[PATCH RFC V2 1/9] mm/migrate: factor out code in move_to_new_folio() and migrate_folio_move()

[Shivank Garg <shivankg@amd.com>]

From: Zi Yan <ziy@nvidia.com>

No function change is intended. The factored out code will be reused in
an upcoming batched folio move function.

Signed-off-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
---
 mm/migrate.c | 101 +++++++++++++++++++++++++++++++++------------------
 1 file changed, 65 insertions(+), 36 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index fb19a18892c8..ce7ddc56e878 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1014,18 +1014,7 @@ static int fallback_migrate_folio(struct address_space *mapping,
 	return migrate_folio(mapping, dst, src, mode);
 }
 
-/*
- * Move a page to a newly allocated page
- * The page is locked and all ptes have been successfully removed.
- *
- * The new page will have replaced the old page if this function
- * is successful.
- *
- * Return value:
- *   < 0 - error code
- *  MIGRATEPAGE_SUCCESS - success
- */
-static int move_to_new_folio(struct folio *dst, struct folio *src,
+static int _move_to_new_folio_prep(struct folio *dst, struct folio *src,
 				enum migrate_mode mode)
 {
 	int rc = -EAGAIN;
@@ -1072,7 +1061,13 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 		WARN_ON_ONCE(rc == MIGRATEPAGE_SUCCESS &&
 				!folio_test_isolated(src));
 	}
+out:
+	return rc;
+}
 
+static void _move_to_new_folio_finalize(struct folio *dst, struct folio *src,
+				int rc)
+{
 	/*
 	 * When successful, old pagecache src->mapping must be cleared before
 	 * src is freed; but stats require that PageAnon be left as PageAnon.
@@ -1099,7 +1094,29 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,
 		if (likely(!folio_is_zone_device(dst)))
 			flush_dcache_folio(dst);
 	}
-out:
+}
+
+
+/*
+ * Move a page to a newly allocated page
+ * The page is locked and all ptes have been successfully removed.
+ *
+ * The new page will have replaced the old page if this function
+ * is successful.
+ *
+ * Return value:
+ *   < 0 - error code
+ *  MIGRATEPAGE_SUCCESS - success
+ */
+static int move_to_new_folio(struct folio *dst, struct folio *src,
+				enum migrate_mode mode)
+{
+	int rc;
+
+	rc = _move_to_new_folio_prep(dst, src, mode);
+
+	_move_to_new_folio_finalize(dst, src, rc);
+
 	return rc;
 }
 
@@ -1341,29 +1358,9 @@ static int migrate_folio_unmap(new_folio_t get_new_folio,
 	return rc;
 }
 
-/* Migrate the folio to the newly allocated folio in dst. */
-static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
-			      struct folio *src, struct folio *dst,
-			      enum migrate_mode mode, enum migrate_reason reason,
-			      struct list_head *ret)
+static void _migrate_folio_move_finalize1(struct folio *src, struct folio *dst,
+					  int old_page_state)
 {
-	int rc;
-	int old_page_state = 0;
-	struct anon_vma *anon_vma = NULL;
-	bool is_lru = !__folio_test_movable(src);
-	struct list_head *prev;
-
-	__migrate_folio_extract(dst, &old_page_state, &anon_vma);
-	prev = dst->lru.prev;
-	list_del(&dst->lru);
-
-	rc = move_to_new_folio(dst, src, mode);
-	if (rc)
-		goto out;
-
-	if (unlikely(!is_lru))
-		goto out_unlock_both;
-
 	/*
 	 * When successful, push dst to LRU immediately: so that if it
 	 * turns out to be an mlocked page, remove_migration_ptes() will
@@ -1379,8 +1376,12 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
 
 	if (old_page_state & PAGE_WAS_MAPPED)
 		remove_migration_ptes(src, dst, 0);
+}
 
-out_unlock_both:
+static void _migrate_folio_move_finalize2(struct folio *src, struct folio *dst,
+					  enum migrate_reason reason,
+					  struct anon_vma *anon_vma)
+{
 	folio_unlock(dst);
 	set_page_owner_migrate_reason(&dst->page, reason);
 	/*
@@ -1400,6 +1401,34 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
 		put_anon_vma(anon_vma);
 	folio_unlock(src);
 	migrate_folio_done(src, reason);
+}
+
+/* Migrate the folio to the newly allocated folio in dst. */
+static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
+			      struct folio *src, struct folio *dst,
+			      enum migrate_mode mode, enum migrate_reason reason,
+			      struct list_head *ret)
+{
+	int rc;
+	int old_page_state = 0;
+	struct anon_vma *anon_vma = NULL;
+	bool is_lru = !__folio_test_movable(src);
+	struct list_head *prev;
+
+	__migrate_folio_extract(dst, &old_page_state, &anon_vma);
+	prev = dst->lru.prev;
+	list_del(&dst->lru);
+
+	rc = move_to_new_folio(dst, src, mode);
+	if (rc)
+		goto out;
+
+	if (unlikely(!is_lru))
+		goto out_unlock_both;
+
+	_migrate_folio_move_finalize1(src, dst, old_page_state);
+out_unlock_both:
+	_migrate_folio_move_finalize2(src, dst, reason, anon_vma);
 
 	return rc;
 out:
-- 
2.34.1