Although we use u64 to pass userspace pointers to the kernel
to avoid compat_ioctl, it doesn't work in some ppc platform.
So wrap them with compat_ptr and add compat_ioctl.

The detailed discussion about compat_ptr can be found in thread
http://lkml.org/lkml/2009/10/27/423.

We indeed met with a bug when testing on ppc(-EFAULT is returned
when using old_path). This patch try to fix this.
I have tested in ppc64(with 32 bit reflink) and x86_64(with i686
reflink), both works.
Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>