[PATCH RFC 18/29] mm: remove __folio_test_movable()

[David Hildenbrand]

Convert to page_has_movable_ops(). While at it, cleanup relevant code
a bit.

The data_race() in migrate_folio_unmap() is questionable: we already
hold a page reference, and concurrent modifications can no longer
happen (iow: __ClearPageMovable() no longer exists). Drop it for now,
we'll rework page_has_movable_ops() soon either way to no longer
rely on page->mapping.

Wherever we cast from folio to page now is a clear sign that this
code has to be decoupled.

Signed-off-by: David Hildenbrand <david at redhat.com>
---
 include/linux/page-flags.h |  6 ------
 mm/migrate.c               | 43 ++++++++++++--------------------------
 mm/vmscan.c                |  6 ++++--
 3 files changed, 17 insertions(+), 38 deletions(-)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index c67163b73c5ec..4c27ebb689e3c 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -744,12 +744,6 @@ static __always_inline bool PageAnon(const struct page *page)
 	return folio_test_anon(page_folio(page));
 }
 
-static __always_inline bool __folio_test_movable(const struct folio *folio)
-{
-	return ((unsigned long)folio->mapping & PAGE_MAPPING_FLAGS) ==
-			PAGE_MAPPING_MOVABLE;
-}
-
 static __always_inline bool page_has_movable_ops(const struct page *page)
 {
 	return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
diff --git a/mm/migrate.c b/mm/migrate.c
index 5f97369eac2f9..37e722fbfee70 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -219,12 +219,7 @@ void putback_movable_pages(struct list_head *l)
 			continue;
 		}
 		list_del(&folio->lru);
-		/*
-		 * We isolated non-lru movable folio so here we can use
-		 * __folio_test_movable because LRU folio's mapping cannot
-		 * have PAGE_MAPPING_MOVABLE.
-		 */
-		if (unlikely(__folio_test_movable(folio))) {
+		if (unlikely(page_has_movable_ops(&folio->page))) {
 			putback_movable_ops_page(&folio->page);
 		} else {
 			node_stat_mod_folio(folio, NR_ISOLATED_ANON +
@@ -237,26 +232,20 @@ void putback_movable_pages(struct list_head *l)
 /* Must be called with an elevated refcount on the non-hugetlb folio */
 bool isolate_folio_to_list(struct folio *folio, struct list_head *list)
 {
-	bool isolated, lru;
-
 	if (folio_test_hugetlb(folio))
 		return folio_isolate_hugetlb(folio, list);
 
-	lru = !__folio_test_movable(folio);
-	if (lru)
-		isolated = folio_isolate_lru(folio);
-	else
-		isolated = isolate_movable_ops_page(&folio->page,
-						    ISOLATE_UNEVICTABLE);
-
-	if (!isolated)
-		return false;
-
-	list_add(&folio->lru, list);
-	if (lru)
+	if (page_has_movable_ops(&folio->page)) {
+		if (!isolate_movable_ops_page(&folio->page,
+					      ISOLATE_UNEVICTABLE))
+			return false;
+	} else {
+		if (!folio_isolate_lru(folio))
+			return false;
 		node_stat_add_folio(folio, NR_ISOLATED_ANON +
 				    folio_is_file_lru(folio));
-
+	}
+	list_add(&folio->lru, list);
 	return true;
 }
 
@@ -1140,12 +1129,7 @@ static void migrate_folio_undo_dst(struct folio *dst, bool locked,
 static void migrate_folio_done(struct folio *src,
 			       enum migrate_reason reason)
 {
-	/*
-	 * Compaction can migrate also non-LRU pages which are
-	 * not accounted to NR_ISOLATED_*. They can be recognized
-	 * as __folio_test_movable
-	 */
-	if (likely(!__folio_test_movable(src)) && reason != MR_DEMOTION)
+	if (likely(!page_has_movable_ops(&src->page)) && reason != MR_DEMOTION)
 		mod_node_page_state(folio_pgdat(src), NR_ISOLATED_ANON +
 				    folio_is_file_lru(src), -folio_nr_pages(src));
 
@@ -1164,7 +1148,6 @@ static int migrate_folio_unmap(new_folio_t get_new_folio,
 	int rc = -EAGAIN;
 	int old_page_state = 0;
 	struct anon_vma *anon_vma = NULL;
-	bool is_lru = data_race(!__folio_test_movable(src));
 	bool locked = false;
 	bool dst_locked = false;
 
@@ -1265,7 +1248,7 @@ static int migrate_folio_unmap(new_folio_t get_new_folio,
 		goto out;
 	dst_locked = true;
 
-	if (unlikely(!is_lru)) {
+	if (unlikely(page_has_movable_ops(&dst->page))) {
 		__migrate_folio_record(dst, old_page_state, anon_vma);
 		return MIGRATEPAGE_UNMAP;
 	}
@@ -1330,7 +1313,7 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
 	prev = dst->lru.prev;
 	list_del(&dst->lru);
 
-	if (unlikely(__folio_test_movable(src))) {
+	if (unlikely(page_has_movable_ops(&src->page))) {
 		rc = migrate_movable_ops_page(&dst->page, &src->page, mode);
 		goto out_unlock_both;
 	}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index efc818a0bbecb..e5d04c98af976 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1651,9 +1651,11 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
 	unsigned int noreclaim_flag;
 
 	list_for_each_entry_safe(folio, next, folio_list, lru) {
+		/* TODO: these pages should not even appear in this list. */
+		if (page_has_movable_ops(&folio->page))
+			continue;
 		if (!folio_test_hugetlb(folio) && folio_is_file_lru(folio) &&
-		    !folio_test_dirty(folio) && !__folio_test_movable(folio) &&
-		    !folio_test_unevictable(folio)) {
+		    !folio_test_dirty(folio) && !folio_test_unevictable(folio)) {
 			folio_clear_active(folio);
 			list_move(&folio->lru, &clean_folios);
 		}
-- 
2.49.0