SUNRPC: Add a new helper rpc_wake_up_queued_task()

In all cases where we currently use rpc_wake_up_task(), we almost always
know on which waitqueue the rpc_task is actually sleeping. This will allows
us to simplify the queue locking in a future patch.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

3 files changed, 34 insertions, 36 deletions

diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index fefb0ab52189..83f67779cf00 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -33,7 +33,6 @@ struct rpc_wait_queue;
 struct rpc_wait {
         struct list_head        list;           /* wait queue links */
         struct list_head        links;          /* Links to related tasks */
-        struct rpc_wait_queue * rpc_waitq;      /* RPC wait queue we're on */
 };
 
 /*
@@ -80,6 +79,7 @@ struct rpc_task {
         struct workqueue_struct *tk_workqueue;  /* Normally rpciod, but could
                                                  * be any workqueue
                                                  */
+        struct rpc_wait_queue   *tk_waitqueue;  /* RPC wait queue we're on */
         union {
                 struct work_struct      tk_work;        /* Async task work queue */
                 struct rpc_wait         tk_wait;        /* RPC wait */
@@ -233,6 +233,8 @@ void		rpc_init_wait_queue(struct rpc_wait_queue *, const char *);
 void            rpc_sleep_on(struct rpc_wait_queue *, struct rpc_task *,
                                         rpc_action action, rpc_action timer);
 void            rpc_wake_up_task(struct rpc_task *);
+void            rpc_wake_up_queued_task(struct rpc_wait_queue *,
+                                        struct rpc_task *);
 void            rpc_wake_up(struct rpc_wait_queue *);
 struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *);
 void            rpc_wake_up_status(struct rpc_wait_queue *, int);
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 8c6a7f1a25e9..fe95bd0ab1e9 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -1535,7 +1535,7 @@ void rpc_show_tasks(void)
                                 proc = -1;
 
                         if (RPC_IS_QUEUED(t))
-                                rpc_waitq = rpc_qname(t->u.tk_wait.rpc_waitq);
+                                rpc_waitq = rpc_qname(t->tk_waitqueue);
 
                         printk("%5u %04d %04x %6d %8p %6d %8p %8ld %8s %8p %8p\n",
                                 t->tk_pid, proc,
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 9433a113862c..9233ace076aa 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -148,7 +148,7 @@ static void __rpc_add_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *
                 list_add(&task->u.tk_wait.list, &queue->tasks[0]);
         else
                 list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
-        task->u.tk_wait.rpc_waitq = queue;
+        task->tk_waitqueue = queue;
         queue->qlen++;
         rpc_set_queued(task);
 
@@ -175,11 +175,8 @@ static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
  * Remove request from queue.
  * Note: must be called with spin lock held.
  */
-static void __rpc_remove_wait_queue(struct rpc_task *task)
+static void __rpc_remove_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
 {
-        struct rpc_wait_queue *queue;
-        queue = task->u.tk_wait.rpc_waitq;
-
         if (RPC_IS_PRIORITY(queue))
                 __rpc_remove_wait_queue_priority(task);
         else
@@ -364,11 +361,12 @@ EXPORT_SYMBOL_GPL(rpc_sleep_on);
 
 /**
  * __rpc_do_wake_up_task - wake up a single rpc_task
+ * @queue: wait queue
  * @task: task to be woken up
  *
  * Caller must hold queue->lock, and have cleared the task queued flag.
  */
-static void __rpc_do_wake_up_task(struct rpc_task *task)
+static void __rpc_do_wake_up_task(struct rpc_wait_queue *queue, struct rpc_task *task)
 {
         dprintk("RPC: %5u __rpc_wake_up_task (now %lu)\n",
                         task->tk_pid, jiffies);
@@ -383,7 +381,7 @@ static void __rpc_do_wake_up_task(struct rpc_task *task)
         }
 
         __rpc_disable_timer(task);
-        __rpc_remove_wait_queue(task);
+        __rpc_remove_wait_queue(queue, task);
 
         rpc_make_runnable(task);
 
@@ -391,36 +389,38 @@ static void __rpc_do_wake_up_task(struct rpc_task *task)
 }
 
