Re: [PATCH] mm/sl{a,u}b: fix wrong usages of folio_page() for getting head pages

[Hyeonggon Yoo <42.hyeyoo@gmail.com>]

On Tue, Jan 10, 2023 at 12:51:24AM +0000, SeongJae Park wrote:
> The standard idiom for getting head page of a given folio is
> '&folio->page', but some are wrongly using 'folio_page(folio, 0)' for
> the purpose.  Fix those to use the idiom.
> 
> Suggested-by: Matthew Wilcox <willy@infradead.org>
> Signed-off-by: SeongJae Park <sj@kernel.org>
> ---
>  mm/slab.c | 4 ++--
>  mm/slub.c | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/slab.c b/mm/slab.c
> index b77be9c6d6b1..a5398676dc60 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -1389,7 +1389,7 @@ static void kmem_freepages(struct kmem_cache *cachep, struct slab *slab)
>  
>  	BUG_ON(!folio_test_slab(folio));
>  	__slab_clear_pfmemalloc(slab);
> -	page_mapcount_reset(folio_page(folio, 0));
> +	page_mapcount_reset(&folio->page);
>  	folio->mapping = NULL;
>  	/* Make the mapping reset visible before clearing the flag */
>  	smp_wmb();
> @@ -1398,7 +1398,7 @@ static void kmem_freepages(struct kmem_cache *cachep, struct slab *slab)
>  	if (current->reclaim_state)
>  		current->reclaim_state->reclaimed_slab += 1 << order;
>  	unaccount_slab(slab, order, cachep);
> -	__free_pages(folio_page(folio, 0), order);
> +	__free_pages(&folio->page, order);
>  }
>  
>  static void kmem_rcu_free(struct rcu_head *head)
> diff --git a/mm/slub.c b/mm/slub.c
> index 67020074ecb4..d5f20c062004 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2066,7 +2066,7 @@ static void __free_slab(struct kmem_cache *s, struct slab *slab)
>  	if (current->reclaim_state)
>  		current->reclaim_state->reclaimed_slab += pages;
>  	unaccount_slab(slab, order, s);
> -	__free_pages(folio_page(folio, 0), order);
> +	__free_pages(&folio->page, order);
>  }
>  
>  static void rcu_free_slab(struct rcu_head *h)
> -- 
> 2.25.1
> 
>

Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>

Thanks!