnd_end = atomic64_cmpxchg(&msk->wnd_end, wnd_end, - new_wnd_end); - if (old_wnd_end == wnd_end) { - if (mptcp_send_head(sk)) - mptcp_schedule_work(sk); - break; - } + if (after64(new_wnd_end, msk->wnd_end)) { + msk->wnd_end = new_wnd_end; + if (mptcp_send_head(sk)) + mptcp_schedule_work(sk); } - while (after64(new_snd_una, old_snd_una)) { - snd_una = old_snd_una; - old_snd_una = atomic64_cmpxchg(&msk->snd_una, snd_una, - new_snd_una); - if (old_snd_una == snd_una) { - mptcp_data_acked(sk); - break; - } + if (after64(new_snd_una, old_snd_una)) { + msk->snd_una = new_snd_una; + __mptcp_data_acked(sk); } + mptcp_data_unlock(sk); } bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 75b4c4c50dbb..51f92f3096bf 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -60,7 +60,7 @@ static struct socket *__mptcp_nmpc_socket(const struct mptcp_sock *msk) /* Returns end sequence number of the receiver's advertised window */ static u64 mptcp_wnd_end(const struct mptcp_sock *msk) { - return atomic64_read(&msk->wnd_end); + return READ_ONCE(msk->wnd_end); } static bool mptcp_is_tcpsk(struct sock *sk) @@ -358,7 +358,7 @@ static void mptcp_check_data_fin_ack(struct sock *sk) /* Look for an acknowledged DATA_FIN */ if (((1 << sk->sk_state) & (TCPF_FIN_WAIT1 | TCPF_CLOSING | TCPF_LAST_ACK)) && - msk->write_seq == atomic64_read(&msk->snd_una)) { + msk->write_seq == READ_ONCE(msk->snd_una)) { mptcp_stop_timer(sk); WRITE_ONCE(msk->snd_data_fin_enable, 0); @@ -764,7 +764,7 @@ bool mptcp_schedule_work(struct sock *sk) return false; } -void mptcp_data_acked(struct sock *sk) +void __mptcp_data_acked(struct sock *sk) { mptcp_reset_timer(sk); @@ -997,11 +997,11 @@ static void mptcp_clean_una(struct sock *sk) * plain TCP */ if (__mptcp_check_fallback(msk)) - atomic64_set(&msk->snd_una, msk->snd_nxt); + msk->snd_una = READ_ONCE(msk->snd_nxt); + mptcp_data_lock(sk); - snd_una = atomic64_read(&msk->snd_una); - + snd_una = msk->snd_una; list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list) { if (after64(dfrag->data_seq + dfrag->data_len, snd_una)) break; @@ -1282,10 +1282,12 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk, /* Zero window and all data acked? Probe. */ avail_size = mptcp_check_allowed_size(msk, data_seq, avail_size); if (avail_size == 0) { - if (skb || atomic64_read(&msk->snd_una) != msk->snd_nxt) + u64 snd_una = READ_ONCE(msk->snd_una); + + if (skb || snd_una != msk->snd_nxt) return 0; zero_window_probe = true; - data_seq = atomic64_read(&msk->snd_una) - 1; + data_seq = snd_una - 1; avail_size = 1; } @@ -1994,12 +1996,8 @@ static void mptcp_retransmit_handler(struct sock *sk) { struct mptcp_sock *msk = mptcp_sk(sk); - if (atomic64_read(&msk->snd_una) == READ_ONCE(msk->snd_nxt)) { - mptcp_stop_timer(sk); - } else { - set_bit(MPTCP_WORK_RTX, &msk->flags); - mptcp_schedule_work(sk); - } + set_bit(MPTCP_WORK_RTX, &msk->flags); + mptcp_schedule_work(sk); } static void mptcp_retransmit_timer(struct timer_list *t) @@ -2621,8 +2619,8 @@ struct sock *mptcp_sk_clone(const struct sock *sk, msk->write_seq = subflow_req->idsn + 1; msk->snd_nxt = msk->write_seq; - atomic64_set(&msk->snd_una, msk->write_seq); - atomic64_set(&msk->wnd_end, msk->snd_nxt + req->rsk_rcv_wnd); + msk->snd_una = msk->write_seq; + msk->wnd_end = msk->snd_nxt + req->rsk_rcv_wnd; if (mp_opt->mp_capable) { msk->can_ack = true; @@ -2658,7 +2656,7 @@ void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk) if (msk->rcvq_space.space == 0) msk->rcvq_space.space = TCP_INIT_CWND * TCP_MSS_DEFAULT; - atomic64_set(&msk->wnd_end, msk->snd_nxt + tcp_sk(ssk)->snd_wnd); + WRITE_ONCE(msk->wnd_end, msk->snd_nxt + tcp_sk(ssk)->snd_wnd); } static struct sock *mptcp_accept(struct sock *sk, int flags, int *err, @@ -2918,7 +2916,7 @@ void mptcp_finish_connect(struct sock *ssk) WRITE_ONCE(msk->ack_seq, ack_seq); WRITE_ONCE(msk->rcv_wnd_sent, ack_seq); WRITE_ONCE(msk->can_ack, 1); - atomic64_set(&msk->snd_una, msk->write_seq); + WRITE_ONCE(msk->snd_una, msk->write_seq); mptcp_pm_new_connection(msk, 0); diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 97c1e5dcb3e2..3c07aafde10e 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -222,8 +222,8 @@ struct mptcp_sock { struct sock *last_snd; int snd_burst; int old_wspace; - atomic64_t snd_una; - atomic64_t wnd_end; + u64 snd_una; + u64 wnd_end; unsigned long timer_ival; u32 token; int rmem_pending; @@ -321,7 +321,7 @@ static inline struct mptcp_data_frag *mptcp_rtx_tail(const struct sock *sk) { struct mptcp_sock *msk = mptcp_sk(sk); - if (!before64(msk->snd_nxt, atomic64_read(&msk->snd_una))) + if (!before64(msk->snd_nxt, READ_ONCE(msk->snd_una))) return NULL; return list_last_entry(&msk->rtx_queue, struct mptcp_data_frag, list); @@ -495,7 +495,7 @@ void mptcp_rcv_space_init(struct mptcp_sock *msk, const struct sock *ssk); void mptcp_data_ready(struct sock *sk, struct sock *ssk); bool mptcp_finish_join(struct sock *sk); bool mptcp_schedule_work(struct sock *sk); -void mptcp_data_acked(struct sock *sk); +void __mptcp_data_acked(struct sock *sk); void mptcp_subflow_eof(struct sock *sk); bool mptcp_update_rcv_data_fin(struct mptcp_sock *msk, u64 data_fin_seq, bool use_64bit); void __mptcp_flush_join_list(struct mptcp_sock *msk);