We have to move lru_lock into lru_note_cost, since it cycle up on memcg
tree, for future per lruvec lru_lock replace. It's a bit ugly and may
cost a bit more locking, but benefit from multiple memcg locking could
cover the lost.

Signed-off-by: Alex Shi <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
 mm/swap.c   | 5 +++--
 mm/vmscan.c | 4 +---
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/mm/swap.c b/mm/swap.c
index 906255db6006..f80ccd6f3cb4 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -269,7 +269,9 @@ void lru_note_cost(struct lruvec *lruvec, bool file, 
unsigned int nr_pages)
 {
        do {
                unsigned long lrusize;
+               struct pglist_data *pgdat = lruvec_pgdat(lruvec);
 
+               spin_lock_irq(&pgdat->lru_lock);
                /* Record cost event */
                if (file)
                        lruvec->file_cost += nr_pages;
@@ -293,15 +295,14 @@ void lru_note_cost(struct lruvec *lruvec, bool file, 
unsigned int nr_pages)
                        lruvec->file_cost /= 2;
                        lruvec->anon_cost /= 2;
                }
+               spin_unlock_irq(&pgdat->lru_lock);
        } while ((lruvec = parent_lruvec(lruvec)));
 }
 
 void lru_note_cost_page(struct page *page)
 {
-       spin_lock_irq(&page_pgdat(page)->lru_lock);
        lru_note_cost(mem_cgroup_page_lruvec(page, page_pgdat(page)),
                      page_is_file_lru(page), thp_nr_pages(page));
-       spin_unlock_irq(&page_pgdat(page)->lru_lock);
 }
 
 static void __activate_page(struct page *page, struct lruvec *lruvec)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index ffccb94defaf..7b7b36bd1448 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1971,19 +1971,17 @@ static int current_may_throttle(void)
                                &stat, false);
 
        spin_lock_irq(&pgdat->lru_lock);
-
        move_pages_to_lru(lruvec, &page_list);
 
        __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
-       lru_note_cost(lruvec, file, stat.nr_pageout);
        item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT;
        if (!cgroup_reclaim(sc))
                __count_vm_events(item, nr_reclaimed);
        __count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
        __count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
-
        spin_unlock_irq(&pgdat->lru_lock);
 
+       lru_note_cost(lruvec, file, stat.nr_pageout);
        mem_cgroup_uncharge_list(&page_list);
        free_unref_page_list(&page_list);
 
-- 
1.8.3.1

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