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Subject: Re: [PATCH 1 of 6] hotplug-memory: refactor online_pages to
	separate zone growth from page onlining
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Yasunori Goto <y-goto@jp.fujitsu.com>, Ingo Molnar <mingo@elte.hu>,
       LKML <linux-kernel@vger.kernel.org>,
       Christoph Lameter <clameter@sgi.com>
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Date: Thu, 03 Apr 2008 18:06:47 -0700
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On Thu, 2008-04-03 at 17:05 -0700, Jeremy Fitzhardinge wrote:
> 
> +static void grow_zone_span(unsigned long start_pfn, unsigned long
> end_pfn)
> +{
>         unsigned long old_zone_end_pfn;
> +       struct zone *zone;
> +       unsigned long flags;
> +
> +       /*
> +        * This doesn't need a lock to do pfn_to_page().
> +        * The section can't be removed here because of the
> +        * memory_block->state_sem.
> +        */
> +       zone = page_zone(pfn_to_page(start_pfn));
> +       pgdat_resize_lock(zone->zone_pgdat, &flags);
> 
>         zone_span_writelock(zone);
> 
> @@ -149,19 +171,9 @@
>                                 zone->zone_start_pfn;
> 
>         zone_span_writeunlock(zone);
> -}
> 
> -static void grow_pgdat_span(struct pglist_data *pgdat,
> -               unsigned long start_pfn, unsigned long end_pfn)
> -{
> -       unsigned long old_pgdat_end_pfn =
> -               pgdat->node_start_pfn + pgdat->node_spanned_pages;
> -
> -       if (start_pfn < pgdat->node_start_pfn)
> -               pgdat->node_start_pfn = start_pfn;
> -
> -       pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
> -                                       pgdat->node_start_pfn;
> +       grow_pgdat_span(zone->zone_pgdat, start_pfn, end_pfn);
> +       pgdat_resize_unlock(zone->zone_pgdat, &flags);
>  }
> 
>  static int online_pages_range(unsigned long start_pfn, unsigned long
> nr_pages,
> @@ -180,16 +192,12 @@
>         return 0;
>  }

I don't particularly like this change to have grow_pgdat_span() called
*from* grow_zone_span().  Seems backwards to me.  But, this diff look
funny (not your fault) so I may just be seeing things. :)

-- Dave