RDS: Make sure we do a signaled send for large-send

WR(Work Requests )always generate a WC(Work Completion) with
signaled send. Default RDS ib code is setup for un-signaled
completion. Since RDS connction is persistent, we can end up
sending the data even after large-send when the remote end is
not active(for any reason).

By doing  a signaled send at least once per large-send,
we can at least detect the problem in work completion
handler there by avoiding sending more data to
inactive remote.
Reviewed-by: NAjaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>
Signed-off-by: NSantosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: NSantosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/rds/ib_send.c

@@ -709,6 +709,11 @@ int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
 	if (scat == &rm->data.op_sg[rm->data.op_count]) {
 		prev->s_op = ic->i_data_op;
 		prev->s_wr.send_flags |= IB_SEND_SOLICITED;
+		if (!(prev->s_wr.send_flags & IB_SEND_SIGNALED)) {
+			ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
+			prev->s_wr.send_flags |= IB_SEND_SIGNALED;
+			nr_sig++;
+		}
 		ic->i_data_op = NULL;
 	}