less free pages for migration targets so it could avoid memory reclaiming
to get free pages, which is another factor increase latency.

Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Michal Nazarewicz <redacted>
Cc: Rik van Riel <redacted>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
 mm/internal.h   |    2 ++
 mm/page_alloc.c |    2 ++
 mm/vmscan.c     |   42 ++++++++++++++++++++++++++++++++++++------
 3 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 3314f79..be09a7e 100644
--- a/mm/internal.h
+++ b/mm/internal.h

@@ -355,3 +355,5 @@ extern unsigned long vm_mmap_pgoff(struct file *, unsigned long,
         unsigned long, unsigned long);
 
 extern void set_pageblock_order(void);
+unsigned long reclaim_clean_pages_from_list(struct zone *zone,
+				struct list_head *page_list);

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ba3100a..bf35e59 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c

@@ -5668,6 +5668,8 @@ static int __alloc_contig_migrate_range(unsigned long start, unsigned long end)
 			break;
 		}
 
+		reclaim_clean_pages_from_list(&cc.migratepages, cc.zone);
+

 		ret = migrate_pages(&cc.migratepages,
 				    __alloc_contig_migrate_alloc,
 				    0, false, MIGRATE_SYNC);

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8d01243..525355e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c

@@ -674,8 +674,10 @@ static enum page_references page_check_references(struct page *page,
 static unsigned long shrink_page_list(struct list_head *page_list,
 				      struct zone *zone,
 				      struct scan_control *sc,
+				      enum ttu_flags ttu_flags,
 				      unsigned long *ret_nr_dirty,
-				      unsigned long *ret_nr_writeback)
+				      unsigned long *ret_nr_writeback,
+				      bool force_reclaim)
 {
 	LIST_HEAD(ret_pages);
 	LIST_HEAD(free_pages);

@@ -689,10 +691,10 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 
 	mem_cgroup_uncharge_start();
 	while (!list_empty(page_list)) {
-		enum page_references references;
 		struct address_space *mapping;
 		struct page *page;
 		int may_enter_fs;
+		enum page_references references = PAGEREF_RECLAIM;
 
 		cond_resched();
 

@@ -758,7 +760,9 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 			wait_on_page_writeback(page);
 		}
 
-		references = page_check_references(page, sc);
+		if (!force_reclaim)
+			references = page_check_references(page, sc);
+
 		switch (references) {
 		case PAGEREF_ACTIVATE:
 			goto activate_locked;

@@ -788,7 +792,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 		 * processes. Try to unmap it here.
 		 */
 		if (page_mapped(page) && mapping) {
-			switch (try_to_unmap(page, TTU_UNMAP)) {
+			switch (try_to_unmap(page, ttu_flags)) {
 			case SWAP_FAIL:
 				goto activate_locked;
 			case SWAP_AGAIN:

@@ -960,6 +964,32 @@ keep:
 	return nr_reclaimed;
 }
 
+unsigned long reclaim_clean_pages_from_list(struct zone *zone,
+					struct list_head *page_list)
+{
+	struct scan_control sc = {
+		.gfp_mask = GFP_KERNEL,
+		.priority = DEF_PRIORITY,
+		.may_unmap = 1,
+	};

+			list_move(&page->lru, &clean_pages);
+		}
+	}
+
+	ret = shrink_page_list(&clean_pages, zone, &sc,
+				TTU_UNMAP|TTU_IGNORE_ACCESS,
+				&dummy1, &dummy2, true);
+	list_splice(&clean_pages, page_list);
+	return ret;
+}
+
 /*
  * Attempt to remove the specified page from its LRU.  Only take this page
  * if it is of the appropriate PageActive status.  Pages which are being

@@ -1278,8 +1308,8 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 	if (nr_taken == 0)
 		return 0;
 
-	nr_reclaimed = shrink_page_list(&page_list, zone, sc,
-						&nr_dirty, &nr_writeback);
+	nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP,
+					&nr_dirty, &nr_writeback, false);
 
 	spin_lock_irq(&zone->lru_lock);