On Fri, Jul 10, 2020 at 08:44:06PM +0100, Matthew Wilcox wrote:
> On Fri, Jul 10, 2020 at 09:40:42PM +0200, Uladzislau Rezki (Sony) wrote:
> > Before triggering a BUG() it would be useful to understand
> > how two areas overlap between each other. Print information
> > about start/end addresses of both VAs and their addresses.
> >
> > For example if both are identical it could mean double free.
> >
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> > ---
> > mm/vmalloc.c | 10 +++++++++-
> > 1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 5a2b55c8dd9a..1679b01febcd 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -549,8 +549,13 @@ find_va_links(struct vmap_area *va,
> > else if (va->va_end > tmp_va->va_start &&
> > va->va_start >= tmp_va->va_end)
> > link = &(*link)->rb_right;
> > - else
> > + else {
> > + pr_err("Overlaps: 0x%px(0x%lx-0x%lx), 0x%px(0x%lx-0x%lx)\n",
> > + va, va->va_start, va->va_end, tmp_va,
> > + tmp_va->va_start, tmp_va->va_end);
>
> It might be helpful to have a "vmalloc:" prefix to that string to indicate
> where to start searching. And I don't think we're supposed to use %px
> without a really good justification these days.
>
That makes sense, i will add such prefix for sure. As for %px i can just
use a casting to (unsigned long) and 0x%lx prefix.
>
> Can we do without the BUG()? Maybe just break out and decline to insert
> the conflicting range?
>
When i developed that logic, i was thinking about that but for some
reason i went with BUG_ON(), do not remember why. But i agree we shold
avoid of it. Let me think about it one more time.
> > BUG();
> > + }
> > } while (*link);
> >
> > *parent = &tmp_va->rb_node;
> > @@ -1993,6 +1998,9 @@ static void vmap_init_free_space(void)
> > insert_vmap_area_augment(free, NULL,
> > &free_vmap_area_root,
> > &free_vmap_area_list);
> > + insert_vmap_area_augment(free, NULL,
> > + &free_vmap_area_root,
> > + &free_vmap_area_list);
>
> This is surely testing code that you forgot to delete?
>
Yes, i forgot to remove it.
Thanks for your comments!
--
Vlad Rezki
