diff options
author | Matthew Wilcox (Oracle) <willy@infradead.org> | 2022-01-17 16:33:26 -0500 |
---|---|---|
committer | Matthew Wilcox (Oracle) <willy@infradead.org> | 2022-03-21 12:59:02 -0400 |
commit | 4ba1119cd53166d853050ff1a9d76079cd8f8e06 (patch) | |
tree | a70d8b819fcce1322e1193bbae30676eb3ce0ebf /mm/util.c | |
parent | 74e8ee4708a8edabbbc7ab8c12ec24d7a561bb41 (diff) |
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.c | 33 |
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. |