Re: [RFC PATCH v2 04/11] mm: khugepaged: add shmem mTHP collapse support

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 6/11/26 2:06 PM, Lance Yang wrote:
> 
> On Wed, Jun 10, 2026 at 06:29:12PM +0800, Baolin Wang wrote:
> [...]
>> @@ -2768,15 +2827,23 @@ static enum scan_result collapse_scan_file(struct mm_struct *mm,
>> 	else
>> 		cc->progress += HPAGE_PMD_NR;
>>
>> -	if (result == SCAN_SUCCEED) {
>> -		if (present < HPAGE_PMD_NR - max_ptes_none) {
>> -			result = SCAN_EXCEED_NONE_PTE;
>> -			count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
>> -		} else {
>> -			result = collapse_file(mm, addr, file, start, cc, HPAGE_PMD_ORDER);
>> -		}
>> +	if (result != SCAN_SUCCEED)
>> +		goto out;
>> +
>> +	if (present < HPAGE_PMD_NR - max_ptes_none) {
>> +		result = SCAN_EXCEED_NONE_PTE;
>> +		count_vm_event(THP_SCAN_EXCEED_NONE_PTE);
>> +		count_mthp_stat(HPAGE_PMD_ORDER,
>> +				MTHP_STAT_COLLAPSE_EXCEED_NONE);
>> +		goto out;
>> 	}
>>
>> +	result = mthp_collapse(mm, file, start, addr, 0, 0, cc, enabled_orders);
> 
> Feels like the second 0 wants to be "swap", no?

It seems so. This reminds me of the issue you’re trying to fix in [1].

[1] https://lore.kernel.org/all/20260609120443.71864-1-lance.yang@linux.dev/