fs: Add helper functions for permanently empty directories.
To ensure it is safe to mount proc and sysfs I need to check if filesystems that are mounted on top of them are mounted on truly empty directories. Given that some directories can gain entries over time, knowing that a directory is empty right now is insufficient. Therefore add supporting infrastructure for permantently empty directories that proc and sysfs can use when they create mount points for filesystems and fs_fully_visible can use to test for permanently empty directories to ensure that nothing will be gained by mounting a fresh copy of proc or sysfs. Cc: firstname.lastname@example.org Signed-off-by: "Eric W. Biederman" <email@example.com>
Showing with 98 additions and 0 deletions