afs: Provide a function to get a ref on a call

Provide a function to get a reference on an afs_call struct.
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/rxrpc.c

@@ -203,20 +203,26 @@ void afs_put_call(struct afs_call *call)
 	}
 }
 
-/*
- * Queue the call for actual work.
- */
-static void afs_queue_call_work(struct afs_call *call)
+static struct afs_call *afs_get_call(struct afs_call *call,
+				     enum afs_call_trace why)
 {
-	if (call->type->work) {
 	int u = atomic_inc_return(&call->usage);
 
-		trace_afs_call(call, afs_call_trace_work, u,
+	trace_afs_call(call, why, u,
 		       atomic_read(&call->net->nr_outstanding_calls),
 		       __builtin_return_address(0));
+	return call;
+}
 
+/*
+ * Queue the call for actual work.
+ */
+static void afs_queue_call_work(struct afs_call *call)
+{
+	if (call->type->work) {
 		INIT_WORK(&call->work, call->type->work);
 
+		afs_get_call(call, afs_call_trace_work);
 		if (!queue_work(afs_wq, &call->work))
 			afs_put_call(call);
 	}