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-rw-r--r--Documentation/networking/ip-sysctl.rst7
-rw-r--r--include/linux/tcp.h14
-rw-r--r--include/net/netns/ipv4.h1
-rw-r--r--include/net/sock.h9
-rw-r--r--net/core/sock.c6
-rw-r--r--net/ipv4/sysctl_net_ipv4.c9
-rw-r--r--net/ipv4/tcp_input.c8
-rw-r--r--net/ipv4/tcp_ipv4.c1
-rw-r--r--net/ipv4/tcp_output.c15
9 files changed, 45 insertions, 25 deletions
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index a66054d0763a..5bfa1837968c 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -745,6 +745,13 @@ tcp_comp_sack_nr - INTEGER
Default : 44
+tcp_backlog_ack_defer - BOOLEAN
+ If set, user thread processing socket backlog tries sending
+ one ACK for the whole queue. This helps to avoid potential
+ long latencies at end of a TCP socket syscall.
+
+ Default : true
+
tcp_slow_start_after_idle - BOOLEAN
If set, provide RFC2861 behavior and time out the congestion
window after an idle period. An idle period is defined at
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 3c5efeeb024f..44d946161d4a 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -463,15 +463,17 @@ enum tsq_enum {
TCP_MTU_REDUCED_DEFERRED, /* tcp_v{4|6}_err() could not call
* tcp_v{4|6}_mtu_reduced()
*/
+ TCP_ACK_DEFERRED, /* TX pure ack is deferred */
};
enum tsq_flags {
- TSQF_THROTTLED = (1UL << TSQ_THROTTLED),
- TSQF_QUEUED = (1UL << TSQ_QUEUED),
- TCPF_TSQ_DEFERRED = (1UL << TCP_TSQ_DEFERRED),
- TCPF_WRITE_TIMER_DEFERRED = (1UL << TCP_WRITE_TIMER_DEFERRED),
- TCPF_DELACK_TIMER_DEFERRED = (1UL << TCP_DELACK_TIMER_DEFERRED),
- TCPF_MTU_REDUCED_DEFERRED = (1UL << TCP_MTU_REDUCED_DEFERRED),
+ TSQF_THROTTLED = BIT(TSQ_THROTTLED),
+ TSQF_QUEUED = BIT(TSQ_QUEUED),
+ TCPF_TSQ_DEFERRED = BIT(TCP_TSQ_DEFERRED),
+ TCPF_WRITE_TIMER_DEFERRED = BIT(TCP_WRITE_TIMER_DEFERRED),
+ TCPF_DELACK_TIMER_DEFERRED = BIT(TCP_DELACK_TIMER_DEFERRED),
+ TCPF_MTU_REDUCED_DEFERRED = BIT(TCP_MTU_REDUCED_DEFERRED),
+ TCPF_ACK_DEFERRED = BIT(TCP_ACK_DEFERRED),
};
#define tcp_sk(ptr) container_of_const(ptr, struct tcp_sock, inet_conn.icsk_inet.sk)
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 7a41c4791536..d96d05b08819 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -132,6 +132,7 @@ struct netns_ipv4 {
u8 sysctl_tcp_syncookies;
u8 sysctl_tcp_migrate_req;
u8 sysctl_tcp_comp_sack_nr;
+ u8 sysctl_tcp_backlog_ack_defer;
int sysctl_tcp_reordering;
u8 sysctl_tcp_retries1;
u8 sysctl_tcp_retries2;
diff --git a/include/net/sock.h b/include/net/sock.h
index b770261fbdaf..676146e9d181 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1823,12 +1823,11 @@ static inline bool sock_owned_by_user_nocheck(const struct sock *sk)
static inline void sock_release_ownership(struct sock *sk)
{
- if (sock_owned_by_user_nocheck(sk)) {
- sk->sk_lock.owned = 0;
+ DEBUG_NET_WARN_ON_ONCE(!sock_owned_by_user_nocheck(sk));
+ sk->sk_lock.owned = 0;
- /* The sk_lock has mutex_unlock() semantics: */
- mutex_release(&sk->sk_lock.dep_map, _RET_IP_);
- }
+ /* The sk_lock has mutex_unlock() semantics: */
+ mutex_release(&sk->sk_lock.dep_map, _RET_IP_);
}
/* no reclassification while locks are held */
diff --git a/net/core/sock.c b/net/core/sock.c
index 16584e2dd648..bb89b88bc1e8 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -3001,6 +3001,9 @@ void __sk_flush_backlog(struct sock *sk)
{
spin_lock_bh(&sk->sk_lock.slock);
__release_sock(sk);
+
+ if (sk->sk_prot->release_cb)
+ sk->sk_prot->release_cb(sk);
spin_unlock_bh(&sk->sk_lock.slock);
}
EXPORT_SYMBOL_GPL(__sk_flush_backlog);
@@ -3519,9 +3522,6 @@ void release_sock(struct sock *sk)
if (sk->sk_backlog.tail)
__release_sock(sk);
- /* Warning : release_cb() might need to release sk ownership,
- * ie call sock_release_ownership(sk) before us.
