linux-kernel - Re: [PATCH] mm: move huge_pmd_set_accessed out of huge

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Date:	Thu, 21 Apr 2016 02:15:12 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	"Shi, Yang" <yang.shi@...aro.org>
cc:	akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
	aarcange@...hat.com, hughd@...gle.com, mgorman@...e.de,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH] mm: move huge_pmd_set_accessed out of huge_memory.c

On Wed, 20 Apr 2016, Shi, Yang wrote:

> Hi folks,
> 
> I didn't realize pmd_* functions are protected by CONFIG_TRANSPARENT_HUGEPAGE
> on the most architectures before I made this change.
> 
> Before I fix all the affected architectures code, I want to check if you guys
> think this change is worth or not?

Thanks for asking: no, it is not worthwhile.

I would much prefer not to have to consider these trivial cleanups
in the huge memory area at this time.  Kirill and I have urgent work
to do in this area, and coping with patch conflicts between different
versions of the source will not help any of us.

Thanks,
Hugh

> 
> Thanks,
> Yang
> 
> On 4/20/2016 11:24 AM, Yang Shi wrote:
> > huge_pmd_set_accessed is only called by __handle_mm_fault from memory.c,
> > move the definition to memory.c and make it static like create_huge_pmd and
> > wp_huge_pmd.
> > 
> > Signed-off-by: Yang Shi <yang.shi@...aro.org>
> > ---
> >   include/linux/huge_mm.h |  4 ----
> >   mm/huge_memory.c        | 23 -----------------------
> >   mm/memory.c             | 23 +++++++++++++++++++++++
> >   3 files changed, 23 insertions(+), 27 deletions(-)
> > 
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index 7008623..c218ab7b 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -8,10 +8,6 @@ extern int do_huge_pmd_anonymous_page(struct mm_struct
> > *mm,
> >   extern int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct
> > *src_mm,
> >   			 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
> >   			 struct vm_area_struct *vma);
> > -extern void huge_pmd_set_accessed(struct mm_struct *mm,
> > -				  struct vm_area_struct *vma,
> > -				  unsigned long address, pmd_t *pmd,
> > -				  pmd_t orig_pmd, int dirty);
> >   extern int do_huge_pmd_wp_page(struct mm_struct *mm, struct
> > vm_area_struct *vma,
> >   			       unsigned long address, pmd_t *pmd,
> >   			       pmd_t orig_pmd);
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index fecbbc5..6c14cb6 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -1137,29 +1137,6 @@ out:
> >   	return ret;
> >   }
> > 
> > -void huge_pmd_set_accessed(struct mm_struct *mm,
> > -			   struct vm_area_struct *vma,
> > -			   unsigned long address,
> > -			   pmd_t *pmd, pmd_t orig_pmd,
> > -			   int dirty)
> > -{
> > -	spinlock_t *ptl;
> > -	pmd_t entry;
> > -	unsigned long haddr;
> > -
> > -	ptl = pmd_lock(mm, pmd);
> > -	if (unlikely(!pmd_same(*pmd, orig_pmd)))
> > -		goto unlock;
> > -
> > -	entry = pmd_mkyoung(orig_pmd);
> > -	haddr = address & HPAGE_PMD_MASK;
> > -	if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
> > -		update_mmu_cache_pmd(vma, address, pmd);
> > -
> > -unlock:
> > -	spin_unlock(ptl);
> > -}
> > -
> >   static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
> >   					struct vm_area_struct *vma,
> >   					unsigned long address,
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 93897f2..6ced4eb 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -3287,6 +3287,29 @@ static int wp_huge_pmd(struct mm_struct *mm, struct
> > vm_area_struct *vma,
> >   	return VM_FAULT_FALLBACK;
> >   }
> > 
> > +static void huge_pmd_set_accessed(struct mm_struct *mm,
> > +				  struct vm_area_struct *vma,
> > +				  unsigned long address,
> > +				  pmd_t *pmd, pmd_t orig_pmd,
> > +				  int dirty)
> > +{
> > +	spinlock_t *ptl;
> > +	pmd_t entry;
> > +	unsigned long haddr;
> > +
> > +	ptl = pmd_lock(mm, pmd);
> > +	if (unlikely(!pmd_same(*pmd, orig_pmd)))
> > +		goto unlock;
> > +
> > +	entry = pmd_mkyoung(orig_pmd);
> > +	haddr = address & HPAGE_PMD_MASK;
> > +	if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
> > +		update_mmu_cache_pmd(vma, address, pmd);
> > +
> > +unlock:
> > +	spin_unlock(ptl);
> > +}
> > +
> >   /*
> >    * These routines also need to handle stuff like marking pages dirty
> >    * and/or accessed for architectures that don't do it in hardware (most