svcrdma: Add a utility workqueue to svcrdma

To handle work in the background, set up an UNBOUND workqueue for
svcrdma. Subsequent patches will make use of it.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

include/linux/sunrpc/svc_rdma.h

@@ -65,6 +65,7 @@ extern unsigned int svcrdma_ord;
 extern unsigned int svcrdma_max_requests;
 extern unsigned int svcrdma_max_bc_requests;
 extern unsigned int svcrdma_max_req_size;
+extern struct workqueue_struct *svcrdma_wq;
 
 extern struct percpu_counter svcrdma_stat_read;
 extern struct percpu_counter svcrdma_stat_recv;

net/sunrpc/xprtrdma/svc_rdma.c

@@ -256,28 +256,44 @@ static int svc_rdma_proc_init(void)
 	return rc;
 }
 
+struct workqueue_struct *svcrdma_wq;
+
 void svc_rdma_cleanup(void)
 {
-	dprintk("SVCRDMA Module Removed, deregister RPC RDMA transport\n");
 	svc_unreg_xprt_class(&svc_rdma_class);
 	svc_rdma_proc_cleanup();
+	if (svcrdma_wq) {
+		struct workqueue_struct *wq = svcrdma_wq;
+
+		svcrdma_wq = NULL;
+		destroy_workqueue(wq);
+	}
+
+	dprintk("SVCRDMA Module Removed, deregister RPC RDMA transport\n");
 }
 
 int svc_rdma_init(void)
 {
+	struct workqueue_struct *wq;
 	int rc;
 
-	dprintk("SVCRDMA Module Init, register RPC RDMA transport\n");
-	dprintk("\tsvcrdma_ord      : %d\n", svcrdma_ord);
-	dprintk("\tmax_requests     : %u\n", svcrdma_max_requests);
-	dprintk("\tmax_bc_requests  : %u\n", svcrdma_max_bc_requests);
-	dprintk("\tmax_inline       : %d\n", svcrdma_max_req_size);
+	wq = alloc_workqueue("svcrdma", WQ_UNBOUND, 0);
+	if (!wq)
+		return -ENOMEM;
 
 	rc = svc_rdma_proc_init();
-	if (rc)
+	if (rc) {
+		destroy_workqueue(wq);
 		return rc;
+	}
 
-	/* Register RDMA with the SVC transport switch */
+	svcrdma_wq = wq;
 	svc_reg_xprt_class(&svc_rdma_class);
+
+	dprintk("SVCRDMA Module Init, register RPC RDMA transport\n");
+	dprintk("\tsvcrdma_ord      : %d\n", svcrdma_ord);
+	dprintk("\tmax_requests     : %u\n", svcrdma_max_requests);
+	dprintk("\tmax_bc_requests  : %u\n", svcrdma_max_bc_requests);
+	dprintk("\tmax_inline       : %d\n", svcrdma_max_req_size);
 	return 0;
 }

net/sunrpc/xprtrdma/svc_rdma_transport.c

@@ -547,6 +547,7 @@ static void __svc_rdma_free(struct work_struct *work)
 	/* This blocks until the Completion Queues are empty */
 	if (rdma->sc_qp && !IS_ERR(rdma->sc_qp))
 		ib_drain_qp(rdma->sc_qp);
+	flush_workqueue(svcrdma_wq);
 
 	svc_rdma_flush_recv_queues(rdma);