linux-kernel - Re: [PATCH v2 1/5] mm: factor out the order calculation into a new helper

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Message-ID: <D5MSXD4BK3E4.2IN0397LA1BWB@samsung.com>
Date: Fri, 15 Nov 2024 14:54:26 +0100
From: Daniel Gomez <da.gomez@...sung.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>,
	<akpm@...ux-foundation.org>, <hughd@...gle.com>
CC: <willy@...radead.org>, <david@...hat.com>, <wangkefeng.wang@...wei.com>,
	<21cnbao@...il.com>, <ryan.roberts@....com>, <ioworker0@...il.com>,
	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] mm: factor out the order calculation into a new
 helper

On Tue Nov 12, 2024 at 8:45 AM CET, Baolin Wang 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>
> Reviewed-by: David Hildenbrand <david@...hat.com>

Reviewed-by: Daniel Gomez <da.gomez@...sung.com>

> ---
>  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);