mm: page_alloc: Make paranoid check in move_freepages a VM_BUG_ON

PATCH In review Mel Gorman 4 participants 4 messages Sep 9, 2014 – Sep 17, 2014

Subsystems (2)

Memory management Page allocator

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Mel Gorman

author

2014-09-09 14:52 UTC #0 lore raw

PATCH 1/1 mm: page_alloc: Make paranoid check in move_freepages a VM_BUG_ON

Since 2.6.24 there has been a paranoid check in move_freepages that looks up the zone of two pages. This is a very slow path and the only time I've seen this bug trigger recently is when memory initialisation was broken during patch development. Despite the fact it's a slow path, this patch converts the check to a VM_BUG_ON anyway as it is served its purpose by now.

Signed-off-by Mel Gorman <[email protected]>

---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

mm/page_alloc.c +1 -1

index 0a7ed33..6fbd814 100644
@@ -1014,7 +1014,7 @@ int move_freepages(struct zone *zone,
 	 * Remove at a later date when no bug reports exist related to
 	 * grouping pages by mobility
 	 */
-	BUG_ON(page_zone(start_page) != page_zone(end_page));
+	VM_BUG_ON(page_zone(start_page) != page_zone(end_page));
 #endif
 
 	for (page = start_page; page <= end_page;) {

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David Rientjes

Acked-by on v1 1/1

2014-09-10 19:02 UTC #1 lore raw

Quoted 7 lines · Mel Gorman

Since 2.6.24 there has been a paranoid check in move_freepages that looks up the zone of two pages. This is a very slow path and the only time I've seen this bug trigger recently is when memory initialisation was broken during patch development. Despite the fact it's a slow path, this patch converts the check to a VM_BUG_ON anyway as it is served its purpose by now.
Signed-off-by Mel Gorman <[email protected]>

Acked-by David Rientjes <[email protected]>

Rik van Riel

Acked-by on v1 1/1

2014-09-10 20:34 UTC #2 lore raw

In reply to Mel Gorman

Quoted 7 lines · Mel Gorman

Since 2.6.24 there has been a paranoid check in move_freepages that looks up the zone of two pages. This is a very slow path and the only time I've seen this bug trigger recently is when memory initialisation was broken during patch development. Despite the fact it's a slow path, this patch converts the check to a VM_BUG_ON anyway as it is served its purpose by now.
Signed-off-by Mel Gorman <[email protected]>

Acked-by Rik van Riel <[email protected]>

Johannes Weiner

reviewer Acked-by on v1 1/1

2014-09-17 18:31 UTC #3 lore raw

In reply to Mel Gorman

Quoted 7 lines · Mel Gorman

Since 2.6.24 there has been a paranoid check in move_freepages that looks up the zone of two pages. This is a very slow path and the only time I've seen this bug trigger recently is when memory initialisation was broken during patch development. Despite the fact it's a slow path, this patch converts the check to a VM_BUG_ON anyway as it is served its purpose by now.
Signed-off-by Mel Gorman <[email protected]>

Acked-by Johannes Weiner <[email protected]>