linux-kernel - Re: [PATCH v4 2/2] mm: avoid slub allocation while holding list

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Date:   Sun, 10 Nov 2019 11:47:21 -0700
From:   Yu Zhao <yuzhao@...gle.com>
To:     Christopher Lameter <cl@...ux.com>
Cc:     Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v4 2/2] mm: avoid slub allocation while holding list_lock

On Sat, Nov 09, 2019 at 11:16:28PM +0000, Christopher Lameter wrote:
> 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.

Maybe I'm not thinking straight -- isn't it what caused the deadlock in
the first place?

Kmalloc slabs can be shut down when memcg is on.