[PATCH -v2 next 3/4] memcg: factor out the replace_stock_objcg function

[Chen Ridong <chenridong@huaweicloud.com>]

From: Chen Ridong <chenridong@huawei.com>

Factor out the 'replace_stock_objcg' function to make the code more
cohesive.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 mm/memcontrol.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 98f84a9fa228..b10e0a8f3375 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2691,6 +2691,20 @@ void __memcg_kmem_uncharge_page(struct page *page, int order)
 	obj_cgroup_put(objcg);
 }
 
+/* Replace the stock objcg with objcg, return the old objcg */
+static struct obj_cgroup *replace_stock_objcg(struct memcg_stock_pcp *stock,
+					     struct obj_cgroup *objcg)
+{
+	struct obj_cgroup *old = NULL;
+
+	old = drain_obj_stock(stock);
+	obj_cgroup_get(objcg);
+	stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes)
+			? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0;
+	WRITE_ONCE(stock->cached_objcg, objcg);
+	return old;
+}
+
 static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
 		     enum node_stat_item idx, int nr)
 {
@@ -2708,11 +2722,7 @@ static void mod_objcg_state(struct obj_cgroup *objcg, struct pglist_data *pgdat,
 	 * changes.
 	 */
 	if (READ_ONCE(stock->cached_objcg) != objcg) {
-		old = drain_obj_stock(stock);
-		obj_cgroup_get(objcg);
-		stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes)
-				? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0;
-		WRITE_ONCE(stock->cached_objcg, objcg);
+		old = replace_stock_objcg(stock, objcg);
 		stock->cached_pgdat = pgdat;
 	} else if (stock->cached_pgdat != pgdat) {
 		/* Flush the existing cached vmstat data */
@@ -2866,11 +2876,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
 
 	stock = this_cpu_ptr(&memcg_stock);
 	if (READ_ONCE(stock->cached_objcg) != objcg) { /* reset if necessary */
-		old = drain_obj_stock(stock);
-		obj_cgroup_get(objcg);
-		WRITE_ONCE(stock->cached_objcg, objcg);
-		stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes)
-				? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0;
+		old = replace_stock_objcg(stock, objcg);
 		allow_uncharge = true;	/* Allow uncharge when objcg changes */
 	}
 	stock->nr_bytes += nr_bytes;
-- 
2.34.1