[v2 PATCH 8/9] mm: memcontrol: reparent nr_deferred when memcg offline

[Yang Shi <shy828301@xxxxxxxxx>]

Now shrinker's nr_deferred is per memcg for memcg aware shrinkers, add to parent's
corresponding nr_deferred when memcg offline.

Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
---
 include/linux/shrinker.h |  4 ++++
 mm/memcontrol.c          | 24 ++++++++++++++++++++++++
 mm/vmscan.c              |  2 +-
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 1eac79ce57d4..85cfc910dde4 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -78,6 +78,10 @@ struct shrinker {
 };
 #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
 
+#ifdef CONFIG_MEMCG
+extern int shrinker_nr_max;
+#endif
+
 /* Flags */
 #define SHRINKER_REGISTERED	(1 << 0)
 #define SHRINKER_NUMA_AWARE	(1 << 1)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 321d1818ce3d..1f191a15bee1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -59,6 +59,7 @@
 #include <linux/tracehook.h>
 #include <linux/psi.h>
 #include <linux/seq_buf.h>
+#include <linux/shrinker.h>
 #include "internal.h"
 #include <net/sock.h>
 #include <net/ip.h>
@@ -612,6 +613,28 @@ void memcg_set_shrinker_bit(struct mem_cgroup *memcg, int nid, int shrinker_id)
 	}
 }
 
+static void memcg_reparent_shrinker_deferred(struct mem_cgroup *memcg)
+{
+	int i, nid;
+	long nr;
+	struct mem_cgroup *parent;
+	struct memcg_shrinker_deferred *child_deferred, *parent_deferred;
+
+	parent = parent_mem_cgroup(memcg);
+	if (!parent)
+		parent = root_mem_cgroup;
+
+	for_each_node(nid) {
+		child_deferred = memcg->nodeinfo[nid]->shrinker_deferred;
+		parent_deferred = parent->nodeinfo[nid]->shrinker_deferred;
+		for (i = 0; i < shrinker_nr_max; i ++) {
+			nr = atomic_long_read(&child_deferred->nr_deferred[i]);
+			atomic_long_add(nr,
+				&parent_deferred->nr_deferred[i]);
+		}
+	}
+}
+
 /**
  * mem_cgroup_css_from_page - css of the memcg associated with a page
  * @page: page of interest
@@ -5543,6 +5566,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
 	page_counter_set_low(&memcg->memory, 0);
 
 	memcg_offline_kmem(memcg);
+	memcg_reparent_shrinker_deferred(memcg);
 	wb_memcg_offline(memcg);
 
 	drain_all_stock(memcg);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8d5bfd818acd..693a41e89969 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -201,7 +201,7 @@ DECLARE_RWSEM(shrinker_rwsem);
 #define SHRINKER_REGISTERING ((struct shrinker *)~0UL)
 
 static DEFINE_IDR(shrinker_idr);
-static int shrinker_nr_max;
+int shrinker_nr_max;
 
 static inline bool is_deferred_memcg_aware(struct shrinker *shrinker)
 {
-- 
2.26.2