Created attachment 1197025 [details]
strace of "rpc.nfsd --debug -N 2 -N 3 8" with comments showing where the two delays occur

Description of problem:
nfs-server configured for only v4.x takes 6 minutes to start without rpcbind, starts instantly with rpcbind

This is unexpected because RHEL/Fedora/nfs-utils documentation says rpcbind is unneeded for NFS 4.

Manually starting rpc.nfsd through strace shows there appear to be two long delays, one when it attempts reading /proc/fs/nfsd/portlist, and another when it attempts writing to it.

This MAY answer the question - it's only visible for RedHat subscribers, which I'm not.  Also, there was a kernel patch in 12/2013 which fixed the same symptom, but was due to a writing fd to kernel failure, which appeared to be instantly fatal rather than cause a delay.  I have no idea if on RHEL what versions this guy has and if it includes this patch or is related.  https://access.redhat.com/solutions/902013

This also happens on Arch Linux, kernel 4.7.2 (-1 Arch), nfs-utils 1.3.4 (-1 Arch).

"This" has been occurring since I started with NFS v4.x using nfs-utils 1.3.2 & 1.3.3.  I quoted "this" because since then, I have thought rpc.nfsd would just never start, and only accidentally found that it does start after a 6 minute delay.


Version-Release number of selected component (if applicable):
Fresh Fedora 24 install, kernel 4.6.7 (-300.fc24.x86_64), nfs-utils 1.3.4 (-1.rc2.fc24), and rpcbind 0.2.3 (-11.rc1.fc24).


How reproducible:
100% reproducible


Steps to Reproduce:
1. Fresh install using Fedora 24 net installer, selecting minimal install
2. # yum install nfs-utils
3. # systemctl enable nfs-server
4. # vi /etc/sysconfig/nfs
{{{ RPCNFSDARGS="-N 2 -N 3" \ RPCMOUNTDOPTS="-N 2 -N 3" }}}
{{{ I've tried -N options with and without spaces, as I've seen it both ways }}}
5. # systemctl reboot
6. # systemctl status nfs-server
{{{ observe after starting, nfs-server started <= 1 second }}}
7. # systemctl mask rpcbind.service rpcbind.socket
8. # systemctl reboot
9. # systemctl status nfs-server
{{{ observe after starting, nfs-server takes 6 minutes to start }}}
10. Interestingly, after nfs-server is finally up, can cat /proc/fs/nfsd/portlist instantly.
11. cat /proc/fs/nfsd/versions
-2 -3 +4 +4.1 +4.2


Actual results:
Sep 01 20:29:00 fedora systemd[1]: Starting NFS server and services...
Sep 01 20:35:22 fedora systemd[1]: Started NFS server and services


Expected results:
For nfs-server to start relatively quickly


Additional info:
I think this is unrelated, but I'll mention it.

nfs-idmapd is failing to start for me on fedora - see https://bugzilla.redhat.com/show_bug.cgi?id=1372489

But, I'm having the same 6 minute delay on Arch Linux also using nfs-utils 1.3.4, and on Arch, nfs-idmapd successfully starts.  So I don't think this bug is caused by nfs-idmapd not starting.