svcrdma: Fix retry loop in svc_rdma_send()

Don't call ib_post_send() at all if the transport is already
shutting down.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

net/sunrpc/xprtrdma/svc_rdma_sendto.c

@@ -320,8 +320,9 @@ static void svc_rdma_wc_send(struct ib_cq *cq, struct ib_wc *wc)
  * that these values remain available after the ib_post_send() call.
  * In some error flow cases, svc_rdma_wc_send() releases @ctxt.
  *
- * Returns zero if the Send WR was posted successfully. Otherwise, a
- * negative errno is returned.
+ * Return values:
+ *   %0: @ctxt's WR chain was posted successfully
+ *   %-ENOTCONN: The connection was lost
  */
 int svc_rdma_send(struct svcxprt_rdma *rdma, struct svc_rdma_send_ctxt *ctxt)
 {
@@ -338,30 +339,35 @@ int svc_rdma_send(struct svcxprt_rdma *rdma, struct svc_rdma_send_ctxt *ctxt)
 				      DMA_TO_DEVICE);
 
 	/* If the SQ is full, wait until an SQ entry is available */
-	while (1) {
+	while (!test_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags)) {
 		if ((atomic_dec_return(&rdma->sc_sq_avail) < 0)) {
 			svc_rdma_wake_send_waiters(rdma, 1);
+
+			/* When the transport is torn down, assume
+			 * ib_drain_sq() will trigger enough Send
+			 * completions to wake us. The XPT_CLOSE test
+			 * above should then cause the while loop to
+			 * exit.
+			 */
 			percpu_counter_inc(&svcrdma_stat_sq_starve);
 			trace_svcrdma_sq_full(rdma, &cid);
 			wait_event(rdma->sc_send_wait,
 				   atomic_read(&rdma->sc_sq_avail) > 0);
-			if (test_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags))
-				return -ENOTCONN;
 			trace_svcrdma_sq_retry(rdma, &cid);
 			continue;
 		}
 
 		trace_svcrdma_post_send(ctxt);
 		ret = ib_post_send(rdma->sc_qp, wr, NULL);
-		if (ret)
+		if (ret) {
+			trace_svcrdma_sq_post_err(rdma, &cid, ret);
+			svc_xprt_deferred_close(&rdma->sc_xprt);
+			svc_rdma_wake_send_waiters(rdma, 1);
 			break;
+		}
 		return 0;
 	}
-
-	trace_svcrdma_sq_post_err(rdma, &cid, ret);
-	svc_xprt_deferred_close(&rdma->sc_xprt);
-	svc_rdma_wake_send_waiters(rdma, 1);
-	return ret;
+	return -ENOTCONN;
 }
 
 /**