rst: Don't lookup ns if current mntns is the same as root's one

Acked-by: Andrew Vagin <avagin@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

mount.c

@@ -1575,13 +1575,10 @@ char *rst_get_mnt_root(int mnt_id)
 	return path;
 }
 
-static int do_restore_task_mnt_ns(struct ns_id *nsid, pid_t pid)
+static int do_restore_task_mnt_ns(struct ns_id *nsid)
 {
 	char path[PATH_MAX];
 
-	if (root_item->ids->mnt_ns_id == nsid->id)
-		return 0;
-
 	if (nsid->pid != getpid()) {
 		int fd;
 
@@ -1616,15 +1613,19 @@ static int do_restore_task_mnt_ns(struct ns_id *nsid, pid_t pid)
 int restore_task_mnt_ns(struct pstree_item *current)
 {
 	if (current->ids && current->ids->has_mnt_ns_id) {
+		unsigned int id = current->ids->mnt_ns_id;
 		struct ns_id *nsid;
 
-		nsid = lookup_ns_by_id(current->ids->mnt_ns_id, &mnt_ns_desc);
+		if (root_item->ids->mnt_ns_id == id)
+			return 0;
+
+		nsid = lookup_ns_by_id(id, &mnt_ns_desc);
 		if (nsid == NULL) {
-			pr_err("Can't find mount namespace %d\n", current->ids->mnt_ns_id);
+			pr_err("Can't find mount namespace %d\n", id);
 			return -1;
 		}
 
-		if (do_restore_task_mnt_ns(nsid, current->pid.real))
+		if (do_restore_task_mnt_ns(nsid))
 			return -1;
 	}