tcp: remove unused min_cwnd member of tcp_congestion_ops

Commit 684bad110757 "tcp: use PRR to reduce cwin in CWR state" removed all
calls to min_cwnd, so we can safely remove it.
Also, remove tcp_reno_min_cwnd because it was only used for min_cwnd.

Signed-off-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/tcp.txt

@@ -30,7 +30,7 @@ A congestion control mechanism can be registered through functions in
 tcp_cong.c. The functions used by the congestion control mechanism are
 registered via passing a tcp_congestion_ops struct to
 tcp_register_congestion_control. As a minimum name, ssthresh,
-cong_avoid, min_cwnd must be valid.
+cong_avoid must be valid.
 
 Private data for a congestion control mechanism is stored in tp->ca_priv.
 tcp_ca(tp) returns a pointer to this space.  This is preallocated space - it

include/net/tcp.h

@@ -791,8 +791,6 @@ struct tcp_congestion_ops {
 
 	/* return slow start threshold (required) */
 	u32 (*ssthresh)(struct sock *sk);
-	/* lower bound for congestion window (optional) */
-	u32 (*min_cwnd)(const struct sock *sk);
 	/* do new cwnd calculation (required) */
 	void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked, u32 in_flight);
 	/* call before changing ca_state (optional) */
@@ -827,7 +825,6 @@ void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w);
 extern struct tcp_congestion_ops tcp_init_congestion_ops;
 u32 tcp_reno_ssthresh(struct sock *sk);
 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked, u32 in_flight);
-u32 tcp_reno_min_cwnd(const struct sock *sk);
 extern struct tcp_congestion_ops tcp_reno;
 
 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)

net/ipv4/tcp_cong.c

@@ -362,21 +362,12 @@ u32 tcp_reno_ssthresh(struct sock *sk)
 }
 EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
 
-/* Lower bound on congestion window with halving. */
-u32 tcp_reno_min_cwnd(const struct sock *sk)
-{
-	const struct tcp_sock *tp = tcp_sk(sk);
-	return tp->snd_ssthresh/2;
-}
-EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);
-
 struct tcp_congestion_ops tcp_reno = {
 	.flags		= TCP_CONG_NON_RESTRICTED,
 	.name		= "reno",
 	.owner		= THIS_MODULE,
 	.ssthresh	= tcp_reno_ssthresh,
 	.cong_avoid	= tcp_reno_cong_avoid,
-	.min_cwnd	= tcp_reno_min_cwnd,
 };
 
 /* Initial congestion control used (until SYN)
@@ -388,6 +379,5 @@ struct tcp_congestion_ops tcp_init_congestion_ops  = {
 	.owner		= THIS_MODULE,
 	.ssthresh	= tcp_reno_ssthresh,
 	.cong_avoid	= tcp_reno_cong_avoid,
-	.min_cwnd	= tcp_reno_min_cwnd,
 };
 EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);

net/ipv4/tcp_highspeed.c

@@ -162,7 +162,6 @@ static struct tcp_congestion_ops tcp_highspeed __read_mostly = {
 	.init		= hstcp_init,
 	.ssthresh	= hstcp_ssthresh,
 	.cong_avoid	= hstcp_cong_avoid,
-	.min_cwnd	= tcp_reno_min_cwnd,
 
 	.owner		= THIS_MODULE,
 	.name		= "highspeed"

net/ipv4/tcp_hybla.c

@@ -166,7 +166,6 @@ static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 acked,
 static struct tcp_congestion_ops tcp_hybla __read_mostly = {
 	.init		= hybla_init,
 	.ssthresh	= tcp_reno_ssthresh,
-	.min_cwnd	= tcp_reno_min_cwnd,
 	.cong_avoid	= hybla_cong_avoid,
 	.set_state	= hybla_state,
 

net/ipv4/tcp_illinois.c

@@ -328,7 +328,6 @@ static struct tcp_congestion_ops tcp_illinois __read_mostly = {
 	.flags		= TCP_CONG_RTT_STAMP,
 	.init		= tcp_illinois_init,
 	.ssthresh	= tcp_illinois_ssthresh,
-	.min_cwnd	= tcp_reno_min_cwnd,
 	.cong_avoid	= tcp_illinois_cong_avoid,
 	.set_state	= tcp_illinois_state,
 	.get_info	= tcp_illinois_info,

net/ipv4/tcp_lp.c

@@ -319,7 +319,6 @@ static struct tcp_congestion_ops tcp_lp __read_mostly = {
 	.init = tcp_lp_init,
 	.ssthresh = tcp_reno_ssthresh,
 	.cong_avoid = tcp_lp_cong_avoid,
-	.min_cwnd = tcp_reno_min_cwnd,
 	.pkts_acked = tcp_lp_pkts_acked,
 
 	.owner = THIS_MODULE,

net/ipv4/tcp_scalable.c

@@ -39,7 +39,6 @@ static u32 tcp_scalable_ssthresh(struct sock *sk)
 static struct tcp_congestion_ops tcp_scalable __read_mostly = {
 	.ssthresh	= tcp_scalable_ssthresh,
 	.cong_avoid	= tcp_scalable_cong_avoid,
-	.min_cwnd	= tcp_reno_min_cwnd,
 
 	.owner		= THIS_MODULE,
 	.name		= "scalable",

net/ipv4/tcp_vegas.c

@@ -310,7 +310,6 @@ static struct tcp_congestion_ops tcp_vegas __read_mostly = {
 	.init		= tcp_vegas_init,
 	.ssthresh	= tcp_reno_ssthresh,
 	.cong_avoid	= tcp_vegas_cong_avoid,
-	.min_cwnd	= tcp_reno_min_cwnd,
 	.pkts_acked	= tcp_vegas_pkts_acked,
 	.set_state	= tcp_vegas_state,
 	.cwnd_event	= tcp_vegas_cwnd_event,

net/ipv4/tcp_westwood.c

@@ -276,7 +276,6 @@ static struct tcp_congestion_ops tcp_westwood __read_mostly = {
 	.init		= tcp_westwood_init,
 	.ssthresh	= tcp_reno_ssthresh,
 	.cong_avoid	= tcp_reno_cong_avoid,
-	.min_cwnd	= tcp_westwood_bw_rttmin,
 	.cwnd_event	= tcp_westwood_event,
 	.get_info	= tcp_westwood_info,
 	.pkts_acked	= tcp_westwood_pkts_acked,

net/ipv4/tcp_yeah.c

@@ -231,7 +231,6 @@ static struct tcp_congestion_ops tcp_yeah __read_mostly = {
 	.init		= tcp_yeah_init,
 	.ssthresh	= tcp_yeah_ssthresh,
 	.cong_avoid	= tcp_yeah_cong_avoid,
-	.min_cwnd	= tcp_reno_min_cwnd,
 	.set_state	= tcp_vegas_state,
 	.cwnd_event	= tcp_vegas_cwnd_event,
 	.get_info	= tcp_vegas_get_info,