vfio: Move vfio_device driver open/close code to a function

This error unwind is getting complicated. Move all the code into two
pair'd function. The functions should be called when the open_count == 1
after incrementing/before decrementing.

Link: https://lore.kernel.org/r/1-v4-42cd2eb0e3eb+335a-vfio_iommufd_jgg@nvidia.comReviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Tested-by: Yi Liu <yi.l.liu@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Lixiao Yang <lixiao.yang@intel.com>
Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
Tested-by: Yu He <yu.he@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/vfio/vfio_main.c

@@ -734,40 +734,68 @@ bool vfio_assert_device_open(struct vfio_device *device)
 	return !WARN_ON_ONCE(!READ_ONCE(device->open_count));
 }
 
-static struct file *vfio_device_open(struct vfio_device *device)
+static int vfio_device_first_open(struct vfio_device *device)
 {
-	struct file *filep;
 	int ret;
 
-	mutex_lock(&device->group->group_lock);
-	ret = vfio_device_assign_container(device);
-	mutex_unlock(&device->group->group_lock);
-	if (ret)
-		return ERR_PTR(ret);
+	lockdep_assert_held(&device->dev_set->lock);
 
-	if (!try_module_get(device->dev->driver->owner)) {
-		ret = -ENODEV;
-		goto err_unassign_container;
-	}
+	if (!try_module_get(device->dev->driver->owner))
+		return -ENODEV;
 
-	mutex_lock(&device->dev_set->lock);
-	device->open_count++;
-	if (device->open_count == 1) {
 	/*
-		 * Here we pass the KVM pointer with the group under the read
-		 * lock.  If the device driver will use it, it must obtain a
-		 * reference and release it during close_device.
+	 * Here we pass the KVM pointer with the group under the lock.  If the
+	 * device driver will use it, it must obtain a reference and release it
+	 * during close_device.
 	 */
 	mutex_lock(&device->group->group_lock);
 	device->kvm = device->group->kvm;
-
 	if (device->ops->open_device) {
 		ret = device->ops->open_device(device);
 		if (ret)
-				goto err_undo_count;
+			goto err_module_put;
 	}
 	vfio_device_container_register(device);
 	mutex_unlock(&device->group->group_lock);
+	return 0;
+
+err_module_put:
+	device->kvm = NULL;
+	mutex_unlock(&device->group->group_lock);
+	module_put(device->dev->driver->owner);
+	return ret;
+}
+
+static void vfio_device_last_close(struct vfio_device *device)
+{
+	lockdep_assert_held(&device->dev_set->lock);
+
+	mutex_lock(&device->group->group_lock);
+	vfio_device_container_unregister(device);
+	if (device->ops->close_device)
+		device->ops->close_device(device);
+	device->kvm = NULL;
+	mutex_unlock(&device->group->group_lock);
+	module_put(device->dev->driver->owner);
+}
+
+static struct file *vfio_device_open(struct vfio_device *device)
+{
+	struct file *filep;
+	int ret;
+
+	mutex_lock(&device->group->group_lock);
+	ret = vfio_device_assign_container(device);
+	mutex_unlock(&device->group->group_lock);
+	if (ret)
+		return ERR_PTR(ret);
+
+	mutex_lock(&device->dev_set->lock);
+	device->open_count++;
+	if (device->open_count == 1) {
+		ret = vfio_device_first_open(device);
+		if (ret)
+			goto err_unassign_container;
 	}
 	mutex_unlock(&device->dev_set->lock);
 
@@ -800,20 +828,11 @@ static struct file *vfio_device_open(struct vfio_device *device)
 
 err_close_device:
 	mutex_lock(&device->dev_set->lock);
-	mutex_lock(&device->group->group_lock);
-	if (device->open_count == 1 && device->ops->close_device) {
-		device->ops->close_device(device);
-
-		vfio_device_container_unregister(device);
-	}
-err_undo_count:
-	mutex_unlock(&device->group->group_lock);
+	if (device->open_count == 1)
+		vfio_device_last_close(device);
+err_unassign_container:
 	device->open_count--;
-	if (device->open_count == 0 && device->kvm)
-		device->kvm = NULL;
 	mutex_unlock(&device->dev_set->lock);
-	module_put(device->dev->driver->owner);
-err_unassign_container:
 	vfio_device_unassign_container(device);
 	return ERR_PTR(ret);
 }
@@ -1016,19 +1035,11 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
 
 	mutex_lock(&device->dev_set->lock);
 	vfio_assert_device_open(device);
-	mutex_lock(&device->group->group_lock);
-	if (device->open_count == 1 && device->ops->close_device)
-		device->ops->close_device(device);
-
-	vfio_device_container_unregister(device);
-	mutex_unlock(&device->group->group_lock);
+	if (device->open_count == 1)
+		vfio_device_last_close(device);
 	device->open_count--;
-	if (device->open_count == 0)
-		device->kvm = NULL;
 	mutex_unlock(&device->dev_set->lock);
 
-	module_put(device->dev->driver->owner);
-
 	vfio_device_unassign_container(device);
 
 	vfio_device_put_registration(device);