[PATCH] svcrdma: Limit ORD based on client's advertised IRD

[Tom Tucker <tom@opengridcomputing.com>]

When adapters have differing IRD limits, the RDMA transport will fail to
connect properly. The RDMA transport should use the client's advertised
inbound read limit when computing it's outbound read limit. For iWARP
transports, there is no exchange of the IRD/ORD during connect request and
so the only way to ensure compatability is to use the
/proc/sys/sunrpc/svc_rdma/max_outbound_read_requests file to control
server ORD.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
---

 net/sunrpc/xprtrdma/svc_rdma_transport.c |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
index 68908b5..b961dc5 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -580,7 +580,7 @@ int svc_rdma_post_recv(struct svcxprt_rdma *xprt)
  * will call the recvfrom method on the listen xprt which will accept the new
  * connection.
  */
-static void handle_connect_req(struct rdma_cm_id *new_cma_id)
+static void handle_connect_req(struct rdma_cm_id *new_cma_id, u8 client_ird)
 {
 	struct svcxprt_rdma *listen_xprt = new_cma_id->context;
 	struct svcxprt_rdma *newxprt;
@@ -597,6 +597,9 @@ static void handle_connect_req(struct rdma_cm_id *new_cma_id)
 	dprintk("svcrdma: Creating newxprt=%p, cm_id=%p, listenxprt=%p\n",
 		newxprt, newxprt->sc_cm_id, listen_xprt);
 
+	/* Save client advertised inbound read limit for use later in accept. */
+	newxprt->sc_ord = client_ird;
+
 	/* Set the local and remote addresses in the transport */
 	sa = (struct sockaddr *)&newxprt->sc_cm_id->route.addr.dst_addr;
 	svc_xprt_set_remote(&newxprt->sc_xprt, sa, svc_addr_len(sa));
@@ -633,7 +636,8 @@ static int rdma_listen_handler(struct rdma_cm_id *cma_id,
 	case RDMA_CM_EVENT_CONNECT_REQUEST:
 		dprintk("svcrdma: Connect request on cma_id=%p, xprt = %p, "
 			"event=%d\n", cma_id, cma_id->context, event->event);
-		handle_connect_req(cma_id);
+		handle_connect_req(cma_id,
+				   event->param.conn.responder_resources);
 		break;
 
 	case RDMA_CM_EVENT_ESTABLISHED:
@@ -807,8 +811,12 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
 				   (size_t)svcrdma_max_requests);
 	newxprt->sc_sq_depth = RPCRDMA_SQ_DEPTH_MULT * newxprt->sc_max_requests;
 
-	newxprt->sc_ord =  min((size_t)devattr.max_qp_rd_atom,
-			       (size_t)svcrdma_ord);
+	/* 
+	 * Limit ORD based on client limit, local device limit, and
+	 * configured svcrdma limit.
+	 */
+	newxprt->sc_ord =  min((size_t)devattr.max_qp_rd_atom, newxprt->sc_ord);
+	newxprt->sc_ord = min((size_t)svcrdma_ord, newxprt->sc_ord);
 
 	newxprt->sc_pd = ib_alloc_pd(newxprt->sc_cm_id->device);
 	if (IS_ERR(newxprt->sc_pd)) {