Re: [PATCH v4 07/11] liveupdate: Auto unregister FLBs on file handler unregistration

Mike Rapoport
2026-04-15T15:31:54Z

On Mon, Apr 13, 2026 at 06:51:23PM +0000, 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>
> Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
> kernel/liveupdate/luo_file.c | 14 +-----
> kernel/liveupdate/luo_flb.c | 85 ++++++++++++++++++++++----------
> kernel/liveupdate/luo_internal.h | 1 +
> 3 files changed, 61 insertions(+), 39 deletions(-)
>
> diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
> index 63ddcf6dcddb..b37bd79974ce 100644
> --- a/kernel/liveupdate/luo_file.c
> +++ b/kernel/liveupdate/luo_file.c
> @@ -926,26 +926,16 @@ 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 13f96d11ecc9..b9f5d452a998 100644
> --- a/kernel/liveupdate/luo_flb.c
> +++ b/kernel/liveupdate/luo_flb.c
> @@ -318,6 +318,63 @@ 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 */
> + lockdep_assert_held_write(&luo_register_rwlock);
> + list_for_each_entry(iter, flb_list, list) {
> + if (iter->flb == flb) {
> + list_del(&iter->list);
> + kfree(iter);
> + found = true;
> + break;
> + }
> + }
> +
> + if (!found) {
> + pr_warn("Failed to unregister FLB '%s': not found in file handler '%s'\n",
> + flb->compatible, fh->compatible);
> + return;
> + }
> +
> + private->users--;
> +
> + /*
> + * If this is the last file-handler with which we are registred, remove
> + * from the global list.
> + */
> + if (!private->users) {
> + list_del_init(&private->list);
> + luo_flb_global.count--;
> + }
> +}
> +
> +/**
> + * luo_flb_unregister_all - Unregister all FLBs associated with a file handler.
> + * @fh: The file handler whose FLBs should be unregistered.
> + *
> + * This function iterates through the list of FLBs associated with the given
> + * file handler and unregisters them all one by one.
> + */
> +void luo_flb_unregister_all(struct liveupdate_file_handler *fh)
> +{
> + struct list_head *flb_list = &ACCESS_PRIVATE(fh, flb_list);
> + struct luo_flb_link *iter, *tmp;
> +
> + if (!liveupdate_enabled())
> + return;
> +
> + lockdep_assert_held_write(&luo_register_rwlock);
> + list_for_each_entry_safe(iter, tmp, flb_list, list)
> + luo_flb_unregister_one(fh, iter->flb);
> +}
> +
> /**
> * liveupdate_register_flb - Associate an FLB with a file handler and register it globally.
> * @fh: The file handler that will now depend on the FLB.
> @@ -426,38 +483,12 @@ int liveupdate_register_flb(struct liveupdate_file_handler *fh,
> int liveupdate_unregister_flb(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;
> - int err = -ENOENT;
> -
> if (!liveupdate_enabled())
> return -EOPNOTSUPP;
>
> guard(rwsem_write)(&luo_register_rwlock);
>
> - /* Find and remove the link from the file handler's list */
> - list_for_each_entry(iter, flb_list, list) {
> - if (iter->flb == flb) {
> - list_del(&iter->list);
> - kfree(iter);
> - err = 0;
> - break;
> - }
> - }
> -
> - if (err)
> - return err;
> -
> - private->users--;
> - /*
> - * If this is the last file-handler with which we are registred, remove
> - * from the global list.
> - */
> - if (!private->users) {
> - list_del_init(&private->list);
> - luo_flb_global.count--;
> - }
> + luo_flb_unregister_one(fh, flb);
>
> return 0;
> }
> diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
> index 40a011bdfa55..22f6901f89ed 100644
> --- a/kernel/liveupdate/luo_internal.h
> +++ b/kernel/liveupdate/luo_internal.h
> @@ -103,6 +103,7 @@ void luo_file_set_destroy(struct luo_file_set *file_set);
> int luo_flb_file_preserve(struct liveupdate_file_handler *fh);
> void luo_flb_file_unpreserve(struct liveupdate_file_handler *fh);
> void luo_flb_file_finish(struct liveupdate_file_handler *fh);
> +void luo_flb_unregister_all(struct liveupdate_file_handler *fh);
> int __init luo_flb_setup_outgoing(void *fdt);
> int __init luo_flb_setup_incoming(void *fdt);
> void luo_flb_serialize(void);
> --
> 2.43.0
>

--
Sincerely yours,
Mike.