[PATCH 3.16 165/217] mm: fix invalid node in alloc_migrate_target()

[Ben Hutchings]

3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Xishi Qiu <qiuxishi@xxxxxxxxxx>

commit 6f25a14a7053b69917e2ebea0d31dd444cd31fd5 upstream.

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.

Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage")
Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Joonsoo Kim <js1304@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: "Laura Abbott" <lauraa@xxxxxxxxxxxxxx>
Cc: Hui Zhu <zhuhui@xxxxxxxxxx>
Cc: Wang Xiaoqiang <wangxq10@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 mm/page_isolation.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -259,11 +259,11 @@ struct page *alloc_migrate_target(struct
 	 * 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))