memory hotplug: fix updating of num_physpages for hot plugged memory

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

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 616236e6343f87d1beb7ac90598a93c087c04e40..efe3e0ec2e614c4a8f132ea8669fb63e274e5140 100644 (file)
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -339,8 +339,11 @@ EXPORT_SYMBOL_GPL(__remove_pages);
 
 void online_page(struct page *page)
 {
+       unsigned long pfn = page_to_pfn(page);
+
        totalram_pages++;
-       num_physpages++;
+       if (pfn >= num_physpages)
+               num_physpages = pfn + 1;
 
 #ifdef CONFIG_HIGHMEM
        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;
 
        setup_per_zone_wmarks();
        calculate_zone_inactive_ratio(zone);