mount: remove root with MS_PRIVATE before cleaning up mntns

Otherwise we will clean up the root mntns too.
Signed-off-by: Andrew Vagin <avagin@openvz.org>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

mount.c

@@ -574,6 +574,11 @@ static int clean_mnt_ns(void)
 	 * Mountinfos were collected at prepare stage
 	 */
 
+	if (mount("none", "/", "none", MS_REC|MS_PRIVATE, NULL)) {
+		pr_perror("Can't remount root with MS_PRIVATE");
+		return -1;
+	}
+
 	pm = mnt_build_tree(mntinfo);
 	if (!pm)
 		return -1;

test/zdtm/live/static/mountpoints.c

@@ -19,6 +19,10 @@ static int test_fn(int argc, char **argv)
 	int fd, tmpfs_fd;
 	unsigned fs_cnt, fs_cnt_last = 0;
 
+	if (mount("none", "/", "none", MS_REC|MS_PRIVATE, NULL)) {
+		err("Can't remount root with MS_PRIVATE");
+		return -1;
+	}
 again:
 	fs_cnt = 0;
 	f = fopen("/proc/self/mountinfo", "r");