[PATCH 3/4] mm, memcg: reset memcg's memory.{min, low} for reclaiming itself

[Yafang Shao <laoar.shao@gmail.com>]

memory.{emin, elow} are set in mem_cgroup_protected(), and the values of
them won't be changed until next recalculation in this function. After
either or both of them are set, the next reclaimer to relcaim this memcg
may be a different reclaimer, e.g. this memcg is also the root memcg of
the new reclaimer, and then in mem_cgroup_protection() in get_scan_count()
the old values of them will be used to calculate scan count, that is not
proper. We should reset them to zero in this case.

Cc: Chris Down <chris@chrisdown.name>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 mm/memcontrol.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f35fcca..234370c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6287,8 +6287,17 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
 
 	if (!root)
 		root = root_mem_cgroup;
-	if (memcg == root)
+	if (memcg == root) {
+		/*
+		 * Reset memory.(emin, elow) for reclaiming the memcg
+		 * itself.
+		 */
+		if (memcg != root_mem_cgroup) {
+			memcg->memory.emin = 0;
+			memcg->memory.emin = 0;
+		}
 		return MEMCG_PROT_NONE;
+	}
 
 	usage = page_counter_read(&memcg->memory);
 	if (!usage)
-- 
1.8.3.1