[PATCH 3/4] mm: migrate: add isolate_folio_to_list()

[Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>]

Add isolate_folio_to_list() helper to try to isolate HugeTLB,
no-LRU movable and LRU folios to a list, which will be reused by
do_migrate_range() from memory hotplug soon.

Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
 mm/internal.h       |  2 ++
 mm/memory-failure.c | 21 +--------------------
 mm/migrate.c        | 27 +++++++++++++++++++++++++++
 3 files changed, 30 insertions(+), 20 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index c5bd24c4fa3a..2484191c0764 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -403,6 +403,8 @@ extern unsigned long highest_memmap_pfn;
  */
 #define MAX_RECLAIM_RETRIES 16
 
+bool isolate_folio_to_list(struct folio *folio, struct list_head *list);
+
 /*
  * in mm/vmscan.c:
  */
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 99d92565cbb0..7e0f143bd51a 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2659,26 +2659,7 @@ EXPORT_SYMBOL(unpoison_memory);
 
 static bool mf_isolate_folio(struct folio *folio, struct list_head *pagelist)
 {
-	bool isolated = false;
-
-	if (folio_test_hugetlb(folio)) {
-		isolated = isolate_hugetlb(folio, pagelist);
-	} else {
-		bool lru = !__folio_test_movable(folio);
-
-		if (lru)
-			isolated = folio_isolate_lru(folio);
-		else
-			isolated = isolate_movable_page(&folio->page,
-							ISOLATE_UNEVICTABLE);
-
-		if (isolated) {
-			list_add(&folio->lru, pagelist);
-			if (lru)
-				node_stat_add_folio(folio, NR_ISOLATED_ANON +
-						    folio_is_file_lru(folio));
-		}
-	}
+	bool isolated = isolate_folio_to_list(folio, pagelist);
 
 	/*
 	 * If we succeed to isolate the folio, we grabbed another refcount on
diff --git a/mm/migrate.c b/mm/migrate.c
index e7296c0fb5d5..51cab1103502 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -177,6 +177,33 @@ void putback_movable_pages(struct list_head *l)
 	}
 }
 
+/* Must be called with an elevated refcount on the folio */
+bool isolate_folio_to_list(struct folio *folio, struct list_head *list)
+{
+	bool isolated = false;
+
+	if (folio_test_hugetlb(folio)) {
+		isolated = isolate_hugetlb(folio, list);
+	} else {
+		bool lru = !__folio_test_movable(folio);
+
+		if (lru)
+			isolated = folio_isolate_lru(folio);
+		else
+			isolated = isolate_movable_page(&folio->page,
+							ISOLATE_UNEVICTABLE);
+
+		if (isolated) {
+			list_add(&folio->lru, list);
+			if (lru)
+				node_stat_add_folio(folio, NR_ISOLATED_ANON +
+						    folio_is_file_lru(folio));
+		}
+	}
+
+	return isolated;
+}
+
 /*
  * Restore a potential migration pte to a working pte entry
  */
-- 
2.27.0