[PATCH v9 40/96] mm: Add folio_mapped

["Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>]

This function is the equivalent of page_mapped().  It is slightly
shorter as we do not need to handle the PageTail() case.  Reimplement
page_mapped() as a wrapper around folio_mapped().

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 include/linux/mm.h |  1 +
 mm/folio-compat.c  |  6 ++++++
 mm/util.c          | 30 +++++++++++++++++-------------
 3 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index bca3e2518e5e..6bfc43309e4b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1779,6 +1779,7 @@ static inline pgoff_t page_index(struct page *page)
 }
 
 bool page_mapped(struct page *page);
+bool folio_mapped(struct folio *folio);
 
 /*
  * Return true only if the page has been allocated with
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 3c83f03b80d7..7044fcc8a8aa 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -35,3 +35,9 @@ void wait_for_stable_page(struct page *page)
 	return folio_wait_stable(page_folio(page));
 }
 EXPORT_SYMBOL_GPL(wait_for_stable_page);
+
+bool page_mapped(struct page *page)
+{
+	return folio_mapped(page_folio(page));
+}
+EXPORT_SYMBOL(page_mapped);
diff --git a/mm/util.c b/mm/util.c
index afd99591cb81..e60b0920f9a7 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -652,28 +652,32 @@ void *page_rmapping(struct page *page)
 	return __page_rmapping(page);
 }
 
-/*
- * Return true if this page is mapped into pagetables.
- * For compound page it returns true if any subpage of compound page is mapped.
+/**
+ * folio_mapped - Is this folio mapped into userspace?
+ * @folio: The folio.
+ *
+ * Return: true if any page in this folio is mapped into pagetables.
  */
-bool page_mapped(struct page *page)
+bool folio_mapped(struct folio *folio)
 {
-	int i;
+	int i, nr;
 
-	if (likely(!PageCompound(page)))
-		return atomic_read(&page->_mapcount) >= 0;
-	page = compound_head(page);
-	if (atomic_read(compound_mapcount_ptr(page)) >= 0)
+	if (folio_single(folio))
+		return atomic_read(&folio->_mapcount) >= 0;
+	if (atomic_read(compound_mapcount_ptr(&folio->page)) >= 0)
 		return true;
-	if (PageHuge(page))
+	if (folio_hugetlb(folio))
 		return false;
-	for (i = 0; i < compound_nr(page); i++) {
-		if (atomic_read(&page[i]._mapcount) >= 0)
+
+	nr = folio_nr_pages(folio);
+	for (i = 0; i < nr; i++) {
+		struct page *page = nth_page(&folio->page, i);
+		if (atomic_read(&page->_mapcount) >= 0)
 			return true;
 	}
 	return false;
 }
-EXPORT_SYMBOL(page_mapped);
+EXPORT_SYMBOL(folio_mapped);
 
 struct anon_vma *page_anon_vma(struct page *page)
 {
-- 
2.30.2