[Linux-cluster] files with unknown state - locking problem?

[German Staltari]

Robert Peterson wrote:
> I suspect you are right: The question marks in ls -l leads me to 
> believe there
> might be a problem somewhere regarding the locking of the files.  My 
> theory is this:
> ls -l calls a kernel stat function to get file statistics.  The stat 
> tries to acquire an internal
> lock (glock), but can't, so it displays what you see instead of valid 
> values.
>
> Perhaps courier imap is locking files, then hanging, and the process 
> is somehow
> hanging around with the lock intact, or else killed abnormally where 
> the lock is not released.
> Do you have any suggestions how we can recreate this problem in our lab?
>
Robert, here is the scenario: we have a pool of webmail servers 
accessing mailboxes in the cluster via IMAP (courier-imap 3.0.8). One 
user may hit the mailbox a couple of times in a short period of time 
when using the webmail (webmail is stateless, so it has to reread all 
mailbox structure in each webmail action).

Maybe the problem is in courier-imap, so I was digging it's source code, 
and found all locking stuff in liblock and maildir directories 
(maildir/maildirlock.c -> maildir_lock(), liblock/mail.c -> 
ll_dotlock()). I know that we are not debugging courier-imap, but it may 
help.
I found a post of Lon 
http://www.redhat.com/archives/linux-cluster/2004-October/msg00306.html, 
that recommends using IMAP_USELOCKS and I've checked our conf and it's 
enabled.

So, maybe the best way to recreate the problem is installing 
courier-imap, and access a mailbox user from different clients at the 
same time (in a short period of time would be best).
I hope this helps,
Thanks for your help and time,
German



So, I think it could be possible