vhost: move worker thread fields to new struct

This is just a prep patch. It moves the worker related fields to a new
vhost_worker struct and moves the code around to create some helpers that
will be used in the next patch.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

drivers/vhost/vhost.c

@@ -255,16 +255,16 @@ void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
 		 * sure it was not in the list.
 		 * test_and_set_bit() implies a memory barrier.
 		 */
-		llist_add(&work->node, &dev->work_list);
-		wake_up_process(dev->worker);
+		llist_add(&work->node, &dev->worker->work_list);
+		wake_up_process(dev->worker->task);
 	}
 }
 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 !llist_empty(&dev->work_list);
+	return dev->worker && !llist_empty(&dev->worker->work_list);
 }
 EXPORT_SYMBOL_GPL(vhost_has_work);
 
@@ -335,7 +335,8 @@ static void vhost_vq_reset(struct vhost_dev *dev,
 
 static int vhost_worker(void *data)
 {
-	struct vhost_dev *dev = data;
+	struct vhost_worker *worker = data;
+	struct vhost_dev *dev = worker->dev;
 	struct vhost_work *work, *work_next;
 	struct llist_node *node;
 
@@ -350,7 +351,7 @@ static int vhost_worker(void *data)
 			break;
 		}
 
-		node = llist_del_all(&dev->work_list);
+		node = llist_del_all(&worker->work_list);
 		if (!node)
 			schedule();
 
@@ -360,7 +361,7 @@ static int vhost_worker(void *data)
 		llist_for_each_entry_safe(work, work_next, node, node) {
 			clear_bit(VHOST_WORK_QUEUED, &work->flags);
 			__set_current_state(TASK_RUNNING);
-			kcov_remote_start_common(dev->kcov_handle);
+			kcov_remote_start_common(worker->kcov_handle);
 			work->fn(work);
 			kcov_remote_stop();
 			if (need_resched())
@@ -479,7 +480,6 @@ void vhost_dev_init(struct vhost_dev *dev,
 	dev->byte_weight = byte_weight;
 	dev->use_worker = use_worker;
 	dev->msg_handler = msg_handler;
-	init_llist_head(&dev->work_list);
 	init_waitqueue_head(&dev->wait);
 	INIT_LIST_HEAD(&dev->read_list);
 	INIT_LIST_HEAD(&dev->pending_list);
@@ -571,10 +571,60 @@ static void vhost_detach_mm(struct vhost_dev *dev)
 	dev->mm = NULL;
 }
 
+static void vhost_worker_free(struct vhost_dev *dev)
+{
+	struct vhost_worker *worker = dev->worker;
+
+	if (!worker)
+		return;
+
+	dev->worker = NULL;
+	WARN_ON(!llist_empty(&worker->work_list));
+	kthread_stop(worker->task);
+	kfree(worker);
+}
+
+static int vhost_worker_create(struct vhost_dev *dev)
+{
+	struct vhost_worker *worker;
+	struct task_struct *task;
+	int ret;
+
+	worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
+	if (!worker)
+		return -ENOMEM;
+
+	dev->worker = worker;
+	worker->dev = dev;
+	worker->kcov_handle = kcov_common_handle();
+	init_llist_head(&worker->work_list);
+
+	task = kthread_create(vhost_worker, worker, "vhost-%d", current->pid);
+	if (IS_ERR(task)) {
+		ret = PTR_ERR(task);
+		goto free_worker;
+	}
+
+	worker->task = task;
+	wake_up_process(task); /* avoid contributing to loadavg */
+
+	ret = vhost_attach_cgroups(dev);
+	if (ret)
+		goto stop_worker;
+
+	return 0;
+
+stop_worker:
+	kthread_stop(worker->task);
+free_worker:
+	kfree(worker);
+	dev->worker = NULL;
+	return ret;
+}
+
 /* Caller should have device mutex */
 long vhost_dev_set_owner(struct vhost_dev *dev)
 {
-	struct task_struct *worker;
 	int err;
 
 	/* Is there an owner already? */
@@ -585,36 +635,21 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
 
 	vhost_attach_mm(dev);
 
-	dev->kcov_handle = kcov_common_handle();
 	if (dev->use_worker) {
-		worker = kthread_create(vhost_worker, dev,
-					"vhost-%d", current->pid);
-		if (IS_ERR(worker)) {
-			err = PTR_ERR(worker);
-			goto err_worker;
-		}
-
-		dev->worker = worker;
-		wake_up_process(worker); /* avoid contributing to loadavg */
-
-		err = vhost_attach_cgroups(dev);
+		err = vhost_worker_create(dev);
 		if (err)
-			goto err_cgroup;
+			goto err_worker;
 	}
 
 	err = vhost_dev_alloc_iovecs(dev);
 	if (err)
-		goto err_cgroup;
+		goto err_iovecs;
 
 	return 0;
-err_cgroup:
-	if (dev->worker) {
-		kthread_stop(dev->worker);
-		dev->worker = NULL;
-	}
+err_iovecs:
+	vhost_worker_free(dev);
 err_worker:
 	vhost_detach_mm(dev);
-	dev->kcov_handle = 0;
 err_mm:
 	return err;
 }
@@ -705,12 +740,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
 	dev->iotlb = NULL;
 	vhost_clear_msg(dev);
 	wake_up_interruptible_poll(&dev->wait, EPOLLIN | EPOLLRDNORM);
-	WARN_ON(!llist_empty(&dev->work_list));
-	if (dev->worker) {
-		kthread_stop(dev->worker);
-		dev->worker = NULL;
-		dev->kcov_handle = 0;
-	}
+	vhost_worker_free(dev);
 	vhost_detach_mm(dev);
 }
 EXPORT_SYMBOL_GPL(vhost_dev_cleanup);

drivers/vhost/vhost.h

@@ -25,6 +25,13 @@ struct vhost_work {
 	unsigned long		flags;
 };
 
+struct vhost_worker {
+	struct task_struct	*task;
+	struct llist_head	work_list;
+	struct vhost_dev	*dev;
+	u64			kcov_handle;
+};
+
 /* Poll a file (eventfd or socket) */
 /* Note: there's nothing vhost specific about this structure. */
 struct vhost_poll {
@@ -147,8 +154,7 @@ struct vhost_dev {
 	struct vhost_virtqueue **vqs;
 	int nvqs;
 	struct eventfd_ctx *log_ctx;
-	struct llist_head work_list;
-	struct task_struct *worker;
+	struct vhost_worker *worker;
 	struct vhost_iotlb *umem;
 	struct vhost_iotlb *iotlb;
 	spinlock_t iotlb_lock;
@@ -158,7 +164,6 @@ struct vhost_dev {
 	int iov_limit;
 	int weight;
 	int byte_weight;
-	u64 kcov_handle;
 	bool use_worker;
 	int (*msg_handler)(struct vhost_dev *dev, u32 asid,
 			   struct vhost_iotlb_msg *msg);