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

[Pasha Tatashin <pasha.tatashin@soleen.com>]

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