[PATCH 2/5] memcg: Reduce nesting in consume_stock() and refill_stock().

[Kuniyuki Iwashima <kuniyu@google.com>]

A later patch adds more code to the most nested block in
consume_stock() and refill_stock().

Let's reduce the nesting to make the later change cleaner.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 mm/memcontrol.c | 59 ++++++++++++++++++++++++++-----------------------
 1 file changed, 31 insertions(+), 28 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c268a7864547..7c722a593cb5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2139,15 +2139,17 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 			continue;
 
 		stock_pages = stock->nr_pages[i];
-		if (stock_pages >= nr_pages) {
-			stock_pages -= nr_pages;
-			WRITE_ONCE(stock->nr_pages[i], stock_pages);
-			if (!stock_pages) {
-				css_put(&memcg->css);
-				WRITE_ONCE(stock->cached[i], NULL);
-			}
-			ret = true;
+		if (stock_pages < nr_pages)
+			break;
+
+		stock_pages -= nr_pages;
+		WRITE_ONCE(stock->nr_pages[i], stock_pages);
+		if (!stock_pages) {
+			css_put(&memcg->css);
+			WRITE_ONCE(stock->cached[i], NULL);
 		}
+
+		ret = true;
 		break;
 	}
 
@@ -2229,7 +2231,6 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 	struct memcg_stock_pcp *stock;
 	struct mem_cgroup *cached;
 	uint8_t stock_pages;
-	bool success = false;
 	int empty_slot = -1;
 	int i;
 
@@ -2257,29 +2258,31 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 		cached = stock->cached[i];
 		if (!cached && empty_slot == -1)
 			empty_slot = i;
-		if (memcg == stock->cached[i]) {
-			stock_pages = stock->nr_pages[i] + nr_pages;
-			WRITE_ONCE(stock->nr_pages[i], stock_pages);
-			if (stock_pages > MEMCG_CHARGE_BATCH)
-				drain_stock(stock, i);
-			success = true;
-			break;
-		}
-	}
 
-	if (!success) {
-		i = empty_slot;
-		if (i == -1) {
-			i = stock->drain_idx++;
-			if (stock->drain_idx == NR_MEMCG_STOCK)
-				stock->drain_idx = 0;
+		if (memcg != cached)
+			continue;
+
+		stock_pages = stock->nr_pages[i] + nr_pages;
+		WRITE_ONCE(stock->nr_pages[i], stock_pages);
+		if (stock_pages > MEMCG_CHARGE_BATCH)
 			drain_stock(stock, i);
-		}
-		css_get(&memcg->css);
-		WRITE_ONCE(stock->cached[i], memcg);
-		WRITE_ONCE(stock->nr_pages[i], nr_pages);
+
+		local_unlock(&memcg_stock.lock);
+		return;
 	}
 
+	i = empty_slot;
+	if (i == -1) {
+		i = stock->drain_idx++;
+		if (stock->drain_idx == NR_MEMCG_STOCK)
+			stock->drain_idx = 0;
+		drain_stock(stock, i);
+	}
+
+	css_get(&memcg->css);
+	WRITE_ONCE(stock->cached[i], memcg);
+	WRITE_ONCE(stock->nr_pages[i], nr_pages);
+
 	local_unlock(&memcg_stock.lock);
 }
 
-- 
2.56.0.212.g129ede20d9-goog