On 24/10/11 11:07AM, Christoph Lameter (Ampere) wrote:
> On Fri, 11 Oct 2024, yuan.gao wrote:
>
> > When an object belonging to the slab got freed later, the remove_full()
> > function is called. Because the slab is neither on the partial list nor
> > on the full list, it eventually lead to a list corruption.
>
> We detect list poison....
>
> > diff --git a/mm/slab.h b/mm/slab.h
> > index 6c6fe6d630ce..7681e71d9a13 100644
> > --- a/mm/slab.h
> > +++ b/mm/slab.h
> > @@ -73,6 +73,10 @@ struct slab {
> > struct {
> > unsigned inuse:16;
> > unsigned objects:15;
> > + /*
> > + * Reuse frozen bit for slab with debug enabled:
>
> "If slab debugging is enabled then the frozen bit can bereused to
> indicate that the slab was corrupted"
>
> > index 5b832512044e..b9265e9f11aa 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -1423,6 +1423,11 @@ static int check_slab(struct kmem_cache *s, struct slab *slab)
> > slab->inuse, slab->objects);
> > return 0;
> > }
> > + if (slab->frozen) {
> > + slab_err(s, slab, "Corrupted slab");
>
>
> "Slab folio disabled due to metadata corruption" ?
>
>
Yes, that's what I meant.
Perhaps I should change the description from "Corrupted slab" to
"Metadata corrupt"?
> > @@ -2744,7 +2750,10 @@ static void *alloc_single_from_partial(struct kmem_cache *s,
> > slab->inuse++;
> >
> > if (!alloc_debug_processing(s, slab, object, orig_size)) {
> > - remove_partial(n, slab);
> > + if (folio_test_slab(slab_folio(slab))) {
>
>
> Does folio_test_slab test for the frozen bit??
>
For slab folios, slab->fronzen has been set to 1.
For non-slab folios, we should not call remove_partial().
I'm not sure if I understand this correctly.
Thanks
