linux-kernel - Re: [PATCH v2 1/2] mm: mmap: map MAP_STACK to VM

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Message-ID: <fuydpgfocdckyzql6hq2h7bfmoul4acanyswv3yappc5xsxqdu@dhpq24pybqth>
Date: Tue, 6 May 2025 12:00:10 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Ignacio.MorenoGonzalez@...a.com
Cc: lorenzo.stoakes@...cle.com, akpm@...ux-foundation.org,
        yang@...amperecomputing.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/2] mm: mmap: map MAP_STACK to VM_NOHUGEPAGE only if
 THP is enabled

* Ignacio Moreno Gonzalez via B4 Relay <devnull+Ignacio.MorenoGonzalez.kuka.com@...nel.org> [250506 09:44]:
> From: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>
> 
> commit c4608d1bf7c6 ("mm: mmap: map MAP_STACK to VM_NOHUGEPAGE") maps
> the mmap option MAP_STACK to VM_NOHUGEPAGE. This is also done if
> CONFIG_TRANSPARENT_HUGETABLES is not defined. But in that case, the
> VM_NOHUGEPAGE does not make sense.
> 
> Fixes: c4608d1bf7c6 ("mm: mmap: map MAP_STACK to VM_NOHUGEPAGE")
> Cc: stable@...r.kernel.org
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Reviewed-by: Yang Shi <yang@...amperecomputing.com>
> Signed-off-by: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>

Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>

> ---
>  include/linux/mman.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/linux/mman.h b/include/linux/mman.h
> index bce214fece16b9af3791a2baaecd6063d0481938..f4c6346a8fcd29b08d43f7cd9158c3eddc3383e1 100644
> --- a/include/linux/mman.h
> +++ b/include/linux/mman.h
> @@ -155,7 +155,9 @@ calc_vm_flag_bits(struct file *file, unsigned long flags)
>  	return _calc_vm_trans(flags, MAP_GROWSDOWN,  VM_GROWSDOWN ) |
>  	       _calc_vm_trans(flags, MAP_LOCKED,     VM_LOCKED    ) |
>  	       _calc_vm_trans(flags, MAP_SYNC,	     VM_SYNC      ) |
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  	       _calc_vm_trans(flags, MAP_STACK,	     VM_NOHUGEPAGE) |
> +#endif
>  	       arch_calc_vm_flag_bits(file, flags);
>  }
>  
> 
> -- 
> 2.39.5
> 
>