Re: [PATCH rfc 3/9] mm: migrate: remove migrate_folio_extra()

[Matthew Wilcox <willy@infradead.org>]

On Mon, Jan 29, 2024 at 03:09:28PM +0800, Kefeng Wang wrote:
> Convert migrate_folio_extra() to __migrate_folio() which will be used
> by migrate_folio() and filemap_migrate_folio(), also directly call
> folio_migrate_mapping() in __migrate_device_pages() to simplify code.

This feels like two patches?  First convert __migrate_device_pages()
then do the other thing?

> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>  include/linux/migrate.h |  2 --
>  mm/migrate.c            | 32 +++++++++++---------------------
>  mm/migrate_device.c     | 13 +++++++------
>  3 files changed, 18 insertions(+), 29 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 cdae25b7105f..a51ceebbe3b1 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -655,22 +655,24 @@ 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, enum migrate_mode mode,
> +			   void *src_private)
>  {
>  	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)
> +		folio_attach_private(dst, folio_detach_private(src));
> +
>  	if (mode != MIGRATE_SYNC_NO_COPY)
>  		folio_migrate_copy(dst, src);
>  	else
>  		folio_migrate_flags(dst, src);
> +
>  	return MIGRATEPAGE_SUCCESS;
>  }
>  
> @@ -689,7 +691,8 @@ int migrate_folio_extra(struct address_space *mapping, struct folio *dst,
>  int migrate_folio(struct address_space *mapping, struct folio *dst,
>  		struct folio *src, enum migrate_mode mode)
>  {
> -	return migrate_folio_extra(mapping, dst, src, mode, 0);
> +	BUG_ON(folio_test_writeback(src));	/* Writeback must be complete */
> +	return __migrate_folio(mapping, dst, src, mode, NULL);
>  }
>  EXPORT_SYMBOL(migrate_folio);
>  
> @@ -843,20 +846,7 @@ EXPORT_SYMBOL_GPL(buffer_migrate_folio_norefs);
>  int filemap_migrate_folio(struct address_space *mapping,
>  		struct folio *dst, struct folio *src, enum migrate_mode mode)
>  {
> -	int ret;
> -
> -	ret = folio_migrate_mapping(mapping, dst, src, 0);
> -	if (ret != MIGRATEPAGE_SUCCESS)
> -		return ret;
> -
> -	if (folio_get_private(src))
> -		folio_attach_private(dst, folio_detach_private(src));
> -
> -	if (mode != MIGRATE_SYNC_NO_COPY)
> -		folio_migrate_copy(dst, src);
> -	else
> -		folio_migrate_flags(dst, src);
> -	return MIGRATEPAGE_SUCCESS;
> +	return __migrate_folio(mapping, dst, src, mode, folio_get_private(src));
>  }
>  EXPORT_SYMBOL_GPL(filemap_migrate_folio);
>  
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index d49a48d87d72..bea71d69295a 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -695,7 +695,7 @@ static void __migrate_device_pages(unsigned long *src_pfns,
>  		struct page *page = migrate_pfn_to_page(src_pfns[i]);
>  		struct address_space *mapping;
>  		struct folio *newfolio, *folio;
> -		int r;
> +		int r, extra_cnt = 0;
>  
>  		if (!newpage) {
>  			src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
> @@ -757,14 +757,15 @@ static void __migrate_device_pages(unsigned long *src_pfns,
>  			continue;
>  		}
>  
> +		BUG_ON(folio_test_writeback(folio));
> +
>  		if (migrate && migrate->fault_page == page)
> -			r = migrate_folio_extra(mapping, newfolio, folio,
> -						MIGRATE_SYNC_NO_COPY, 1);
> -		else
> -			r = migrate_folio(mapping, newfolio, folio,
> -					  MIGRATE_SYNC_NO_COPY);
> +			extra_cnt = 1;
> +		r = folio_migrate_mapping(mapping, newfolio, folio, extra_cnt);
>  		if (r != MIGRATEPAGE_SUCCESS)
>  			src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
> +		else
> +			folio_migrate_flags(newfolio, folio);
>  	}
>  
>  	if (notified)
> -- 
> 2.27.0
>