mm: Add folio_mapcount()

This implements the same algorithm as total_mapcount(), which is
transformed into a wrapper function.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 70f0ca2..0d380dc 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -825,8 +825,14 @@ static inline int page_mapcount(struct page *page)
        return atomic_read(&page->_mapcount) + 1;
 }
 
+int folio_mapcount(struct folio *folio);
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-int total_mapcount(struct page *page);
+static inline int total_mapcount(struct page *page)
+{
+       return folio_mapcount(page_folio(page));
+}
+
 int page_trans_huge_mapcount(struct page *page);
 #else
 static inline int total_mapcount(struct page *page)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9afca01..beebe41 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2465,30 +2465,6 @@ static void __split_huge_page(struct page *page, struct list_head *list,
        }
 }
 
-int total_mapcount(struct page *page)
-{
-       int i, compound, nr, ret;
-
-       VM_BUG_ON_PAGE(PageTail(page), page);
-
-       if (likely(!PageCompound(page)))
-               return atomic_read(&page->_mapcount) + 1;
-
-       compound = compound_mapcount(page);
-       nr = compound_nr(page);
-       if (PageHuge(page))
-               return compound;
-       ret = compound;
-       for (i = 0; i < nr; i++)
-               ret += atomic_read(&page[i]._mapcount) + 1;
-       /* File pages has compound_mapcount included in _mapcount */
-       if (!PageAnon(page))
-               return ret - compound * nr;
-       if (PageDoubleMap(page))
-               ret -= nr;
-       return ret;
-}
-
 /*
  * This calculates accurately how many mappings a transparent hugepage
  * has (unlike page_mapcount() which isn't fully accurate). This full

diff --git a/mm/util.c b/mm/util.c
index 7e43369..b614f42 100644 (file)
--- a/mm/util.c
+++ b/mm/util.c
@@ -741,6 +741,39 @@ int __page_mapcount(struct page *page)
 EXPORT_SYMBOL_GPL(__page_mapcount);
 
 /**
+ * folio_mapcount() - Calculate the number of mappings of this folio.
+ * @folio: The folio.
+ *
+ * A large folio tracks both how many times the entire folio is mapped,
+ * and how many times each individual page in the folio is mapped.
+ * This function calculates the total number of times the folio is
+ * mapped.
+ *
+ * Return: The number of times this folio is mapped.
+ */
+int folio_mapcount(struct folio *folio)
+{
+       int i, compound, nr, ret;
+
+       if (likely(!folio_test_large(folio)))
+               return atomic_read(&folio->_mapcount) + 1;
+
+       compound = folio_entire_mapcount(folio);
+       nr = folio_nr_pages(folio);
+       if (folio_test_hugetlb(folio))
+               return compound;
+       ret = compound;
+       for (i = 0; i < nr; i++)
+               ret += atomic_read(&folio_page(folio, i)->_mapcount) + 1;
+       /* File pages has compound_mapcount included in _mapcount */
+       if (!folio_test_anon(folio))
+               return ret - compound * nr;
+       if (folio_test_double_map(folio))
+               ret -= nr;
+       return ret;
+}
+
+/**
  * folio_copy - Copy the contents of one folio to another.
  * @dst: Folio to copy to.
  * @src: Folio to copy from.