Did you try to ask the same question at the linux-rdma mailing list? It might be much more efficient as this module is not strictly related to Mellanox hardware.
At the same time, do you use Mellanox OFED or inbox kernel driver? Maybe the issue doesn't exist in the latest version of the software? The latest MOFED is 4.0 and 4.1 will be released soon.
I will check it in linux-rdma mailing list. Using redhat inbox drivers.