[PATCH v5 4/4] mm/vmalloc.c: switch to WARN_ON() and move it under unlink_va()

["Uladzislau Rezki (Sony)" <urezki@gmail.com>]

Trigger a warning if an object that is about to be freed is detached.
We used to have a BUG_ON(), but even though it is considered as faulty
behaviour that is not a good reason to break a system.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
 mm/vmalloc.c | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index a4bdf5fc3512..899a250e4eb6 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -534,20 +534,17 @@ link_va(struct vmap_area *va, struct rb_root *root,
 static __always_inline void
 unlink_va(struct vmap_area *va, struct rb_root *root)
 {
-	/*
-	 * During merging a VA node can be empty, therefore
-	 * not linked with the tree nor list. Just check it.
-	 */
-	if (!RB_EMPTY_NODE(&va->rb_node)) {
-		if (root == &free_vmap_area_root)
-			rb_erase_augmented(&va->rb_node,
-				root, &free_vmap_area_rb_augment_cb);
-		else
-			rb_erase(&va->rb_node, root);
+	if (WARN_ON(RB_EMPTY_NODE(&va->rb_node)))
+		return;
 
-		list_del(&va->list);
-		RB_CLEAR_NODE(&va->rb_node);
-	}
+	if (root == &free_vmap_area_root)
+		rb_erase_augmented(&va->rb_node,
+			root, &free_vmap_area_rb_augment_cb);
+	else
+		rb_erase(&va->rb_node, root);
+
+	list_del(&va->list);
+	RB_CLEAR_NODE(&va->rb_node);
 }
 
 #if DEBUG_AUGMENT_PROPAGATE_CHECK
@@ -1162,8 +1159,6 @@ EXPORT_SYMBOL_GPL(unregister_vmap_purge_notifier);
 
 static void __free_vmap_area(struct vmap_area *va)
 {
-	BUG_ON(RB_EMPTY_NODE(&va->rb_node));
-
 	/*
 	 * Remove from the busy tree/list.
 	 */
-- 
2.11.0