linux-kernel - Re: [PATCH] slub: fix __kmem_cache_empty for !CONFIG_SLUB

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Date:   Wed, 20 Jun 2018 15:09:38 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Shakeel Butt <shakeelb@...gle.com>,
        "Jason A . Donenfeld" <Jason@...c4.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH] slub: fix __kmem_cache_empty for !CONFIG_SLUB_DEBUG



On 06/20/2018 12:33 AM, Shakeel Butt wrote:
> For !CONFIG_SLUB_DEBUG, SLUB does not maintain the number of slabs
> allocated per node for a kmem_cache. Thus, slabs_node() in
> __kmem_cache_empty() will always return 0. So, in such situation, it is
> required to check per-cpu slabs to make sure if a kmem_cache is empty or
> not.
> 
> Please note that __kmem_cache_shutdown() and __kmem_cache_shrink() are
> not affected by !CONFIG_SLUB_DEBUG as they call flush_all() to clear
> per-cpu slabs.

So what? Yes, they call flush_all() and then check if there are non-empty slabs left.
And that check doesn't work in case of disabled CONFIG_SLUB_DEBUG.
How is flush_all() or per-cpu slabs even relevant here?