[RFC 07/11] khugepaged: generalize __collapse_huge_page_* for mTHP support

Nico Pache
2025-01-08T23:34:05Z

generalize the order of the __collapse_huge_page_* functions
to support future mTHP collapse.

No functional changes in this patch.

Signed-off-by: Nico Pache <npache@redhat.com>
---
mm/khugepaged.c | 36 +++++++++++++++++++-----------------
1 file changed, 19 insertions(+), 17 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 6daf3a943a1a..9eb161b04ee4 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -565,7 +565,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
unsigned long address,
pte_t *pte,
struct collapse_control *cc,
- struct list_head *compound_pagelist)
+ struct list_head *compound_pagelist,
+ u8 order)
{
struct page *page = NULL;
struct folio *folio = NULL;
@@ -573,7 +574,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0;
bool writable = false;

- for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
+ for (_pte = pte; _pte < pte + (1 << order);
_pte++, address += PAGE_SIZE) {
pte_t pteval = ptep_get(_pte);
if (pte_none(pteval) || (pte_present(pteval) &&
@@ -711,14 +712,15 @@ static void __collapse_huge_page_copy_succeeded(pte_t *pte,
struct vm_area_struct *vma,
unsigned long address,
spinlock_t *ptl,
- struct list_head *compound_pagelist)
+ struct list_head *compound_pagelist,
+ u8 order)
{
struct folio *src, *tmp;
pte_t *_pte;
pte_t pteval;

- for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
- _pte++, address += PAGE_SIZE) {
+ for (_pte = pte; _pte < pte + (1 << order);
+ _pte++, address += PAGE_SIZE) {
pteval = ptep_get(_pte);
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
@@ -764,7 +766,8 @@ static void __collapse_huge_page_copy_failed(pte_t *pte,
pmd_t *pmd,
pmd_t orig_pmd,
struct vm_area_struct *vma,
- struct list_head *compound_pagelist)
+ struct list_head *compound_pagelist,
+ u8 order)
{
spinlock_t *pmd_ptl;

@@ -781,7 +784,7 @@ static void __collapse_huge_page_copy_failed(pte_t *pte,
* Release both raw and compound pages isolated
* in __collapse_huge_page_isolate.
*/
- release_pte_pages(pte, pte + HPAGE_PMD_NR, compound_pagelist);
+ release_pte_pages(pte, pte + (1 << order), compound_pagelist);
}

/*
@@ -802,7 +805,7 @@ static void __collapse_huge_page_copy_failed(pte_t *pte,
static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,
pmd_t *pmd, pmd_t orig_pmd, struct vm_area_struct *vma,
unsigned long address, spinlock_t *ptl,
- struct list_head *compound_pagelist)
+ struct list_head *compound_pagelist, u8 order)
{
unsigned int i;
int result = SCAN_SUCCEED;
@@ -810,7 +813,7 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,
/*
* Copying pages' contents is subject to memory poison at any iteration.
*/
- for (i = 0; i < HPAGE_PMD_NR; i++) {
+ for (i = 0; i < (1 << order); i++) {
pte_t pteval = ptep_get(pte + i);
struct page *page = folio_page(folio, i);
unsigned long src_addr = address + i * PAGE_SIZE;
@@ -829,10 +832,10 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,

if (likely(result == SCAN_SUCCEED))
__collapse_huge_page_copy_succeeded(pte, vma, address, ptl,
- compound_pagelist);
+ compound_pagelist, order);
else
__collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
- compound_pagelist);
+ compound_pagelist, order);

return result;
}
@@ -996,11 +999,11 @@ static int check_pmd_still_valid(struct mm_struct *mm,
static int __collapse_huge_page_swapin(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long haddr, pmd_t *pmd,
- int referenced)
+ int referenced, u8 order)
{
int swapped_in = 0;
vm_fault_t ret = 0;
- unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE);
+ unsigned long address, end = haddr + ((1 << order) * PAGE_SIZE);
int result;
pte_t *pte = NULL;
spinlock_t *ptl;
@@ -1110,7 +1113,6 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
int result = SCAN_FAIL;
struct vm_area_struct *vma;
struct mmu_notifier_range range;
-
VM_BUG_ON(address & ~HPAGE_PMD_MASK);

/*
@@ -1145,7 +1147,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
* that case. Continuing to collapse causes inconsistency.
*/
result = __collapse_huge_page_swapin(mm, vma, address, pmd,
- referenced);
+ referenced, HPAGE_PMD_ORDER);
if (result != SCAN_SUCCEED)
goto out_nolock;
}
@@ -1192,7 +1194,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl);
if (pte) {
result = __collapse_huge_page_isolate(vma, address, pte, cc,
- &compound_pagelist);
+ &compound_pagelist, HPAGE_PMD_ORDER);
spin_unlock(pte_ptl);
} else {
result = SCAN_PMD_NULL;
@@ -1222,7 +1224,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,

result = __collapse_huge_page_copy(pte, folio, pmd, _pmd,
vma, address, pte_ptl,
- &compound_pagelist);
+ &compound_pagelist, HPAGE_PMD_ORDER);
pte_unmap(pte);
if (unlikely(result != SCAN_SUCCEED))
goto out_up_write;
--
2.47.1