[PATCH v1 11/29] mm/migrate: move movable_ops page handling out of move_to_new_folio()

David Hildenbrand
2025-06-30T13:00:52Z

Let's move that handling directly into migrate_folio_move(), so we can
simplify move_to_new_folio(). While at it, fixup the documentation a
bit.

Note that unmap_and_move_huge_page() does not care, because it only
deals with actual folios. (we only support migration of
individual movable_ops pages)

Reviewed-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/migrate.c | 63 +++++++++++++++++++++++++---------------------------
1 file changed, 30 insertions(+), 33 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 0898ddd2f661f..22c115710d0e2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1024,11 +1024,12 @@ static int fallback_migrate_folio(struct address_space *mapping,
}

/*
- * Move a page to a newly allocated page
- * The page is locked and all ptes have been successfully removed.
+ * Move a src folio to a newly allocated dst folio.
*
- * The new page will have replaced the old page if this function
- * is successful.
+ * The src and dst folios are locked and the src folios was unmapped from
+ * the page tables.
+ *
+ * On success, the src folio was replaced by the dst folio.
*
* Return value:
* < 0 - error code
@@ -1037,34 +1038,30 @@ static int fallback_migrate_folio(struct address_space *mapping,
static int move_to_new_folio(struct folio *dst, struct folio *src,
enum migrate_mode mode)
{
+ struct address_space *mapping = folio_mapping(src);
int rc = -EAGAIN;
- bool is_lru = !__folio_test_movable(src);

VM_BUG_ON_FOLIO(!folio_test_locked(src), src);
VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst);

- if (likely(is_lru)) {
- struct address_space *mapping = folio_mapping(src);
-
- if (!mapping)
- rc = migrate_folio(mapping, dst, src, mode);
- else if (mapping_inaccessible(mapping))
- rc = -EOPNOTSUPP;
- else if (mapping->a_ops->migrate_folio)
- /*
- * Most folios have a mapping and most filesystems
- * provide a migrate_folio callback. Anonymous folios
- * are part of swap space which also has its own
- * migrate_folio callback. This is the most common path
- * for page migration.
- */
- rc = mapping->a_ops->migrate_folio(mapping, dst, src,
- mode);
- else
- rc = fallback_migrate_folio(mapping, dst, src, mode);
+ if (!mapping)
+ rc = migrate_folio(mapping, dst, src, mode);
+ else if (mapping_inaccessible(mapping))
+ rc = -EOPNOTSUPP;
+ else if (mapping->a_ops->migrate_folio)
+ /*
+ * Most folios have a mapping and most filesystems
+ * provide a migrate_folio callback. Anonymous folios
+ * are part of swap space which also has its own
+ * migrate_folio callback. This is the most common path
+ * for page migration.
+ */
+ rc = mapping->a_ops->migrate_folio(mapping, dst, src,
+ mode);
+ else
+ rc = fallback_migrate_folio(mapping, dst, src, mode);

- if (rc != MIGRATEPAGE_SUCCESS)
- goto out;
+ if (rc == MIGRATEPAGE_SUCCESS) {
/*
* For pagecache folios, src->mapping must be cleared before src
* is freed. Anonymous folios must stay anonymous until freed.
@@ -1074,10 +1071,7 @@ static int move_to_new_folio(struct folio *dst, struct folio *src,

if (likely(!folio_is_zone_device(dst)))
flush_dcache_folio(dst);
- } else {
- rc = migrate_movable_ops_page(&dst->page, &src->page, mode);
}
-out:
return rc;
}

@@ -1328,20 +1322,23 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private,
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);

+ if (unlikely(__folio_test_movable(src))) {
+ rc = migrate_movable_ops_page(&dst->page, &src->page, mode);
+ if (rc)
+ goto out;
+ goto out_unlock_both;
+ }
+
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
--
2.49.0