Merge "Add /mnt/androidwritable for MOUNT_EXTERNAL_ANDROID_WRITABLE apps" into...

    // slave to the /mnt/user mount, and at the same time /mnt/installer in the

    // bootstrap namespace shares a peer group with /mnt/installer in the

    // default namespace.

    // /mnt/androidwritable is similar to /mnt/installer but serves for

    // MOUNT_EXTERNAL_ANDROID_WRITABLE apps.

    if (!mkdir_recursive("/mnt/user", 0755)) return false;

    if (!mkdir_recursive("/mnt/installer", 0755)) return false;

    if (!mkdir_recursive("/mnt/androidwritable", 0755)) return false;

    if (!(BindMount("/mnt/user", "/mnt/installer", true))) return false;

    // First, make /mnt/installer a slave bind mount

    if (!(BindMount("/mnt/user", "/mnt/androidwritable", true))) return false;

    // First, make /mnt/installer and /mnt/androidwritable a slave bind mount

    if (!(MakeSlave("/mnt/installer"))) return false;

    if (!(MakeSlave("/mnt/androidwritable"))) return false;

    // Then, make it shared again - effectively creating a new peer group, that

    // will be inherited by new mount namespaces.

    if (!(MakeShared("/mnt/installer"))) return false;

    if (!(MakeShared("/mnt/androidwritable"))) return false;

    bootstrap_ns_fd.reset(OpenMountNamespace());

    bootstrap_ns_id = GetMountNamespaceId();