From mboxrd@z Thu Jan  1 00:00:00 1970
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: Corruption with O_DIRECT and unaligned user buffers
Date: Fri, 19 Dec 2008 21:14:31 +0900 (JST)
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	Andrea Arcangeli <aarcange@redhat.com>,
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	Tim LaBerge <tim.laberge@quantum.com>, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org, Wang Chen <wangchen@cn.fujitsu.com>
To: Li Zefan <lizf@cn.fujitsu.com>
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> > diff -ur rhel-5.2/kernel/fork.c x/kernel/fork.c
> > --- rhel-5.2/kernel/fork.c	2008-07-10 17:26:43.000000000 +0200
> > +++ x/kernel/fork.c	2008-12-18 15:57:31.000000000 +0100
> > @@ -368,7 +368,7 @@
> >  		rb_parent = &tmp->vm_rb;
> >  
> >  		mm->map_count++;
> > -		retval = copy_page_range(mm, oldmm, mpnt);
> > +		retval = copy_page_range(mm, oldmm, tmp);
> >  
> 
> Could you explain a bit why this change is needed?

maybe..

__handle_mm_fault() change rmap of passwd vma.
we need to parent process has original page, child process has new page.
then we need child vma.


> Seems this is a revert of the following commit:
> 
> commit 0b0db14c536debd92328819fe6c51a49717e8440
> Author: Hugh Dickins <hugh@veritas.com>
> Date:   Mon Nov 21 21:32:20 2005 -0800
> 
>     [PATCH] unpaged: copy_page_range vma
> 
>     For copy_one_pte's print_bad_pte to show the task correctly (instead of
>     "???"), dup_mmap must pass down parent vma rather than child vma.

I think you are right.
This patch reintroduce the same problem.

end up, print_bad_pte() need parent vma.
__handle_mm_fault() need child vma.

corrent?