RPC/RDMA: suppress retransmit on RPC/RDMA clients.

An RPC/RDMA client cannot retransmit on an unbroken connection,
doing so violates its flow control with the server.

Signed-off-by: Tom Talpey <talpey@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

3 files changed, 15 insertions, 4 deletions

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index e55427f73dfe..721dae795d68 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -681,6 +681,8 @@ rpcrdma_conn_func(struct rpcrdma_ep *ep)
         struct rpc_xprt *xprt = ep->rep_xprt;
 
         spin_lock_bh(&xprt->transport_lock);
+        if (++xprt->connect_cookie == 0)        /* maintain a reserved value */
+                ++xprt->connect_cookie;
         if (ep->rep_connected > 0) {
                 if (!xprt_test_and_set_connected(xprt))
                         xprt_wake_pending_tasks(xprt, 0);
diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
index 89970b0a4cc9..0aefc6485385 100644
--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -587,6 +587,7 @@ xprt_rdma_allocate(struct rpc_task *task, size_t size)
         }
         dprintk("RPC:       %s: size %zd, request 0x%p\n", __func__, size, req);
 out:
+        req->rl_connect_cookie = 0;     /* our reserved value */
         return req->rl_xdr_buf;
 
 outfail:
@@ -690,13 +691,20 @@ xprt_rdma_send_request(struct rpc_task *task)
                 req->rl_reply->rr_xprt = xprt;
         }
 
-        if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req)) {
-                xprt_disconnect_done(xprt);
-                return -ENOTCONN;       /* implies disconnect */
-        }
+        /* Must suppress retransmit to maintain credits */
+        if (req->rl_connect_cookie == xprt->connect_cookie)
+                goto drop_connection;
+        req->rl_connect_cookie = xprt->connect_cookie;
+
+        if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
+                goto drop_connection;
 
         rqst->rq_bytes_sent = 0;
         return 0;
+
+drop_connection:
+        xprt_disconnect_done(xprt);
+        return -ENOTCONN;       /* implies disconnect */
 }
 
 static void xprt_rdma_print_stats(struct rpc_xprt *xprt, struct seq_file *seq)
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 05b7898e1f4b..2db2344d487e 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -181,6 +181,7 @@ struct rpcrdma_req {
         size_t          rl_size;        /* actual length of buffer */
         unsigned int    rl_niovs;       /* 0, 2 or 4 */
         unsigned int    rl_nchunks;     /* non-zero if chunks */
+        unsigned int    rl_connect_cookie;      /* retry detection */
         struct rpcrdma_buffer *rl_buffer; /* home base for this structure */
         struct rpcrdma_rep      *rl_reply;/* holder for reply buffer */
         struct rpcrdma_mr_seg rl_segments[RPCRDMA_MAX_SEGS];/* chunk segments */