linux-kernel - Re: [PATCH v2 1/2] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM

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Message-ID: <1364911655-wel87i2g-mutt-n-horiguchi@ah.jp.nec.com>
Date:	Tue, 02 Apr 2013 10:07:35 -0400
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	HATAYAMA Daisuke <d.hatayama@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/2] hugetlbfs: stop setting VM_DONTDUMP in
 initializing vma(VM_HUGETLB)

On Tue, Apr 02, 2013 at 08:32:33PM +0900, HATAYAMA Daisuke wrote:
> 2013/4/2 Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> 
> > Currently we fail to include any data on hugepages into coredump,
> > because VM_DONTDUMP is set on hugetlbfs's vma. This behavior was recently
> > introduced by commit 314e51b98 "mm: kill vma flag VM_RESERVED and
> > mm->reserved_vm counter". This looks to me a serious regression,
> > so let's fix it.
> >
> > ChangeLog v2:
> >  - add 'return 0' in hugepage memory check
> >
> <cut>
> 
> > @@ -1137,6 +1137,7 @@ static unsigned long vma_dump_size(struct
> > vm_area_struct *vma,
> >                         goto whole;
> >                 if (!(vma->vm_flags & VM_SHARED) &&
> > FILTER(HUGETLB_PRIVATE))
> >                         goto whole;
> > +               return 0;
> >         }
> >
> 
> You should split this part into another patch. This fix is orthogonal to
> the bug this patch tries to fix.

Fair enough, thanks.

> The bug you're trying to fix implicitly here is the filtering behaviour
> that doesn't follow
> the description in Documentation/filesystems/proc.txt that:
> 
>   Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
>   effected by bit 5-6.
> 
> Right?

Right. Without this return, we will go into the subsequent flag checks
of bit 0-4 for vma(VM_HUGETLB).

Thanks,
Naoya Horiguchi
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