linux-kernel - Re: [PATCH v3 17/29] s390: introduce arch_zone_limits

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Message-ID: <aWSkELL7xJ04QAct@kernel.org>
Date: Mon, 12 Jan 2026 09:34:40 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Alexander Gordeev <agordeev@...ux.ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Alex Shi <alexs@...nel.org>,
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Subject: Re: [PATCH v3 17/29] s390: introduce arch_zone_limits_init()

Hi,

On Mon, Jan 12, 2026 at 08:02:48AM +0100, Alexander Gordeev wrote:
> On Sun, Jan 11, 2026 at 10:20:51AM +0200, Mike Rapoport wrote:
> 
> Hi Mike,
> 
> ...
> > +void __init arch_zone_limits_init(unsigned long *max_zone_pfns)
> > +{
> > +	max_zone_pfns[ZONE_DMA] = virt_to_pfn(MAX_DMA_ADDRESS);
> > +	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
> > +}
> > +
> >  /*
> >   * paging_init() sets up the page tables
> >   */
> > @@ -97,8 +103,7 @@ void __init paging_init(void)
> >  	sparse_init();
> >  	zone_dma_limit = DMA_BIT_MASK(31);
> >  	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
> > -	max_zone_pfns[ZONE_DMA] = virt_to_pfn(MAX_DMA_ADDRESS);
> > -	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
> > +	arch_zone_limits_init(max_zone_pfns);
> 
> You move initialization of max_zone_pfns[] to a function, name the
> function arch_zone_limits_init(), but leave the initializatio of
> max_zone_pfns[] to zeroes outside. Should not it be brought along?

The idea is that is the caller responsibility to initialize max_zone_pfns
to zero. After patch 24: "arch, mm: consolidate initialization of
SPARSE memory model" there is a single caller of arch_zone_limits_init()
and having initialization of max_zone_pfns() there is more optimal than
having 20-something of those.
 
> >  	free_area_init(max_zone_pfns);
> >  }
> 
> Thanks!

-- 
Sincerely yours,
Mike.