This is far less efficient for the lagging filesystems which still
use page_offset(), but it removes an access to page->index. It also
fixes a bug -- if any filesystem passed a tail page to page_offset(),
it would return garbage which might result in the filesystem choosing
to not writeback a dirty page. There probably aren't any examples
of this, but I can't be certain.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
include/linux/pagemap.h | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index ad7c0f615e9b..8c52a637d42b 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -1019,21 +1019,23 @@ static inline pgoff_t page_pgoff(const struct folio *folio,
return folio->index + folio_page_idx(folio, page);
}
-/*
- * Return byte-offset into filesystem object for page.
+/**
+ * folio_pos - Returns the byte position of this folio in its file.
+ * @folio: The folio.
*/
-static inline loff_t page_offset(struct page *page)
+static inline loff_t folio_pos(const struct folio *folio)
{
- return ((loff_t)page->index) << PAGE_SHIFT;
+ return ((loff_t)folio->index) * PAGE_SIZE;
}
-/**
- * folio_pos - Returns the byte position of this folio in its file.
- * @folio: The folio.
+/*
+ * Return byte-offset into filesystem object for page.
*/
-static inline loff_t folio_pos(struct folio *folio)
+static inline loff_t page_offset(struct page *page)
{
- return page_offset(&folio->page);
+ struct folio *folio = page_folio(page);
+
+ return folio_pos(folio) + folio_page_idx(folio, page) * PAGE_SIZE;
}
/*
--
2.47.2
