Connection errors might occur between an NFS server and client that are using Remote Direct Memory Access (RDMA). Because of these errors, the buffer pool resources are exhausted and the system panics. The following error message is displayed:
rpcib: WARNING: rib_rbuf_alloc: No free buffers!
Workaround: Choose one of the following workarounds:
Configure the NFS server to enable TCP. In the /etc/default/nfs file, change (NFSD_PROTOCOL=tcp).
Mount the NFS file system from the client side with the proto=tcp mount option.