Re: [PATCH 01/10] vfio: Move vfio_device driver open/close code to a function

[Yi Liu <yi.l.liu@xxxxxxxxx>]

On 2022/10/26 02:17, Jason Gunthorpe wrote:
> 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.
>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> ---
>   drivers/vfio/vfio_main.c | 95 ++++++++++++++++++++++------------------
>   1 file changed, 53 insertions(+), 42 deletions(-)

Reviewed-by: Yi Liu <yi.l.liu@xxxxxxxxx>

> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index 2d168793d4e1ce..d043383fc3ba2b 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -734,6 +734,51 @@ bool vfio_assert_device_open(struct vfio_device *device)
>   	return !WARN_ON_ONCE(!READ_ONCE(device->open_count));
>   }
>   
> +static int vfio_device_first_open(struct vfio_device *device)
> +{
> +	int ret;
> +
> +	lockdep_assert_held(&device->dev_set->lock);
> +
> +	if (!try_module_get(device->dev->driver->owner))
> +		return -ENODEV;
> +
> +	/*
> +	 * 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.
> +	 */
> +	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_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;
> @@ -745,29 +790,12 @@ static struct file *vfio_device_open(struct vfio_device *device)
>   	if (ret)
>   		return ERR_PTR(ret);
>   
> -	if (!try_module_get(device->dev->driver->owner)) {
> -		ret = -ENODEV;
> -		goto err_unassign_container;
> -	}
> -
>   	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.
> -		 */
> -		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;
> -		}
> -		vfio_device_container_register(device);
> -		mutex_unlock(&device->group->group_lock);
> +		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);

--
Regards,
Yi Liu