The client-side HSM coordinator patches in http://review.whamcloud.com/5029 and http://review.whamcloud.com/5030 were landed, but Oleg realized that there are no client-side limits on the number of concurrent RPCs that can be sent.

This could potentially overwhelm the MDS service threads and block all other requests if they become blocked handling HSM requests, or if they are not being processed very quickly.

Please institue a client-side RPC limit, like cl_max_rpcs_in_flight, but for HSM requests, that introduces some reasonable limit.

The ticket is assigned to Jinshan, but only because we cannot currently assign it to someone external.