vfs_suser — check
    if credentials have superuser privileges for a mount point
The
    vfs_suser()
    function checks if the credentials given include superuser powers for the
    given mount point. It will check to see if the thread passed in has the same
    credentials as the user that mounted the file system. If so, it returns 0,
    otherwise it returns what
    priv_check(9)
    would have returned.
The vfs_suser() function returns 0 if the
    user has superuser powers and EPERM otherwise. This
    is the
    reverse
    logic of some other implementations of
    suser() in which a TRUE response indicates superuser
    powers.
The vfs_suser() function was introduced in
    FreeBSD 5.2.
This manual page was written by Alfred
    Perlstein.