Patrick, could you please check how you are disabling SELinux?
On my SL 6.2 (with a 2.6.32-220.23.1.el6.x86_64) test system, adding a boot parameter of selinux=0 avoids creating the selinux_inode_security cache, and that is what should happen by looking at the code.
The only other way that I am aware of for disabling SELinux (i.e. completely, not just turning it into permissive mode) is to write to /selinux/disable, likely from within initramfs, if CONFIG_SECURITY_SELINUX_DISABLE is set and selinuxfs is mounted.
The former case should print a "SELinux: Disabled at boot." string on the kernel ring buffer, and the latter should print a "SELinux: Disabled at runtime." string. In the latter case the selinux_inode_security cache does not get destroyed when SELinux is disabled, and a new object gets allocated from selinux_inode_security for every new inode that gets created.
In case you are not aware, you can check the status of SELinux using sestatus(8) from the policycoreutils package.