Re: [PATCH] mm/slab_common: fix slab_caches list corruption after kmem_cache_destroy()

[Rafael Aquini]

On Sat, Sep 09, 2023 at 02:16:00AM +0100, Matthew Wilcox wrote:
> On Fri, Sep 08, 2023 at 07:06:49PM -0400, Rafael Aquini wrote:
> > This patch fixes this issue by properly checking shutdown_cache()'s
> > return value before taking the kmem_cache_release() branch.
> 
> Is this the right way to fix this problem?  If the module destroys the
> slab cache, it's not going to be possible to free any of the objects
> still allocated from the cache.  I feel that we should treat this as
> implicitly freeing all the objects that were allocated from the cache
> rather than saying the cache is still busy.
>

Leaving the cache with the unfreeable slabs "alone" is how it was historically 
done, and we have to fix this corner case opened by 0495e337b703 this way to 
address the corruption on stable releases without changing their established 
and expected behavior.

I think your proposal for a different behavior upon cache destruction is
something we should discuss for future releases, but it is orthogonal to
this required follow-up fix.