- */
if (sk->sk_prot->release_cb)
sk->sk_prot->release_cb(sk);
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 6ac890b4073f..e7f024d93572 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -1367,6 +1367,15 @@ static struct ctl_table ipv4_net_table[] = {
.extra1 = SYSCTL_ZERO,
},
{
+ .procname = "tcp_backlog_ack_defer",
+ .data = &init_net.ipv4.sysctl_tcp_backlog_ack_defer,
+ .maxlen = sizeof(u8),
+ .mode = 0644,
+ .proc_handler = proc_dou8vec_minmax,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = SYSCTL_ONE,
+ },
+ {
.procname = "tcp_reflect_tos",
.data = &init_net.ipv4.sysctl_tcp_reflect_tos,
.maxlen = sizeof(u8),
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 06fe1cf645d5..41b471748437 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5553,6 +5553,14 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
tcp_in_quickack_mode(sk) ||
/* Protocol state mandates a one-time immediate ACK */
inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOW) {
+ /* If we are running from __release_sock() in user context,
+ * Defer the ack until tcp_release_cb().
+ */
+ if (sock_owned_by_user_nocheck(sk) &&
+ READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_backlog_ack_defer)) {
+ set_bit(TCP_ACK_DEFERRED, &sk->sk_tsq_flags);
+ return;
+ }
send_now:
tcp_send_ack(sk);
return;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 27140e5cdc06..f13eb7e23d03 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -3263,6 +3263,7 @@ static int __net_init tcp_sk_init(struct net *net)
net->ipv4.sysctl_tcp_comp_sack_delay_ns = NSEC_PER_MSEC;
net->ipv4.sysctl_tcp_comp_sack_slack_ns = 100 * NSEC_PER_USEC;
net->ipv4.sysctl_tcp_comp_sack_nr = 44;
+ net->ipv4.sysctl_tcp_backlog_ack_defer = 1;
net->ipv4.sysctl_tcp_fastopen = TFO_CLIENT_ENABLE;
net->ipv4.sysctl_tcp_fastopen_blackhole_timeout = 0;
atomic_set(&net->ipv4.tfo_active_disable_times, 0);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index ccfc8bbf7455..1fc1f879cfd6 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1077,7 +1077,8 @@ static void tcp_tasklet_func(struct tasklet_struct *t)
#define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
TCPF_WRITE_TIMER_DEFERRED | \
TCPF_DELACK_TIMER_DEFERRED | \
- TCPF_MTU_REDUCED_DEFERRED)
+ TCPF_MTU_REDUCED_DEFERRED | \
+ TCPF_ACK_DEFERRED)
/**
* tcp_release_cb - tcp release_sock() callback
* @sk: socket
@@ -1101,16 +1102,6 @@ void tcp_release_cb(struct sock *sk)
tcp_tsq_write(sk);
__sock_put(sk);
}
- /* Here begins the tricky part :
- * We are called from release_sock() with :
- * 1) BH disabled
- * 2) sk_lock.slock spinlock held
- * 3) socket owned by us (sk->sk_lock.owned == 1)
- *
- * But following code is meant to be called from BH handlers,
- * so we should keep BH disabled, but early release socket ownership
- */
- sock_release_ownership(sk);
if (flags & TCPF_WRITE_TIMER_DEFERRED) {
tcp_write_timer_handler(sk);
@@ -1124,6 +1115,8 @@ void tcp_release_cb(struct sock *sk)
inet_csk(sk)->icsk_af_ops->mtu_reduced(sk);
__sock_put(sk);
}
+ if ((flags & TCPF_ACK_DEFERRED) && inet_csk_ack_scheduled(sk))
+ tcp_send_ack(sk);
}
EXPORT_SYMBOL(tcp_release_cb);