During configure, these zfs tests all fail:
checking if zfs defines dsl_pool_config_enter/exit
checking if zfs defines dsl_sync_task_do_nowait
checking if zfs defines sa_spill_alloc
checking if zfs defines spa_maxblocksize
due to conflicting definitions in "/usr/src/compat-rdma/include/linux/kthread.h" and "include/linux/kthread.h".

These config test errors lead to compilation failures when making osd-zfs.

My configure command:
./configure --disable-ldiskfs --disable-gss --with-o2ib=/usr/src/compat-rdma --with-zfs=/usr/src/zfs-0.6.5.3 --with-zfs-obj=/var/lib/dkms/zfs/0.6.5.3/2.6.32-573.8.1.el6.x86_64/x86_64 --with-spl=/usr/src/spl-0.6.5.3 --with-spl-obj=/var/lib/dkms/spl/0.6.5.3/2.6.32-573.8.1.el6.x86_64/x86_64 --with-linux=/usr/src/kernels/2.6.32-573.8.1.el6.x86_64

Attempted workaround: add this to test programs in config/lustre-build-zfs.m4:
#ifdef HAVE_COMPAT_RDMA
#undef PACKAGE_NAME
#undef PACKAGE_TARNAME
#undef PACKAGE_VERSION
#undef PACKAGE_STRING
#undef PACKAGE_BUGREPORT
#undef PACKAGE_URL
#include <linux/compat-2.6.h>
#endif

Result: Compiles and installs, works with tcp(eth0) and tcp(ib0), but o2ib fails. This probably just superficially hid the kthread.h conflict.

Successful workaround: uninstall OFED and use in-kernel IB drivers. Everything compiles and runs well. I have no idea if performance is affected.