xprtrdma: disconnect and flush cqs before freeing buffers

Otherwise a FRMR completion can cause a touch-after-free crash.

In xprt_rdma_destroy(), call rpcrdma_buffer_destroy() only after calling
rpcrdma_ep_destroy().

In rpcrdma_ep_destroy(), disconnect the cm_id first which should flush the
qp, then drain the cqs, then destroy the qp, and finally destroy the cqs.
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Tested-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/transport.c

@@ -270,8 +270,8 @@ xprt_rdma_destroy(struct rpc_xprt *xprt)
 
 	xprt_clear_connected(xprt);
 
-	rpcrdma_buffer_destroy(&r_xprt->rx_buf);
 	rpcrdma_ep_destroy(&r_xprt->rx_ep, &r_xprt->rx_ia);
+	rpcrdma_buffer_destroy(&r_xprt->rx_buf);
 	rpcrdma_ia_close(&r_xprt->rx_ia);
 
 	xprt_rdma_free_addresses(xprt);

net/sunrpc/xprtrdma/verbs.c

@@ -755,19 +755,22 @@ rpcrdma_ep_destroy(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
 
 	cancel_delayed_work_sync(&ep->rep_connect_worker);
 
-	if (ia->ri_id->qp) {
+	if (ia->ri_id->qp)
 		rpcrdma_ep_disconnect(ep, ia);
+
+	rpcrdma_clean_cq(ep->rep_attr.recv_cq);
+	rpcrdma_clean_cq(ep->rep_attr.send_cq);
+
+	if (ia->ri_id->qp) {
 		rdma_destroy_qp(ia->ri_id);
 		ia->ri_id->qp = NULL;
 	}
 
-	rpcrdma_clean_cq(ep->rep_attr.recv_cq);
 	rc = ib_destroy_cq(ep->rep_attr.recv_cq);
 	if (rc)
 		dprintk("RPC:       %s: ib_destroy_cq returned %i\n",
 			__func__, rc);
 
-	rpcrdma_clean_cq(ep->rep_attr.send_cq);
 	rc = ib_destroy_cq(ep->rep_attr.send_cq);
 	if (rc)
 		dprintk("RPC:       %s: ib_destroy_cq returned %i\n",