linux-kernel - [PATCH 2/2] mm: convert do_set

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Message-ID: <a2faee74256c22cff2238487a86b154d5520c334.1746609191.git.baolin.wang@linux.alibaba.com>
Date: Wed,  7 May 2025 17:26:13 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: akpm@...ux-foundation.org,
	willy@...radead.org,
	david@...hat.com
Cc: hannes@...xchg.org,
	lorenzo.stoakes@...cle.com,
	Liam.Howlett@...cle.com,
	npache@...hat.com,
	ryan.roberts@....com,
	dev.jain@....com,
	ziy@...dia.com,
	vbabka@...e.cz,
	rppt@...nel.org,
	surenb@...gle.com,
	mhocko@...e.com,
	baolin.wang@...ux.alibaba.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] mm: convert do_set_pmd() to take a folio

In do_set_pmd(), we always use the folio->page to build PMD mappings for
the entire folio. Since all callers of do_set_pmd() already hold a stable
folio, converting do_set_pmd() to take a folio is safe and more straightforward.

Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 include/linux/mm.h |  2 +-
 mm/filemap.c       |  3 +--
 mm/khugepaged.c    |  2 +-
 mm/memory.c        | 12 ++++++------
 4 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 43748c8f3454..e00d81b9eb2a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1237,7 +1237,7 @@ 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 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 7b90cbeb4a1a..fbf8d7b76ab7 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3532,8 +3532,7 @@ 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, 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 0215ef6095d9..575a3384d046 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1479,7 +1479,7 @@ static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
 	VM_BUG_ON(!folio_test_large(folio));
 	mmap_assert_locked(vma->vm_mm);
 
-	if (do_set_pmd(&vmf, &folio->page))
+	if (do_set_pmd(&vmf, folio))
 		return SCAN_FAIL;
 
 	folio_get(folio);
diff --git a/mm/memory.c b/mm/memory.c
index 68c1d962d0ad..0f5c8d8d59b0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5176,14 +5176,14 @@ static void deposit_prealloc_pte(struct vm_fault *vmf)
 	vmf->prealloc_pte = NULL;
 }
 
-vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
+vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
 	struct vm_area_struct *vma = vmf->vma;
 	bool write = vmf->flags & FAULT_FLAG_WRITE;
 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 	pmd_t entry;
 	vm_fault_t ret = VM_FAULT_FALLBACK;
+	struct page *page;
 
 	/*
 	 * It is too late to allocate a small folio, we already have a large
@@ -5251,7 +5251,7 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
 	return ret;
 }
 #else
-vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
+vm_fault_t do_set_pmd(struct vm_fault *vmf, struct folio *folio)
 {
 	return VM_FAULT_FALLBACK;
 }
@@ -5345,6 +5345,7 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
 	else
 		page = vmf->page;
 
+	folio = page_folio(page);
 	/*
 	 * check even for read faults because we might have lost our CoWed
 	 * page
@@ -5356,8 +5357,8 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
 	}
 
 	if (pmd_none(*vmf->pmd)) {
-		if (PageTransCompound(page)) {
-			ret = do_set_pmd(vmf, page);
+		if (folio_test_pmd_mappable(folio)) {
+			ret = do_set_pmd(vmf, folio);
 			if (ret != VM_FAULT_FALLBACK)
 				return ret;
 		}
@@ -5368,7 +5369,6 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
 			return VM_FAULT_OOM;
 	}
 
-	folio = page_folio(page);
 	nr_pages = folio_nr_pages(folio);
 
 	/*
-- 
2.43.5