mm/vmalloc.c: switch to WARN_ON() and move it under unlink_va()

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.

Link: http://lkml.kernel.org/r/20190606120411.8298-5-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 15 deletions

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 857dd8415a2e..84f50d7e40bc 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.
          */