Re: [PATCH v3 07/10] liveupdate: Auto unregister FLBs on file handler unregistration

[Pratyush Yadav <pratyush@kernel.org>]

On Fri, Mar 27 2026, Pasha Tatashin wrote:

> To ensure that unregistration is always successful and doesn't leave
> dangling resources, introduce auto-unregistration of FLBs: when a file
> handler is unregistered, all FLBs associated with it are automatically
> unregistered.
>
> Introduce a new helper luo_flb_unregister_all() which unregisters all
> FLBs linked to the given file handler.
>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> ---
>  kernel/liveupdate/luo_file.c     | 14 +-----
>  kernel/liveupdate/luo_flb.c      | 84 ++++++++++++++++++++++----------
>  kernel/liveupdate/luo_internal.h |  1 +
>  3 files changed, 60 insertions(+), 39 deletions(-)
>
> diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
> index 439177c10723..80f4e3b796a6 100644
> --- a/kernel/liveupdate/luo_file.c
> +++ b/kernel/liveupdate/luo_file.c
> @@ -895,26 +895,16 @@ int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
>   */
>  int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
>  {
> -	int err = -EBUSY;
> -
>  	if (!liveupdate_enabled())
>  		return -EOPNOTSUPP;
>  
>  	liveupdate_test_unregister(fh);
>  
> -	down_write(&luo_register_rwlock);
> -	if (!list_empty(&ACCESS_PRIVATE(fh, flb_list)))
> -		goto err_unlock;
> -
> +	guard(rwsem_write)(&luo_register_rwlock);
> +	luo_flb_unregister_all(fh);
>  	list_del(&ACCESS_PRIVATE(fh, list));
> -	up_write(&luo_register_rwlock);
>  
>  	module_put(fh->ops->owner);
>  
>  	return 0;
> -
> -err_unlock:
> -	up_write(&luo_register_rwlock);
> -	liveupdate_test_register(fh);
> -	return err;
>  }
> diff --git a/kernel/liveupdate/luo_flb.c b/kernel/liveupdate/luo_flb.c
> index ac6fa5b34b43..f8348138de70 100644
> --- a/kernel/liveupdate/luo_flb.c
> +++ b/kernel/liveupdate/luo_flb.c
> @@ -335,6 +335,62 @@ void luo_flb_file_finish(struct liveupdate_file_handler *fh)
>  		luo_flb_file_finish_one(iter->flb);
>  }
>  
> +static void luo_flb_unregister_one(struct liveupdate_file_handler *fh,
> +				   struct liveupdate_flb *flb)
> +{
> +	struct luo_flb_private *private = luo_flb_get_private(flb);
> +	struct list_head *flb_list = &ACCESS_PRIVATE(fh, flb_list);
> +	struct luo_flb_link *iter;
> +	bool found = false;
> +
> +	/* Find and remove the link from the file handler's list */

Nit: it would be nice to have a lockdep_assert_held_write() here to
clearly show that the luo_register_rwlock must be held when modifying
the list. I know that luo_flb_unregister_all() already has one, but in
case we refactor later or add another caller.

Other than this,

Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>

> +	list_for_each_entry(iter, flb_list, list) {
> +		if (iter->flb == flb) {
> +			list_del(&iter->list);
> +			kfree(iter);
> +			found = true;
> +			break;
> +		}
> +	}
> +
[...]

-- 
Regards,
Pratyush Yadav