memory hotplug: fix page_zone() calculation in test_pages_isolated()

PATCH In review Gerald Schaefer 3 participants 3 messages Oct 29, 2008 – Oct 30, 2008

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Memory management Page allocator

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Gerald Schaefer

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2008-10-29 14:25 UTC #0 lore raw

PATCH 1/1 memory hotplug: fix page_zone() calculation in test_pages_isolated()

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 <[email protected]>

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

mm/page_isolation.c +3 -2

Index: 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);

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Nathan Fontenot

Acked-by on v1 1/1

2008-10-29 18:00 UTC #1 lore raw

Looks like you beat me to it, and with a nicer fix too.

Quoted 8 lines · Gerald Schaefer

From: Gerald Schaefer <[email protected]>
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().

Quoted 4 lines

Now I use __first_valid_page() again after the loop to find a valid page for page_zone().
Signed-off-by Gerald Schaefer <[email protected]>

Acked-by Nathan Fontenot <[email protected]>

KAMEZAWA Hiroyuki

Reviewed-by on v1 1/1

2008-10-30 00:10 UTC #2 lore raw

In reply to Gerald Schaefer

Quoted 8 lines · On Wed, 29 Oct 2008 15:25:30 +0100 Gerald Schaefer…

From: Gerald Schaefer <[email protected]>
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().

Quoted 5 lines

Now I use __first_valid_page() again after the loop to find a valid page for page_zone().
Signed-off-by Gerald Schaefer <[email protected]>

Thanks.

Reviewed-by KAMEZAWA Hiroyuki <[email protected]>

Quoted 14 lines

---
 mm/page_isolation.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
Index: linux-2.6/mm/page_isolation.c
===================================================================
mm/page_isolation.c +0 -0
@@ -130,10 +130,11 @@ int test_pages_isolated(unsigned long st
 		if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
 			break;
 	}

mm/page_isolation.c int test_pages_isolated(unsigned long st · line 140

Quoted 10 lines

mm/page_isolation.c +3 -2

-	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);