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Subject: [PATCH REBASED 3/4] mm: Remove pages_to_free argument of
 move_active_pages_to_lru()
From:   Kirill Tkhai <ktkhai@virtuozzo.com>
To:     akpm@linux-foundation.org, daniel.m.jordan@oracle.com,
        mhocko@suse.com, ktkhai@virtuozzo.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Date:   Mon, 18 Mar 2019 12:28:10 +0300
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We may use input argument list as output argument too.
This makes the function more similar to putback_inactive_pages().

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>

v2: Fix comment spelling.
---
 mm/vmscan.c |   19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index d2adabe4457d..1794ec7b21d8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2004,10 +2004,10 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 
 static unsigned move_active_pages_to_lru(struct lruvec *lruvec,
 				     struct list_head *list,
-				     struct list_head *pages_to_free,
 				     enum lru_list lru)
 {
 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
+	LIST_HEAD(pages_to_free);
 	struct page *page;
 	int nr_pages;
 	int nr_moved = 0;
@@ -2034,12 +2034,17 @@ static unsigned move_active_pages_to_lru(struct lruvec *lruvec,
 				(*get_compound_page_dtor(page))(page);
 				spin_lock_irq(&pgdat->lru_lock);
 			} else
-				list_add(&page->lru, pages_to_free);
+				list_add(&page->lru, &pages_to_free);
 		} else {
 			nr_moved += nr_pages;
 		}
 	}
 
+	/*
+	 * To save our caller's stack, now use input list for pages to free.
+	 */
+	list_splice(&pages_to_free, list);
+
 	return nr_moved;
 }
 
@@ -2129,8 +2134,10 @@ static void shrink_active_list(unsigned long nr_to_scan,
 	 */
 	reclaim_stat->recent_rotated[file] += nr_rotated;
 
-	nr_activate = move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru);
-	nr_deactivate = move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE);
+	nr_activate = move_active_pages_to_lru(lruvec, &l_active, lru);
+	nr_deactivate = move_active_pages_to_lru(lruvec, &l_inactive, lru - LRU_ACTIVE);
+	/* Keep all free pages in l_active list */
+	list_splice(&l_inactive, &l_active);
 
 	__count_vm_events(PGDEACTIVATE, nr_deactivate);
 	__count_memcg_events(lruvec_memcg(lruvec), PGDEACTIVATE, nr_deactivate);
@@ -2138,8 +2145,8 @@ static void shrink_active_list(unsigned long nr_to_scan,
 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
 	spin_unlock_irq(&pgdat->lru_lock);
 
-	mem_cgroup_uncharge_list(&l_hold);
-	free_unref_page_list(&l_hold);
+	mem_cgroup_uncharge_list(&l_active);
+	free_unref_page_list(&l_active);
 	trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate,
 			nr_deactivate, nr_rotated, sc->priority, file);
 }