[RFC 07/16] mm/page_isolation: watch out zone range overlap

From: Joonsoo Kim
Date: Thu Feb 12 2015 - 02:33:36 EST

In the following patches, new zone, ZONE_CMA, will be introduced and
it would be overlapped with other zones. Currently, many places
iterating pfn range doesn't consider possibility of zone overlap and
this would cause a problem such as printing wrong statistics information.
To prevent this situation, this patch add some code to consider zone
overlapping before adding ZONE_CMA.

pfn range argument provieded to test_pages_isolated() should be in
a single zone. If not, zone lock doesn't work to protect free state of
buddy freepage.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
mm/page_isolation.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index c8778f7..883e78d 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -210,8 +210,8 @@ int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
* Returns 1 if all pages in the range are isolated.
static int
-__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
- bool skip_hwpoisoned_pages)
+__test_page_isolated_in_pageblock(struct zone *zone, unsigned long pfn,
+ unsigned long end_pfn, bool skip_hwpoisoned_pages)
struct page *page;

@@ -221,6 +221,9 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
page = pfn_to_page(pfn);
+ if (page_zone(page) != zone)
+ break;
if (PageBuddy(page)) {
* If race between isolatation and allocation happens,
@@ -281,7 +284,7 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
/* Check all pages are free or marked as ISOLATED */
zone = page_zone(page);
spin_lock_irqsave(&zone->lock, flags);
- ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
+ ret = __test_page_isolated_in_pageblock(zone, start_pfn, end_pfn,
spin_unlock_irqrestore(&zone->lock, flags);
return ret ? 0 : -EBUSY;

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