linux-kernel - Re: [PATCH v1 1/2] mm/ksm: support fork/exec for prctl

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Date:   Wed, 20 Sep 2023 12:00:16 +0200
From:   Carl Klemm <carl@...s.xyz>
To:     Stefan Roesch <shr@...kernel.io>, kernel-team@...com
Cc:     akpm@...ux-foundation.org, david@...hat.com, hannes@...xchg.org,
        riel@...riel.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v1 1/2] mm/ksm: support fork/exec for prctl

On Tue, 2023-09-19 at 13:51 -0700, Stefan Roesch wrote:
> A process can enable KSM with the prctl system call. When the process
> is
> forked the KSM flag is inherited by the child process. However if the
> process is executing an exec system call directly after the fork, the
> KSM setting is cleared. This patch addresses this problem.
> 
> Signed-off-by: Stefan Roesch <shr@...kernel.io>
> Reported-by: Carl Klemm <carl@...s.xyz>
> ---
>  include/linux/sched/coredump.h | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/sched/coredump.h
> b/include/linux/sched/coredump.h
> index 0ee96ea7a0e9..205aa9917394 100644
> --- a/include/linux/sched/coredump.h
> +++ b/include/linux/sched/coredump.h
> @@ -87,8 +87,11 @@ static inline int get_dumpable(struct mm_struct
> *mm)
>  
>  #define MMF_DISABLE_THP_MASK   (1 << MMF_DISABLE_THP)
>  
> +#define MMF_VM_MERGE_ANY       29
> +#define MMF_VM_MERGE_ANY_MASK  (1 << MMF_VM_MERGE_ANY)
> +
>  #define MMF_INIT_MASK          (MMF_DUMPABLE_MASK |
> MMF_DUMP_FILTER_MASK |\
> -                                MMF_DISABLE_THP_MASK |
> MMF_HAS_MDWE_MASK)
> +                                MMF_DISABLE_THP_MASK |
> MMF_HAS_MDWE_MASK |\
> +                                MMF_VM_MERGE_ANY_MASK)
>  
> -#define MMF_VM_MERGE_ANY       29
>  #endif /* _LINUX_SCHED_COREDUMP_H */

I can confirm that this patch works as intended for my usecase, you can
have my:

Tested-by: Carl Klemm <carl@...s.xyz>