linux-kernel - Re: [PATCH] arm64/mm: Remove add_huge_page

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Date:   Thu, 7 May 2020 09:37:37 +0100
From:   Will Deacon <will@...nel.org>
To:     Gavin Shan <gshan@...hat.com>
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
        catalin.marinas@....com, linux-kernel@...r.kernel.org,
        shan.gavin@...il.com
Subject: Re: [PATCH] arm64/mm: Remove add_huge_page_size()

On Thu, May 07, 2020 at 10:15:59AM +1000, Gavin Shan wrote:
> On 5/6/20 5:19 PM, Will Deacon wrote:
> > On Wed, May 06, 2020 at 12:36:43PM +0530, Anshuman Khandual wrote:
> > > 
> > > 
> > > On 05/06/2020 12:16 PM, Gavin Shan wrote:
> > > > The function add_huge_page_size(), wrapper of hugetlb_add_hstate(),
> > > > avoids to register duplicated huge page states for same size. However,
> > > > the same logic has been included in hugetlb_add_hstate(). So it seems
> > > > unnecessary to keep add_huge_page_size() and this just removes it.
> > > 
> > > Makes sense.
> > > 
> > > > 
> > > > Signed-off-by: Gavin Shan <gshan@...hat.com>
> > > > ---
> > > >   arch/arm64/mm/hugetlbpage.c | 18 +++++-------------
> > > >   1 file changed, 5 insertions(+), 13 deletions(-)
> > > > 
> > > > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> > > > index bbeb6a5a6ba6..ed7530413941 100644
> > > > --- a/arch/arm64/mm/hugetlbpage.c
> > > > +++ b/arch/arm64/mm/hugetlbpage.c
> > > > @@ -441,22 +441,14 @@ void huge_ptep_clear_flush(struct vm_area_struct *vma,
> > > >   	clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
> > > >   }
> > > > -static void __init add_huge_page_size(unsigned long size)
> > > > -{
> > > > -	if (size_to_hstate(size))
> > > > -		return;
> > > > -
> > > > -	hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT);
> > > > -}
> > > > -
> > > >   static int __init hugetlbpage_init(void)
> > > >   {
> > > >   #ifdef CONFIG_ARM64_4K_PAGES
> > > > -	add_huge_page_size(PUD_SIZE);
> > > > +	hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
> > > >   #endif
> > > > -	add_huge_page_size(CONT_PMD_SIZE);
> > > > -	add_huge_page_size(PMD_SIZE);
> > > > -	add_huge_page_size(CONT_PTE_SIZE);
> > > > +	hugetlb_add_hstate(CONT_PMD_SHIFT + PMD_SHIFT - PAGE_SHIFT);
> > > > +	hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
> > > > +	hugetlb_add_hstate(CONT_PTE_SHIFT);
> > 
> > Something similar has already been done in linux-next.
> > 
> 
> Thanks, Will. I didn't check linux-next before posting this patch.
> Please ignore it then :)
> 
> > > Should these page order values be converted into macros instead. Also
> > > we should probably keep (CONT_PTE_SHIFT + PAGE_SHIFT - PAGE_SHIFT) as
> > > is to make things more clear.
> > 
> > I think the real confusion stems from us not being consistent with your
> > *_SHIFT definitions on arm64. It's madness for CONT_PTE_SHIFT to be smaller
> > than PAGE_SHIFT imo, but it's just cosmetic I guess.
> > 
> 
> Yeah, Do you want me to post a patch, to fix it?

Let's wait until 5.8 is out the door first, since we've already got a fair
amount of activity in this area and it would be a pity if we broke something
as a result of cleanup!

Cheers,

Will