linux-kernel - Re: [PATCH 2/3] mm: thp: Fix the update_mmu_cache() last argument passing in mm/huge

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Message-ID: <20120912155135.GD10698@arm.com>
Date:	Wed, 12 Sep 2012 16:51:35 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Will Deacon <Will.Deacon@....com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	Steve Capper <Steve.Capper@....com>
Subject: Re: [PATCH 2/3] mm: thp: Fix the update_mmu_cache() last argument
 passing in mm/huge_memory.c

On Wed, Sep 12, 2012 at 04:40:37PM +0100, Michal Hocko wrote:
> On Tue 11-09-12 17:47:15, Will Deacon wrote:
> > From: Catalin Marinas <catalin.marinas@....com>
> > 
> > The update_mmu_cache() takes a pointer (to pte_t by default) as the last
> > argument but the huge_memory.c passes a pmd_t value. The patch changes
> > the argument to the pmd_t * pointer.
> > 
> > Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> > Signed-off-by: Steve Capper <steve.capper@....com>
> > Signed-off-by: Will Deacon <will.deacon@....com>
> > ---
> >  mm/huge_memory.c |    6 +++---
> >  1 files changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index 57c4b93..4aa6d02 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -934,7 +934,7 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
> >  		entry = pmd_mkyoung(orig_pmd);
> >  		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
> >  		if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
> > -			update_mmu_cache(vma, address, entry);
> > +			update_mmu_cache(vma, address, pmd);
> 
> I am not sure but shouldn't we use the new entry rather than the given
> pmd?

The pmd pointer is the new pmd and 'entry' is the new value derived from
orig_pmd. update_mmu_cache() expects a pointer to pte_t or pmd_t rather
than it's value.

-- 
Catalin
--
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