Re: [PATCH] mm/ksm: remove redundant code in ksm_fork

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 2 Apr 2024 10:49:34 +0800 Jinjiang Tu <tujinjiang@huawei.com> wrote:

> Since commit 3c6f33b7273a ("mm/ksm: support fork/exec for prctl"), when a
> child process is forked, the MMF_VM_MERGE_ANY flag will be inherited in
> mm_init(). So, it's unnecessary to set the flag in ksm_fork().
> 
> ...
>
> --- a/include/linux/ksm.h
> +++ b/include/linux/ksm.h
> @@ -45,16 +45,8 @@ static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
>  
>  static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
>  {
> -	int ret;
> -
> -	if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) {
> -		ret = __ksm_enter(mm);
> -		if (ret)
> -			return ret;
> -	}
> -
> -	if (test_bit(MMF_VM_MERGE_ANY, &oldmm->flags))
> -		set_bit(MMF_VM_MERGE_ANY, &mm->flags);
> +	if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
> +		return __ksm_enter(mm);
>  
>  	return 0;

Thanks, I shall queue this up for testing and shall await review input
from Stefan and hopefully others.