mnt: Fix mountinfo collecting issues

1. Mountinfo should be collected after we have forked into new namespace (strictly
   speaking this is so)
2. When restoring a mnt ns we can reuse the collected mntinfos rather than reading
   them again.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -102,9 +102,6 @@ static int prepare_shared(void)
 	if (collect_eventpoll())
 		return -1;
 
-	if (collect_mount_info())
-		return -1;
-
 	if (collect_inotify())
 		return -1;
 
@@ -661,6 +658,10 @@ static int restore_task_with_children(void *_arg)
 	if (ret < 0)
 		exit(1);
 
+	if (me->parent == NULL)
+		if (collect_mount_info())
+			exit(-1);
+
 	if (ca->clone_flags) {
 		ret = prepare_namespace(me->pid.virt, ca->clone_flags);
 		if (ret)

mount.c

@@ -36,6 +36,8 @@ int open_mount(unsigned int s_dev)
 
 int collect_mount_info(void)
 {
+	pr_info("Collecting mountinfo\n");
+
 	mntinfo = parse_mountinfo(getpid());
 	if (!mntinfo) {
 		pr_err("Parsing mountinfo %d failed\n", getpid());
@@ -390,13 +392,11 @@ static int clean_mnt_ns(void)
 
 	pr_info("Cleaning mount namespace\n");
 
-	pm = parse_mountinfo(getpid());
-	if (!pm) {
-		pr_err("Can't parse my new mount namespace\n");
-		return -1;
-	}
+	/*
+	 * Mountinfos were collected at prepare stage
+	 */
 
-	pm = mnt_build_tree(pm);
+	pm = mnt_build_tree(mntinfo);
 	if (!pm)
 		return -1;