Re: [PATCH v9 mm-unstable 11/18] mm/zsmalloc: convert reset_page to reset_zpdesc

[Matthew Wilcox <willy@infradead.org>]

On Tue, Dec 17, 2024 at 12:04:42AM +0900, Hyeonggon Yoo wrote:
> From: Alex Shi <alexs@kernel.org>
> 
> zpdesc.zspage matches with page.private, zpdesc.next matches with
> page.index. They will be reset in reset_page() which is called prior to
> free base pages of a zspage.
> 
> Since the fields that need to be initialized are independent of the
> order in struct zpdesc, Keep it to use struct page to ensure robustness
> against potential rearrangements of struct zpdesc fields in the future.
> 
> [42.hyeyoo: keep reset_zpdesc() to use struct page fields]

Ummm ... why did you make this change?  Now page->index still has a user
in zsmalloc ;-(

> Signed-off-by: Alex Shi <alexs@kernel.org>
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> ---
>  mm/zsmalloc.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 432e78e61d2e..dded6d1f3b7a 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -843,8 +843,10 @@ static inline bool obj_allocated(struct zpdesc *zpdesc, void *obj,
>  	return true;
>  }
>  
> -static void reset_page(struct page *page)
> +static void reset_zpdesc(struct zpdesc *zpdesc)
>  {
> +	struct page *page = zpdesc_page(zpdesc);
> +
>  	__ClearPageMovable(page);
>  	ClearPagePrivate(page);
>  	set_page_private(page, 0);
> @@ -887,7 +889,7 @@ static void __free_zspage(struct zs_pool *pool, struct size_class *class,
>  	do {
>  		VM_BUG_ON_PAGE(!PageLocked(page), page);
>  		next = get_next_page(page);
> -		reset_page(page);
> +		reset_zpdesc(page_zpdesc(page));
>  		unlock_page(page);
>  		dec_zone_page_state(page, NR_ZSPAGES);
>  		put_page(page);
> @@ -1865,7 +1867,7 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
>  		zpdesc_inc_zone_page_state(newzpdesc);
>  	}
>  
> -	reset_page(page);
> +	reset_zpdesc(zpdesc);
>  	zpdesc_put(zpdesc);
>  
>  	return MIGRATEPAGE_SUCCESS;
> -- 
> 2.43.5
>