linux-kernel - Re: [PATCH] futex: bugfix for futex-key conflict when futex use hugepage

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Date:	Tue, 16 Apr 2013 11:47:49 -0700
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Dave Hansen <dave.hansen@...ux.intel.com>
CC:	zhang.yi20@....com.cn, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] futex: bugfix for futex-key conflict when futex use hugepage



On 04/16/2013 11:37 AM, Dave Hansen wrote:
> Instead of bothering to store the index, why not just calculate it, like:
> 
> On 04/15/2013 08:37 PM, zhang.yi20@....com.cn wrote:
>> +static inline int get_page_compound_index(struct page *page)
>> +{
>> +       if (PageHead(page))
>> +               return 0;
>> +       return compound_head(page) - page;
>> +}
> 
> BTW, you've really got to get your mail client fixed.  Your patch is
> still line-wrapped.

And with this it would no longer be necessary to store this index at
all, eliminating all changes to the MM other than this accessor function
- which if not needed there could be added to futex.c, or even replaced with
"page_head - page" in get_futex_key() right?

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Technical Lead - Linux Kernel
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