linux-kernel - Re: [PATCH v5] mm: mmap: map MAP_STACK to VM

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Message-ID: <b44ba934-cb95-4229-89da-06b1fc1f8683@redhat.com>
Date: Wed, 7 May 2025 16:15:14 +0200
From: David Hildenbrand <david@...hat.com>
To: Ignacio.MorenoGonzalez@...a.com, lorenzo.stoakes@...cle.com
Cc: Liam.Howlett@...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 v5] mm: mmap: map MAP_STACK to VM_NOHUGEPAGE only if THP
 is enabled

On 07.05.25 15:28, Ignacio Moreno Gonzalez via B4 Relay wrote:
> 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_HUGEPAGE is not defined. But in that case, the
> VM_NOHUGEPAGE does not make sense.
> 
> I discovered this issue when trying to use the tool CRIU to checkpoint
> and restore a container. Our running kernel is compiled without
> CONFIG_TRANSPARENT_HUGEPAGE. CRIU parses the output of
> /proc/<pid>/smaps and saves the "nh" flag. When trying to restore the
> container, CRIU fails to restore the "nh" mappings, since madvise()
> MADV_NOHUGEPAGE always returns an error because
> CONFIG_TRANSPARENT_HUGEPAGE is not defined.
> 
> 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>
> Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> Signed-off-by: Ignacio Moreno Gonzalez <Ignacio.MorenoGonzalez@...a.com>

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb