bp_upload_dir()

function bp_upload_dir() {
	$bp = buddypress();

	if ( empty( $bp->upload_dir ) ) {
		$need_switch = (bool) ( is_multisite() && ! bp_is_root_blog() );

		// Maybe juggle to root blog.
		if ( true === $need_switch ) {
			switch_to_blog( bp_get_root_blog_id() );
		}

		// Get the upload directory (maybe for root blog).
		$wp_upload_dir = wp_upload_dir();

		// Maybe juggle back to current blog.
		if ( true === $need_switch ) {
			restore_current_blog();
		}

		// Bail if an error occurred.
		if ( ! empty( $wp_upload_dir['error'] ) ) {
			return false;
		}

		$bp->upload_dir = $wp_upload_dir;
	}

	return $bp->upload_dir;
}