Add a case to the locked mount test: - a bind of the mount namespace file of a grandchild moved beneath a locked cover must fail with EINVAL - a bind of an ordinary file beneath it takes the lock over, the old cover can go and the new one can't - the file is still covered after unshare(CLONE_NEWNS) Link: https://patch.msgid.link/20261014-work-namei-locked-mnt_ns_file-v1-2-24035bd5d8e9@kernel.org Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>