Re: Possible regression in "slab, slub: skip unnecessary kasan_cache_shutdown()"

[Andrey Ryabinin <aryabinin@virtuozzo.com>]

On 06/19/2018 05:51 AM, Jason A. Donenfeld wrote:
> Hello Shakeel,
> 
> It may be the case that f9e13c0a5a33d1eaec374d6d4dab53a4f72756a0 has
> introduced a regression. I've bisected a failing test to this commit,
> and after staring at the my code for a long time, I'm unable to find a
> bug that this commit might have unearthed. Rather, it looks like this
> commit introduces a performance optimization, rather than a
> correctness fix, so it seems that whatever test case is failing is
> likely an incorrect failure. Does that seem like an accurate
> possibility to you?
> 
> Below is a stack trace when things go south. Let me know if you'd like
> to run my test suite, and I can send additional information.
> 
> Regards,
> Jason
> 
> 

What's the status of CONFIG_SLUB_DEBUG in your config?

AFAICS __kmem_cache_empty() is broken for CONFIG_SLUB_DEBUG=n. We use slabs_node() there
which is always 0 for CONFIG_SLUB_DEBUG=n.

The problem seems not limited to __kmem_cache_empty(), __kmem_cache_shutdown() and __kmem_cache_shrink()
are also rely on correctness of the slabs_node(). Presumably this might cause some problems while
destroying memcg kmem caches.