linux-kernel - [PATCH v9 03/14] khugepaged: generalize hugepage_vma

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Message-ID: <20250714003207.113275-4-npache@redhat.com>
Date: Sun, 13 Jul 2025 18:31:56 -0600
From: Nico Pache <npache@...hat.com>
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Subject: [PATCH v9 03/14] khugepaged: generalize hugepage_vma_revalidate for mTHP support

For khugepaged to support different mTHP orders, we must generalize this
to check if the PMD is not shared by another VMA and the order is enabled.

To ensure madvise_collapse can support working on mTHP orders without the
PMD order enabled, we need to convert hugepage_vma_revalidate to take a
bitmap of orders.

No functional change in this patch.

Reviewed-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
Co-developed-by: Dev Jain <dev.jain@....com>
Signed-off-by: Dev Jain <dev.jain@....com>
Signed-off-by: Nico Pache <npache@...hat.com>
---
 mm/khugepaged.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 47a80638af97..fa0642e66790 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -907,7 +907,7 @@ static int collapse_find_target_node(struct collapse_control *cc)
 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
 				   bool expect_anon,
 				   struct vm_area_struct **vmap,
-				   struct collapse_control *cc)
+				   struct collapse_control *cc, unsigned long orders)
 {
 	struct vm_area_struct *vma;
 	unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0;
@@ -919,9 +919,10 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
 	if (!vma)
 		return SCAN_VMA_NULL;
 
+	/* Always check the PMD order to insure its not shared by another VMA */
 	if (!thp_vma_suitable_order(vma, address, PMD_ORDER))
 		return SCAN_ADDRESS_RANGE;
-	if (!thp_vma_allowable_order(vma, vma->vm_flags, tva_flags, PMD_ORDER))
+	if (!thp_vma_allowable_orders(vma, vma->vm_flags, tva_flags, orders))
 		return SCAN_VMA_CHECK;
 	/*
 	 * Anon VMA expected, the address may be unmapped then
@@ -1123,7 +1124,8 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
 		goto out_nolock;
 
 	mmap_read_lock(mm);
-	result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
+	result = hugepage_vma_revalidate(mm, address, true, &vma, cc,
+					 BIT(HPAGE_PMD_ORDER));
 	if (result != SCAN_SUCCEED) {
 		mmap_read_unlock(mm);
 		goto out_nolock;
@@ -1157,7 +1159,8 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
 	 * mmap_lock.
 	 */
 	mmap_write_lock(mm);
-	result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
+	result = hugepage_vma_revalidate(mm, address, true, &vma, cc,
+					 BIT(HPAGE_PMD_ORDER));
 	if (result != SCAN_SUCCEED)
 		goto out_up_write;
 	/* check if the pmd is still valid */
@@ -2788,7 +2791,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start,
 			mmap_read_lock(mm);
 			mmap_locked = true;
 			result = hugepage_vma_revalidate(mm, addr, false, &vma,
-							 cc);
+							 cc, BIT(HPAGE_PMD_ORDER));
 			if (result  != SCAN_SUCCEED) {
 				last_fail = result;
 				goto out_nolock;
-- 
2.50.0