[PATCH v6 09/10] mm/memcg: fold lock in lock_page_lru

[Alex Shi]

According to the calling path of commit_charge, the lrucare is bound
with PageLRU, so we could just fold it under PageLRU. This has no
functional change.

Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: cgroups@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
 mm/memcontrol.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 138f298b694f..f8e279487e1d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2621,9 +2621,10 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
 
 static struct lruvec *lock_page_lru(struct page *page, int *isolated)
 {
-	struct lruvec *lruvec = lock_page_lruvec_irq(page);
+	struct lruvec *lruvec = NULL;
 
 	if (PageLRU(page)) {
+		lruvec = lock_page_lruvec_irq(page);
 
 		ClearPageLRU(page);
 		del_page_from_lru_list(page, lruvec, page_lru(page));
@@ -2637,17 +2638,18 @@ static struct lruvec *lock_page_lru(struct page *page, int *isolated)
 static void unlock_page_lru(struct page *page, int isolated,
 				struct lruvec *locked_lruvec)
 {
-	struct lruvec *lruvec;
+	if (isolated) {
+		struct lruvec *lruvec;
 
-	unlock_page_lruvec_irq(locked_lruvec);
-	lruvec = lock_page_lruvec_irq(page);
+		if (locked_lruvec)
+			unlock_page_lruvec_irq(locked_lruvec);
+		lruvec = lock_page_lruvec_irq(page);
 
-	if (isolated) {
 		VM_BUG_ON_PAGE(PageLRU(page), page);
 		SetPageLRU(page);
 		add_page_to_lru_list(page, lruvec, page_lru(page));
+		unlock_page_lruvec_irq(lruvec);
 	}
-	unlock_page_lruvec_irq(lruvec);
 }
 
 static void commit_charge(struct page *page, struct mem_cgroup *memcg,
-- 
1.8.3.1