Thread (114 messages) flat view 114 messages, 9 authors, 2026-06-05

Re: [PATCH mm-unstable v18 10/14] mm/khugepaged: introduce collapse_allowable_orders helper function

From: "David Hildenbrand (Arm)" <david@kernel.org>
Date: 2026-05-31 20:18:30
Also in: linux-doc, linux-mm, lkml

On 5/22/26 17:00, 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.
It would have been good to describe here that, for now, it only ever returns
PMDs, and that it will be extended next.

Logically, this patch belongs to #12, not #11 ... so seeing it before #11 was a bit

... and there, it is clear that we don't even want to know the orders?

So can we just call this function

"collapse_possible" and make it return a boolean?
quoted hunk ↗ jump to hunk
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Nico Pache <redacted>
---
 mm/khugepaged.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 4534025bc81d..64ceebc9d8a7 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -552,12 +552,21 @@ 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);
 	}
 }
@@ -2680,7 +2689,7 @@ 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;
 		}
@@ -2989,7 +2998,7 @@ 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);
Having a simple

static bool collapse_possible(...)
{
	return collapse_allowable_orders(...)
}

Would make the above slightly more readable.

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David
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