Created attachment 1425594 [details]
reproducer1 start/stop the rpcbind/rpcbind.socket

Description of problem:
During tests of the NFSv4-only server configure procedure (Bug 1387694), just found that rpc-statd.service sometimes gets failed when trying start. The key to reproduce this scenario is just trying to mount NFS version 3 (or v2) after rpc-statd is masked, certainly it gets failed as expected. But after recovering it, always fail to start the service rpc-statd then.

I just simplify the reproducer as following.


Version-Release number of selected component (if applicable):
# latest rhel7 nfs-utils
nfs-utils-1.3.0-0.54.el7
# upstream also has the same issue
nfs-utils-2.2.1-4.rc2.fc27


How reproducible:
100% easy


Steps to Reproduce:
1. systemctl mask --now rpc-statd
2. mount localhost:/tmp /mnt -o vers=3 <<< should fail
3. systemctl unmask rpc-statd.service
4. systemctl start rpc-statd           <<< get failed


The failure workaround:
a. If we stop/start the rpcbind/rpcbind.socket at the same time, we can work around it by just starting the rpc-statd one more time.
b. If removing other operations (rpcbind/rpcbind.socket), looks like a daemon "rpc.statd --no-notify" starts immediately when unmasking the service. We can kill that daemon and try to start it then.


Actual results:
[root@hp-dl360g9-01 ~]# rpm -q nfs-utils
nfs-utils-1.3.0-0.54.el7.x86_64
[root@hp-dl360g9-01 ~]# ./repro1.sh 
# systemctl stop rpc-statd
# systemctl stop rpcbind
Warning: Stopping rpcbind.service, but it can still be activated by:
  rpcbind.socket
# systemctl stop rpcbind.socket
# systemctl mask --now rpc-statd
Created symlink from /etc/systemd/system/rpc-statd.service to /dev/null.
# mount localhost:/tmp /mnt -o vers=3  # should fail
Failed to start rpc-statd.service: Unit is masked.
mount.nfs: rpc.statd is not running but is required for remote locking.
mount.nfs: Either use '-o nolock' to keep locks local, or start statd.
mount.nfs: an incorrect mount option was specified
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
# systemctl start rpcbind
# systemctl unmask rpc-statd.service
Removed symlink /etc/systemd/system/rpc-statd.service.
# systemctl start rpc-statd  # should not fail
Job for rpc-statd.service failed because the control process exited with error code. See "systemctl status rpc-statd.service" and "journalctl -xe" for details.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ *reproduced*
# systemctl start rpc-statd  # workaround
rpcuser   2885  0.0  0.0  42420  1740 ?        Ss   04:47   0:00 /usr/sbin/rpc.statd
[root@hp-dl360g9-01 ~]

[root@hp-dl360g9-01 ~]# ./repro2.sh 
# systemctl stop rpc-statd
# systemctl mask --now rpc-statd
Created symlink from /etc/systemd/system/rpc-statd.service to /dev/null.
# mount localhost:/tmp /mnt -o vers=3  # should fail
Failed to start rpc-statd.service: Unit is masked.
mount.nfs: access denied by server while mounting localhost:/tmp
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
# systemctl unmask rpc-statd.service
Removed symlink /etc/systemd/system/rpc-statd.service.
rpcuser   2933  0.0  0.0  42420  1740 ?        Ss   04:49   0:00 rpc.statd --no-notify
# systemctl start rpc-statd  # should not fail
Job for rpc-statd.service failed because the control process exited with error code. See "systemctl status rpc-statd.service" and "journalctl -xe" for details.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ *reproduced*
rpcuser   2933  0.0  0.0  42420  1740 ?        Ss   04:49   0:00 rpc.statd --no-notify
# pkill rpc.statd  # workaround
# systemctl start rpc-statd  # workaround
rpcuser   2982  0.0  0.0  42420  1744 ?        Ss   04:49   0:00 /usr/sbin/rpc.statd
[root@hp-dl360g9-01 ~]# 


Expected results:
Service rpc.statd can be started successfully after unmasking it.


Additional info:
Just setting priority as "low" for now as there is workaround for this problem.
However, if the NFSv4-only server configuration is getting more and more popular, customer may sometimes encounter this problem too.