[PATCH v1 07/29] mm/migrate: rename isolate_movable_page() to isolate_movable_ops_page()

David Hildenbrand
2025-06-30T13:00:45Z

... and start moving back to per-page things that will absolutely not be
folio things in the future. Add documentation and a comment that the
remaining folio stuff (lock, refcount) will have to be reworked as well.

While at it, convert the VM_BUG_ON() into a WARN_ON_ONCE() and handle
it gracefully (relevant with further changes), and convert a
WARN_ON_ONCE() into a VM_WARN_ON_ONCE_PAGE().

Note that we will leave anything that needs a rework (lock, refcount,
->lru) to be using folios for now: that perfectly highlights the
problematic bits.

Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/migrate.h | 4 ++--
mm/compaction.c | 2 +-
mm/migrate.c | 39 +++++++++++++++++++++++++++++----------
3 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index aaa2114498d6d..c0ec7422837bd 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -69,7 +69,7 @@ int migrate_pages(struct list_head *l, new_folio_t new, free_folio_t free,
unsigned long private, enum migrate_mode mode, int reason,
unsigned int *ret_succeeded);
struct folio *alloc_migration_target(struct folio *src, unsigned long private);
-bool isolate_movable_page(struct page *page, isolate_mode_t mode);
+bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode);
bool isolate_folio_to_list(struct folio *folio, struct list_head *list);

int migrate_huge_page_move_mapping(struct address_space *mapping,
@@ -90,7 +90,7 @@ static inline int migrate_pages(struct list_head *l, new_folio_t new,
static inline struct folio *alloc_migration_target(struct folio *src,
unsigned long private)
{ return NULL; }
-static inline bool isolate_movable_page(struct page *page, isolate_mode_t mode)
+static inline bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode)
{ return false; }
static inline bool isolate_folio_to_list(struct folio *folio, struct list_head *list)
{ return false; }
diff --git a/mm/compaction.c b/mm/compaction.c
index 3925cb61dbb8f..17455c5a4be05 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1093,7 +1093,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
locked = NULL;
}

- if (isolate_movable_page(page, mode)) {
+ if (isolate_movable_ops_page(page, mode)) {
folio = page_folio(page);
goto isolate_success;
}
diff --git a/mm/migrate.c b/mm/migrate.c
index 767f503f08758..d4b4a7eefb6bd 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -51,8 +51,26 @@
#include "internal.h"
#include "swap.h"

-bool isolate_movable_page(struct page *page, isolate_mode_t mode)
+/**
+ * isolate_movable_ops_page - isolate a movable_ops page for migration
+ * @page: The page.
+ * @mode: The isolation mode.
+ *
+ * Try to isolate a movable_ops page for migration. Will fail if the page is
+ * not a movable_ops page, if the page is already isolated for migration
+ * or if the page was just was released by its owner.
+ *
+ * Once isolated, the page cannot get freed until it is either putback
+ * or migrated.
+ *
+ * Returns true if isolation succeeded, otherwise false.
+ */
+bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode)
{
+ /*
+ * TODO: these pages will not be folios in the future. All
+ * folio dependencies will have to be removed.
+ */
struct folio *folio = folio_get_nontail_page(page);
const struct movable_operations *mops;

@@ -73,7 +91,7 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode)
* we use non-atomic bitops on newly allocated page flags so
* unconditionally grabbing the lock ruins page's owner side.
*/
- if (unlikely(!__folio_test_movable(folio)))
+ if (unlikely(!__PageMovable(page)))
goto out_putfolio;

/*
@@ -90,18 +108,19 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode)
if (unlikely(!folio_trylock(folio)))
goto out_putfolio;

- if (!folio_test_movable(folio) || folio_test_isolated(folio))
+ if (!PageMovable(page) || PageIsolated(page))
goto out_no_isolated;

- mops = folio_movable_ops(folio);
- VM_BUG_ON_FOLIO(!mops, folio);
+ mops = page_movable_ops(page);
+ if (WARN_ON_ONCE(!mops))
+ goto out_no_isolated;

- if (!mops->isolate_page(&folio->page, mode))
+ if (!mops->isolate_page(page, mode))
goto out_no_isolated;

/* Driver shouldn't use the isolated flag */
- WARN_ON_ONCE(folio_test_isolated(folio));
- folio_set_isolated(folio);
+ VM_WARN_ON_ONCE_PAGE(PageIsolated(page), page);
+ SetPageIsolated(page);
folio_unlock(folio);

return true;
@@ -175,8 +194,8 @@ bool isolate_folio_to_list(struct folio *folio, struct list_head *list)
if (lru)
isolated = folio_isolate_lru(folio);
else
- isolated = isolate_movable_page(&folio->page,
- ISOLATE_UNEVICTABLE);
+ isolated = isolate_movable_ops_page(&folio->page,
+ ISOLATE_UNEVICTABLE);

if (!isolated)
return false;
--
2.49.0