direct-io: eliminate the offset argument to ->direct_IO

Including blkdev_direct_IO and dax_do_io.  It has to be ki_pos to actually
work, so eliminate the superflous argument.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/mm/page_io.c b/mm/page_io.c
index cd92e3d..8927560 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -279,7 +279,7 @@
 
 		set_page_writeback(page);
 		unlock_page(page);
-		ret = mapping->a_ops->direct_IO(&kiocb, &from, kiocb.ki_pos);
+		ret = mapping->a_ops->direct_IO(&kiocb, &from);
 		if (ret == PAGE_SIZE) {
 			count_vm_event(PSWPOUT);
 			ret = 0;