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Date:   Sat, 9 Nov 2019 23:16:28 +0000 (UTC)
From:   Christopher Lameter <cl@linux.com>
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To:     Yu Zhao <yuzhao@google.com>
cc:     Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH v4 2/2] mm: avoid slub allocation while holding
 list_lock
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References: <20190914000743.182739-1-yuzhao@google.com> <20191108193958.205102-1-yuzhao@google.com> <20191108193958.205102-2-yuzhao@google.com> <alpine.DEB.2.21.1911092024560.9034@www.lameter.com> <20191109230147.GA75074@google.com>
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On Sat, 9 Nov 2019, Yu Zhao wrote:

> >  	struct page *page, *h;
> > +	unsigned long *map = bitmap_alloc(oo_objects(s->max), GFP_KERNEL);
> > +
> > +	if (!map)
> > +		return;
>
> What would happen if we are trying to allocate from the slab that is
> being shut down? And shouldn't the allocation be conditional (i.e.,
> only when CONFIG_SLUB_DEBUG=y)?

Kmalloc slabs are never shut down.

The allocation does not hurt and CONFIG_SLUB_DEBUG is on in most
configurations.