Re: [vchkpw] Fwd: Re: NFS, maildir++ and -ve quota

[Nick Harring]

I've got about 50K boxes on NFS with maildir++. I'm running vpopmail 
5.2.1 though. The only problem I've ever seen is every once in a great 
while Courier-IMAP will return a wildly wrong negative value for number 
of unread messages, which breaks some other stuff I run, but I doubt 
there's a correlation.

Cheers,
Nick Harring
Tim Hasson wrote:

This is a followup for the problem discussed last week.

Is there anyone even running maildir on nfs with maildir++ quotas enabled??

----- Forwarded message from Sam Varshavchik <[EMAIL PROTECTED]> -----
   Date: Mon, 22 Sep 2003 23:55:26 -0400
   From: Sam Varshavchik <[EMAIL PROTECTED]>
Reply-To: Sam Varshavchik <[EMAIL PROTECTED]>
Subject: Re: NFS, maildir++ and -ve quota
     To: Tim Hasson <[EMAIL PROTECTED]>
Tim Hasson writes:

 

Quoting Sam Varshavchik <[EMAIL PROTECTED]>:

   

Tim Hasson writes:

     

Mr Sam,

I have switched over to maildrop instead of vdelivermail, by calling it 
from .qmail-default for all my domains. Everything looked good for a few
       

days, 
     

until I see the problem occuring with one of the users that had the same 
problem before with vdelivermail.

So I ran a shell script that removes any maildirsize file with negatives 
       

in
 

it, then recreate the maildirsize file for that user by running "vuserinfo
       

-Q 
     

[EMAIL PROTECTED]" and setting the chown/chgrp vpopmail/vchkpw on the
       

maildirsize 
     

file. Just in case some bad stuff stayed around..
       

I am not familiar with vuserinfo.  I can tell you, though, that maildirmake 
-q should recalculate the current quota.
     

The `vuserinfo -Q [EMAIL PROTECTED] calculates the quota, displays usage 
percentage on screen, and creates maildirsize in the user's maildir if it 
   

does 
 

not already exist.

   

Few days, and the problem happens to another account. There is 1.1MB in 
user/Maildir, his trash is only few kb, but getquota ROOT on courierimap 
reports -ve value.
       

What exactly is a "-ve" value?

     

Lousy abbreviations: (-)ve == negative
   

Well, somehow messages that are added to the maildir are not added to the 
quota, so when the messages are removed, the subtracted quota becomes 
negative.

I don't have an immediate idea why.  Although Maildir++ certainly trades in 
some known race conditions in favor of lock-free operation, race condition 
that would lead to such a situations should be very rare.  Perhaps NFS 
exaggerates the conditions that lead to a race condition.

But that's pure speculation.  What's needed is a reproducible way to create 
this scenario.

One potential workaround you can explore is to forcibly recompute the quota 
if the apparent quota is negative.

Try hacking the quota code to call maildir_quota_recalculate(), just once,
if the apparent quota is negative, then try again.


----- End forwarded message -----

Respectfully,
Tim Hasson