[NCLUG] autofs behaviour

[Michael Coffman]

I have a question about the behaviour of autofs.  It seems like it is
very easy to hit a situation where autofs will unmount a file system
and an active process will lose access to a file and fail to read it.
This seems to happen with both direct and indirect mapping.

Specifics about what I am running:

    autofs-4.1.3-199.3
    kernel - 2.6.9-55.ELsmp
    arch - x86_64
    OS - Red Hat Enterprise Linux WS release 4 (Nahant Update 5

autofs is configured to use the defaults and has host mapping
enabled.  When I run the following simple test:

   date;while [[ -r /net/hostname/test ]]; do :; done; date

command output:
   Fri Jul 11 09:02:46 MDT 2008
   Fri Jul 11 09:03:59 MDT 2008
command output run 2:
   Fri Jul 11 09:11:42 MDT 2008
   Fri Jul 11 09:12:45 MDT 2008

As you can see, I lose read access typically shortly after the mount is 
supposed to time out.

I believe that after the timeout, autofs tries to unmount file systems and 
if they are busy, resets the timeout counter and remounts any unmounted 
mount points if it is a host map.

But in general, I would think that I should never lose read access to the
file.  Shouldn't autofs just remount it if it has been unmounted?

Anyone have any insight?

BTW: am-utils (amd) does not behave this way.  I am guessing this
      has to do with the fact that it runs in user space.

-- 
-MichaelC