[PATCH] memory hotplug: fix page_zone() calculation in test_pages_isolated()

Gerald Schaefer
2008-10-29T14:25:38Z

My last bugfix here (adding zone->lock) introduced a new problem: Using
page_zone(pfn_to_page(pfn)) to get the zone after the for() loop is wrong.
pfn will then be >= end_pfn, which may be in a different zone or not
present at all. This may lead to an addressing exception in page_zone()
or spin_lock_irqsave().

Now I use __first_valid_page() again after the loop to find a valid page
for page_zone().

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>

---
mm/page_isolation.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

Index: linux-2.6/mm/page_isolation.c
===================================================================
--- linux-2.6.orig/mm/page_isolation.c
+++ linux-2.6/mm/page_isolation.c
@@ -130,10 +130,11 @@ int test_pages_isolated(unsigned long st
if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
break;
}
- if (pfn < end_pfn)
+ page = __first_valid_page(start_pfn, end_pfn - start_pfn);
+ if ((pfn < end_pfn) || !page)
return -EBUSY;
/* Check all pages are free or Marked as ISOLATED */
- zone = page_zone(pfn_to_page(pfn));
+ zone = page_zone(page);
spin_lock_irqsave(&zone->lock, flags);
ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn);
spin_unlock_irqrestore(&zone->lock, flags);