[Bug 525154] Re: mountall for /var or other nfs mount races with rpc.statd

[Steve Langasek]

On Mon, Jul 18, 2011 at 07:05:51PM -0000, Brian J. Murrell wrote:
> On 11-07-18 02:49 PM, Steve Langasek wrote:

> > Oh.  Can you give me some specific bug numbers there?

> Not at the moment I'm afraid.  The number of bugs i have in my
> subscribed list is just way to big to go searching right now, but off
> the top of my head, there is the ureadahead bug, where people have
> actually posted solutions and afaik, it's still open.

This appears to be bug #523484.

To the best of my understanding, this describes a feature that is missing
when using a separate /var (the ureadahead job will run but not do anything
useful).  This is certainly a bug, but not something that we are likely to
backport to lucid even when a fix becomes available.  I think you would be
hard pressed to convince any of the Ubuntu developers that it has a major
impact on the usability of Ubuntu that systems with a separate /var don't
get the boot speed enhancement from ureadahead!

Also, you say that people have posted solutions; I've reviewed the bug log
and there are no solutions to the bug there.  Most of the proposals would
work *only* on systems with detached /var, so are not suitable for
inclusion in the distribution; the closest thing to a fix is Clint's
proposal to add a signal handler and an additional upstart job, but that
code hasn't actually been written.

So I'm afraid I regard this bug's current prioritization as "medium" to be
correct, sorry.  Patches welcome, but I think it's unlikely that this is
going to be worked on soon otherwise.

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek at ubuntu.com                                     vorlon at debian.org

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https://bugs.launchpad.net/bugs/525154

Title:
  mountall for /var or other nfs mount races with rpc.statd

Status in “mountall” package in Ubuntu:
  Invalid
Status in “nfs-utils” package in Ubuntu:
  Fix Released
Status in “portmap” package in Ubuntu:
  Fix Released
Status in “mountall” source package in Lucid:
  Invalid
Status in “nfs-utils” source package in Lucid:
  Fix Released
Status in “portmap” source package in Lucid:
  Fix Released
Status in “mountall” source package in Maverick:
  Invalid
Status in “nfs-utils” source package in Maverick:
  Fix Released
Status in “portmap” source package in Maverick:
  Fix Released
Status in “mountall” source package in Natty:
  Invalid
Status in “nfs-utils” source package in Natty:
  Fix Released
Status in “portmap” source package in Natty:
  Fix Released

Bug description:
  If one has /var (or /var/lib or /var/lib/nfs for that matter) on its
  own filesystem the statd.conf start races with the mounting of /var as
  rpc.statd needs /var/lib/nfs to be available in order to work.

  I am sure this is not the only occurrence of this type of problem.

  A knee-jerk solution is to simply spin in statd.conf waiting for
  /var/lib/nfs to be available, but polling sucks, especially for
  something like upstart whose whole purpose is to be an event driven
  action manager.

  SRU justification: NFS mounts do not start reliably on boot in lucid
  and maverick (depending on the filesystem layout of the client system)
  due to race conditions in the startup of statd.  This should be fixed
  so users of the latest LTS can make reliable use of NFS.

  Regression potential:  Some systems may fail to mount NFS filesystems
  at boot time that didn't fail before.  Some systems may hang at boot.
  Some systems may hang while upgrading the packages (this version or in
  a future SRU).  I believe the natty update adequately guards against
  all of these possibilities, but the risk is there.

  TEST CASE:
  1. Configure a system with /var as a separate partition.
  2. Add one or more mounts of type 'nfs' to /etc/fstab.
  3. Boot the system.
  4. Verify whether statd has started (status statd) and whether all NFS filesystems have been mounted.
  5. Repeat 3-4 until the race condition is triggered.
  6. Upgrade to the new version of portmap and nfs-common from -proposed.
  7. Repeat steps 3-4 until satisfied that statd now starts reliably and all non-gss-authenticated NFSv3 filesystems mount correctly at boot time.

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