[PATCH net-next 1/2] net/smc: Introduce a specific sysctl for TEST_LINK time

Wen Gu
2022-09-20T02:54:14Z

SMC-R tests the viability of link by sending out TEST_LINK LLC
messages over RoCE fabric when connections on link have been
idle for a time longer than keepalive interval (testlink time).

But using tcp_keepalive_time as testlink time maybe not quite
suitable because it is default no less than two hours[1], which
is too long for single link to find peer dead. The active host
will still use peer-dead link (QP) sending messages, and can't
find out until get IB_WC_RETRY_EXC_ERR error CQEs, which takes
more time than TEST_LINK timeout (SMC_LLC_WAIT_TIME) normally.

So this patch introduces a independent sysctl for SMC-R to set
link keepalive time, in order to detect link down in time. The
default value is 30 seconds.

[1] https://www.rfc-editor.org/rfc/rfc1122#page-101

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
Documentation/networking/smc-sysctl.rst | 7 +++++++
include/net/netns/smc.h | 1 +
net/smc/smc_llc.c | 2 +-
net/smc/smc_llc.h | 1 +
net/smc/smc_sysctl.c | 14 ++++++++++++++
5 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/smc-sysctl.rst b/Documentation/networking/smc-sysctl.rst
index 742e90e..f8c3d59 100644
--- a/Documentation/networking/smc-sysctl.rst
+++ b/Documentation/networking/smc-sysctl.rst
@@ -34,3 +34,10 @@ smcr_buf_type - INTEGER
- 1 - Use virtually contiguous buffers
- 2 - Mixed use of the two types. Try physically contiguous buffers first.
If not available, use virtually contiguous buffers then.
+
+smcr_testlink_time - INTEGER
+ How frequently SMC-R link sends out TEST_LINK LLC messages to confirm
+ viability, after the last activity of connections on it. The maximum
+ value is (INT_MAX / HZ) seconds, the minimum value is 1 second.
+
+ Default: 30 seconds.
diff --git a/include/net/netns/smc.h b/include/net/netns/smc.h
index 2adbe2b..d295e2c 100644
--- a/include/net/netns/smc.h
+++ b/include/net/netns/smc.h
@@ -19,5 +19,6 @@ struct netns_smc {
#endif
unsigned int sysctl_autocorking_size;
unsigned int sysctl_smcr_buf_type;
+ int sysctl_smcr_testlink_time;
};
#endif
diff --git a/net/smc/smc_llc.c b/net/smc/smc_llc.c
index 175026a..388bd2e 100644
--- a/net/smc/smc_llc.c
+++ b/net/smc/smc_llc.c
@@ -2127,7 +2127,7 @@ void smc_llc_lgr_init(struct smc_link_group *lgr, struct smc_sock *smc)
init_waitqueue_head(&lgr->llc_flow_waiter);
init_waitqueue_head(&lgr->llc_msg_waiter);
mutex_init(&lgr->llc_conf_mutex);
- lgr->llc_testlink_time = READ_ONCE(net->ipv4.sysctl_tcp_keepalive_time);
+ lgr->llc_testlink_time = READ_ONCE(net->smc.sysctl_smcr_testlink_time) * HZ;
}

/* called after lgr was removed from lgr_list */
diff --git a/net/smc/smc_llc.h b/net/smc/smc_llc.h
index 4404e52..1de9a29 100644
--- a/net/smc/smc_llc.h
+++ b/net/smc/smc_llc.h
@@ -19,6 +19,7 @@

#define SMC_LLC_WAIT_FIRST_TIME (5 * HZ)
#define SMC_LLC_WAIT_TIME (2 * HZ)
+#define SMC_LLC_TESTLINK_DEFAULT_TIME 30

enum smc_llc_reqresp {
SMC_LLC_REQ,
diff --git a/net/smc/smc_sysctl.c b/net/smc/smc_sysctl.c
index 0613868..7f68520 100644
--- a/net/smc/smc_sysctl.c
+++ b/net/smc/smc_sysctl.c
@@ -16,8 +16,12 @@

#include "smc.h"
#include "smc_core.h"
+#include "smc_llc.h"
#include "smc_sysctl.h"

+static int smcr_testlink_time_min = 1;
+static int smcr_testlink_time_max = (INT_MAX / HZ);
+
static struct ctl_table smc_table[] = {
{
.procname = "autocorking_size",
@@ -35,6 +39,15 @@
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_TWO,
},
+ {
+ .procname = "smcr_testlink_time",
+ .data = &init_net.smc.sysctl_smcr_testlink_time,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &smcr_testlink_time_min,
+ .extra2 = &smcr_testlink_time_max,
+ },
{ }
};

@@ -60,6 +73,7 @@ int __net_init smc_sysctl_net_init(struct net *net)

net->smc.sysctl_autocorking_size = SMC_AUTOCORKING_DEFAULT_SIZE;
net->smc.sysctl_smcr_buf_type = SMCR_PHYS_CONT_BUFS;
+ net->smc.sysctl_smcr_testlink_time = SMC_LLC_TESTLINK_DEFAULT_TIME;

return 0;

--
1.8.3.1