Convert fio->page to a folio then use it where folio APIs exist.
Removes a reference to page->mapping and a hidden call to
compound_head().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>