direct_IO: use iov_iter_rw() instead of rw everywhere

The rw parameter to direct_IO is redundant with iov_iter->type, and
treated slightly differently just about everywhere it's used: some users
do rw & WRITE, and others do rw == WRITE where they should be doing a
bitwise check. Simplify this with the new iov_iter_rw() helper, which
always returns either READ or WRITE.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ext2/inode.c

@@ -866,7 +866,7 @@ ext2_direct_IO(int rw, struct kiocb *iocb, struct iov_iter *iter,
 	else
 		ret = blockdev_direct_IO(iocb, inode, iter, offset,
 					 ext2_get_block);
-	if (ret < 0 && (rw & WRITE))
+	if (ret < 0 && iov_iter_rw(iter) == WRITE)
 		ext2_write_failed(mapping, offset + count);
 	return ret;
 }