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

[German Staltari <gstaltari arnet net ar>]

Hi, we have a 6 node cluster with FC4, kernel 2.6.16 and the CVS STABLE 
branch of the cluster software. Sometimes, some processes (courier imap) 
hangs in D state. When I execute "ls -la" in the "tmp" directory (the 
directory is always the same, the same mailbox) of the mailbox that it's 
triyng to access the process, the answer is really slow and this is the 
output:

?---------  ? ?        ?           ?            ? 
1151074448.M345358P6861_courierlock.qmail-be-04
?---------  ? ?        ?           ?            ? 
1151074497.M326691P7647_courierlock.qmail-be-04
?---------  ? ?        ?           ?            ? 
1151074534.M524707P2198_courierlock.qmail-be-05
-rw-r--r--  1 mailuser mailuser   17 Jun 23 12:07 
1151074538.M785749P13408_courierlock.qmail-be-03
-rw-r--r--  1 mailuser mailuser   16 Jun 23 12:09 
1151074588.M917441P3132_courierlock.qmail-be-05
-rw-r--r--  1 mailuser mailuser   16 Jun 23 12:09 
1151074593.M62901P3189_courierlock.qmail-be-05
?---------  ? ?        ?           ?            ? 
1151074649.M845223P5214_courierlock.qmail-be-02
-rw-r--r--  1 mailuser mailuser   17 Jun 23 12:09 
1151074656.M448306P28724_courierlock.qmail-be-06
-rw-r--r--  1 mailuser mailuser   16 Jun 23 12:07 
1151074657.M188653P5302_courierlock.qmail-be-02
?---------  ? ?        ?           ?            ? 
1151074679.M821433P4979_courierlock.qmail-be-05
-rw-r--r--  1 mailuser mailuser   16 Jun 23 12:07 
1151074690.M360083P5741_courierlock.qmail-be-02
-rw-r--r--  1 mailuser mailuser   17 Jun 23 12:07 
1151074701.M709923P29422_courierlock.qmail-be-06
-rw-r--r--  1 mailuser mailuser   16 Jun 23 12:07 
1151074716.M544858P6016_courierlock.qmail-be-02
-rw-r--r--  1 mailuser mailuser   16 Jun 23 12:07 
1151074731.M21587P6179_courierlock.qmail-be-02
?---------  ? ?        ?           ?            ? 
1151074804.M241436P7410_courierlock.qmail-be-02
?---------  ? ?        ?           ?            ? 
1151074831.M678238P17302_courierlock.qmail-be-03
?---------  ? ?        ?           ?            ? 
1151074917.M42708P8494_courierlock.qmail-be-05
-rw-r--r--  1 mailuser mailuser   17 Jun 23 12:08 
1151074918.M541477P14716_courierlock.qmail-be-04
-rw-r--r--  1 mailuser mailuser   17 Jun 23 12:08 
1151074946.M520653P15248_courierlock.qmail-be-04
?---------  ? ?        ?           ?            ? 
1151075037.M234721P11020_courierlock.qmail-be-02
?---------  ? ?        ?           ?            ? 
1151075065.M951224P8598_courierlock.qmail-be-01
-rw-r--r--  1 mailuser mailuser   17 Jun 23 12:09 
1151075082.M788480P11712_courierlock.qmail-be-02
-rw-r--r--  1 mailuser mailuser   17 Jun 23 12:09 
1151075186.M911867P18565_courierlock.qmail-be-04
-rw-r--r--  1 mailuser mailuser   17 Jun 23 12:08 
1151075210.M366861P13891_courierlock.qmail-be-02
-rw-r--r--  1 mailuser mailuser   17 Jun 23 12:09 
1151075217.M850817P13366_courierlock.qmail-be-05
?---------  ? ?        ?           ?            ? 
1151075252.M599978P32483_imapuid_4.qmail-be-05

It seems like a lock problem, but not sure. Is there any other tool that 
I can use to debug this?
Thanks
German