linux-kernel - Re: [PATCH] x86/mm/pat: Do a small optimization in reserve

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Message-ID: <20150721065555.GB520@nazgul.tnic>
Date:	Tue, 21 Jul 2015 08:55:55 +0200
From:	Borislav Petkov <bp@...e.de>
To:	Pan Xinhui <xinhuix.pan@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, toshi.kani@...com, jgross@...e.com,
	mcgrof@...e.com, "mnipxh@....com" <mnipxh@....com>
Subject: Re: [PATCH] x86/mm/pat: Do a small optimization in reserve_memtype

On Tue, Jul 21, 2015 at 02:29:35PM +0800, Pan Xinhui wrote:
> From: Pan Xinhui <xinhuix.pan@...el.com>
> 
> It's safe and more reasonable to unlock memtype_lock right after
> rbt_memtype_check_insert.
> 
> Signed-off-by: Pan Xinhui <xinhuix.pan@...el.com>
> ---
>  arch/x86/mm/pat.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
> index 188e3e0..cb75639 100644
> --- a/arch/x86/mm/pat.c
> +++ b/arch/x86/mm/pat.c
> @@ -538,20 +538,17 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type,
>  	new->type	= actual_type;
>  
>  	spin_lock(&memtype_lock);
> -
>  	err = rbt_memtype_check_insert(new, new_type);
> +	spin_unlock(&memtype_lock);
> +
>  	if (err) {
>  		pr_info("x86/PAT: reserve_memtype failed [mem %#010Lx-%#010Lx], track %s, req %s\n",
>  			start, end - 1,
>  			cattr_name(new->type), cattr_name(req_type));
>  		kfree(new);
> -		spin_unlock(&memtype_lock);
> -
>  		return err;
>  	}
>  
> -	spin_unlock(&memtype_lock);
> -
>  	dprintk("reserve_memtype added [mem %#010Lx-%#010Lx], track %s, req %s, ret %s\n",
>  		start, end - 1, cattr_name(new->type), cattr_name(req_type),
>  		new_type ? cattr_name(*new_type) : "-");

While you're at it, please fix a similar issue in lookup_memtype() and also
improve the comments over memtype_lock to explain what exactly it protects.

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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