[PATCH] mm: remove redundant page parameter from do_set_pmd()

[Ye Liu <ye.liu@linux.dev>]

From: Ye Liu <liuye@kylinos.cn>

The page parameter passed to do_set_pmd() was always overwritten with
&folio->page immediately upon function entry (line 5369 in memory.c),
making the parameter completely redundant. This confused callers who
computed different page values only to have them ignored.

Changes:
- Convert page from a function parameter to a local variable
- Update function signature in both implementations and stub
- Remove unnecessary folio_file_page() calculation in filemap.c
- Update all three call sites to remove the page argument

This simplifies the API since folio already contains all the page
information needed. The function still uses &folio->page internally
for cache flushing and rmap operations.

Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
 include/linux/mm.h | 2 +-
 mm/filemap.c       | 3 +--
 mm/khugepaged.c    | 6 +++---
 mm/memory.c        | 7 ++++---
 4 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 710d20fc954b..cb1fe75575c3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1490,7 +1490,7 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
 	return pte;
 }
 
-vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio, struct page *page);
+vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio);
 void set_pte_range(struct vm_fault *vmf, struct folio *folio,
 		struct page *page, unsigned int nr, unsigned long addr);
 
diff --git a/mm/filemap.c b/mm/filemap.c
index ebd75684cb0a..4be5f3f5b8d6 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3678,8 +3678,7 @@ static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio,
 	}
 
 	if (pmd_none(*vmf->pmd) && folio_test_pmd_mappable(folio)) {
-		struct page *page = folio_file_page(folio, start);
-		vm_fault_t ret = do_set_pmd(vmf, folio, page);
+		vm_fault_t ret = do_set_pmd(vmf, folio);
 		if (!ret) {
 			/* The page is mapped successfully, reference consumed. */
 			folio_unlock(folio);
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 9f790ec34400..2d7b23efa11b 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1442,7 +1442,7 @@ static void collect_mm_slot(struct mm_slot *slot)
 
 /* folio must be locked, and mmap_lock must be held */
 static enum scan_result set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
-				     pmd_t *pmdp, struct folio *folio, struct page *page)
+				     pmd_t *pmdp, struct folio *folio)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	struct vm_fault vmf = {
@@ -1470,7 +1470,7 @@ static enum scan_result set_huge_pmd(struct vm_area_struct *vma, unsigned long a
 	}
 
 	vmf.pmd = pmdp;
-	if (do_set_pmd(&vmf, folio, page))
+	if (do_set_pmd(&vmf, folio))
 		return SCAN_FAIL;
 
 	folio_get(folio);
@@ -1678,7 +1678,7 @@ static enum scan_result try_collapse_pte_mapped_thp(struct mm_struct *mm, unsign
 maybe_install_pmd:
 	/* step 5: install pmd entry */
 	result = install_pmd
-			? set_huge_pmd(vma, haddr, pmd, folio, &folio->page)
+			? set_huge_pmd(vma, haddr, pmd, folio)
 			: SCAN_SUCCEED;
 	goto drop_folio;
 abort:
diff --git a/mm/memory.c b/mm/memory.c
index 30a897018482..8b29ecbfe7fa 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5342,8 +5342,9 @@ static void deposit_prealloc_pte(struct vm_fault *vmf)
 	vmf->prealloc_pte = NULL;
 }
 
-vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio, struct page *page)
+vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio)
 {
+	struct page *page;
 	struct vm_area_struct *vma = vmf->vma;
 	bool write = vmf->flags & FAULT_FLAG_WRITE;
 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
@@ -5418,7 +5419,7 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio, struct page *pa
 	return ret;
 }
 #else
-vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio, struct page *page)
+vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio)
 {
 	return VM_FAULT_FALLBACK;
 }
@@ -5542,7 +5543,7 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
 
 	if (pmd_none(*vmf->pmd)) {
 		if (!needs_fallback && folio_test_pmd_mappable(folio)) {
-			ret = do_set_pmd(vmf, folio, page);
+			ret = do_set_pmd(vmf, folio);
 			if (ret != VM_FAULT_FALLBACK)
 				return ret;
 		}
-- 
2.43.0