Re: [PATCH 02/10] vfio: Move vfio_device_assign_container() into vfio_device_first_open()

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

On 2022/10/26 02:17, Jason Gunthorpe wrote:
> The only thing this function does is assert the group has an assigned
> container and incrs refcounts.
>
> The overall model we have is that once a conatiner_users refcount is

typo.

s/conatiner_users/container_users

> incremented it cannot be de-assigned from the group -
> vfio_group_ioctl_unset_container() will fail and the group FD cannot be
> closed.
>
> Thus we do not need to check this on evey device FD open, just the

s/evey/every

> first. Reorganize the code so that only the first open and last close
> manages the container.
>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> ---
>   drivers/vfio/container.c |  4 ++--
>   drivers/vfio/vfio_main.c | 18 ++++++++----------
>   2 files changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/vfio/container.c b/drivers/vfio/container.c
> index d74164abbf401d..dd79a66ec62cad 100644
> --- a/drivers/vfio/container.c
> +++ b/drivers/vfio/container.c
> @@ -531,11 +531,11 @@ int vfio_device_assign_container(struct vfio_device *device)
>   
>   void vfio_device_unassign_container(struct vfio_device *device)
>   {
> -	mutex_lock(&device->group->group_lock);
> +	lockdep_assert_held_write(&device->group->group_lock);
> +
>   	WARN_ON(device->group->container_users <= 1);
>   	device->group->container_users--;
>   	fput(device->group->opened_file);
> -	mutex_unlock(&device->group->group_lock);
>   }
>   
>   /*
> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> index d043383fc3ba2b..204443ba3b3cd9 100644
> --- a/drivers/vfio/vfio_main.c
> +++ b/drivers/vfio/vfio_main.c
> @@ -749,16 +749,22 @@ static int vfio_device_first_open(struct vfio_device *device)
>   	 * it during close_device.
>   	 */
>   	mutex_lock(&device->group->group_lock);
> +	ret = vfio_device_assign_container(device);
> +	if (ret)
> +		goto err_module_put;
> +
>   	device->kvm = device->group->kvm;
>   	if (device->ops->open_device) {
>   		ret = device->ops->open_device(device);
>   		if (ret)
> -			goto err_module_put;
> +			goto err_container;
>   	}
>   	vfio_device_container_register(device);
>   	mutex_unlock(&device->group->group_lock);
>   	return 0;
>   
> +err_container:
> +	vfio_device_unassign_container(device);
>   err_module_put:
>   	device->kvm = NULL;
>   	mutex_unlock(&device->group->group_lock);
> @@ -775,6 +781,7 @@ static void vfio_device_last_close(struct vfio_device *device)
>   	if (device->ops->close_device)
>   		device->ops->close_device(device);
>   	device->kvm = NULL;
> +	vfio_device_unassign_container(device);
>   	mutex_unlock(&device->group->group_lock);
>   	module_put(device->dev->driver->owner);
>   }
> @@ -784,12 +791,6 @@ 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) {
> @@ -833,7 +834,6 @@ static struct file *vfio_device_open(struct vfio_device *device)
>   err_unassign_container:

should the err_unassign_container be renamed to be err_dec_count?

other parts look good to me.

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

>   	device->open_count--;
>   	mutex_unlock(&device->dev_set->lock);
> -	vfio_device_unassign_container(device);
>   	return ERR_PTR(ret);
>   }
>   
> @@ -1040,8 +1040,6 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
>   	device->open_count--;
>   	mutex_unlock(&device->dev_set->lock);
>   
> -	vfio_device_unassign_container(device);
> -
>   	vfio_device_put_registration(device);
>   
>   	return 0;

--
Regards,
Yi Liu