[PATCH] slab: initialize unused alien cache entry as NULL at alloc_alien_cache().

[Haicheng Li]

Memory hotplug would online new node in runtime, then reap timer will add this new node as 
a reap node. In such case, for each existing kmem_list, we need to ensure that the alien 
cache entry corresponding to this new added node is NULL. Otherwise, it might cause BUG 
when reap_alien() affecting the new added node.

Signed-off-by: Haicheng Li <haicheng.li@xxxxxxxxxxxxxxx>
---
 mm/slab.c |    7 +++----
 1 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 7dfa481..a9486a0 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -966,18 +966,17 @@ static void *alternate_node_alloc(struct kmem_cache *, gfp_t);
 static struct array_cache **alloc_alien_cache(int node, int limit, gfp_t gfp)
 {
 	struct array_cache **ac_ptr;
-	int memsize = sizeof(void *) * nr_node_ids;
+	int memsize = sizeof(void *) * MAX_NUMNODES;
 	int i;

 	if (limit > 1)
 		limit = 12;
 	ac_ptr = kmalloc_node(memsize, gfp, node);
 	if (ac_ptr) {
+		memset(ac_ptr, 0, memsize);
 		for_each_node(i) {
-			if (i == node || !node_online(i)) {
-				ac_ptr[i] = NULL;
+			if (i == node || !node_online(i))
 				continue;
-			}
 			ac_ptr[i] = alloc_arraycache(node, limit, 0xbaadf00d, gfp);
 			if (!ac_ptr[i]) {
 				for (i--; i >= 0; i--)
--
1.6.0.rc1
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