SUNRPC: Refactor the transport request pinning

We are going to need to pin for both send and receive.
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

include/linux/sunrpc/sched.h

@@ -142,8 +142,7 @@ struct rpc_task_setup {
 #define RPC_TASK_ACTIVE		2
 #define RPC_TASK_NEED_XMIT	3
 #define RPC_TASK_NEED_RECV	4
-#define RPC_TASK_MSG_RECV	5
-#define RPC_TASK_MSG_RECV_WAIT	6
+#define RPC_TASK_MSG_PIN_WAIT	5
 
 #define RPC_IS_RUNNING(t)	test_bit(RPC_TASK_RUNNING, &(t)->tk_runstate)
 #define rpc_set_running(t)	set_bit(RPC_TASK_RUNNING, &(t)->tk_runstate)

include/linux/sunrpc/xprt.h

@@ -103,6 +103,7 @@ struct rpc_rqst {
 						/* A cookie used to track the
 						   state of the transport
 						   connection */
+	atomic_t		rq_pin;
 	
 	/*
 	 * Partial send handling

net/sunrpc/xprt.c

@@ -847,16 +847,22 @@ struct rpc_rqst *xprt_lookup_rqst(struct rpc_xprt *xprt, __be32 xid)
 }
 EXPORT_SYMBOL_GPL(xprt_lookup_rqst);
 
+static bool
+xprt_is_pinned_rqst(struct rpc_rqst *req)
+{
+	return atomic_read(&req->rq_pin) != 0;
+}
+
 /**
  * xprt_pin_rqst - Pin a request on the transport receive list
  * @req: Request to pin
  *
  * Caller must ensure this is atomic with the call to xprt_lookup_rqst()
- * so should be holding the xprt transport lock.
+ * so should be holding the xprt receive lock.
  */
 void xprt_pin_rqst(struct rpc_rqst *req)
 {
-	set_bit(RPC_TASK_MSG_RECV, &req->rq_task->tk_runstate);
+	atomic_inc(&req->rq_pin);
 }
 EXPORT_SYMBOL_GPL(xprt_pin_rqst);
 
@@ -864,31 +870,22 @@ EXPORT_SYMBOL_GPL(xprt_pin_rqst);
  * xprt_unpin_rqst - Unpin a request on the transport receive list
  * @req: Request to pin
  *
- * Caller should be holding the xprt transport lock.
+ * Caller should be holding the xprt receive lock.
  */
 void xprt_unpin_rqst(struct rpc_rqst *req)
 {
-	struct rpc_task *task = req->rq_task;
-
-	clear_bit(RPC_TASK_MSG_RECV, &task->tk_runstate);
-	if (test_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate))
-		wake_up_bit(&task->tk_runstate, RPC_TASK_MSG_RECV);
+	if (!test_bit(RPC_TASK_MSG_PIN_WAIT, &req->rq_task->tk_runstate)) {
+		atomic_dec(&req->rq_pin);
+		return;
+	}
+	if (atomic_dec_and_test(&req->rq_pin))
+		wake_up_var(&req->rq_pin);
 }
 EXPORT_SYMBOL_GPL(xprt_unpin_rqst);
 
 static void xprt_wait_on_pinned_rqst(struct rpc_rqst *req)
-__must_hold(&req->rq_xprt->recv_lock)
 {
-	struct rpc_task *task = req->rq_task;
-
-	if (task && test_bit(RPC_TASK_MSG_RECV, &task->tk_runstate)) {
-		spin_unlock(&req->rq_xprt->recv_lock);
-		set_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate);
-		wait_on_bit(&task->tk_runstate, RPC_TASK_MSG_RECV,
-				TASK_UNINTERRUPTIBLE);
-		clear_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate);
-		spin_lock(&req->rq_xprt->recv_lock);
-	}
+	wait_var_event(&req->rq_pin, !xprt_is_pinned_rqst(req));
 }
 
 /**
@@ -1388,7 +1385,13 @@ void xprt_release(struct rpc_task *task)
 	spin_lock(&xprt->recv_lock);
 	if (!list_empty(&req->rq_list)) {
 		list_del_init(&req->rq_list);
-		xprt_wait_on_pinned_rqst(req);
+		if (xprt_is_pinned_rqst(req)) {
+			set_bit(RPC_TASK_MSG_PIN_WAIT, &req->rq_task->tk_runstate);
+			spin_unlock(&xprt->recv_lock);
+			xprt_wait_on_pinned_rqst(req);
+			spin_lock(&xprt->recv_lock);
+			clear_bit(RPC_TASK_MSG_PIN_WAIT, &req->rq_task->tk_runstate);
+		}
 	}
 	spin_unlock(&xprt->recv_lock);
 	spin_lock_bh(&xprt->transport_lock);