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Message-ID: <5639693a-a89a-47c8-978e-1aab59268413@arm.com>
Date: Thu, 22 Jan 2026 14:49:17 +0530
From: Dev Jain <dev.jain@....com>
To: Shivank Garg <shivankg@....com>, Andrew Morton
<akpm@...ux-foundation.org>, David Hildenbrand <david@...nel.org>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Zi Yan <ziy@...dia.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>,
"Liam R . Howlett" <Liam.Howlett@...cle.com>, Nico Pache
<npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
Barry Song <baohua@...nel.org>, Lance Yang <lance.yang@...ux.dev>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 4/5] mm/khugepaged: use enum scan_result for result
variables and return types
On 19/01/26 12:52 am, Shivank Garg wrote:
> Convert result variables and return types from int to enum scan_result
> throughout khugepaged code. This improves type safety and code clarity
> by making the intent explicit.
>
> No functional change.
>
> Reviewed-by: Zi Yan <ziy@...dia.com>
> Signed-off-by: Shivank Garg <shivankg@....com>
Reviewed-by: Dev Jain <dev.jain@....com>
> ---
> mm/khugepaged.c | 99 +++++++++++++++++++++++--------------------------
> 1 file changed, 46 insertions(+), 53 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 17f3f0043368..1667abae6d8d 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -537,17 +537,16 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte,
> }
> }
>
> -static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> - unsigned long start_addr,
> - pte_t *pte,
> - struct collapse_control *cc,
> - struct list_head *compound_pagelist)
> +static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma,
> + unsigned long start_addr, pte_t *pte, struct collapse_control *cc,
> + struct list_head *compound_pagelist)
> {
> struct page *page = NULL;
> struct folio *folio = NULL;
> unsigned long addr = start_addr;
> pte_t *_pte;
> - int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0;
> + int none_or_zero = 0, shared = 0, referenced = 0;
> + enum scan_result result = SCAN_FAIL;
>
> for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
> _pte++, addr += PAGE_SIZE) {
> @@ -780,13 +779,13 @@ static void __collapse_huge_page_copy_failed(pte_t *pte,
> * @ptl: lock on raw pages' PTEs
> * @compound_pagelist: list that stores compound pages
> */
> -static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,
> +static enum scan_result __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)
> {
> unsigned int i;
> - int result = SCAN_SUCCEED;
> + enum scan_result result = SCAN_SUCCEED;
>
> /*
> * Copying pages' contents is subject to memory poison at any iteration.
> @@ -898,10 +897,8 @@ static int hpage_collapse_find_target_node(struct collapse_control *cc)
> * Returns enum scan_result value.
> */
>
> -static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
> - bool expect_anon,
> - struct vm_area_struct **vmap,
> - struct collapse_control *cc)
> +static enum scan_result hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
> + bool expect_anon, struct vm_area_struct **vmap, struct collapse_control *cc)
> {
> struct vm_area_struct *vma;
> enum tva_type type = cc->is_khugepaged ? TVA_KHUGEPAGED :
> @@ -930,7 +927,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
> return SCAN_SUCCEED;
> }
>
> -static inline int check_pmd_state(pmd_t *pmd)
> +static inline enum scan_result check_pmd_state(pmd_t *pmd)
> {
> pmd_t pmde = pmdp_get_lockless(pmd);
>
> @@ -953,9 +950,8 @@ static inline int check_pmd_state(pmd_t *pmd)
> return SCAN_SUCCEED;
> }
>
> -static int find_pmd_or_thp_or_none(struct mm_struct *mm,
> - unsigned long address,
> - pmd_t **pmd)
> +static enum scan_result find_pmd_or_thp_or_none(struct mm_struct *mm,
> + unsigned long address, pmd_t **pmd)
> {
> *pmd = mm_find_pmd(mm, address);
> if (!*pmd)
> @@ -964,12 +960,11 @@ static int find_pmd_or_thp_or_none(struct mm_struct *mm,
> return check_pmd_state(*pmd);
> }
>
> -static int check_pmd_still_valid(struct mm_struct *mm,
> - unsigned long address,
> - pmd_t *pmd)
> +static enum scan_result check_pmd_still_valid(struct mm_struct *mm,
> + unsigned long address, pmd_t *pmd)
> {
> pmd_t *new_pmd;
> - int result = find_pmd_or_thp_or_none(mm, address, &new_pmd);
> + enum scan_result result = find_pmd_or_thp_or_none(mm, address, &new_pmd);
>
> if (result != SCAN_SUCCEED)
> return result;
> @@ -985,15 +980,14 @@ static int check_pmd_still_valid(struct mm_struct *mm,
> * Called and returns without pte mapped or spinlocks held.
> * Returns result: if not SCAN_SUCCEED, mmap_lock has been released.
