linux-kernel - Re: [PATCH v2 1/3] mm: pagewalk: simplify hugepage boundary calculation using min()

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Message-ID: <aea7ec01-bf81-4172-b44c-5c43e347f479@kernel.org>
Date: Mon, 24 Nov 2025 11:53:52 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Sahil Chandna <chandna.sahil@...il.com>, akpm@...ux-foundation.org,
 lorenzo.stoakes@...cle.com, mhocko@...e.com, vbabka@...e.cz,
 rppt@...nel.org, surenb@...gle.com, hannes@...xchg.org,
 shakeel.butt@...ux.dev, zhengqi.arch@...edance.com, Liam.Howlett@...cle.com,
 weixugc@...gle.com, axelrasmussen@...gle.com, yuanchu@...gle.com,
 yosry.ahmed@...ux.dev, nphamcs@...il.com, chengming.zhou@...ux.dev,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: Matthew Wilcox <willy@...radead.org>,
 David Laight <david.laight.linux@...il.com>
Subject: Re: [PATCH v2 1/3] mm: pagewalk: simplify hugepage boundary
 calculation using min()

On 11/23/25 04:04, Sahil Chandna wrote:
> Use the kernel-provided min() macro to compute the minimum value instead
> of an explicit ternary expression. This improves readability and matches
> common kernel style. Also change the return hugepage boundary expression
> by using bitmask for better clarity.
> 
> This was flagged by Coccinelle
> (misc/minmax.cocci) as an opportunity to use min().
> 
> Found by: make coccicheck MODE=report M=mm/
> No functional change intended.
> 
> Suggested-by: Matthew Wilcox <willy@...radead.org>
> Suggested-by: David Laight <david.laight.linux@...il.com>
> Signed-off-by: Sahil Chandna <chandna.sahil@...il.com>
> ---
> changes since v1:
> - Updated boundary calculation of huge page range for better clarity.
> - No Functional changes intended.
> link to v1: https://lore.kernel.org/all/ff24b3c573b766b187b55a38497fbad0a319b9f8.1763227530.git.chandna.sahil@gmail.com/
> ---
>   mm/pagewalk.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
> index 9f91cf85a5be..1d38763a502a 100644
> --- a/mm/pagewalk.c
> +++ b/mm/pagewalk.c
> @@ -312,8 +312,7 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
>   static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
>   				       unsigned long end)
>   {
> -	unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
> -	return boundary < end ? boundary : end;
> +	return min((addr | ~huge_page_mask(h)) + 1, end);

I know Willy suggested that, but I wonder if we could simplify that to 
something a bit easier to digest:

	return min(ALIGN(addr, huge_page_size(h)), end);

At least I can make sense of that a bit faster.

(I don't think we're interested in micro-optimizations in this code here 
in particular :) )

-- 
Cheers

David