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

Pasha Tatashin
2026-04-13T18:51:39Z

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>
---
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