linux-kernel - Re: [PATCH 1/2] mm: fix logic error of page_expected

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Date:   Wed, 14 Sep 2022 12:35:31 +0800
From:   Zhaoyang Huang <huangzhaoyang@...il.com>
To:     "zhaoyang.huang" <zhaoyang.huang@...soc.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Matthew Wilcox <willy@...radead.org>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, Ke Wang <ke.wang@...soc.com>
Subject: Re: [PATCH 1/2] mm: fix logic error of page_expected_state

On Wed, Sep 14, 2022 at 11:37 AM zhaoyang.huang
<zhaoyang.huang@...soc.com> wrote:
>
> From: Zhaoyang Huang <zhaoyang.huang@...soc.com>
>
> The page with special page type will be deemed as bad page wrongly since
> type share the same address with mapcount.
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...soc.com>
> ---
>  include/linux/page-flags.h | 4 ++--
>  mm/page_alloc.c            | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index e66f7aa..5d3274b 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -946,9 +946,9 @@ static inline bool is_page_hwpoison(struct page *page)
>  #define PageType(page, flag)                                           \
>         ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
>
> -static inline int page_has_type(struct page *page)
> +static inline bool page_has_type(struct page *page)
>  {
> -       return (int)page->page_type < PAGE_MAPCOUNT_RESERVE;
> +       return (int)page->page_type < PAGE_MAPCOUNT_RESERVE;
amend the type conversion
>  }
>
>  #define PAGE_TYPE_OPS(uname, lname)                                    \
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e008a3d..3714680 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1164,7 +1164,7 @@ int split_free_page(struct page *free_page,
>  static inline bool page_expected_state(struct page *page,
>                                         unsigned long check_flags)
>  {
> -       if (unlikely(atomic_read(&page->_mapcount) != -1))
> +       if (unlikely(!page_has_type(page) && atomic_read(&page->_mapcount) != -1))
>                 return false;
>
>         if (unlikely((unsigned long)page->mapping |
> --
> 1.9.1
>