Every single user passes in '0'.  I think we had non-zero users back in
some stone age when selinux_inode_permission() was implemented in terms
of inode_has_perm(), but that complicated case got split up into a
totally separate code-path so that we could optimize the much simpler
special cases.

See commit 2e334057 ("SELinux: delay initialization of audit data in
selinux_inode_permission") for example.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>