linux-kernel - Re: [PATCH 11/13] mm/treewide: Replace pXd_huge() with pXd

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Date: Thu, 14 Mar 2024 08:59:22 -0400
From: Peter Xu <peterx@...hat.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	Matthew Wilcox <willy@...radead.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"x86@...nel.org" <x86@...nel.org>, Mike Rapoport <rppt@...nel.org>,
	Muchun Song <muchun.song@...ux.dev>,
	"sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
	Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [PATCH 11/13] mm/treewide: Replace pXd_huge() with pXd_leaf()

On Thu, Mar 14, 2024 at 08:50:20AM +0000, Christophe Leroy wrote:
> 
> 
> Le 13/03/2024 à 22:47, peterx@...hat.com a écrit :
> > From: Peter Xu <peterx@...hat.com>
> > 
> > Now after we're sure all pXd_huge() definitions are the same as pXd_leaf(),
> > reuse it.  Luckily, pXd_huge() isn't widely used.
> > 
> > Signed-off-by: Peter Xu <peterx@...hat.com>
> > ---
> >   arch/arm/include/asm/pgtable-3level.h | 2 +-
> >   arch/arm64/include/asm/pgtable.h      | 2 +-
> >   arch/arm64/mm/hugetlbpage.c           | 4 ++--
> >   arch/loongarch/mm/hugetlbpage.c       | 2 +-
> >   arch/mips/mm/tlb-r4k.c                | 2 +-
> >   arch/powerpc/mm/pgtable_64.c          | 6 +++---
> >   arch/x86/mm/pgtable.c                 | 4 ++--
> >   mm/gup.c                              | 4 ++--
> >   mm/hmm.c                              | 2 +-
> >   mm/memory.c                           | 2 +-
> >   10 files changed, 15 insertions(+), 15 deletions(-)
> > 
> > diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
> > index e7aecbef75c9..9e3c44f0aea2 100644
> > --- a/arch/arm/include/asm/pgtable-3level.h
> > +++ b/arch/arm/include/asm/pgtable-3level.h
> > @@ -190,7 +190,7 @@ static inline pte_t pte_mkspecial(pte_t pte)
> >   #define pmd_dirty(pmd)		(pmd_isset((pmd), L_PMD_SECT_DIRTY))
> >   
> >   #define pmd_hugewillfault(pmd)	(!pmd_young(pmd) || !pmd_write(pmd))
> > -#define pmd_thp_or_huge(pmd)	(pmd_huge(pmd) || pmd_trans_huge(pmd))
> > +#define pmd_thp_or_huge(pmd)	(pmd_leaf(pmd) || pmd_trans_huge(pmd))
> 
> Previous patch said pmd_trans_huge() implies pmd_leaf().

Ah here I remember I kept this arm definition there because I think we
should add a patch to drop pmd_thp_or_huge() completely.  If you won't mind
I can add one more patch instead of doing it here.  Then I keep this patch
purely as a replacement patch without further changes on arch-cleanups.

> 
> Or is that only for GUP ?

I think it should apply to all.

> 
> >   
> >   #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> >   #define pmd_trans_huge(pmd)	(pmd_val(pmd) && !pmd_table(pmd))
> 
> 
> > diff --git a/mm/hmm.c b/mm/hmm.c
> > index c95b9ec5d95f..93aebd9cc130 100644
> > --- a/mm/hmm.c
> > +++ b/mm/hmm.c
> > @@ -429,7 +429,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
> >   		return hmm_vma_walk_hole(start, end, -1, walk);
> >   	}
> >   
> > -	if (pud_huge(pud) && pud_devmap(pud)) {
> > +	if (pud_leaf(pud) && pud_devmap(pud)) {
> 
> Didn't previous patch say devmap implies leaf ? Or is it only for GUP ?

This is an extra safety check that I didn't remove.  Devmap used separate
bits even though I'm not clear on why.  It should still imply a leaf though.

Thanks,

> 
> >   		unsigned long i, npages, pfn;
> >   		unsigned int required_fault;
> >   		unsigned long *hmm_pfns;
> 
> 

-- 
Peter Xu