[PATCH mmotm] memcg: avoid reclaim_stat oops when disabled

[Hugh Dickins <hugh@veritas.com>]

mem_cgroup_get_reclaim_stat_from_page() oopses in page_cgroup_zoneinfo()
when you boot with cgroup_disabled=memory: it needs to check for that.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---
Follow memcg-add-zone_reclaim_stat-reclaim-stat-trivial-fixes.patch

 mm/memcontrol.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- mmotm/mm/memcontrol.c	2008-12-16 18:05:31.000000000 +0000
+++ fixed/mm/memcontrol.c	2008-12-16 19:30:02.000000000 +0000
@@ -496,9 +496,14 @@ struct zone_reclaim_stat *mem_cgroup_get
 struct zone_reclaim_stat *
 mem_cgroup_get_reclaim_stat_from_page(struct page *page)
 {
-	struct page_cgroup *pc = lookup_page_cgroup(page);
-	struct mem_cgroup_per_zone *mz = page_cgroup_zoneinfo(pc);
+	struct page_cgroup *pc;
+	struct mem_cgroup_per_zone *mz;
 
+	if (mem_cgroup_disabled())
+		return NULL;
+
+	pc = lookup_page_cgroup(page);
+	mz = page_cgroup_zoneinfo(pc);
 	if (!mz)
 		return NULL;
 

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