linux-kernel - Re: [PATCH v1 06/29] mm/zsmalloc: make PageZsmalloc() sticky until the page is freed

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Message-ID: <74894b3e-9a64-4600-aa3a-e212d2f63e1b@lucifer.local>
Date: Mon, 30 Jun 2025 17:03:45 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
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Subject: Re: [PATCH v1 06/29] mm/zsmalloc: make PageZsmalloc() sticky until
 the page is freed

On Mon, Jun 30, 2025 at 02:59:47PM +0200, David Hildenbrand wrote:
> Let the page freeing code handle clearing the page type.
>
> Acked-by: Zi Yan <ziy@...dia.com>
> Reviewed-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> Acked-by: Harry Yoo <harry.yoo@...cle.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>

On basis of sanity of UINT_MAX thing:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  mm/zpdesc.h   | 5 -----
>  mm/zsmalloc.c | 3 +--
>  2 files changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/mm/zpdesc.h b/mm/zpdesc.h
> index 5cb7e3de43952..5763f36039736 100644
> --- a/mm/zpdesc.h
> +++ b/mm/zpdesc.h
> @@ -163,11 +163,6 @@ static inline void __zpdesc_set_zsmalloc(struct zpdesc *zpdesc)
>  	__SetPageZsmalloc(zpdesc_page(zpdesc));
>  }
>
> -static inline void __zpdesc_clear_zsmalloc(struct zpdesc *zpdesc)
> -{
> -	__ClearPageZsmalloc(zpdesc_page(zpdesc));
> -}
> -
>  static inline struct zone *zpdesc_zone(struct zpdesc *zpdesc)
>  {
>  	return page_zone(zpdesc_page(zpdesc));
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 7f1431f2be98f..f98747aed4330 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -880,7 +880,7 @@ static void reset_zpdesc(struct zpdesc *zpdesc)
>  	ClearPagePrivate(page);
>  	zpdesc->zspage = NULL;
>  	zpdesc->next = NULL;
> -	__ClearPageZsmalloc(page);
> +	/* PageZsmalloc is sticky until the page is freed to the buddy. */
>  }
>
>  static int trylock_zspage(struct zspage *zspage)
> @@ -1055,7 +1055,6 @@ static struct zspage *alloc_zspage(struct zs_pool *pool,
>  		if (!zpdesc) {
>  			while (--i >= 0) {
>  				zpdesc_dec_zone_page_state(zpdescs[i]);

Maybe for consistency put a

/* PageZsmalloc is sticky until the page is freed to the buddy. */

comment here also?

> -				__zpdesc_clear_zsmalloc(zpdescs[i]);
>  				free_zpdesc(zpdescs[i]);
>  			}
>  			cache_free_zspage(pool, zspage);
> --
> 2.49.0
>