There was a bug in posix open / create calls that JRA and I discovered at Connectathon this year. I'm preparing to add patches to CIFS in RHEL5.4 to make it use POSIX open calls.
When CIFS does this and the server is broken, it pops a printk:
CIFS VFS: server 10.10.10.10 of type Samba 3.0.33-3.7.el5 returned unexpected error on SMB posix open, disabling posix open support. Check if server update available.
...obviously it would be good if 5.4's samba didn't cause this to pop.
I'll see if I can find the commit...
Upstream commit in master branch:
commit 3d7cde5dd3603ba3a7e78e8ca9a28d5bbf816b80
Author: Jeremy Allison <jra>
Date: Wed Feb 25 12:53:45 2009 -0800
Fix bug in processing of open modes in POSIX open.
Was missing case of "If file exists open. If file doesn't exist error."
Damn damn damn. CIFSFS client will have to have fallback cases
for this error for a long time.
Jeremy.
:100644 100644 433b8a0... 369830b... M source3/smbd/trans2.c
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
http://rhn.redhat.com/errata/RHBA-2009-1416.html