Re: [PATCH mm-new v3 3/3] mm/khugepaged: merge PTE scanning logic into a new helper

[Lance Yang <lance.yang@linux.dev>]

On 2025/10/9 09:07, Andrew Morton wrote:
> On Wed,  8 Oct 2025 12:37:48 +0800 Lance Yang <lance.yang@linux.dev> wrote:
> 
>> +		if (!cc->is_khugepaged ||
>> +		    *unmapped <= khugepaged_max_ptes_swap) {
>> +			/*
>> +			 * Always be strict with uffd-wp enabled swap
>> +			 * entries. Please see comment below for
>> +			 * pte_uffd_wp().
>> +			 */
>> +			if (pte_swp_uffd_wp(pte)) {
>> +				*scan_result = SCAN_PTE_UFFD_WP;
>> +				return PTE_CHECK_FAIL;
>> +			}
>> +			return PTE_CHECK_CONTINUE;
>> +		} else {
>> +			*scan_result = SCAN_EXCEED_SWAP_PTE;
>> +			count_vm_event(THP_SCAN_EXCEED_SWAP_PTE);
>> +			return PTE_CHECK_FAIL;
>> +		}
> 
> I'm inclined to agree with checkpatch here.

Thanks!

> 
> WARNING: else is not generally useful after a break or return
> #81: FILE: mm/khugepaged.c:574:
> +			return PTE_CHECK_CONTINUE;
> +		} else {
> 
> did you see this and disagree or did you forget to run checkpatch?

Yes, I saw the warning. I kept the original style because this is just a 
code move ...

> 
> --- a/mm/khugepaged.c~mm-khugepaged-merge-pte-scanning-logic-into-a-new-helper-checkpatch-fixes
> +++ a/mm/khugepaged.c
> @@ -571,11 +571,10 @@ static inline int thp_collapse_check_pte
>   		    (!cc->is_khugepaged ||
>   		     *none_or_zero <= khugepaged_max_ptes_none)) {
>   			return PTE_CHECK_CONTINUE;
> -		} else {
> -			*scan_result = SCAN_EXCEED_NONE_PTE;
> -			count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
> -			return PTE_CHECK_FAIL;
>   		}
> +		*scan_result = SCAN_EXCEED_NONE_PTE;
> +		count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
> +		return PTE_CHECK_FAIL;
>   	} else if (!pte_present(pte)) {
>   		if (!unmapped) {
>   			*scan_result = SCAN_PTE_NON_PRESENT;
> @@ -600,11 +599,10 @@ static inline int thp_collapse_check_pte
>   				return PTE_CHECK_FAIL;
>   			}
>   			return PTE_CHECK_CONTINUE;
> -		} else {
> -			*scan_result = SCAN_EXCEED_SWAP_PTE;
> -			count_vm_event(THP_SCAN_EXCEED_SWAP_PTE);
> -			return PTE_CHECK_FAIL;
>   		}
> +		*scan_result = SCAN_EXCEED_SWAP_PTE;
> +		count_vm_event(THP_SCAN_EXCEED_SWAP_PTE);
> +		return PTE_CHECK_FAIL;
>   	} else if (pte_uffd_wp(pte)) {
>   		/*
>   		 * Don't collapse the page if any of the small PTEs are
> _
>