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

David Hildenbrand
2025-07-01T08:30:02Z

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@nvidia.com>
>> Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>
> Seesm reasonable to me so:
>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.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))
>
> 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