> */
> -static int __collapse_huge_page_swapin(struct mm_struct *mm,
> - struct vm_area_struct *vma,
> - unsigned long start_addr, pmd_t *pmd,
> - int referenced)
> +static enum scan_result __collapse_huge_page_swapin(struct mm_struct *mm,
> + struct vm_area_struct *vma, unsigned long start_addr, pmd_t *pmd,
> + int referenced)
> {
> int swapped_in = 0;
> vm_fault_t ret = 0;
> unsigned long addr, end = start_addr + (HPAGE_PMD_NR * PAGE_SIZE);
> - int result;
> + enum scan_result result;
> pte_t *pte = NULL;
> spinlock_t *ptl;
>
> @@ -1062,8 +1056,8 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
> return result;
> }
>
> -static int alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,
> - struct collapse_control *cc)
> +static enum scan_result alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,
> + struct collapse_control *cc)
> {
> gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() :
> GFP_TRANSHUGE);
> @@ -1090,9 +1084,8 @@ static int alloc_charge_folio(struct folio **foliop, struct mm_struct *mm,
> return SCAN_SUCCEED;
> }
>
> -static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> - int referenced, int unmapped,
> - struct collapse_control *cc)
> +static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long address,
> + int referenced, int unmapped, struct collapse_control *cc)
> {
> LIST_HEAD(compound_pagelist);
> pmd_t *pmd, _pmd;
> @@ -1100,7 +1093,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> pgtable_t pgtable;
> struct folio *folio;
> spinlock_t *pmd_ptl, *pte_ptl;
> - int result = SCAN_FAIL;
> + enum scan_result result = SCAN_FAIL;
> struct vm_area_struct *vma;
> struct mmu_notifier_range range;
>
> @@ -1246,15 +1239,14 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> return result;
> }
>
> -static int hpage_collapse_scan_pmd(struct mm_struct *mm,
> - struct vm_area_struct *vma,
> - unsigned long start_addr, bool *mmap_locked,
> - struct collapse_control *cc)
> +static enum scan_result hpage_collapse_scan_pmd(struct mm_struct *mm,
> + struct vm_area_struct *vma, unsigned long start_addr, bool *mmap_locked,
> + struct collapse_control *cc)
> {
> pmd_t *pmd;
> pte_t *pte, *_pte;
> - int result = SCAN_FAIL, referenced = 0;
> - int none_or_zero = 0, shared = 0;
> + int none_or_zero = 0, shared = 0, referenced = 0;
> + enum scan_result result = SCAN_FAIL;
> struct page *page = NULL;
> struct folio *folio = NULL;
> unsigned long addr;
> @@ -1441,8 +1433,8 @@ static void collect_mm_slot(struct mm_slot *slot)
> }
>
> /* folio must be locked, and mmap_lock must be held */
> -static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
> - pmd_t *pmdp, struct folio *folio, struct page *page)
> +static enum scan_result set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
> + pmd_t *pmdp, struct folio *folio, struct page *page)
> {
> struct mm_struct *mm = vma->vm_mm;
> struct vm_fault vmf = {
> @@ -1477,10 +1469,11 @@ static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
> return SCAN_SUCCEED;
> }
>
> -static int try_collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
> +static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
> bool install_pmd)
> {
> - int nr_mapped_ptes = 0, result = SCAN_FAIL;
> + enum scan_result result = SCAN_FAIL;
> + int nr_mapped_ptes = 0;
> unsigned int nr_batch_ptes;
> struct mmu_notifier_range range;
> bool notified = false;
> @@ -1862,9 +1855,8 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
> * + unlock old pages
> * + unlock and free huge page;
> */
> -static int collapse_file(struct mm_struct *mm, unsigned long addr,
> - struct file *file, pgoff_t start,
> - struct collapse_control *cc)
> +static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr,
> + struct file *file, pgoff_t start, struct collapse_control *cc)
> {
> struct address_space *mapping = file->f_mapping;
> struct page *dst;
> @@ -1872,7 +1864,8 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> pgoff_t index = 0, end = start + HPAGE_PMD_NR;
> LIST_HEAD(pagelist);
> XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
> - int nr_none = 0, result = SCAN_SUCCEED;
> + enum scan_result result = SCAN_SUCCEED;
> + int nr_none = 0;
> bool is_shmem = shmem_file(file);
>
> VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
> @@ -2293,16 +2286,15 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> return result;
> }
>
> -static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
> - struct file *file, pgoff_t start,
> - struct collapse_control *cc)
> +static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
> + struct file *file, pgoff_t start, struct collapse_control *cc)
> {
> struct folio *folio = NULL;
> struct address_space *mapping = file->f_mapping;
> XA_STATE(xas, &mapping->i_pages, start);
> int present, swap;
> int node = NUMA_NO_NODE;
> - int result = SCAN_SUCCEED;
> + enum scan_result result = SCAN_SUCCEED;
>
> present = 0;
> swap = 0;
> @@ -2400,7 +2392,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
> return result;
> }
>
> -static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result,
> +static unsigned int khugepaged_scan_mm_slot(unsigned int pages, enum scan_result *result,
> struct collapse_control *cc)
> __releases(&khugepaged_mm_lock)
> __acquires(&khugepaged_mm_lock)
> @@ -2562,7 +2554,7 @@ static void khugepaged_do_scan(struct collapse_control *cc)
> unsigned int progress = 0, pass_through_head = 0;
> unsigned int pages = READ_ONCE(khugepaged_pages_to_scan);
> bool wait = true;
> - int result = SCAN_SUCCEED;
> + enum scan_result result = SCAN_SUCCEED;
>
> lru_add_drain_all();
>
> @@ -2775,7 +2767,8 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start,
> struct collapse_control *cc;
> struct mm_struct *mm = vma->vm_mm;
> unsigned long hstart, hend, addr;
> - int thps = 0, last_fail = SCAN_FAIL;
> + enum scan_result last_fail = SCAN_FAIL;
> + int thps = 0;
> bool mmap_locked = true;
>
> BUG_ON(vma->vm_start > start);
> @@ -2796,7 +2789,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start,
> hend = end & HPAGE_PMD_MASK;
>
> for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) {
> - int result = SCAN_FAIL;
> + enum scan_result result = SCAN_FAIL;
> bool triggered_wb = false;
>
> retry:
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