[RFC PATCH 5/7] mm: Make /proc/pid/smaps use the new generic pagewalk API

Oscar Salvador
2026-04-12T17:43:05Z

Have /proc/pid/smaps make use of the new generic API, and remove
the code which was using the old one.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
fs/proc/task_mmu.c | 309 ++++++++++++---------------------------------
1 file changed, 84 insertions(+), 225 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e091931d7ca1..afbcdb11ad80 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -915,7 +915,7 @@ static void smaps_page_accumulate(struct mem_size_stats *mss,

static void smaps_account(struct mem_size_stats *mss, struct page *page,
bool compound, bool young, bool dirty, bool locked,
- bool present)
+ bool present, int ssize)
{
struct folio *folio = page_folio(page);
int i, nr = compound ? compound_nr(page) : 1;
@@ -923,6 +923,11 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
bool exclusive;
int mapcount;

+ if (ssize) {
+ nr = ssize / PAGE_SIZE;
+ size = ssize;
+ }
+
/*
* First accumulate quantities that depend only on |size| and the type
* of the compound page.
@@ -988,150 +993,6 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
}
}

-#ifdef CONFIG_SHMEM
-static int smaps_pte_hole(unsigned long addr, unsigned long end,
- __always_unused int depth, struct mm_walk *walk)
-{
- struct mem_size_stats *mss = walk->private;
- struct vm_area_struct *vma = walk->vma;
-
- mss->swap += shmem_partial_swap_usage(walk->vma->vm_file->f_mapping,
- linear_page_index(vma, addr),
- linear_page_index(vma, end));
-
- return 0;
-}
-#else
-#define smaps_pte_hole NULL
-#endif /* CONFIG_SHMEM */
-
-static void smaps_pte_hole_lookup(unsigned long addr, struct mm_walk *walk)
-{
-#ifdef CONFIG_SHMEM
- if (walk->ops->pte_hole) {
- /* depth is not used */
- smaps_pte_hole(addr, addr + PAGE_SIZE, 0, walk);
- }
-#endif
-}
-
-static void smaps_pte_entry(pte_t *pte, unsigned long addr,
- struct mm_walk *walk)
-{
- struct mem_size_stats *mss = walk->private;
- struct vm_area_struct *vma = walk->vma;
- bool locked = !!(vma->vm_flags & VM_LOCKED);
- struct page *page = NULL;
- bool present = false, young = false, dirty = false;
- pte_t ptent = ptep_get(pte);
-
- if (pte_present(ptent)) {
- page = vm_normal_page(vma, addr, ptent);
- young = pte_young(ptent);
- dirty = pte_dirty(ptent);
- present = true;
- } else if (pte_none(ptent)) {
- smaps_pte_hole_lookup(addr, walk);
- } else {
- const softleaf_t entry = softleaf_from_pte(ptent);
-
- if (softleaf_is_swap(entry)) {
- int mapcount;
-
- mss->swap += PAGE_SIZE;
- mapcount = swp_swapcount(entry);
- if (mapcount >= 2) {
- u64 pss_delta = (u64)PAGE_SIZE << PSS_SHIFT;
-
- do_div(pss_delta, mapcount);
- mss->swap_pss += pss_delta;
- } else {
- mss->swap_pss += (u64)PAGE_SIZE << PSS_SHIFT;
- }
- } else if (softleaf_has_pfn(entry)) {
- if (softleaf_is_device_private(entry))
- present = true;
- page = softleaf_to_page(entry);
- }
- }
-
- if (!page)
- return;
-
- smaps_account(mss, page, false, young, dirty, locked, present);
-}
-
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
- struct mm_walk *walk)
-{
- struct mem_size_stats *mss = walk->private;
- struct vm_area_struct *vma = walk->vma;
- bool locked = !!(vma->vm_flags & VM_LOCKED);
- struct page *page = NULL;
- bool present = false;
- struct folio *folio;
-
- if (pmd_none(*pmd))
- return;
- if (pmd_present(*pmd)) {
- page = vm_normal_page_pmd(vma, addr, *pmd);
- present = true;
- } else if (unlikely(thp_migration_supported())) {
- const softleaf_t entry = softleaf_from_pmd(*pmd);
-
- if (softleaf_has_pfn(entry))
- page = softleaf_to_page(entry);
- }
- if (IS_ERR_OR_NULL(page))
- return;
- folio = page_folio(page);
- if (folio_test_anon(folio))
- mss->anonymous_thp += HPAGE_PMD_SIZE;
- else if (folio_test_swapbacked(folio))
- mss->shmem_thp += HPAGE_PMD_SIZE;
- else if (folio_is_zone_device(folio))
- /* pass */;
- else
- mss->file_thp += HPAGE_PMD_SIZE;
-
- smaps_account(mss, page, true, pmd_young(*pmd), pmd_dirty(*pmd),
- locked, present);
-}
-#else
-static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
- struct mm_walk *walk)
-{
-}
-#endif
-
-static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
- struct mm_walk *walk)
-{
- struct vm_area_struct *vma = walk->vma;
- pte_t *pte;
- spinlock_t *ptl;
-
- ptl = pmd_trans_huge_lock(pmd, vma);
- if (ptl) {
- smaps_pmd_entry(pmd, addr, walk);
- spin_unlock(ptl);
- goto out;
- }
-
- pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
- if (!pte) {
- walk->action = ACTION_AGAIN;
- return 0;
- }
- for (; addr != end; pte++, addr += PAGE_SIZE)
- smaps_pte_entry(pte, addr, walk);
- pte_unmap_unlock(pte - 1, ptl);
-out:
- cond_resched();
- return 0;
-}
-
static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
{
/*
@@ -1228,58 +1089,6 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
seq_putc(m, '\n');
}

