[Bug 1569925] Re: Shutdown hang on 16.04 with iscsi targets

[Chris Osgood]

Seeing a similar issue here with so called "diskless" clients. That is,
all of their filesystems are network mounts including the root
filesystem. These systems use iscsi targets for the root filesystem and
during shutdown the network is turned off before the file I/O operations
are completed which causes the system to hang with filesystem IO errors.

I'm currently looking to see if there is some way to make systemd keep
the network up no matter what, all the way until the machine physically
reboots or shuts down (ie. disable the network shutdown completely).

This worked in 14.04 and got broken in 16.04 apparently due to the
switch to systemd as far as I can tell (great tool, isn't it?).

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Title:
  Shutdown hang on 16.04 with iscsi targets

Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  I have 4 servers running the latest 16.04 updates from the development
  branch (as of right now).

  Each server is connected to NetApp storage using iscsi software
  initiator.  There are a total of 56 volumes spread across two NetApp
  arrays.  Each volume has 4 paths available to it which are being
  managed by device mapper.

  While logged into the iscsi sessions all I have to do is reboot the
  server and I get a hang.

  I see a message that says:

    "Reached target Shutdown"

  followed by

    "systemd-shutdown[1]: Failed to finalize DM devices, ignoring"

  and then I see 8 lines that say:

    "connection1:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
    "connection2:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
    "connection3:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
    "connection4:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
    "connection5:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
    "connection6:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
    "connection7:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
    "connection8:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4311815***, last ping 43118164**, now 4311817***"
    NOTE: the actual values of the *'s differ for each line above.

  This seems like a bug somewhere but I am unaware of any additional
  logging that I could turn on to pinpoint the problem.

  Note I also have similar setups that are not doing iscsi and they
  don't have this problem.

  Here is a screenshot of what I see on the shell when I try to reboot:

  (https://launchpadlibrarian.net/291303059/Screenshot.jpg)

  This is being tracked in NetApp bug tracker CQ number 860251.

  If I log out of all iscsi sessions before rebooting then I do not
  experience the hang:

  iscsiadm -m node -U all

  We are wondering if this could be some kind of shutdown ordering
  problem.  Like the network devices have already disappeared and then
  iscsi tries to perform some operation (hence the ping timeouts).

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