linux-kernel - Re: [PATCH 3/4] HWPOISON: Report correct address granuality for AO huge page errors

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Message-ID: <20101007084529.GH5010@basil.fritz.box>
Date:	Thu, 7 Oct 2010 10:45:29 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	fengguang.wu@...el.com, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 3/4] HWPOISON: Report correct address granuality for AO
 huge page errors

On Thu, Oct 07, 2010 at 05:41:01PM +0900, Naoya Horiguchi wrote:
> On Thu, Oct 07, 2010 at 09:38:48AM +0200, Andi Kleen wrote:
> > On Thu, Oct 07, 2010 at 09:31:20AM +0900, Naoya Horiguchi wrote:
> > > > @@ -198,7 +199,8 @@ static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
> > > >  #ifdef __ARCH_SI_TRAPNO
> > > >  	si.si_trapno = trapno;
> > > >  #endif
> > > > -	si.si_addr_lsb = PAGE_SHIFT;
> > > > +	order = PageCompound(page) ? huge_page_order(page) : PAGE_SHIFT;
> > >                                                      ^^^^
> > >                                      huge_page_order(page_hstate(page)) ?
> > 
> > Ok.
> 
> order seems to represent a least significant bit of corrupted address,
> so is huge_page_order() + PAGE_SHIFT or huge_page_shift() correct?

Both I guess.

> And since @page can be a tail page, compound_head() is needed as Wu-san pointed out.
> So huge_page_shift(page_hstate(compound_head(page))) looks good for me.

I used compound_order(compound_head(page)) + PAGE_SHIFT now.
This even works for non compound, so the special case check
can be dropped.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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