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

[David Hildenbrand]

On 30.06.25 18:24, Lorenzo Stoakes wrote:
> On Mon, Jun 30, 2025 at 02:59:48PM +0200, David Hildenbrand wrote:
> > ... 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@xxxxxxxxxx>
> > Reviewed-by: Harry Yoo <harry.yoo@xxxxxxxxxx>
> > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
>
> Seesm reasonable to me so:
>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
>
> > ---
> >   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