SUNRPC: Allow caller of rpc_sleep_on() to select priority levels

Currently, the caller has to change the value of task->tk_priority if
it wants to select on which priority level the task will sleep.

This patch allows the caller to select a priority level at sleep time
rather than always using task->tk_priority.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/sunrpc/sched.h

@@ -227,6 +227,10 @@ void		rpc_init_wait_queue(struct rpc_wait_queue *, const char *);
 void		rpc_destroy_wait_queue(struct rpc_wait_queue *);
 void		rpc_sleep_on(struct rpc_wait_queue *, struct rpc_task *,
 					rpc_action action);
+void		rpc_sleep_on_priority(struct rpc_wait_queue *,
+					struct rpc_task *,
+					rpc_action action,
+					int priority);
 void		rpc_wake_up_queued_task(struct rpc_wait_queue *,
 					struct rpc_task *);
 void		rpc_wake_up(struct rpc_wait_queue *);

net/sunrpc/sched.c

@@ -97,14 +97,16 @@ __rpc_add_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
 /*
  * Add new request to a priority queue.
  */
-static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue, struct rpc_task *task)
+static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue,
+		struct rpc_task *task,
+		unsigned char queue_priority)
 {
 	struct list_head *q;
 	struct rpc_task *t;
 
 	INIT_LIST_HEAD(&task->u.tk_wait.links);
-	q = &queue->tasks[task->tk_priority];
-	if (unlikely(task->tk_priority > queue->maxpriority))
+	q = &queue->tasks[queue_priority];
+	if (unlikely(queue_priority > queue->maxpriority))
 		q = &queue->tasks[queue->maxpriority];
 	list_for_each_entry(t, q, u.tk_wait.list) {
 		if (t->tk_owner == task->tk_owner) {
@@ -123,12 +125,14 @@ static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue, struct r
  * improve overall performance.
  * Everyone else gets appended to the queue to ensure proper FIFO behavior.
  */
-static void __rpc_add_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
+static void __rpc_add_wait_queue(struct rpc_wait_queue *queue,
+		struct rpc_task *task,
+		unsigned char queue_priority)
 {
 	BUG_ON (RPC_IS_QUEUED(task));
 
 	if (RPC_IS_PRIORITY(queue))
-		__rpc_add_wait_queue_priority(queue, task);
+		__rpc_add_wait_queue_priority(queue, task, queue_priority);
 	else if (RPC_IS_SWAPPER(task))
 		list_add(&task->u.tk_wait.list, &queue->tasks[0]);
 	else
@@ -311,13 +315,15 @@ static void rpc_make_runnable(struct rpc_task *task)
  * NB: An RPC task will only receive interrupt-driven events as long
  * as it's on a wait queue.
  */
-static void __rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
-			rpc_action action)
+static void __rpc_sleep_on_priority(struct rpc_wait_queue *q,
+		struct rpc_task *task,
+		rpc_action action,
+		unsigned char queue_priority)
 {
 	dprintk("RPC: %5u sleep_on(queue \"%s\" time %lu)\n",
 			task->tk_pid, rpc_qname(q), jiffies);
 
-	__rpc_add_wait_queue(q, task);
+	__rpc_add_wait_queue(q, task, queue_priority);
 
 	BUG_ON(task->tk_callback != NULL);
 	task->tk_callback = action;
@@ -334,11 +340,25 @@ void rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
 	 * Protect the queue operations.
 	 */
 	spin_lock_bh(&q->lock);
-	__rpc_sleep_on(q, task, action);
+	__rpc_sleep_on_priority(q, task, action, task->tk_priority);
 	spin_unlock_bh(&q->lock);
 }
 EXPORT_SYMBOL_GPL(rpc_sleep_on);
 
+void rpc_sleep_on_priority(struct rpc_wait_queue *q, struct rpc_task *task,
+		rpc_action action, int priority)
+{
+	/* We shouldn't ever put an inactive task to sleep */
+	BUG_ON(!RPC_IS_ACTIVATED(task));
+
+	/*
+	 * Protect the queue operations.
+	 */
+	spin_lock_bh(&q->lock);
+	__rpc_sleep_on_priority(q, task, action, priority - RPC_PRIORITY_LOW);
+	spin_unlock_bh(&q->lock);
+}
+
 /**
  * __rpc_do_wake_up_task - wake up a single rpc_task
  * @queue: wait queue