linux-kernel - Re: [PATCH 1/4] mm: factor out the order calculation into a new helper

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Message-ID: <CAGsJ_4y86Ma=yJOVppEBCts8XZO=vxV2bxF21FD03azNFONvLA@mail.gmail.com>
Date: Fri, 8 Nov 2024 17:29:42 +1300
From: Barry Song <21cnbao@...il.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, hughd@...gle.com, willy@...radead.org, 
	david@...hat.com, wangkefeng.wang@...wei.com, ryan.roberts@....com, 
	ioworker0@...il.com, da.gomez@...sung.com, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] mm: factor out the order calculation into a new helper

On Fri, Nov 8, 2024 at 5:13 PM Baolin Wang
<baolin.wang@...ux.alibaba.com> wrote:
>
> Factor out the order calculation into a new helper, which can be reused
> by shmem in the following patch.
>
> Suggested-by: Matthew Wilcox <willy@...radead.org>
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>

Reviewed-by: Barry Song <baohua@...nel.org>

> ---
>  include/linux/pagemap.h | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index bcf0865a38ae..d796c8a33647 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -727,6 +727,16 @@ typedef unsigned int __bitwise fgf_t;
>
>  #define FGP_WRITEBEGIN         (FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE)
>
> +static inline unsigned int filemap_get_order(size_t size)
> +{
> +       unsigned int shift = ilog2(size);
> +
> +       if (shift <= PAGE_SHIFT)
> +               return 0;
> +
> +       return shift - PAGE_SHIFT;
> +}
> +
>  /**
>   * fgf_set_order - Encode a length in the fgf_t flags.
>   * @size: The suggested size of the folio to create.
> @@ -740,11 +750,11 @@ typedef unsigned int __bitwise fgf_t;
>   */
>  static inline fgf_t fgf_set_order(size_t size)
>  {
> -       unsigned int shift = ilog2(size);
> +       unsigned int order = filemap_get_order(size);
>
> -       if (shift <= PAGE_SHIFT)
> +       if (!order)
>                 return 0;
> -       return (__force fgf_t)((shift - PAGE_SHIFT) << 26);
> +       return (__force fgf_t)(order << 26);
>  }
>
>  void *filemap_get_entry(struct address_space *mapping, pgoff_t index);
> --
> 2.39.3
>