Re: [PATCH v11 11/15] khugepaged: introduce collapse_allowable_orders helper function

[Baolin Wang]

On 2025/9/12 11:28, Nico Pache wrote:

Add collapse_allowable_orders() to generalize THP order eligibility. The
function determines which THP orders are permitted based on collapse
context (khugepaged vs madv_collapse).

This consolidates collapse configuration logic and provides a clean
interface for future mTHP collapse support where the orders may be
different.

Signed-off-by: Nico Pache <npa...@redhat.com>

LGTM.
Reviewed-by: Baolin Wang <baolin.w...@linux.alibaba.com>

---
  mm/khugepaged.c | 15 ++++++++++++---
  1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5b45ef575446..d224fa97281a 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -485,7 +485,16 @@ static int collapse_max_ptes_none(unsigned int order)
        else
                max_ptes_none = khugepaged_max_ptes_none;
        return max_ptes_none >> (HPAGE_PMD_ORDER - order);
+}
+
+/* Check what orders are allowed based on the vma and collapse type */
+static unsigned long collapse_allowable_orders(struct vm_area_struct *vma,
+                       vm_flags_t vm_flags, bool is_khugepaged)
+{
+       enum tva_type tva_flags = is_khugepaged ? TVA_KHUGEPAGED : 
TVA_FORCED_COLLAPSE;
+       unsigned long orders = BIT(HPAGE_PMD_ORDER);

+ return thp_vma_allowable_orders(vma, vm_flags, tva_flags, orders);

  }

void khugepaged_enter_vma(struct vm_area_struct *vma,

@@ -493,7 +502,7 @@ void khugepaged_enter_vma(struct vm_area_struct *vma,
  {
        if (!mm_flags_test(MMF_VM_HUGEPAGE, vma->vm_mm) &&
            hugepage_pmd_enabled()) {
-               if (thp_vma_allowable_order(vma, vm_flags, TVA_KHUGEPAGED, 
PMD_ORDER))
+               if (collapse_allowable_orders(vma, vm_flags, true))
                        __khugepaged_enter(vma->vm_mm);
        }
  }
@@ -2557,7 +2566,7 @@ static unsigned int collapse_scan_mm_slot(unsigned int 
pages, int *result,
                        progress++;
                        break;
                }
-               if (!thp_vma_allowable_order(vma, vma->vm_flags, 
TVA_KHUGEPAGED, PMD_ORDER)) {
+               if (!collapse_allowable_orders(vma, vma->vm_flags, true)) {
  skip:
                        progress++;
                        continue;
@@ -2865,7 +2874,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned 
long start,
        BUG_ON(vma->vm_start > start);
        BUG_ON(vma->vm_end < end);

- if (!thp_vma_allowable_order(vma, vma->vm_flags, TVA_FORCED_COLLAPSE, PMD_ORDER))

+       if (!collapse_allowable_orders(vma, vma->vm_flags, false))
                return -EINVAL;

cc = kmalloc(sizeof(*cc), GFP_KERNEL);