Re: [PATCH v1 04/11] mm: migrate: remove migrate_folio_extra()

[Miaohe Lin <linmiaohe@huawei.com>]

On 2024/4/17 9:43, Kefeng Wang wrote:
> 
> 
> On 2024/4/16 20:40, Miaohe Lin wrote:
>> On 2024/3/21 11:27, Kefeng Wang wrote:
>>> The migrate_folio_extra() only called in migrate.c now, convert it
>>> a static function and take a new src_private argument which could
>>> be shared by migrate_folio() and filemap_migrate_folio() to simplify
>>> code a bit.
>>>
>>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>>> ---
>>>   include/linux/migrate.h |  2 --
>>>   mm/migrate.c            | 33 +++++++++++----------------------
>>>   2 files changed, 11 insertions(+), 24 deletions(-)
>>>
>>> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
>>> index 2ce13e8a309b..517f70b70620 100644
>>> --- a/include/linux/migrate.h
>>> +++ b/include/linux/migrate.h
>>> @@ -63,8 +63,6 @@ extern const char *migrate_reason_names[MR_TYPES];
>>>   #ifdef CONFIG_MIGRATION
>>>     void putback_movable_pages(struct list_head *l);
>>> -int migrate_folio_extra(struct address_space *mapping, struct folio *dst,
>>> -        struct folio *src, enum migrate_mode mode, int extra_count);
>>>   int migrate_folio(struct address_space *mapping, struct folio *dst,
>>>           struct folio *src, enum migrate_mode mode);
>>>   int migrate_pages(struct list_head *l, new_folio_t new, free_folio_t free,
>>> diff --git a/mm/migrate.c b/mm/migrate.c
>>> index cb4cbaa42a35..c006b0b44013 100644
>>> --- a/mm/migrate.c
>>> +++ b/mm/migrate.c
>>> @@ -658,18 +658,19 @@ EXPORT_SYMBOL(folio_migrate_copy);
>>>    *                    Migration functions
>>>    ***********************************************************/
>>>   -int migrate_folio_extra(struct address_space *mapping, struct folio *dst,
>>> -        struct folio *src, enum migrate_mode mode, int extra_count)
>>> +static int __migrate_folio(struct address_space *mapping, struct folio *dst,
>>> +               struct folio *src, void *src_private,
>>> +               enum migrate_mode mode)
>>>   {
>>>       int rc;
>>>   -    BUG_ON(folio_test_writeback(src));    /* Writeback must be complete */
>>> -
>>> -    rc = folio_migrate_mapping(mapping, dst, src, extra_count);
>>> -
>>> +    rc = folio_migrate_mapping(mapping, dst, src, 0);
>>>       if (rc != MIGRATEPAGE_SUCCESS)
>>>           return rc;
>>>   +    if (src_private)
>>
>> src_private seems unneeded. It can be replaced with folio_get_private(src)?
>>
> 
> __migrate_folio() is used by migrate_folio() and filemap_migrate_folio(),
> but migrate_folio() is for LRU folio, when swapcache folio, the
> folio->private is handled from folio_migrate_mapping(), we should not
> try to call folio_detach_private/folio_attach_private().

I see. Swapcache folio will use private field while without using PagePrivate/PagePrivate2.
We can't handle this case if src_private is removed.
Thanks.
.

> 
>> Thanks.
>> .
> .