From eb5202cb83f1a243cf2eaf18dbc60ec2ad7f67dd Mon Sep 17 00:00:00 2001 From: Tony Lu Date: Mon, 31 Jan 2022 02:02:55 +0800 Subject: [PATCH] net/smc: Send directly when TCP_CORK is cleared [ Upstream commit ea785a1a573b390a150010b3c5b81e1ccd8c98a8 ] According to the man page of TCP_CORK [1], if set, don't send out partial frames. All queued partial frames are sent when option is cleared again. When applications call setsockopt to disable TCP_CORK, this call is protected by lock_sock(), and tries to mod_delayed_work() to 0, in order to send pending data right now. However, the delayed work smc_tx_work is also protected by lock_sock(). There introduces lock contention for sending data. To fix it, send pending data directly which acts like TCP, without lock_sock() protected in the context of setsockopt (already lock_sock()ed), and cancel unnecessary dealyed work, which is protected by lock. [1] https://linux.die.net/man/7/tcp Signed-off-by: Tony Lu Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/smc/af_smc.c | 4 ++-- net/smc/smc_tx.c | 25 +++++++++++++++---------- net/smc/smc_tx.h | 1 + 3 files changed, 18 insertions(+), 12 deletions(-) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index 284befa90967..67fc72047c9c 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -2636,8 +2636,8 @@ static int smc_setsockopt(struct socket *sock, int level, int optname, sk->sk_state != SMC_CLOSED) { if (!val) { SMC_STAT_INC(smc, cork_cnt); - mod_delayed_work(smc->conn.lgr->tx_wq, - &smc->conn.tx_work, 0); + smc_tx_pending(&smc->conn); + cancel_delayed_work(&smc->conn.tx_work); } } break; diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c index be241d53020f..7b0b6e24582f 100644 --- a/net/smc/smc_tx.c +++ b/net/smc/smc_tx.c @@ -597,6 +597,20 @@ int smc_tx_sndbuf_nonempty(struct smc_connection *conn) return rc; } +void smc_tx_pending(struct smc_connection *conn) +{ + struct smc_sock *smc = container_of(conn, struct smc_sock, conn); + int rc; + + if (smc->sk.sk_err) + return; + + rc = smc_tx_sndbuf_nonempty(conn); + if (!rc && conn->local_rx_ctrl.prod_flags.write_blocked && + !atomic_read(&conn->bytes_to_rcv)) + conn->local_rx_ctrl.prod_flags.write_blocked = 0; +} + /* Wakeup sndbuf consumers from process context * since there is more data to transmit */ @@ -606,18 +620,9 @@ void smc_tx_work(struct work_struct *work) struct smc_connection, tx_work); struct smc_sock *smc = container_of(conn, struct smc_sock, conn); - int rc; lock_sock(&smc->sk); - if (smc->sk.sk_err) - goto out; - - rc = smc_tx_sndbuf_nonempty(conn); - if (!rc && conn->local_rx_ctrl.prod_flags.write_blocked && - !atomic_read(&conn->bytes_to_rcv)) - conn->local_rx_ctrl.prod_flags.write_blocked = 0; - -out: + smc_tx_pending(conn); release_sock(&smc->sk); } diff --git a/net/smc/smc_tx.h b/net/smc/smc_tx.h index 07e6ad76224a..a59f370b8b43 100644 --- a/net/smc/smc_tx.h +++ b/net/smc/smc_tx.h @@ -27,6 +27,7 @@ static inline int smc_tx_prepared_sends(struct smc_connection *conn) return smc_curs_diff(conn->sndbuf_desc->len, &sent, &prep); } +void smc_tx_pending(struct smc_connection *conn); void smc_tx_work(struct work_struct *work); void smc_tx_init(struct smc_sock *smc); int smc_tx_sendmsg(struct smc_sock *smc, struct msghdr *msg, size_t len);