linux-kernel - Re: [FIX] slub: Remove kmalloc under list_lock from list_slab

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Message-ID: <alpine.DEB.2.21.2001130132580.1578@www.lameter.com>
Date:   Mon, 13 Jan 2020 01:34:38 +0000 (UTC)
From:   Christopher Lameter <cl@...ux.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
cc:     Vlastimil Babka <vbabka@...e.cz>, Yu Zhao <yuzhao@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        "Kirill A . Shutemov" <kirill@...temov.name>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [FIX] slub: Remove kmalloc under list_lock from list_slab_objects()
 V2

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.