net/smc: add sysctl for max conns per lgr for SMC-R v2.1

Add a new sysctl: net.smc.smcr_max_conns_per_lgr, which is
used to control the preferred max connections per lgr for
SMC-R v2.1. The default value of this sysctl is 255, and
the acceptable value ranges from 16 to 255.
Signed-off-by: Guangguan Wang <guangguan.wang@linux.alibaba.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/smc-sysctl.rst

@@ -65,3 +65,9 @@ smcr_max_links_per_lgr - INTEGER
 	for SMC-R v2.1 and later.
 
 	Default: 2
+
+smcr_max_conns_per_lgr - INTEGER
+	Controls the max number of connections can be added to a SMC-R link group. The
+	acceptable value ranges from 16 to 255. Only for SMC-R v2.1 and later.
+
+	Default: 255

include/net/netns/smc.h

@@ -23,5 +23,6 @@ struct netns_smc {
 	int				sysctl_wmem;
 	int				sysctl_rmem;
 	int				sysctl_max_links_per_lgr;
+	int				sysctl_max_conns_per_lgr;
 };
 #endif

net/smc/smc_clc.c

@@ -944,7 +944,7 @@ int smc_clc_send_proposal(struct smc_sock *smc, struct smc_init_info *ini)
 	}
 	if (smcr_indicated(ini->smc_type_v2)) {
 		memcpy(v2_ext->roce, ini->smcrv2.ib_gid_v2, SMC_GID_SIZE);
-		v2_ext->max_conns = SMC_CONN_PER_LGR_PREFER;
+		v2_ext->max_conns = net->smc.sysctl_max_conns_per_lgr;
 		v2_ext->max_links = net->smc.sysctl_max_links_per_lgr;
 	}
 
@@ -1191,7 +1191,8 @@ int smc_clc_srv_v2x_features_validate(struct smc_sock *smc,
 		return SMC_CLC_DECL_NOV2EXT;
 
 	if (ini->smcr_version & SMC_V2) {
-		ini->max_conns = min_t(u8, pclc_v2_ext->max_conns, SMC_CONN_PER_LGR_PREFER);
+		ini->max_conns = min_t(u8, pclc_v2_ext->max_conns,
+				       net->smc.sysctl_max_conns_per_lgr);
 		if (ini->max_conns < SMC_CONN_PER_LGR_MIN)
 			return SMC_CLC_DECL_MAXCONNERR;
 

net/smc/smc_sysctl.c

@@ -27,6 +27,8 @@ static const int net_smc_wmem_init = (64 * 1024);
 static const int net_smc_rmem_init = (64 * 1024);
 static int links_per_lgr_min = SMC_LINKS_ADD_LNK_MIN;
 static int links_per_lgr_max = SMC_LINKS_ADD_LNK_MAX;
+static int conns_per_lgr_min = SMC_CONN_PER_LGR_MIN;
+static int conns_per_lgr_max = SMC_CONN_PER_LGR_MAX;
 
 static struct ctl_table smc_table[] = {
 	{
@@ -79,6 +81,15 @@ static struct ctl_table smc_table[] = {
 		.extra1		= &links_per_lgr_min,
 		.extra2		= &links_per_lgr_max,
 	},
+	{
+		.procname	= "smcr_max_conns_per_lgr",
+		.data		= &init_net.smc.sysctl_max_conns_per_lgr,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &conns_per_lgr_min,
+		.extra2		= &conns_per_lgr_max,
+	},
 	{  }
 };
 
@@ -109,6 +120,7 @@ int __net_init smc_sysctl_net_init(struct net *net)
 	WRITE_ONCE(net->smc.sysctl_wmem, net_smc_wmem_init);
 	WRITE_ONCE(net->smc.sysctl_rmem, net_smc_rmem_init);
 	net->smc.sysctl_max_links_per_lgr = SMC_LINKS_PER_LGR_MAX_PREFER;
+	net->smc.sysctl_max_conns_per_lgr = SMC_CONN_PER_LGR_PREFER;
 
 	return 0;
 

net/smc/smc_sysctl.h

@@ -24,6 +24,7 @@ static inline int smc_sysctl_net_init(struct net *net)
 {
 	net->smc.sysctl_autocorking_size = SMC_AUTOCORKING_DEFAULT_SIZE;
 	net->smc.sysctl_max_links_per_lgr = SMC_LINKS_PER_LGR_MAX_PREFER;
+	net->smc.sysctl_max_conns_per_lgr = SMC_CONN_PER_LGR_PREFER;
 	return 0;
 }