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

[Baolin Wang]

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@xxxxxxxxx/