Re: [Patch]Fix spanned_pages is not updated at a case of memoryhot-add.
From: Dave Hansen
Date: Tue May 23 2006 - 12:27:59 EST
On Tue, 2006-05-23 at 17:29 +0900, Yasunori Goto wrote:
> I found there is a bug in grow_zone_span() and grow_pgdat_span().
> @@ -95,16 +95,18 @@ EXPORT_SYMBOL_GPL(__add_pages);
> static void grow_zone_span(struct zone *zone,
> unsigned long start_pfn, unsigned long end_pfn)
> - unsigned long old_zone_end_pfn;
> + unsigned long new_zone_end_pfn;
> - old_zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
> + new_zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
I really don't like the idea of having this variable called "new_"
something. That implies that this is what the new end_pfn is going to
be. The *new* one. In reality, it is what it _might_ have been. How
This practice of dealing with spanned_pages is a real pain.
I generally try to avoid max/min in code, but this struck me as possibly
being useful. Do you find this easier to read, or your patch?
diff -puN mm/memory_hotplug.c~fix-spanned-pages mm/memory_hotplug.c
--- work/mm/memory_hotplug.c~fix-spanned-pages 2006-05-23 09:04:31.000000000 -0700
+++ work-dave/mm/memory_hotplug.c 2006-05-23 09:22:18.000000000 -0700
@@ -91,8 +91,8 @@ static void grow_zone_span(struct zone *
if (start_pfn < zone->zone_start_pfn)
zone->zone_start_pfn = start_pfn;
- if (end_pfn > old_zone_end_pfn)
- zone->spanned_pages = end_pfn - zone->zone_start_pfn;
+ zone->spanned_pages = max(old_zone_end_pfn, end_pfn) -
@@ -106,8 +106,8 @@ static void grow_pgdat_span(struct pglis
if (start_pfn < pgdat->node_start_pfn)
pgdat->node_start_pfn = start_pfn;
- if (end_pfn > old_pgdat_end_pfn)
- pgdat->node_spanned_pages = end_pfn - pgdat->node_start_pfn;
+ pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
int online_pages(unsigned long pfn, unsigned long nr_pages)
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