unshared mount namespace

% sudo unshare --mount=/tmp/mnt1 /bin/bash
unshare: mount /proc/1178/ns/mnt on /tmp/mnt1 failed: Not a directory 

ENOTDIR
              target, or a prefix of source, is not a directory.

static int bind_ns_files(pid_t pid)
{
   struct namespace_file *ns;
   char src[PATH_MAX];

   for (ns = namespace_files; ns->name; ns++) {
      if (!ns->target)
         continue;

      snprintf(src, sizeof(src), "/proc/%u/%s", (unsigned) pid, ns->name);

      if (mount(src, ns->target, NULL, MS_BIND, NULL) != 0)
         err(EXIT_FAILURE, _("mount %s on %s failed"), src, ns->target);  /* здесь происходит ошибка */
   }

   return 0;
}

static void bind_ns_files_from_child(pid_t *child, int fds[2])
{
   char ch;
   pid_t ppid = getpid();
   ino_t ino = get_mnt_ino(ppid);
   
   if (pipe(fds) < 0)
      err(EXIT_FAILURE, _("pipe failed"));
      
   *child = fork();
   
   switch (*child) {
   case -1:
      err(EXIT_FAILURE, _("fork failed"));
      
   case 0:  /* child */
      close(fds[1]);
      fds[1] = -1;
      
      /* wait for parent */
      if (read_all(fds[0], &ch, 1) != 1 && ch != PIPE_SYNC_BYTE)
         err(EXIT_FAILURE, _("failed to read pipe"));
      if (get_mnt_ino(ppid) == ino)
         exit(EXIT_FAILURE);
      bind_ns_files(ppid);
      exit(EXIT_SUCCESS);
      break;

   default: /* parent */
      close(fds[0]);
      fds[0] = -1;
      break;
}

...

if (npersists && (unshare_flags & CLONE_NEWNS))
   bind_ns_files_from_child(&pid, fds);

if (-1 == unshare(unshare_flags))
   err(EXIT_FAILURE, _("unshare failed"));