linux-kernel - [PATCH] mm: fix invalid node in alloc_migrate

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Date:	Fri, 25 Mar 2016 14:56:04 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Joonsoo Kim <js1304@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"Laura Abbott" <lauraa@...eaurora.org>, <zhuhui@...omi.com>,
	<wangxq10@....edu.cn>
CC:	Xishi Qiu <qiuxishi@...wei.com>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] mm: fix invalid node in alloc_migrate_target()

It is incorrect to use next_node to find a target node, it will
return MAX_NUMNODES or invalid node. This will lead to crash in
buddy system allocation.

Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
---
 mm/page_isolation.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 92c4c36..31555b6 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -289,11 +289,11 @@ struct page *alloc_migrate_target(struct page *page, unsigned long private,
 	 * now as a simple work-around, we use the next node for destination.
 	 */
 	if (PageHuge(page)) {
-		nodemask_t src = nodemask_of_node(page_to_nid(page));
-		nodemask_t dst;
-		nodes_complement(dst, src);
+		int node = next_online_node(page_to_nid(page));
+		if (node == MAX_NUMNODES)
+			node = first_online_node;
 		return alloc_huge_page_node(page_hstate(compound_head(page)),
-					    next_node(page_to_nid(page), dst));
+					    node);
 	}
 
 	if (PageHighMem(page))
-- 
1.8.3.1