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net/smc: Send directly when TCP_CORK is cleared
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 <tonylu@linux.alibaba.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -2523,8 +2523,8 @@ static int smc_setsockopt(struct socket *sock, int level, int optname,
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sk->sk_state != SMC_CLOSED) {
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if (!val) {
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SMC_STAT_INC(smc, cork_cnt);
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mod_delayed_work(smc->conn.lgr->tx_wq,
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&smc->conn.tx_work, 0);
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smc_tx_pending(&smc->conn);
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cancel_delayed_work(&smc->conn.tx_work);
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}
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}
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break;
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@ -597,6 +597,20 @@ int smc_tx_sndbuf_nonempty(struct smc_connection *conn)
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return rc;
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}
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void smc_tx_pending(struct smc_connection *conn)
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{
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struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
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int rc;
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if (smc->sk.sk_err)
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return;
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rc = smc_tx_sndbuf_nonempty(conn);
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if (!rc && conn->local_rx_ctrl.prod_flags.write_blocked &&
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!atomic_read(&conn->bytes_to_rcv))
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conn->local_rx_ctrl.prod_flags.write_blocked = 0;
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}
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/* Wakeup sndbuf consumers from process context
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* since there is more data to transmit
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*/
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@ -606,18 +620,9 @@ void smc_tx_work(struct work_struct *work)
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struct smc_connection,
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tx_work);
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struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
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int rc;
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lock_sock(&smc->sk);
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if (smc->sk.sk_err)
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goto out;
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rc = smc_tx_sndbuf_nonempty(conn);
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if (!rc && conn->local_rx_ctrl.prod_flags.write_blocked &&
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!atomic_read(&conn->bytes_to_rcv))
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conn->local_rx_ctrl.prod_flags.write_blocked = 0;
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out:
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smc_tx_pending(conn);
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release_sock(&smc->sk);
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}
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@ -27,6 +27,7 @@ static inline int smc_tx_prepared_sends(struct smc_connection *conn)
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return smc_curs_diff(conn->sndbuf_desc->len, &sent, &prep);
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}
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void smc_tx_pending(struct smc_connection *conn);
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void smc_tx_work(struct work_struct *work);
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void smc_tx_init(struct smc_sock *smc);
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int smc_tx_sendmsg(struct smc_sock *smc, struct msghdr *msg, size_t len);
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