[PATCH 2/2] mm: Drop all references of writable and SCAN_PAGE_RO

Dev Jain
2025-09-03T05:46:56Z

Now that all actionable outcomes from checking pte_write() are gone,
drop the related references.

Signed-off-by: Dev Jain <dev.jain@arm.com>
---
include/trace/events/huge_memory.h | 19 ++++++-------------
mm/khugepaged.c | 14 +++-----------
2 files changed, 9 insertions(+), 24 deletions(-)

diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index 2305df6cb485..dd94d14a2427 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -19,7 +19,6 @@
EM( SCAN_PTE_NON_PRESENT, "pte_non_present") \
EM( SCAN_PTE_UFFD_WP, "pte_uffd_wp") \
EM( SCAN_PTE_MAPPED_HUGEPAGE, "pte_mapped_hugepage") \
- EM( SCAN_PAGE_RO, "no_writable_page") \
EM( SCAN_LACK_REFERENCED_PAGE, "lack_referenced_page") \
EM( SCAN_PAGE_NULL, "page_null") \
EM( SCAN_SCAN_ABORT, "scan_aborted") \
@@ -55,15 +54,14 @@ SCAN_STATUS

TRACE_EVENT(mm_khugepaged_scan_pmd,

- TP_PROTO(struct mm_struct *mm, struct folio *folio, bool writable,
+ TP_PROTO(struct mm_struct *mm, struct folio *folio,
int referenced, int none_or_zero, int status, int unmapped),

- TP_ARGS(mm, folio, writable, referenced, none_or_zero, status, unmapped),
+ TP_ARGS(mm, folio, referenced, none_or_zero, status, unmapped),

TP_STRUCT__entry(
__field(struct mm_struct *, mm)
__field(unsigned long, pfn)
- __field(bool, writable)
__field(int, referenced)
__field(int, none_or_zero)
__field(int, status)
@@ -73,17 +71,15 @@ TRACE_EVENT(mm_khugepaged_scan_pmd,
TP_fast_assign(
__entry->mm = mm;
__entry->pfn = folio ? folio_pfn(folio) : -1;
- __entry->writable = writable;
__entry->referenced = referenced;
__entry->none_or_zero = none_or_zero;
__entry->status = status;
__entry->unmapped = unmapped;
),

- TP_printk("mm=%p, scan_pfn=0x%lx, writable=%d, referenced=%d, none_or_zero=%d, status=%s, unmapped=%d",
+ TP_printk("mm=%p, scan_pfn=0x%lx, referenced=%d, none_or_zero=%d, status=%s, unmapped=%d",
__entry->mm,
__entry->pfn,
- __entry->writable,
__entry->referenced,
__entry->none_or_zero,
__print_symbolic(__entry->status, SCAN_STATUS),
@@ -117,15 +113,14 @@ TRACE_EVENT(mm_collapse_huge_page,
TRACE_EVENT(mm_collapse_huge_page_isolate,

TP_PROTO(struct folio *folio, int none_or_zero,
- int referenced, bool writable, int status),
+ int referenced, int status),

- TP_ARGS(folio, none_or_zero, referenced, writable, status),
+ TP_ARGS(folio, none_or_zero, referenced, status),

TP_STRUCT__entry(
__field(unsigned long, pfn)
__field(int, none_or_zero)
__field(int, referenced)
- __field(bool, writable)
__field(int, status)
),

@@ -133,15 +128,13 @@ TRACE_EVENT(mm_collapse_huge_page_isolate,
__entry->pfn = folio ? folio_pfn(folio) : -1;
__entry->none_or_zero = none_or_zero;
__entry->referenced = referenced;
- __entry->writable = writable;
__entry->status = status;
),

- TP_printk("scan_pfn=0x%lx, none_or_zero=%d, referenced=%d, writable=%d, status=%s",
+ TP_printk("scan_pfn=0x%lx, none_or_zero=%d, referenced=%d, status=%s",
__entry->pfn,
__entry->none_or_zero,
__entry->referenced,
- __entry->writable,
__print_symbolic(__entry->status, SCAN_STATUS))
);

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index a0f1df2a7ae6..af5f5c80fe4e 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -39,7 +39,6 @@ enum scan_result {
SCAN_PTE_NON_PRESENT,
SCAN_PTE_UFFD_WP,
SCAN_PTE_MAPPED_HUGEPAGE,
- SCAN_PAGE_RO,
SCAN_LACK_REFERENCED_PAGE,
SCAN_PAGE_NULL,
SCAN_SCAN_ABORT,
@@ -557,7 +556,6 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
struct folio *folio = NULL;
pte_t *_pte;
int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0;
- bool writable = false;

for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
_pte++, address += PAGE_SIZE) {
@@ -671,9 +669,6 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
folio_test_referenced(folio) || mmu_notifier_test_young(vma->vm_mm,
address)))
referenced++;
-
- if (pte_write(pteval))
- writable = true;
}

if (unlikely(cc->is_khugepaged && !referenced)) {
@@ -681,13 +676,13 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
} else {
result = SCAN_SUCCEED;
trace_mm_collapse_huge_page_isolate(folio, none_or_zero,
- referenced, writable, result);
+ referenced, result);
return result;
}
out:
release_pte_pages(pte, _pte, compound_pagelist);
trace_mm_collapse_huge_page_isolate(folio, none_or_zero,
- referenced, writable, result);
+ referenced, result);
return result;
}

@@ -1280,7 +1275,6 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
unsigned long _address;
spinlock_t *ptl;
int node = NUMA_NO_NODE, unmapped = 0;
- bool writable = false;

VM_BUG_ON(address & ~HPAGE_PMD_MASK);

@@ -1344,8 +1338,6 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
result = SCAN_PTE_UFFD_WP;
goto out_unmap;
}
- if (pte_write(pteval))
- writable = true;

page = vm_normal_page(vma, _address, pteval);
if (unlikely(!page) || unlikely(is_zone_device_page(page))) {
@@ -1435,7 +1427,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
*mmap_locked = false;
}
out:
- trace_mm_khugepaged_scan_pmd(mm, folio, writable, referenced,
+ trace_mm_khugepaged_scan_pmd(mm, folio, referenced,
none_or_zero, result, unmapped);
return result;
}
--
2.30.2