linux-kernel - Re: [PATCH] mm: madvise: make MADV

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Message-ID: <wpxllvzvr5yxmmz6cjcbxc3gkpfdlfxikvoyt3xoyjcjriqys6@befrpxo3o7fh>
Date: Thu, 8 May 2025 15:04:47 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Ignacio.MorenoGonzalez@...a.com
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        yang@...amperecomputing.com, willy@...radead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: madvise: make MADV_NOHUGEPAGE a no-op if !THP

* Ignacio Moreno Gonzalez via B4 Relay <devnull+Ignacio.MorenoGonzalez.kuka.com@...nel.org> [250508 06:20]:
> From: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>
> 
> VM_NOHUGEPAGE is a no-op if CONFIG_TRANSPARENT_HUGEPAGE is disabled. So
> it makes no sense to return an error when calling madvise() with
> MADV_NOHUGEPAGE in that case.
> 
> Suggested-by: Matthew Wilcox <willy@...radead.org>
> Signed-off-by: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>
> ---
> https://lore.kernel.org/linux-mm/20250502-map-map_stack-to-vm_nohugepage-only-if-thp-is-enabled-v1-1-113cc634cd51@kuka.com
> 
> Here it is presented as a separate thread to avoid mixing stable and
> non-stable patches.
> 
> This change makes calling madvise(addr, size, MADV_NOHUGEPAGE) on !THP
> kernels to return 0 instead of -EINVAL.

Sorry, maybe I missed something here.

Which one should Cc stable, I don't see it on either patch?

Thanks,
Liam

> ---
>  include/linux/huge_mm.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index e893d546a49f464f7586db639fe216231f03651a..5fca742dc5ba784ffccea055b07247707d16cc67 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -509,6 +509,8 @@ bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr,
>  
>  #else /* CONFIG_TRANSPARENT_HUGEPAGE */
>  
> +#include <uapi/asm/mman.h>
> +
>  static inline bool folio_test_pmd_mappable(struct folio *folio)
>  {
>  	return false;
> @@ -598,6 +600,9 @@ static inline bool unmap_huge_pmd_locked(struct vm_area_struct *vma,
>  static inline int hugepage_madvise(struct vm_area_struct *vma,
>  				   unsigned long *vm_flags, int advice)
>  {
> +	/* On a !THP kernel, MADV_NOHUGEPAGE is a no-op, but MADV_NOHUGEPAGE is not supported */
> +	if (advice == MADV_NOHUGEPAGE)
> +		return 0;
>  	return -EINVAL;
>  }
>  
> 
> ---
> base-commit: fc96b232f8e7c0a6c282f47726b2ff6a5fb341d2
> change-id: 20250508-madvise-nohugepage-noop-without-thp-e0721b973d82
> 
> Best regards,
> -- 
> Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>
> 
>