On 30.06.25 18:24, Lorenzo Stoakes wrote:

On Mon, Jun 30, 2025 at 02:59:48PM +0200, David Hildenbrand wrote:

quoted

... 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 <redacted>
Signed-off-by: David Hildenbrand <redacted>

Seesm reasonable to me so:

Reviewed-by: Lorenzo Stoakes <redacted>

quoted

---
  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))

I wonder, in the wonderful future where PageXXX() always refers to a page, can
we use something less horrible than these macros?

Good question. It all interacts with how we believe compound pages will 
work / look like in the future.

Doing a change from PageXXX() to page_test_XXX() might be reasonable 
change in the future. But, I mean, there are more important things to 
clean up that that :)

-- 
Cheers,

David / dhildenb