Hello,
On Thu, Feb 13, 2020 at 03:51:40PM +0800, Yufen Yu wrote:
> If we destroy the device asynchronously by call_rcu(), we may need to
> add a new member 'rcu_head' into struct backing_dev_info. Right?
Yes.
> The code may be like:
>
> bdi_unregister()
> {
> ...
> if (bdi->dev) {
> ...
> device_get(bdi->dev);
> device_unregister(bdi->dev);
> bdi->dev = NULL; //XXX
> bdi_get(bdi); //avoiding bdi to be freed before calling bdi_release_device
> call_rcu(&bdi->rcu_head, bdi_release_device);
> }
> ...
> }
>
> bdi_release_device()
> {
> ...
> put_device(bdi->dev);//XXX
> bdi_put(bdi);
> }
>
> But, the problem is how do we get 'bdi->dev' in bdi_release_device().
> If we do not set bdi->dev as 'NULL', re-registration bdi may cannot work well.
So, unregistering can leave ->dev along and re-registering can test
whether it's NULL and if not put the existing one and put a new one
there. Wouldn't that work?
Thanks.
--
tejun
