linux-kernel - Re: [RFC PATCH 4/8] mm: Provide mm_struct and address to huge_ptep

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Date: Mon, 25 Mar 2024 13:35:59 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Peter Xu <peterx@...hat.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: Re: [RFC PATCH 4/8] mm: Provide mm_struct and address to
 huge_ptep_get()

On Mon, Mar 25, 2024 at 03:55:57PM +0100, Christophe Leroy wrote:

>  arch/arm64/include/asm/hugetlb.h |  2 +-
>  fs/hugetlbfs/inode.c             |  2 +-
>  fs/proc/task_mmu.c               |  8 +++---
>  fs/userfaultfd.c                 |  2 +-
>  include/asm-generic/hugetlb.h    |  2 +-
>  include/linux/swapops.h          |  2 +-
>  mm/damon/vaddr.c                 |  6 ++---
>  mm/gup.c                         |  2 +-
>  mm/hmm.c                         |  2 +-
>  mm/hugetlb.c                     | 46 ++++++++++++++++----------------
>  mm/memory-failure.c              |  2 +-
>  mm/mempolicy.c                   |  2 +-
>  mm/migrate.c                     |  4 +--
>  mm/mincore.c                     |  2 +-
>  mm/userfaultfd.c                 |  2 +-
>  15 files changed, 43 insertions(+), 43 deletions(-)
> 
> diff --git a/arch/qarm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
> index 2ddc33d93b13..1af39a74e791 100644
> --- a/arch/arm64/include/asm/hugetlb.h
> +++ b/arch/arm64/include/asm/hugetlb.h
> @@ -46,7 +46,7 @@ extern pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
>  extern void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
>  			   pte_t *ptep, unsigned long sz);
>  #define __HAVE_ARCH_HUGE_PTEP_GET
> -extern pte_t huge_ptep_get(pte_t *ptep);
> +extern pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr, pte_t *ptep);

The header changed but not the implementation? This will need to do
riscv and s390 too.

Though, really, I think the right path is to work toward removing
huge_ptep_get() from the arch code..

riscv and arm are doing the same thing - propogating dirty/young bits
from the contig PTEs to the results. The core code can do this, maybe
with a ARCH #define opt in.

s390.. Ouchy - is this because hugetlb wants to pretend that every
level is encoded as a PTE so it takes the PGD and recodes the flags to
the PTE layout??

Jason