mm/khugepaged: use start_addr/addr for improved readability

When collapsing a pmd, there are two address in use:

  * address points to the start of pmd
  * address points to each individual page

Current naming makes it difficult to distinguish these two and is hence
error prone.

Considering the plan to collapse mTHP, name the first one `start_addr' and
the second `addr' for better readability and consistency.

Link: https://lkml.kernel.org/r/20250922140938.27343-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Nico Pache <npache@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: RichardWeiYang

mm/khugepaged.c

@@ -537,18 +537,19 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte,
 }
 
 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
-					unsigned long address,
+					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;
 
 	for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
-	     _pte++, address += PAGE_SIZE) {
+	     _pte++, addr += PAGE_SIZE) {
 		pte_t pteval = ptep_get(_pte);
 		if (pte_none(pteval) || (pte_present(pteval) &&
 				is_zero_pfn(pte_pfn(pteval)))) {
@@ -571,7 +572,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 			result = SCAN_PTE_UFFD_WP;
 			goto out;
 		}
-		page = vm_normal_page(vma, address, pteval);
+		page = vm_normal_page(vma, addr, pteval);
 		if (unlikely(!page) || unlikely(is_zone_device_page(page))) {
 			result = SCAN_PAGE_NULL;
 			goto out;
@@ -656,8 +657,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		 */
 		if (cc->is_khugepaged &&
 		    (pte_young(pteval) || folio_test_young(folio) ||
-		     folio_test_referenced(folio) || mmu_notifier_test_young(vma->vm_mm,
-								     address)))
+		     folio_test_referenced(folio) ||
+		     mmu_notifier_test_young(vma->vm_mm, addr)))
 			referenced++;
 	}
 
@@ -986,21 +987,21 @@ static int check_pmd_still_valid(struct mm_struct *mm,
  */
 static int __collapse_huge_page_swapin(struct mm_struct *mm,
 				       struct vm_area_struct *vma,
-				       unsigned long haddr, pmd_t *pmd,
+				       unsigned long start_addr, pmd_t *pmd,
 				       int referenced)
 {
 	int swapped_in = 0;
 	vm_fault_t ret = 0;
-	unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE);
+	unsigned long addr, end = start_addr + (HPAGE_PMD_NR * PAGE_SIZE);
 	int result;
 	pte_t *pte = NULL;
 	spinlock_t *ptl;
 
-	for (address = haddr; address < end; address += PAGE_SIZE) {
+	for (addr = start_addr; addr < end; addr += PAGE_SIZE) {
 		struct vm_fault vmf = {
 			.vma = vma,
-			.address = address,
-			.pgoff = linear_page_index(vma, address),
+			.address = addr,
+			.pgoff = linear_page_index(vma, addr),
 			.flags = FAULT_FLAG_ALLOW_RETRY,
 			.pmd = pmd,
 		};
@@ -1010,7 +1011,7 @@ static int __collapse_huge_page_swapin(struct mm_struct *mm,
 			 * Here the ptl is only used to check pte_same() in
 			 * do_swap_page(), so readonly version is enough.
 			 */
-			pte = pte_offset_map_ro_nolock(mm, pmd, address, &ptl);
+			pte = pte_offset_map_ro_nolock(mm, pmd, addr, &ptl);
 			if (!pte) {
 				mmap_read_unlock(mm);
 				result = SCAN_PMD_NULL;
@@ -1253,7 +1254,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
 
 static int hpage_collapse_scan_pmd(struct mm_struct *mm,
 				   struct vm_area_struct *vma,
-				   unsigned long address, bool *mmap_locked,
+				   unsigned long start_addr, bool *mmap_locked,
 				   struct collapse_control *cc)
 {
 	pmd_t *pmd;
@@ -1262,26 +1263,26 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
 	int none_or_zero = 0, shared = 0;
 	struct page *page = NULL;
 	struct folio *folio = NULL;
-	unsigned long _address;
+	unsigned long addr;
 	spinlock_t *ptl;
 	int node = NUMA_NO_NODE, unmapped = 0;
 
-	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
+	VM_BUG_ON(start_addr & ~HPAGE_PMD_MASK);
 
-	result = find_pmd_or_thp_or_none(mm, address, &pmd);
+	result = find_pmd_or_thp_or_none(mm, start_addr, &pmd);
 	if (result != SCAN_SUCCEED)
 		goto out;
 
 	memset(cc->node_load, 0, sizeof(cc->node_load));
 	nodes_clear(cc->alloc_nmask);
-	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
+	pte = pte_offset_map_lock(mm, pmd, start_addr, &ptl);
 	if (!pte) {
 		result = SCAN_PMD_NULL;
 		goto out;
 	}
 
-	for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR;
-	     _pte++, _address += PAGE_SIZE) {
+	for (addr = start_addr, _pte = pte; _pte < pte + HPAGE_PMD_NR;
+	     _pte++, addr += PAGE_SIZE) {
 		pte_t pteval = ptep_get(_pte);
 		if (is_swap_pte(pteval)) {
 			++unmapped;
@@ -1329,7 +1330,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
 			goto out_unmap;
 		}
 
-		page = vm_normal_page(vma, _address, pteval);
+		page = vm_normal_page(vma, addr, pteval);
 		if (unlikely(!page) || unlikely(is_zone_device_page(page))) {
 			result = SCAN_PAGE_NULL;
 			goto out_unmap;
@@ -1398,7 +1399,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
 		if (cc->is_khugepaged &&
 		    (pte_young(pteval) || folio_test_young(folio) ||
 		     folio_test_referenced(folio) ||
-		     mmu_notifier_test_young(vma->vm_mm, _address)))
+		     mmu_notifier_test_young(vma->vm_mm, addr)))
 			referenced++;
 	}
 	if (cc->is_khugepaged &&
@@ -1411,7 +1412,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
 out_unmap:
 	pte_unmap_unlock(pte, ptl);
 	if (result == SCAN_SUCCEED) {
-		result = collapse_huge_page(mm, address, referenced,
+		result = collapse_huge_page(mm, start_addr, referenced,
 					    unmapped, cc);
 		/* collapse_huge_page will return with the mmap_lock released */
 		*mmap_locked = false;