[PATCH 05/11] memcg: add null check to page_cgroup_zoneinfo()

[KOSAKI Motohiro]

if CONFIG_CGROUP_MEM_RES_CTLR_SWAP=y, page_cgroup::mem_cgroup can be NULL.
Therefore null checking is better.

latter patch use this function.


Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
---
 mm/memcontrol.c |    3 +++
 1 file changed, 3 insertions(+)

Index: b/mm/memcontrol.c
===================================================================
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -231,6 +231,9 @@ page_cgroup_zoneinfo(struct page_cgroup 
 	int nid = page_cgroup_nid(pc);
 	int zid = page_cgroup_zid(pc);
 
+	if (!mem)
+		return NULL;
+
 	return mem_cgroup_zoneinfo(mem, nid, zid);
 }
 


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