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.y...@linux.dev/