linux-kernel - Re: [PATCH 2/2] m2p_find_override: use list_for_each_entry

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Date:	Tue, 27 Mar 2012 10:26:55 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com
Subject: Re: [PATCH 2/2] m2p_find_override: use list_for_each_entry_safe

On Tue, Mar 27, 2012 at 02:52:44PM +0100, Stefano Stabellini wrote:
> Use list_for_each_entry_safe and remove the spin_lock acquisition in
> m2p_find_override.

So this would allow us to get stale entries. Is that OK?

> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> ---
>  arch/x86/xen/p2m.c |    8 ++------
>  1 files changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> index 1b267e7..7ed8cc3 100644
> --- a/arch/x86/xen/p2m.c
> +++ b/arch/x86/xen/p2m.c
> @@ -809,21 +809,17 @@ struct page *m2p_find_override(unsigned long mfn)
>  {
>  	unsigned long flags;
>  	struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
> -	struct page *p, *ret;
> +	struct page *p, *t, *ret;
>  
>  	ret = NULL;
>  
> -	spin_lock_irqsave(&m2p_override_lock, flags);
> -
> -	list_for_each_entry(p, bucket, lru) {
> +	list_for_each_entry_safe(p, t, bucket, lru) {
>  		if (page_private(p) == mfn) {
>  			ret = p;
>  			break;
>  		}
>  	}
>  
> -	spin_unlock_irqrestore(&m2p_override_lock, flags);
> -
>  	return ret;
>  }
>  
> -- 
> 1.7.2.5
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