Re: [PATCH 3/5] mm/vmalloc: Initialize VA's list node after unlink

Uladzislau Rezki
2022-06-09T12:36:42Z

>
> On 06/07/22 at 11:34am, Uladzislau Rezki (Sony) wrote:
> > A vmap_area can travel between different places. For example
> > attached/detached to/from different rb-trees. In order to
> > prevent fancy bugs, initialize a VA's list node after it is
> > removed from the list, so it pairs with VA's rb_node which
> > is also initialized.
> >
> > There is no functional change as a result of this patch.
> >
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > ---
> > mm/vmalloc.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 745e89eb6ca1..82771e555273 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -978,7 +978,7 @@ __unlink_va(struct vmap_area *va, struct rb_root *root, bool augment)
> > else
> > rb_erase(&va->rb_node, root);
> >
> > - list_del(&va->list);
> > + list_del_init(&va->list);
>
> Don't object this change, while list_del poison members, which is also
> not bad?
>
It is not bad for sure. The main aim was to be align with what the
RB_CLEAR_NODE() does, i.e. initialize VA when it is detached
and be safe with list manipulation when it is detached. For example
whether it is empty or not: list_empty(), etc.

--
Uladzislau Rezki