linux-kernel - [PATCH] mm: page_alloc: Make paranoid check in move_freepages a VM_BUG

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Date:	Tue, 9 Sep 2014 15:52:28 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...uxfoundation.org>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] 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 <mgorman@...e.de>
---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0a7ed33..6fbd814 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -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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