linux-kernel - [RFC PATCH v2 09/25] page_alloc: when dynamic numa is enabled, don't check that all pages in a block belong to the same zone

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Date:	Thu, 11 Apr 2013 18:13:41 -0700
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Mel Gorman <mgorman@...e.de>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>,
	Simon Jeons <simon.jeons@...il.com>
Subject: [RFC PATCH v2 09/25] page_alloc: when dynamic numa is enabled, don't check that all pages in a block belong to the same zone

When dynamic numa is enabled, the last or first page in a pageblock may
have been transplanted to a new zone (or may not yet be transplanted to
a new zone).

Disable a BUG_ON() which checks that the start_page and end_page are in
the same zone, if they are not in the proper zone they will simply be
skipped.

Signed-off-by: Cody P Schafer <cody@...ux.vnet.ibm.com>
---
 mm/page_alloc.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 75192eb..95e4a23 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -959,13 +959,16 @@ int move_freepages(struct zone *zone,
 	int pages_moved = 0;
 	int zone_nid = zone_to_nid(zone);
 
-#ifndef CONFIG_HOLES_IN_ZONE
+#if !defined(CONFIG_HOLES_IN_ZONE) && !defined(CONFIG_DYNAMIC_NUMA)
 	/*
-	 * page_zone is not safe to call in this context when
-	 * CONFIG_HOLES_IN_ZONE is set. This bug check is probably redundant
-	 * anyway as we check zone boundaries in move_freepages_block().
-	 * Remove at a later date when no bug reports exist related to
-	 * grouping pages by mobility
+	 * With CONFIG_HOLES_IN_ZONE set, this check is unsafe as start_page or
+	 * end_page may not be "valid".
+	 * With CONFIG_DYNAMIC_NUMA set, this condition is a valid occurence &
+	 * not a bug.
+	 *
+	 * This bug check is probably redundant anyway as we check zone
+	 * boundaries in move_freepages_block().  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));
 #endif
-- 
1.8.2.1

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