In 2.6.28, the prototype of the open handler was changed.  The
kernel.org aoe driver was modified by this commit:

  commit 94562c175113cf91204a77269eabeea32e1f38db
  Author: Al Viro <viro@zeniv.linux.org.uk>
  Date:   Sun Mar 2 09:23:18 2008 -0500
  
      [PATCH] switch aoeblk
  
Basically, they stopped using a pointer to struct inode.