rpc.mountd high CPU usage

[Owen Dunn]

Description: Ubuntu 14.04.3 LTS
Release: 14.04

nfs-kernel-server version 1:1.2.8-6ubuntu1.2

I have a system with ~1900 ZFS filesystems, which I am exporting over NFS.

When one of these filesystems is mounted by a client rpc.mountd on the
server climbs to 100% CPU. stracing rpc.mountd reveals that it is calling
newfstat() for every device on the system addressed by every possible
route for every export. (I've attached a fragment of the strace output.)

This seems to be the problem described in this thread:

http://www.spinics.net/lists/linux-nfs/msg40946.html

and applying the patch at:

http://www.spinics.net/lists/linux-nfs/msg41193.html

fixed the problem for me. Could this patch be applied to the Ubuntu package,
please?

Owen