memory hotplug: fix updating of num_physpages for hot plugged memory
Jan Beulich [Tue, 22 Sep 2009 00:03:03 +0000 (17:03 -0700)]
Sizing of memory allocations shouldn't depend on the number of physical
pages found in a system, as that generally includes (perhaps a huge amount
of) non-RAM pages.  The amount of what actually is usable as storage
should instead be used as a basis here.

In line with that, the memory hotplug code should update num_physpages in
a way that it retains its original (post-boot) meaning; in particular,
decreasing the value should at best be done with great care - this patch
doesn't try to ever decrease this value at all as it doesn't really seem
meaningful to do so.

Signed-off-by: Jan Beulich <>
Acked-by: Rusty Russell <>
Cc: Yasunori Goto <>
Cc: Badari Pulavarty <>
Cc: Minchan Kim <>
Cc: Mel Gorman <>
Cc: Dave Hansen <>
Cc: KAMEZAWA Hiroyuki <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Linus Torvalds <>


index 616236e..efe3e0e 100644 (file)
@@ -339,8 +339,11 @@ EXPORT_SYMBOL_GPL(__remove_pages);
 void online_page(struct page *page)
+       unsigned long pfn = page_to_pfn(page);
-       num_physpages++;
+       if (pfn >= num_physpages)
+               num_physpages = pfn + 1;
        if (PageHighMem(page))
@@ -832,7 +835,6 @@ repeat:
        zone->present_pages -= offlined_pages;
        zone->zone_pgdat->node_present_pages -= offlined_pages;
        totalram_pages -= offlined_pages;
-       num_physpages -= offlined_pages;