Re: [PATCH v2 4/5] mm: mincore: improve mincore_hugetlb()

["David Hildenbrand (Arm)" <david@kernel.org>]

On 7/10/26 14:00, Kefeng Wang wrote:
> The walk_hugetlb_range() always passes a non-NULL pte, so remove the
> dead NULL check. Replace the per-page iteration loop with memset()
> for better performance.
> 
> Reviewed-by: Pedro Falcato <pfalcato@suse.de>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>  mm/mincore.c | 27 +++++++--------------------
>  1 file changed, 7 insertions(+), 20 deletions(-)
> 
> diff --git a/mm/mincore.c b/mm/mincore.c
> index 8b5e6afefb91..9952bc3edf76 100644
> --- a/mm/mincore.c
> +++ b/mm/mincore.c
> @@ -28,30 +28,17 @@ static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
>  			unsigned long end, struct mm_walk *walk)
>  {
>  #ifdef CONFIG_HUGETLB_PAGE
> -	unsigned char present;
> +	unsigned long nr = (end - addr) >> PAGE_SHIFT;
>  	unsigned char *vec = walk->private;
> +	unsigned char present;
>  	spinlock_t *ptl;
> +	pte_t ptep;
>  
>  	ptl = huge_pte_lock(hstate_vma(walk->vma), walk->mm, pte);
> -
> -	/*
> -	 * Hugepages under user process are always in RAM and never
> -	 * swapped out, but theoretically it needs to be checked.
> -	 */
> -	if (!pte) {
> -		present = 0;
> -	} else {
> -		const pte_t ptep = huge_ptep_get(walk->mm, addr, pte);
> -
> -		if (huge_pte_none(ptep) || pte_is_marker(ptep))
> -			present = 0;
> -		else
> -			present = 1;
> -	}
> -
> -	for (; addr != end; vec++, addr += PAGE_SIZE)
> -		*vec = present;
> -	walk->private = vec;
> +	ptep = huge_ptep_get(walk->mm, addr, pte);
> +	present = !(huge_pte_none(ptep) || pte_is_marker(ptep));

Easier to read as

	present = !huge_pte_none(ptep) && !pte_is_marker(ptep);

But now I wonder "why not pte_present()".

Calling this "present" is misleading. It's maybe "resident"?

I guess we want to indicate migration entries and hwpoison entries as "1".

-- 
Cheers,

David