In order to make policy decisions on directories in an HSM-archived directory tree, there should be some state/flag stored on the directory itself that it was created as part of an HSM restore operation, or is part of an archived directory tree.

For example, if a directory is created because an archived bucket is restored and using "/" or "\" separators in the object names to create a directory hierarchy, then it would be useful to add a marker (e.g. flag or trusted.hsm xattr) on the directory.

Since this HSM state on the directory needs to be understood by the MDS when a file or directory therein is being accessed/modified, it cannot be an arbitrary xattr stored on the file without adding overhead to each operation.