linux-kernel - Re: [PATCH 2/6] mm/page_alloc.c: simplify the code by using macro K()

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Date:   Tue, 31 Aug 2021 10:54:24 +0200
From:   Oleksandr Natalenko <oleksandr@...alenko.name>
To:     akpm@...ux-foundation.org, Miaohe Lin <linmiaohe@...wei.com>
Cc:     vbabka@...e.cz, sfr@...b.auug.org.au, peterz@...radead.org,
        mgorman@...hsingularity.net, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linmiaohe@...wei.com
Subject: Re: [PATCH 2/6] mm/page_alloc.c: simplify the code by using macro K()

Hello.

On pondělí 30. srpna 2021 16:10:47 CEST Miaohe Lin wrote:
> Use helper macro K() to convert the pages to the corresponding size.
> Minor readability improvement.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  mm/page_alloc.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index dbb3338d9287..d3983244f56f 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8134,8 +8134,7 @@ unsigned long free_reserved_area(void *start, void
> *end, int poison, const char }
> 
>  	if (pages && s)
> -		pr_info("Freeing %s memory: %ldK\n",
> -			s, pages << (PAGE_SHIFT - 10));
> +		pr_info("Freeing %s memory: %ldK\n", s, K(pages));
> 
>  	return pages;
>  }
> @@ -8180,14 +8179,13 @@ void __init mem_init_print_info(void)
>  		", %luK highmem"
>  #endif
>  		")\n",
> -		nr_free_pages() << (PAGE_SHIFT - 10),
> -		physpages << (PAGE_SHIFT - 10),
> +		K(nr_free_pages()), K(physpages),
>  		codesize >> 10, datasize >> 10, rosize >> 10,
>  		(init_data_size + init_code_size) >> 10, bss_size >> 10,
> -		(physpages - totalram_pages() - totalcma_pages) << (PAGE_SHIFT 
- 10),
> -		totalcma_pages << (PAGE_SHIFT - 10)
> +		K(physpages - totalram_pages() - totalcma_pages),
> +		K(totalcma_pages)
>  #ifdef	CONFIG_HIGHMEM
> -		, totalhigh_pages() << (PAGE_SHIFT - 10)
> +		, K(totalhigh_pages())
>  #endif
>  		);
>  }

(my concern is not quite within the scope of this submission, but I'll ask 
anyway)

Given we have this:

```
git grep '#define K(x)' v5.14
v5.14:drivers/base/node.c:#define K(x) ((x) << (PAGE_SHIFT - 10))
v5.14:drivers/net/hamradio/scc.c:#define K(x) kiss->x
v5.14:kernel/debug/kdb/kdb_main.c:#define K(x) ((x) << (PAGE_SHIFT - 10))
v5.14:mm/backing-dev.c:#define K(x) ((x) << (PAGE_SHIFT - 10))
v5.14:mm/memcontrol.c:#define K(x) ((x) << (PAGE_SHIFT-10))
v5.14:mm/oom_kill.c:#define K(x) ((x) << (PAGE_SHIFT-10))
v5.14:mm/page_alloc.c:#define K(x) ((x) << (PAGE_SHIFT-10))
```

Shouldn't this macro go to some header file instead to get rid of define 
repetitions?

Thanks.

-- 
Oleksandr Natalenko (post-factum)