linux-kernel - Re: [PATCH] mm: make some vars and functions static or _

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Date:   Thu, 16 Dec 2021 16:59:44 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Ting Liu <liuting.0x7c00@...edance.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Shakeel Butt <shakeelb@...gle.com>,
        Matthew Wilcox <willy@...radead.org>, sjpark@...zon.de
Subject: Re: [PATCH] mm: make some vars and functions static or __init

On Wed, Dec 15, 2021 at 1:27 PM Ting Liu <liuting.0x7c00@...edance.com> wrote:
>
> From: "liuting.0x7c00" <liuting.0x7c00@...edance.com>
>
> "page_idle_ops" as a global var, but its scope of use within this
> document. So it should be static.
> "page_ext_ops" is a var used in the kernel initial phase. And other
> functions are aslo used in the kernel initial phase. So they should be
> __init or __initdata to reclaim memory.
>
> Signed-off-by: liuting.0x7c00 <liuting.0x7c00@...edance.com>
> ---
>  include/linux/page_idle.h | 1 -
>  mm/page_ext.c             | 4 ++--
>  mm/page_owner.c           | 4 ++--
>  3 files changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/page_idle.h b/include/linux/page_idle.h
> index 83abf95e9fa7..4663dfed1293 100644
> --- a/include/linux/page_idle.h
> +++ b/include/linux/page_idle.h
> @@ -13,7 +13,6 @@
>   * If there is not enough space to store Idle and Young bits in page flags, use
>   * page ext flags instead.
>   */
> -extern struct page_ext_operations page_idle_ops;
>
>  static inline bool folio_test_young(struct folio *folio)
>  {
> diff --git a/mm/page_ext.c b/mm/page_ext.c
> index 6242afb24d84..2193e3f10e56 100644
> --- a/mm/page_ext.c
> +++ b/mm/page_ext.c
> @@ -63,12 +63,12 @@ static bool need_page_idle(void)

Should need_page_idle be marked as __init?
It is used in the initialization stage.

>  {
>         return true;
>  }
> -struct page_ext_operations page_idle_ops = {
> +static struct page_ext_operations page_idle_ops = {
>         .need = need_page_idle,
>  };

page_idle_ops is also used in the initialization stage.
It also can be marked as __initdata.


>  #endif
>
> -static struct page_ext_operations *page_ext_ops[] = {
> +static struct page_ext_operations *page_ext_ops[] __initdata = {
>  #ifdef CONFIG_PAGE_OWNER
>         &page_owner_ops,
>  #endif
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 4f924957ce7a..5eea061bb1e5 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -46,7 +46,7 @@ static int __init early_page_owner_param(char *buf)
>  }
>  early_param("page_owner", early_page_owner_param);
>
> -static bool need_page_owner(void)
> +static __init bool need_page_owner(void)
>  {
>         return page_owner_enabled;
>  }
> @@ -75,7 +75,7 @@ static noinline void register_early_stack(void)
>         early_handle = create_dummy_stack();
>  }
>
> -static void init_page_owner(void)
> +static __init void init_page_owner(void)
>  {
>         if (!page_owner_enabled)
>                 return;
> --
> 2.20.1
>