mm/vmscan: introduce helper function reclaim_page_list()

Introduce helper function reclaim_page_list() to eliminate the duplicated
code of doing shrink_page_list() and putback_lru_page.  Also we can
separate node reclaim from node page list operation this way.  No
functional change intended.

Link: https://lkml.kernel.org/r/20220425111232.23182-3-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmscan.c

@@ -2536,14 +2536,12 @@ static void shrink_active_list(unsigned long nr_to_scan,
 			nr_deactivate, nr_rotated, sc->priority, file);
 }
 
-unsigned long reclaim_pages(struct list_head *page_list)
+static unsigned int reclaim_page_list(struct list_head *page_list,
+				      struct pglist_data *pgdat)
 {
-	int nid = NUMA_NO_NODE;
-	unsigned int nr_reclaimed = 0;
-	LIST_HEAD(node_page_list);
 	struct reclaim_stat dummy_stat;
-	struct page *page;
-	unsigned int noreclaim_flag;
+	unsigned int nr_reclaimed;
+	struct folio *folio;
 	struct scan_control sc = {
 		.gfp_mask = GFP_KERNEL,
 		.may_writepage = 1,
@@ -2552,6 +2550,24 @@ unsigned long reclaim_pages(struct list_head *page_list)
 		.no_demotion = 1,
 	};
 
+	nr_reclaimed = shrink_page_list(page_list, pgdat, &sc, &dummy_stat, false);
+	while (!list_empty(page_list)) {
+		folio = lru_to_folio(page_list);
+		list_del(&folio->lru);
+		folio_putback_lru(folio);
+	}
+
+	return nr_reclaimed;
+}
+
+unsigned long reclaim_pages(struct list_head *page_list)
+{
+	int nid = NUMA_NO_NODE;
+	unsigned int nr_reclaimed = 0;
+	LIST_HEAD(node_page_list);
+	struct page *page;
+	unsigned int noreclaim_flag;
+
 	noreclaim_flag = memalloc_noreclaim_save();
 
 	while (!list_empty(page_list)) {
@@ -2565,28 +2581,12 @@ unsigned long reclaim_pages(struct list_head *page_list)
 			continue;
 		}
 
-		nr_reclaimed += shrink_page_list(&node_page_list,
-						NODE_DATA(nid),
-						&sc, &dummy_stat, false);
-		while (!list_empty(&node_page_list)) {
-			page = lru_to_page(&node_page_list);
-			list_del(&page->lru);
-			putback_lru_page(page);
-		}
-
+		nr_reclaimed += reclaim_page_list(&node_page_list, NODE_DATA(nid));
 		nid = NUMA_NO_NODE;
 	}
 
-	if (!list_empty(&node_page_list)) {
-		nr_reclaimed += shrink_page_list(&node_page_list,
-						NODE_DATA(nid),
-						&sc, &dummy_stat, false);
-		while (!list_empty(&node_page_list)) {
-			page = lru_to_page(&node_page_list);
-			list_del(&page->lru);
-			putback_lru_page(page);
-		}
-	}
+	if (!list_empty(&node_page_list))
+		nr_reclaimed += reclaim_page_list(&node_page_list, NODE_DATA(nid));
 
 	memalloc_noreclaim_restore(noreclaim_flag);