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