RDS: add receive message trace used by application

Socket option to tap receive path latency in various stages
in nano seconds. It can be enabled on selective sockets using
using SO_RDS_MSG_RXPATH_LATENCY socket option. RDS will return
the data to application with RDS_CMSG_RXPATH_LATENCY in defined
format. Scope is left to add more trace points for future
without need of change in the interface.

Reviewed-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/net/rds/af_rds.c b/net/rds/af_rds.c
index 2ac1e6194be3..fd8217404162 100644
--- a/net/rds/af_rds.c
+++ b/net/rds/af_rds.c
@@ -298,6 +298,30 @@ static int rds_enable_recvtstamp(struct sock *sk, char __user *optval,
 	return 0;
 }
 
+static int rds_recv_track_latency(struct rds_sock *rs, char __user *optval,
+				  int optlen)
+{
+	struct rds_rx_trace_so trace;
+	int i;
+
+	if (optlen != sizeof(struct rds_rx_trace_so))
+		return -EFAULT;
+
+	if (copy_from_user(&trace, optval, sizeof(trace)))
+		return -EFAULT;
+
+	rs->rs_rx_traces = trace.rx_traces;
+	for (i = 0; i < rs->rs_rx_traces; i++) {
+		if (trace.rx_trace_pos[i] > RDS_MSG_RX_DGRAM_TRACE_MAX) {
+			rs->rs_rx_traces = 0;
+			return -EFAULT;
+		}
+		rs->rs_rx_trace[i] = trace.rx_trace_pos[i];
+	}
+
+	return 0;
+}
+
 static int rds_setsockopt(struct socket *sock, int level, int optname,
 			  char __user *optval, unsigned int optlen)
 {
@@ -338,6 +362,9 @@ static int rds_setsockopt(struct socket *sock, int level, int optname,
 		ret = rds_enable_recvtstamp(sock->sk, optval, optlen);
 		release_sock(sock->sk);
 		break;
+	case SO_RDS_MSG_RXPATH_LATENCY:
+		ret = rds_recv_track_latency(rs, optval, optlen);
+		break;
 	default:
 		ret = -ENOPROTOOPT;
 	}
@@ -484,6 +511,7 @@ static int __rds_create(struct socket *sock, struct sock *sk, int protocol)
 	INIT_LIST_HEAD(&rs->rs_cong_list);
 	spin_lock_init(&rs->rs_rdma_lock);
 	rs->rs_rdma_keys = RB_ROOT;
+	rs->rs_rx_traces = 0;
 
 	spin_lock_bh(&rds_sock_lock);
 	list_add_tail(&rs->rs_item, &rds_sock_list);