-#ifdef CONFIG_HUGETLB_PAGE
-static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
- unsigned long addr, unsigned long end,
- struct mm_walk *walk)
-{
- struct mem_size_stats *mss = walk->private;
- struct vm_area_struct *vma = walk->vma;
- struct folio *folio = NULL;
- bool present = false;
- spinlock_t *ptl;
- pte_t ptent;
-
- ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
- ptent = huge_ptep_get(walk->mm, addr, pte);
- if (pte_present(ptent)) {
- folio = page_folio(pte_page(ptent));
- present = true;
- } else {
- const softleaf_t entry = softleaf_from_pte(ptent);
-
- if (softleaf_has_pfn(entry))
- folio = softleaf_to_folio(entry);
- }
-
- if (folio) {
- /* We treat non-present entries as "maybe shared". */
- if (!present || folio_maybe_mapped_shared(folio) ||
- hugetlb_pmd_shared(pte))
- mss->shared_hugetlb += huge_page_size(hstate_vma(vma));
- else
- mss->private_hugetlb += huge_page_size(hstate_vma(vma));
- }
- spin_unlock(ptl);
- return 0;
-}
-#else
-#define smaps_hugetlb_range NULL
-#endif /* HUGETLB_PAGE */
-
-static const struct mm_walk_ops smaps_walk_ops = {
- .pmd_entry = smaps_pte_range,
- .hugetlb_entry = smaps_hugetlb_range,
- .walk_lock = PGWALK_RDLOCK,
-};
-
-static const struct mm_walk_ops smaps_shmem_walk_ops = {
- .pmd_entry = smaps_pte_range,
- .hugetlb_entry = smaps_hugetlb_range,
- .pte_hole = smaps_pte_hole,
- .walk_lock = PGWALK_RDLOCK,
-};
-
/*
* Gather mem stats from @vma with the indicated beginning
* address @start, and keep them in @mss.
@@ -1287,40 +1096,90 @@ static const struct mm_walk_ops smaps_shmem_walk_ops = {
* Use vm_start of @vma as the beginning address if @start is 0.
*/
static void smap_gather_stats(struct vm_area_struct *vma,
- struct mem_size_stats *mss, unsigned long start)
+ struct mem_size_stats *mss,
+ unsigned long start)
{
- const struct mm_walk_ops *ops = &smaps_walk_ops;
-
- /* Invalid start */
- if (start >= vma->vm_end)
- return;
+ struct pt_range_walk ptw = {
+ .mm = vma->vm_mm
+ };
+ enum pt_range_walk_type type;
+ pt_type_flags_t flags = PT_TYPE_ALL;

