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net/smc: Send directly when TCP_CORK is cleared 

[ Upstream commit ea785a1a57 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Tony Lu 2022-01-31 02:02:55 +08:00 committed by Greg Kroah-Hartman
parent 646d533af2
commit eb5202cb83
3 changed files with 18 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
net/smc/af_smc.c
View File

@ -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;

25
net/smc/smc_tx.c
View File

@ -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);
}

1
net/smc/smc_tx.h
View File

@ -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);