linux-kernel - Re: [PATCH v10 3/4] mm: hugetlb_vmemmap: use kstrtobool for hugetlb

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Date:   Thu, 12 May 2022 19:23:49 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     corbet@....net, mike.kravetz@...cle.com, akpm@...ux-foundation.org,
        mcgrof@...nel.org, keescook@...omium.org, yzaikin@...gle.com,
        osalvador@...e.de, masahiroy@...nel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        duanxiongchun@...edance.com, smuchun@...il.com
Subject: Re: [PATCH v10 3/4] mm: hugetlb_vmemmap: use kstrtobool for
 hugetlb_vmemmap param parsing

On Thu, May 12, 2022 at 09:41:22AM +0200, David Hildenbrand wrote:
> 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@...edance.com>
> > Reviewed-by: Mike Kravetz <mike.kravetz@...cle.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.

Got it. How about also telling users "on/1 | off/0"? Because 0 and
1 are also widely used to disable/enable a knob.

> >  
> > -			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@...hat.com>
>

Thanks.

> -- 
> Thanks,
> 
> David / dhildenb
> 
>