- if (vma->vm_file && shmem_mapping(vma->vm_file->f_mapping)) {
- /*
- * For shared or readonly shmem mappings we know that all
- * swapped out pages belong to the shmem object, and we can
- * obtain the swap value much more efficiently. For private
- * writable mappings, we might have COW pages that are
- * not affected by the parent swapped out pages of the shmem
- * object, so we have to distinguish them during the page walk.
- * Unless we know that the shmem object (or the part mapped by
- * our VMA) has no swapped out pages at all.
- */
- unsigned long shmem_swapped = shmem_swap_usage(vma);
+ if (!start)
+ start = vma->vm_start;
+
+ flags &= ~(PT_TYPE_NONE|PT_TYPE_PFN);
+
+ type = pt_range_walk_start(&ptw, vma, start, vma->vm_end, flags);
+ while (type != PTW_DONE) {
+ bool locked = !!(vma->vm_flags & VM_LOCKED);
+ bool compound = false, account = false;
+ unsigned long swap_size;
+ int mapcount;
+
+ switch (type) {
+ case PTW_FOLIO:
+ case PTW_MIGRATION:
+ case PTW_HWPOISON:
+ case PTW_DEVICE:
+ /*
+ * We either have a folio because vm_normal_folio was
+ * successful, or because we had a special swap entry
+ * and could retrieve it with softleaf_to_page.
+ */
+ if (is_vm_hugetlb_page(vma)) {
+ /* HugeTLB */
+ unsigned long size = huge_page_size(hstate_vma(ptw.vma));
+
+ if (!ptw.present || folio_maybe_mapped_shared(ptw.folio) ||
+ ptw.pmd_shared)
+ mss->shared_hugetlb += size;
+ else
+ mss->private_hugetlb += size;
+ } else {
+ account = true;
+ if (ptw.level == PTW_PMD_LEVEL) {
+ /* THP */
+ compound = true;
+ if (folio_test_anon(ptw.folio))
+ mss->anonymous_thp += ptw.size;
+ else if (folio_test_swapbacked(ptw.folio))
+ mss->shmem_thp += ptw.size;
+ else if (folio_is_zone_device(ptw.folio))
+ /* pass */;
+ else
+ mss->file_thp += ptw.size;
+ } else if (ptw.level == PTW_PTE_LEVEL && ptw.nr_entries > 1) {
+ compound = true;
+ }
+ }
+ break;
+ case PTW_SWAP:
+ account = true;
+ swap_size = PAGE_SIZE * ptw.nr_entries;
+ mss->swap += swap_size;
+ mapcount = swp_swapcount(ptw.softleaf_entry);
+ if (mapcount >= 2) {
+ u64 pss_delta = (u64)swap_size << PSS_SHIFT;

- if (!start && (!shmem_swapped || (vma->vm_flags & VM_SHARED) ||
- !(vma->vm_flags & VM_WRITE))) {
- mss->swap += shmem_swapped;
- } else {
- ops = &smaps_shmem_walk_ops;
+ do_div(pss_delta, mapcount);
+ mss->swap_pss += pss_delta;
+ } else {
+ mss->swap_pss += (u64)swap_size << PSS_SHIFT;
+ }
+ break;
+ default:
+ /* Ooops */
+ break;
}
+
+ if (account && ptw.folio)
+ smaps_account(mss, ptw.page, compound, ptw.young,
+ ptw.dirty, locked, ptw.present, ptw.size);
+ type = pt_range_walk_next(&ptw, vma, start, vma->vm_end, flags);
}

- /* mmap_lock is held in m_start */
- if (!start)
- walk_page_vma(vma, ops, mss);
- else
- walk_page_range(vma->vm_mm, start, vma->vm_end, ops, mss);
+ pt_range_walk_done(&ptw);
}

#define SEQ_PUT_DEC(str, val) \
--
2.35.3