[$] The trouble with SMC-R

By corbet Among the many features merged for the 4.11
was the “shared memory communications over RDMA” (SMC-R)
protocol from IBM. SMC-R is a
high-speed data-center communications protocol that is claimed to be much
more efficient than basic TCP sockets. As it turns
out, though, the merging of this code was a surprise — and an unpleasant
one at that — to a relevant segment of the kernel development community.
This issue and the difficulties in resolving it are an indicator of how the
increasingly fast-paced kernel development community can go off track.

From: LWN