1 files changed, 25 insertions, 27 deletions

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 73dd16d0f587..0061a7bd85f6 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -168,7 +168,7 @@ static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
 
 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
 {
-	INIT_LIST_HEAD(&work->node);
+	clear_bit(VHOST_WORK_QUEUED, &work->flags);
 	work->fn = fn;
 	init_waitqueue_head(&work->done);
 }
@@ -246,15 +246,16 @@ EXPORT_SYMBOL_GPL(vhost_poll_flush);
 
 void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 {
-	unsigned long flags;
+	if (!dev->worker)
+		return;
 
-	spin_lock_irqsave(&dev->work_lock, flags);
-	if (list_empty(&work->node)) {
-		list_add_tail(&work->node, &dev->work_list);
-		spin_unlock_irqrestore(&dev->work_lock, flags);
+	if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
+		/* We can only add the work to the list after we're
+		 * sure it was not in the list.
+		 */
+		smp_mb();
+		llist_add(&work->node, &dev->work_list);
 		wake_up_process(dev->worker);
-	} else {
-		spin_unlock_irqrestore(&dev->work_lock, flags);
 	}
 }
 EXPORT_SYMBOL_GPL(vhost_work_queue);
@@ -262,7 +263,7 @@ EXPORT_SYMBOL_GPL(vhost_work_queue);
 /* A lockless hint for busy polling code to exit the loop */
 bool vhost_has_work(struct vhost_dev *dev)
 {
-	return !list_empty(&dev->work_list);
+	return !llist_empty(&dev->work_list);
 }
 EXPORT_SYMBOL_GPL(vhost_has_work);
 
@@ -305,7 +306,8 @@ static void vhost_vq_reset(struct vhost_dev *dev,
 static int vhost_worker(void *data)
 {
 	struct vhost_dev *dev = data;
-	struct vhost_work *work = NULL;
+	struct vhost_work *work, *work_next;
+	struct llist_node *node;
 	mm_segment_t oldfs = get_fs();
 
 	set_fs(USER_DS);
@@ -315,29 +317,25 @@ static int vhost_worker(void *data)
 		/* mb paired w/ kthread_stop */
 		set_current_state(TASK_INTERRUPTIBLE);
 
-		spin_lock_irq(&dev->work_lock);
-
 		if (kthread_should_stop()) {
-			spin_unlock_irq(&dev->work_lock);
 			__set_current_state(TASK_RUNNING);
 			break;
 		}
-		if (!list_empty(&dev->work_list)) {
-			work = list_first_entry(&dev->work_list,
-						struct vhost_work, node);
-			list_del_init(&work->node);
-		} else
-			work = NULL;
-		spin_unlock_irq(&dev->work_lock);
 
-		if (work) {
+		node = llist_del_all(&dev->work_list);
+		if (!node)
+			schedule();
+
+		node = llist_reverse_order(node);
+		/* make sure flag is seen after deletion */
+		smp_wmb();
+		llist_for_each_entry_safe(work, work_next, node, node) {
+			clear_bit(VHOST_WORK_QUEUED, &work->flags);
 			__set_current_state(TASK_RUNNING);
 			work->fn(work);
 			if (need_resched())
 				schedule();
-		} else
-			schedule();
-
+		}
 	}
 	unuse_mm(dev->mm);
 	set_fs(oldfs);
@@ -398,9 +396,9 @@ void vhost_dev_init(struct vhost_dev *dev,
 	dev->log_file = NULL;
 	dev->memory = NULL;
 	dev->mm = NULL;
-	spin_lock_init(&dev->work_lock);
-	INIT_LIST_HEAD(&dev->work_list);
 	dev->worker = NULL;
+	init_llist_head(&dev->work_list);
+
 
 	for (i = 0; i < dev->nvqs; ++i) {
 		vq = dev->vqs[i];
@@ -566,7 +564,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
 	/* No one will access memory at this point */
 	kvfree(dev->memory);
 	dev->memory = NULL;
-	WARN_ON(!list_empty(&dev->work_list));
+	WARN_ON(!llist_empty(&dev->work_list));
 	if (dev->worker) {
 		kthread_stop(dev->worker);
 		dev->worker = NULL;