On 6/12/26 6:22 PM, Nico Pache wrote:


On 6/10/26 6:44 AM, Lance Yang wrote:

On Wed, Jun 10, 2026 at 06:29:12PM +0800, Baolin Wang wrote:
[...]
@@ -1512,8 +1517,12 @@ static enum scan_result mthp_collapse(struct mm_struct 
*mm,
                        enum scan_result ret;

                        collapse_address = address + offset * PAGE_SIZE;
-                       ret = collapse_huge_page(mm, collapse_address, 
referenced,
-                                                unmapped, cc, order);
+                       if (file)
+                               ret = collapse_file(mm, collapse_address, file,
+                                               start + offset, cc, order);
+                       else
+                               ret = collapse_huge_page(mm, collapse_address,
+                                               referenced, unmapped, cc, 
order);

                        switch (ret) {
                        /* Cases where we continue to next collapse candidate */
@@ -1521,6 +1530,7 @@ static enum scan_result mthp_collapse(struct mm_struct 
*mm,
                                collapsed += nr_ptes;
                                fallthrough;
                        case SCAN_PTE_MAPPED_HUGEPAGE:

Looks like SCAN_PTE_MAPPED_HUGEPAGE from collapse_file() get lost for
the PMD-order case.

This is kinda my fault... I reused the enum PTE_MAPPED_HUGEPAGE (which was only
really used in file collapse) when reporting that a collapse attempts is smaller
or equal to the current order of the folio.

if (!is_pmd_order(order) && folio_order(folio) >= order) {

I will change that in my follow up to use its own (or a different enum).

Maybe use SCAN_PAGE_COMPOUND? Anyway, I’ve already fixed the issue Lance raised locally.

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