SUNRPC: cleanup common code in backchannel request

Create a helper function for common code between rdma
and tcp backchannel handling of the backchannel request.
Make sure that access is protected by the bc_pa_lock
lock.

Signed-off-by: Olga Kornievskaia <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

include/linux/sunrpc/bc_xprt.h

···
 void xprt_free_bc_request(struct rpc_rqst *req);
 int xprt_setup_backchannel(struct rpc_xprt *, unsigned int min_reqs);
 void xprt_destroy_backchannel(struct rpc_xprt *, unsigned int max_reqs);
+void xprt_enqueue_bc_request(struct rpc_rqst *req);
 
 /* Socket backchannel transport methods */
 int xprt_setup_bc(struct rpc_xprt *xprt, unsigned int min_reqs);

net/sunrpc/backchannel_rqst.c

···
 void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
 {
 	struct rpc_xprt *xprt = req->rq_xprt;
-	struct svc_serv *bc_serv = xprt->bc_serv;
 
 	spin_lock(&xprt->bc_pa_lock);
 	list_del(&req->rq_bc_pa_list);
···
 	set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
 
 	dprintk("RPC:       add callback request to list\n");
-	xprt_get(xprt);
-	lwq_enqueue(&req->rq_bc_list, &bc_serv->sv_cb_list);
-	svc_pool_wake_idle_thread(&bc_serv->sv_pools[0]);
+	xprt_enqueue_bc_request(req);
 }
+
+void xprt_enqueue_bc_request(struct rpc_rqst *req)
+{
+	struct rpc_xprt *xprt = req->rq_xprt;
+	struct svc_serv *bc_serv;
+
+	xprt_get(xprt);
+	spin_lock(&xprt->bc_pa_lock);
+	bc_serv = xprt->bc_serv;
+	if (bc_serv) {
+		lwq_enqueue(&req->rq_bc_list, &bc_serv->sv_cb_list);
+		svc_pool_wake_idle_thread(&bc_serv->sv_pools[0]);
+	}
+	spin_unlock(&xprt->bc_pa_lock);
+}
+EXPORT_SYMBOL_GPL(xprt_enqueue_bc_request);

net/sunrpc/xprtrdma/backchannel.c

···
 #include <linux/sunrpc/svc.h>
 #include <linux/sunrpc/svc_xprt.h>
 #include <linux/sunrpc/svc_rdma.h>
+#include <linux/sunrpc/bc_xprt.h>
 
 #include "xprt_rdma.h"
 #include <trace/events/rpcrdma.h>
···
 			     struct rpcrdma_rep *rep)
 {
 	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
-	struct svc_serv *bc_serv;
 	struct rpcrdma_req *req;
 	struct rpc_rqst *rqst;
 	struct xdr_buf *buf;
···
 	trace_xprtrdma_cb_call(r_xprt, rqst);
 
 	/* Queue rqst for ULP's callback service */
-	bc_serv = xprt->bc_serv;
-	xprt_get(xprt);
-	lwq_enqueue(&rqst->rq_bc_list, &bc_serv->sv_cb_list);
-
-	svc_pool_wake_idle_thread(&bc_serv->sv_pools[0]);
+	xprt_enqueue_bc_request(rqst);
 
 	r_xprt->rx_stats.bcall_count++;
 	return;