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Date:   Mon, 13 Jan 2020 01:34:38 +0000 (UTC)
From:   Christopher Lameter <cl@linux.com>
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To:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
cc:     Vlastimil Babka <vbabka@suse.cz>, Yu Zhao <yuzhao@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        "Kirill A . Shutemov" <kirill@shutemov.name>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [FIX] slub: Remove kmalloc under list_lock from list_slab_objects()
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On Sun, 12 Jan 2020, Tetsuo Handa wrote:

> On 2020/01/10 23:11, Vlastimil Babka wrote:
> Hmm, this one? Even non-ML destinations are sometimes rejected (e.g.
>   554 5.7.1 Service unavailable; Client host [202.181.97.72] blocked using b.barracudacentral.org; http://www.barracudanetworks.com/reputation/?pr=1&ip=202.181.97.72
> ). Anyway, I just worried whether it is really safe to do memory allocation
> which might involve memory reclaim. You MM guys know better...

We are talking about a call to destroy the kmem_cache. This is not done
under any lock. The lock was taken inside that function before the call to
list_slab_objects. That can be avoided.