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

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Message-ID: <59165861-b6b5-4b10-8b04-f33c51a2debe@lucifer.local>
Date: Thu, 15 May 2025 14:03:24 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>
Cc: James Houghton <jthoughton@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Liam R. Howlett" <Liam.Howlett@...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

Hi Igancio,

I can package this up in a series with the fix below and with the
appropriate tags (signed-off by you) to enforce the correct ordering
between the s390 patch and this one if that works for you?

Let me know if my sending this revised patch in series with these changes
and your signed-off works for you?

Cheers, Lorenzo

On Thu, May 15, 2025 at 09:03:19AM +0200, Ignacio Moreno Gonzalez wrote:
> On 5/14/2025 10:15 PM, James Houghton wrote:
> > On Thu, May 8, 2025 at 3:20 AM Ignacio Moreno Gonzalez via B4 Relay
> > <devnull+Ignacio.MorenoGonzalez.kuka.com@...nel.org> wrote:
> >>
> >> 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.
> >> ---
> >>  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 */
> >
> > Do you mean "but MADV_HUGEPAGE is not supported"? Just want to make
> > sure; it seems like no one else has asked about this yet.
> >
>
> Yes, this is a typo. It should be MADV_HUGEPAGE. Thanks!
>
> >> +       if (advice == MADV_NOHUGEPAGE)
> >> +               return 0;
> >>         return -EINVAL;
> >>  }
> >
>