Re: [PATCH RFC v2 01/20] mm/slab: add rcu_barrier() to kvfree_rcu_barrier_on_cache()

[Suren Baghdasaryan <surenb@google.com>]

On Wed, Jan 14, 2026 at 1:02 PM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 1/14/26 12:14, Harry Yoo wrote:
> > For the record, an accurate analysis of the problem (as discussed
> > off-list):
> >
> > It turns out the object freed by sheaf_flush_unused() was in KASAN
> > percpu quarantine list (confirmed by dumping the list) by the time
> > __kmem_cache_shutdown() returns an error.
> >
> > Quarantined objects are supposed to be flushed by kasan_cache_shutdown(),
> > but things go wrong if the rcu callback (rcu_free_sheaf_nobarn()) is
> > processed after kasan_cache_shutdown() finishes.
> >
> > That's why rcu_barrier() in __kmem_cache_shutdown() didn't help,
> > because it's called after kasan_cache_shutdown().
> >
> > Calling rcu_barrier() in kvfree_rcu_barrier_on_cache() guarantees
> > that it'll be added to the quarantine list before kasan_cache_shutdown()
> > is called. So it's a valid fix!
>
> Thanks a lot! Will incorporate to commit log.
> This being KASAN-only means further reducing the urgency.

Thanks for the detailed explanation!

Reviewed-by: Suren Baghdasaryan <surenb@google.com>