[PATCH mm-unstable v17 10/14] mm/khugepaged: introduce collapse_allowable_orders helper function

[Nico Pache <npache@redhat.com>]

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.

Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Nico Pache <npache@redhat.com>
---
 mm/khugepaged.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index f28066069437..3492b135d667 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -545,12 +545,21 @@ void __khugepaged_enter(struct mm_struct *mm)
 		wake_up_interruptible(&khugepaged_wait);
 }
 
+/* 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, enum tva_type tva_flags)
+{
+	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,
 			  vm_flags_t vm_flags)
 {
 	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, TVA_KHUGEPAGED))
 			__khugepaged_enter(vma->vm_mm);
 	}
 }
@@ -2673,7 +2682,7 @@ static void collapse_scan_mm_slot(unsigned int progress_max,
 			cc->progress++;
 			break;
 		}
-		if (!thp_vma_allowable_order(vma, vma->vm_flags, TVA_KHUGEPAGED, PMD_ORDER)) {
+		if (!collapse_allowable_orders(vma, vma->vm_flags, TVA_KHUGEPAGED)) {
 			cc->progress++;
 			continue;
 		}
@@ -2983,7 +2992,7 @@ 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, TVA_FORCED_COLLAPSE))
 		return -EINVAL;
 
 	cc = kmalloc_obj(*cc);
-- 
2.54.0