[PATCH 12/14] vhost: replace single worker pointer with xarray

[Mike Christie <michael.christie@xxxxxxxxxx>]

The next patch allows userspace to create multiple workers per device,
so this patch replaces the vhost_worker pointer with an xarray so we
can store mupltiple workers and look them up.

Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
---
 drivers/vhost/vhost.c | 48 +++++++++++++++++++++++++++++++++----------
 drivers/vhost/vhost.h |  3 ++-
 2 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 930b703eb6b6..4b0b82292379 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -271,7 +271,11 @@ EXPORT_SYMBOL_GPL(vhost_vq_work_queue);
 
 void vhost_dev_flush(struct vhost_dev *dev)
 {
-	vhost_work_flush_on(dev->worker);
+	struct vhost_worker *worker;
+	unsigned long i;
+
+	xa_for_each(&dev->worker_xa, i, worker)
+		vhost_work_flush_on(worker);
 }
 EXPORT_SYMBOL_GPL(vhost_dev_flush);
 
@@ -489,7 +493,6 @@ void vhost_dev_init(struct vhost_dev *dev,
 	dev->umem = NULL;
 	dev->iotlb = NULL;
 	dev->mm = NULL;
-	dev->worker = NULL;
 	dev->iov_limit = iov_limit;
 	dev->weight = weight;
 	dev->byte_weight = byte_weight;
@@ -499,7 +502,7 @@ void vhost_dev_init(struct vhost_dev *dev,
 	INIT_LIST_HEAD(&dev->read_list);
 	INIT_LIST_HEAD(&dev->pending_list);
 	spin_lock_init(&dev->iotlb_lock);
-
+	xa_init_flags(&dev->worker_xa, XA_FLAGS_ALLOC);
 
 	for (i = 0; i < dev->nvqs; ++i) {
 		vq = dev->vqs[i];
@@ -562,30 +565,46 @@ static void vhost_detach_mm(struct vhost_dev *dev)
 	dev->mm = NULL;
 }
 
-static void vhost_worker_free(struct vhost_dev *dev)
+static void vhost_worker_destroy(struct vhost_dev *dev,
+				 struct vhost_worker *worker)
 {
-	struct vhost_worker *worker = dev->worker;
-
 	if (!worker)
 		return;
 
-	dev->worker = NULL;
 	WARN_ON(!llist_empty(&worker->work_list));
+	xa_erase(&dev->worker_xa, worker->id);
 	vhost_task_stop(worker->vtsk);
 	kfree(worker);
 }
 
+static void vhost_workers_free(struct vhost_dev *dev)
+{
+	struct vhost_worker *worker;
+	unsigned long i;
+
+	if (!dev->use_worker)
+		return;
+	/*
+	 * Free the default worker we created and cleanup workers userspace
+	 * created but couldn't clean up (it forgot or crashed).
+	 */
+	xa_for_each(&dev->worker_xa, i, worker)
+		vhost_worker_destroy(dev, worker);
+	xa_destroy(&dev->worker_xa);
+}
+
 static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
 {
 	struct vhost_worker *worker;
 	struct vhost_task *vtsk;
 	char name[TASK_COMM_LEN];
+	int ret;
+	u32 id;
 
 	worker = kzalloc(sizeof(*worker), GFP_KERNEL_ACCOUNT);
 	if (!worker)
 		return NULL;
 
-	dev->worker = worker;
 	worker->kcov_handle = kcov_common_handle();
 	init_llist_head(&worker->work_list);
 	snprintf(name, sizeof(name), "vhost-%d", current->pid);
@@ -596,11 +615,18 @@ static struct vhost_worker *vhost_worker_create(struct vhost_dev *dev)
 
 	worker->vtsk = vtsk;
 	vhost_task_start(vtsk);
+
+	ret = xa_alloc(&dev->worker_xa, &id, worker, xa_limit_32b, GFP_KERNEL);
+	if (ret < 0)
+		goto stop_worker;
+	worker->id = id;
+
 	return worker;
 
+stop_worker:
+	vhost_task_stop(vtsk);
 free_worker:
 	kfree(worker);
-	dev->worker = NULL;
 	return NULL;
 }
 
@@ -654,7 +680,7 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
 
 	return 0;
 err_iovecs:
-	vhost_worker_free(dev);
+	vhost_workers_free(dev);
 err_worker:
 	vhost_detach_mm(dev);
 err_mm:
@@ -747,7 +773,7 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
 	dev->iotlb = NULL;
 	vhost_clear_msg(dev);
 	wake_up_interruptible_poll(&dev->wait, EPOLLIN | EPOLLRDNORM);
-	vhost_worker_free(dev);
+	vhost_workers_free(dev);
 	vhost_detach_mm(dev);
 }
 EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 395707c680e5..2eea20d54134 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -30,6 +30,7 @@ struct vhost_worker {
 	struct vhost_task	*vtsk;
 	struct llist_head	work_list;
 	u64			kcov_handle;
+	u32			id;
 };
 
 /* Poll a file (eventfd or socket) */
@@ -156,7 +157,6 @@ struct vhost_dev {
 	struct vhost_virtqueue **vqs;
 	int nvqs;
 	struct eventfd_ctx *log_ctx;
-	struct vhost_worker *worker;
 	struct vhost_iotlb *umem;
 	struct vhost_iotlb *iotlb;
 	spinlock_t iotlb_lock;
@@ -166,6 +166,7 @@ struct vhost_dev {
 	int iov_limit;
 	int weight;
 	int byte_weight;
+	struct xarray worker_xa;
 	bool use_worker;
 	int (*msg_handler)(struct vhost_dev *dev, u32 asid,
 			   struct vhost_iotlb_msg *msg);
-- 
2.25.1

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