[PATCH V3 4/5] mm/khugepaged: use enum scan_result for result variables and return types

[Shivank Garg <shivankg@amd.com>]

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@nvidia.com>
Signed-off-by: Shivank Garg <shivankg@amd.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:
-- 
2.43.0