 /*
- * Wake up the specified task
+ * Wake up a queued task while the queue lock is being held
  */
-static void __rpc_wake_up_task(struct rpc_task *task)
+static void rpc_wake_up_task_queue_locked(struct rpc_wait_queue *queue, struct rpc_task *task)
 {
+        if (!RPC_IS_QUEUED(task) || task->tk_waitqueue != queue)
+                return;
         if (rpc_start_wakeup(task)) {
-                if (RPC_IS_QUEUED(task))
-                        __rpc_do_wake_up_task(task);
+                        __rpc_do_wake_up_task(queue, task);
                 rpc_finish_wakeup(task);
         }
 }
 
 /*
- * Wake up the specified task
+ * Wake up a task on a specific queue
  */
-void rpc_wake_up_task(struct rpc_task *task)
+void rpc_wake_up_queued_task(struct rpc_wait_queue *queue, struct rpc_task *task)
 {
         rcu_read_lock_bh();
-        if (rpc_start_wakeup(task)) {
-                if (RPC_IS_QUEUED(task)) {
-                        struct rpc_wait_queue *queue = task->u.tk_wait.rpc_waitq;
-
-                        /* Note: we're already in a bh-safe context */
-                        spin_lock(&queue->lock);
-                        __rpc_do_wake_up_task(task);
-                        spin_unlock(&queue->lock);
-                }
-                rpc_finish_wakeup(task);
-        }
+        spin_lock(&queue->lock);
+        rpc_wake_up_task_queue_locked(queue, task);
+        spin_unlock(&queue->lock);
         rcu_read_unlock_bh();
 }
+EXPORT_SYMBOL_GPL(rpc_wake_up_queued_task);
+
+/*
+ * Wake up the specified task
+ */
+void rpc_wake_up_task(struct rpc_task *task)
+{
+        rpc_wake_up_queued_task(task->tk_waitqueue, task);
+}
 EXPORT_SYMBOL_GPL(rpc_wake_up_task);
 
 /*
@@ -471,7 +471,7 @@ new_queue:
 new_owner:
         rpc_set_waitqueue_owner(queue, task->tk_owner);
 out:
-        __rpc_wake_up_task(task);
+        rpc_wake_up_task_queue_locked(queue, task);
         return task;
 }
 
@@ -490,7 +490,7 @@ struct rpc_task * rpc_wake_up_next(struct rpc_wait_queue *queue)
                 task = __rpc_wake_up_next_priority(queue);
         else {
                 task_for_first(task, &queue->tasks[0])
-                        __rpc_wake_up_task(task);
+                        rpc_wake_up_task_queue_locked(queue, task);
         }
         spin_unlock(&queue->lock);
         rcu_read_unlock_bh();
@@ -515,7 +515,7 @@ void rpc_wake_up(struct rpc_wait_queue *queue)
         head = &queue->tasks[queue->maxpriority];
         for (;;) {
                 list_for_each_entry_safe(task, next, head, u.tk_wait.list)
-                        __rpc_wake_up_task(task);
+                        rpc_wake_up_task_queue_locked(queue, task);
                 if (head == &queue->tasks[0])
                         break;
                 head--;
@@ -543,7 +543,7 @@ void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
         for (;;) {
                 list_for_each_entry_safe(task, next, head, u.tk_wait.list) {
                         task->tk_status = status;
-                        __rpc_wake_up_task(task);
+                        rpc_wake_up_task_queue_locked(queue, task);
                 }
                 if (head == &queue->tasks[0])
                         break;
@@ -562,10 +562,8 @@ static void rpc_run_timer(unsigned long ptr)
         struct rpc_task *task = (struct rpc_task *)ptr;
         void (*callback)(struct rpc_task *);
 
-        if (!rpc_start_wakeup(task))
-                goto out;
         if (RPC_IS_QUEUED(task)) {
-                struct rpc_wait_queue *queue = task->u.tk_wait.rpc_waitq;
+                struct rpc_wait_queue *queue = task->tk_waitqueue;
                 callback = task->tk_timeout_fn;
 
                 dprintk("RPC: %5u running timer\n", task->tk_pid);
@@ -573,11 +571,9 @@ static void rpc_run_timer(unsigned long ptr)
                         callback(task);
                 /* Note: we're already in a bh-safe context */
                 spin_lock(&queue->lock);
-                __rpc_do_wake_up_task(task);
+                rpc_wake_up_task_queue_locked(queue, task);
                 spin_unlock(&queue->lock);
         }
-        rpc_finish_wakeup(task);
-out:
         smp_mb__before_clear_bit();
         clear_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate);
         smp_mb__after_clear_bit();