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Date:      Wed, 11 Aug 1999 13:18:19 -0400
From:      "Sean O'Connell" <sean@stat.Duke.EDU>
To:        FreeBSD stable <freebsd-stable@FreeBSD.ORG>
Subject:   NFS weirdness
Message-ID:  <19990811131819.E22386@stat.Duke.EDU>

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Hi All-

I am in the process of updating all of the departements FreeBSD
boxes to 3.2-STABLE.  I have set up one of my test machines, and
I have noticed something weird wrt email (we are currently still
using nfs-mounted /var/spool/mail directory, for now ...).  This
version of the OS was cvsup'd on 1999 Jul 30 after most of the 
big NFS changes were MFC'd---I believe.

I am running tkpostage---a cute mail counter utility that uses
tcl's file(n) call to keep track mod time changes and then an
open(n) call to then regex(n) to get the count and the subject
portion.  When I manipulate my spool file (using mutt) on one of 
our client Digital Unix boxes (spool file located on Digital Unix
server), the FreeBSD machine sees the changes in my spool file: 
the size and mod times adjust properly _but_ the content of the 
file is not updated.  It seems just truncate the previous version
to the new size.  If I happen to get a new email message, the 
file content is then updated properly.  Since we are hopelessly 
dependent on NFS (people's home directories, email (for now), etc),
this looks like a disaster waiting to happen---especially with 
running and commercial software: Matlab, Splus, Mathematica, Netscape 
(doesn't seem to enforce disk cache quotas over nfs), etc.

Is this a FreeBSD mmap/nfs type bug?
 - It is quite reproducible.

Is this a FreeBSD mmap/nfs interaction with tcl/tk?
 - It seems to update properly when this is not running.
 - Could it be bad tcl coding?

Or am I using the wrong the nfs mount options?
 - I am not doing anything other nfs mounting the /var/spool/mail
   off the Digital Unix box.

Or should I just bite the bullet and run current?     :)

Details:

relevant fstab entry:
server:/var/spool/mail /var/mail       nfs     rw,bg,intr,nodev        0 0

output from sysctl vfs.nfs:
vfs.nfs.nfs_privport: 0
vfs.nfs.async: 0
vfs.nfs.gatherdelay: 10000
vfs.nfs.gatherdelay_v3: 0
vfs.nfs.defect: 0
vfs.nfs.diskless_valid: 0
vfs.nfs.diskless_rootpath: 
vfs.nfs.diskless_swappath: 
vfs.nfs.access_cache_timeout: 2
vfs.nfs.access_cache_hits: 16321
vfs.nfs.access_cache_fills: 13715

Looking at a quick tcpdump, it is doing nfs over udp... not sure 
which version, but I would guess version 3.

Thanks,
S
-- 
-----------------------------------------------------------------------
Sean O'Connell                                Email: sean@stat.Duke.EDU
Institute of Statistics and Decision Sciences Phone: (919) 684-5419
Duke University                               Fax:   (919) 684-8594


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