[PATCH v1 14/18] mm/migrate_device: use folio_mapcount() in migrate_vma_check_page()

David Hildenbrand
2024-04-09T19:26:24Z

We want to limit the use of page_mapcount() to the places where it is
absolutely necessary. Let's convert migrate_vma_check_page() to work on
a folio internally so we can remove the page_mapcount() usage.

Note that we reject any large folios.

There is a lot more folio conversion to be had, but that has to wait for
another day. No functional change intended.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/migrate_device.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index d40b46ae9d65..b929b450b77c 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -324,6 +324,8 @@ static void migrate_vma_collect(struct migrate_vma *migrate)
*/
static bool migrate_vma_check_page(struct page *page, struct page *fault_page)
{
+ struct folio *folio = page_folio(page);
+
/*
* One extra ref because caller holds an extra reference, either from
* isolate_lru_page() for a regular page, or migrate_vma_collect() for
@@ -336,18 +338,18 @@ static bool migrate_vma_check_page(struct page *page, struct page *fault_page)
* check them than regular pages, because they can be mapped with a pmd
* or with a pte (split pte mapping).
*/
- if (PageCompound(page))
+ if (folio_test_large(folio))
return false;

/* Page from ZONE_DEVICE have one extra reference */
- if (is_zone_device_page(page))
+ if (folio_is_zone_device(folio))
extra++;

/* For file back page */
- if (page_mapping(page))
- extra += 1 + page_has_private(page);
+ if (folio_mapping(folio))
+ extra += 1 + folio_has_private(folio);

- if ((page_count(page) - extra) > page_mapcount(page))
+ if ((folio_ref_count(folio) - extra) > folio_mapcount(folio))
return false;

return true;
--
2.44.0