Dunno - I think there was a fairly lovely hack a while back to deal with the fact that the autofs ABI for 32-bit applications on 64-bit kernels wasn't compatible with the ABI for 32-bit applications on 32-bit kernels, and this was breaking stuff. Someone inserted a hack to fix this, which then broke another application which had its own hack to work around the kernel bug.

So Linus had to add a hack to unbreak this other application's hack to work around a kernel bug that no longer existed: http://lwn.net/Articles/494993/