Linux 3.11-rc1 was released a few days ago. With it comes a kernel-level API change related to VFS. Specifically, struct file_operations no longer contains the function pointer readdir and vfs_readdir() which was defined in fs/readdir.c is now gone. They are both superseded by iterate and iterate_dir() respectively. Unfortunately, these changes broke the compilation of the vmblock fs module.
So, here is a simple patch I've written for anyone who is interested. Note that you also have to apply the vmblock patch for linux 3.10 if you haven't already. Otherwise, the compilation would fail.
As usual, apply the patch and do:
Verification to show that the patch works properly: