[PATCH v2 6/8] liveupdate: Auto unregister FLBs on file handler unregistration

[Pasha Tatashin]

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@xxxxxxxxxx>
---
 kernel/liveupdate/luo_file.c     | 17 +-----
 kernel/liveupdate/luo_flb.c      | 93 ++++++++++++++++++++------------
 kernel/liveupdate/luo_internal.h |  1 +
 3 files changed, 61 insertions(+), 50 deletions(-)

diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index c0ce08d55747..b9ba1b8dce84 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -873,15 +873,6 @@ int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
  *
  * Unregisters the file handler from the liveupdate core. This function
  * reverses the operations of liveupdate_register_file_handler().
- *
- * It ensures safe removal by checking that:
- * No FLB registered with this file handler.
- *
- * If the unregistration fails, the internal test state is reverted.
- *
- * Return: 0 Success. -EOPNOTSUPP when live update is not enabled. -EBUSY A live
- * update is in progress, FLB is registred with
- * this file handler.
  */
 int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
 {
@@ -891,15 +882,9 @@ int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
 	liveupdate_test_unregister(fh);
 
 	scoped_guard(rwsem_write, &luo_file_handler_lock) {
-		if (!list_empty(&ACCESS_PRIVATE(fh, flb_list)))
-			goto err_register;
-
+		luo_flb_unregister_all(fh);
 		list_del(&ACCESS_PRIVATE(fh, list));
 	}
 
 	return 0;
-
-err_register:
-	liveupdate_test_register(fh);
-	return -EBUSY;
 }
diff --git a/kernel/liveupdate/luo_flb.c b/kernel/liveupdate/luo_flb.c
index 8bbe11a7286b..5b61c0844a49 100644
--- a/kernel/liveupdate/luo_flb.c
+++ b/kernel/liveupdate/luo_flb.c
@@ -316,6 +316,64 @@ 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 */
+	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;
+
+	guard(rwsem_write)(&luo_flb_lock);
+	guard(rwsem_write)(&ACCESS_PRIVATE(fh, flb_lock));
+
+	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.
@@ -417,50 +475,17 @@ int liveupdate_register_flb(struct liveupdate_file_handler *fh,
  * the FLB is removed from the global registry and the reference to its
  * owner module (acquired during registration) is released.
  *
- * Context: This function ensures the session is quiesced (no active FDs
- *          being created) during the update. It is typically called from a
- *          subsystem's module exit function.
- * Return: 0 on success.
- *         -EOPNOTSUPP if live update is disabled.
- *         -EBUSY if the live update session is active and cannot be quiesced.
- *         -ENOENT if the FLB was not found in the file handler's list.
  */
 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_flb_lock);
 	guard(rwsem_write)(&ACCESS_PRIVATE(fh, flb_lock));
 
-	/* 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 ec949f91c8c1..730c3faa7616 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -101,6 +101,7 @@ 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);
-- 
2.53.0.851.ga537e3e6e9-goog