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Message-ID: <D9E6B402-528B-46F2-B4B0-9CD9549A449F@nvidia.com>
Date: Tue, 16 Dec 2025 10:38:54 -0500
From: Zi Yan <ziy@...dia.com>
To: Shivank Garg <shivankg@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
David Hildenbrand <david@...nel.org>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.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>, Dev Jain <dev.jain@....com>,
Barry Song <baohua@...nel.org>, Lance Yang <lance.yang@...ux.dev>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] mm/khugepaged: use enum scan_result for result
variables
On 16 Dec 2025, at 6:11, Shivank Garg wrote:
> Use enum scan_result for local variables and the result pointer in
> khugepaged_scan_mm_slot(), instead of plain int. This improves code
> readability and clarifies intent,
>
> No functional change.
>
> Signed-off-by: Shivank Garg <shivankg@....com>
> ---
> mm/khugepaged.c | 29 ++++++++++++++++-------------
> 1 file changed, 16 insertions(+), 13 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 107146f012b1..65b1b778378a 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -547,7 +547,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
The return type could be changed too.
> 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) {
> @@ -786,7 +787,7 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,
Ditto.
> 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.
> @@ -969,7 +970,7 @@ static int check_pmd_still_valid(struct mm_struct *mm,
> pmd_t *pmd)
Ditto.
> {
> 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;
> @@ -993,7 +994,7 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
Ditto.
> 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;
>
> @@ -1100,7 +1101,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
Ditto.
> 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;
>
> @@ -1253,8 +1254,8 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
> {
Ditto.
> 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;
> @@ -1492,7 +1493,8 @@ static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
Same here.
> int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
> bool install_pmd)
> {
And here.
> - 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;
> @@ -1866,7 +1868,8 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
Same here.
> 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);
> @@ -2296,7 +2299,7 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr,
Same here.
> 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;
> @@ -2394,7 +2397,7 @@ 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)
> @@ -2555,7 +2558,7 @@ 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();
>
> @@ -2790,7 +2793,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start,
>
> for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) {
> bool retried = false;
> - int result = SCAN_FAIL;
> + enum scan_result result = SCAN_FAIL;
>
> if (!mmap_locked) {
> retry:
> --
In addition, the return types of find_pmd_or_thp_or_none(),
hugepage_vma_revalidate(), alloc_charge_folio(), and check_pmd_state() need to be changed to enum scan_result too.
Best Regards,
Yan, Zi
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