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authorMatthew Wilcox (Oracle) <willy@infradead.org>2022-01-18 00:33:26 +0300
committerMatthew Wilcox (Oracle) <willy@infradead.org>2022-03-21 19:59:02 +0300
commit4ba1119cd53166d853050ff1a9d76079cd8f8e06 (patch)
treea70d8b819fcce1322e1193bbae30676eb3ce0ebf /mm/util.c
parent74e8ee4708a8edabbbc7ab8c12ec24d7a561bb41 (diff)
downloadlinux-4ba1119cd53166d853050ff1a9d76079cd8f8e06.tar.xz
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>
Diffstat (limited to 'mm/util.c')
-rw-r--r--mm/util.c33
1 files changed, 33 insertions, 0 deletions
diff --git a/mm/util.c b/mm/util.c
index 7e43369064c8..b614f423aaa4 100644
--- 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.