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Message-ID: <21aae898-d54d-cc4b-a11f-1bb7fddcfffa@redhat.com>
Date:   Thu, 12 May 2022 09:41:22 +0200
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Subject: Re: [PATCH v10 3/4] mm: hugetlb_vmemmap: use kstrtobool for
 hugetlb_vmemmap param parsing
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To:     Muchun Song <songmuchun@bytedance.com>, corbet@lwn.net,
        mike.kravetz@oracle.com, akpm@linux-foundation.org,
        mcgrof@kernel.org, keescook@chromium.org, yzaikin@google.com,
        osalvador@suse.de, masahiroy@kernel.org
Cc:     linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com
References: <20220509062703.64249-1-songmuchun@bytedance.com>
 <20220509062703.64249-4-songmuchun@bytedance.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <20220509062703.64249-4-songmuchun@bytedance.com>
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On 09.05.22 08:27, Muchun Song wrote:
> Use kstrtobool rather than open coding "on" and "off" parsing in
> mm/hugetlb_vmemmap.c,  which is more powerful to handle all kinds
> of parameters like 'Yy1Nn0' or [oO][NnFf] for "on" and "off".
> 
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  6 +++---
>  mm/hugetlb_vmemmap.c                            | 10 +++++-----
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 308da668bbb1..43b8385073ad 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1703,10 +1703,10 @@
>  			enabled.
>  			Allows heavy hugetlb users to free up some more
>  			memory (7 * PAGE_SIZE for each 2MB hugetlb page).
> -			Format: { on | off (default) }
> +			Format: { [oO][Nn]/Y/y/1 | [oO][Ff]/N/n/0 (default) }

Really? Can we make the syntax even harder to parse for human beings?! :)

Not to mention that it's partially wrong? What about "oFf" ? That would
have to be [oO][Ff][Ff]

Honestly, "on | off" is good enough. That "oN" and friends work is just
a "nice to have" IMHO. No need to over-complicate this description.
>  
> -			on:  enable the feature
> -			off: disable the feature
> +			[oO][Nn]/Y/y/1: enable the feature
> +			[oO][Ff]/N/n/0: disable the feature
>  
>  			Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
>  			the default is on.
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index 6254bb2d4ae5..cc4ec752ec16 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -28,15 +28,15 @@ EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);
>  
>  static int __init hugetlb_vmemmap_early_param(char *buf)
>  {
> -	if (!buf)
> +	bool enable;
> +
> +	if (kstrtobool(buf, &enable))
>  		return -EINVAL;
>  
> -	if (!strcmp(buf, "on"))
> +	if (enable)
>  		static_branch_enable(&hugetlb_optimize_vmemmap_key);
> -	else if (!strcmp(buf, "off"))
> -		static_branch_disable(&hugetlb_optimize_vmemmap_key);
>  	else
> -		return -EINVAL;
> +		static_branch_disable(&hugetlb_optimize_vmemmap_key);
>  
>  	return 0;
>  }


Apart from that

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb