[PATCH] memcg: Free spare array to avoid memory leak

[Sha Zhengju <handai.szj@gmail.com>]

From: Sha Zhengju <handai.szj@taobao.com>

When the last event is unregistered, there is no need to keep the spare
array anymore. So free it to avoid memory leak.

Signed-off-by: Sha Zhengju <handai.szj@taobao.com>

---
 mm/memcontrol.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 22d94f5..3c09a84 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4412,6 +4412,12 @@ static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp,
 swap_buffers:
 	/* Swap primary and spare array */
 	thresholds->spare = thresholds->primary;
+	/* If all events are unregistered, free the spare array */
+	if (!new) {
+		kfree(thresholds->spare);
+		thresholds->spare = NULL;
+	}
+
 	rcu_assign_pointer(thresholds->primary, new);
 
 	/* To be sure that nobody uses thresholds */
-- 
1.7.4.1

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