Aug 1 22:58:16 dreadnought kernel: CIFS VFS: No response to cmd 46 mid 25661 
Aug 1 22:58:16 dreadnought kernel: CIFS VFS: Send error in read = -11
Aug 1 22:58:16 dreadnought kernel: CIFS VFS: No response for cmd 50 mid 25664
Aug 1 22:58:16 dreadnought kernel: CIFS VFS: No response to cmd 47 mid 25663
Aug 1 22:58:20 dreadnought kernel: CIFS VFS: No response to cmd 47 mid 25662
Aug 1 22:58:20 dreadnought kernel: CIFS VFS: Write2 ret -11, written = 0
Aug 1 22:58:20 dreadnought kernel: CIFS VFS: Send error in read = -9
Aug 1 22:58:20 dreadnought kernel: CIFS VFS: Write2 ret -9, written = 0
Aug 1 22:59:52 dreadnought kernel: CIFS VFS: No writable handles for inode
Aug 1 23:00:29 dreadnought kernel: CIFS VFS: close with pending writes
Aug 1 23:00:36 dreadnought kernel: CIFS VFS: close with pending writes
Aug 1 23:01:16 dreadnought kernel: CIFS VFS: No writable handles for inode
Aug 1 23:02:28 dreadnought kernel: CIFS VFS: close with pending writes
Aug 1 23:03:23 dreadnought kernel: CIFS VFS: close with pending writes
Aug 1 23:03:44 dreadnought kernel: CIFS VFS: close with pending writes
Aug 1 23:05:35 dreadnought kernel: CIFS VFS: No writable handles for inode
Aug 1 23:06:18 dreadnought kernel: CIFS VFS: close with pending writes
Aug 1 23:06:35 dreadnought kernel: CIFS VFS: close with pending writes
Aug 1 23:06:46 dreadnought kernel: CIFS VFS: No writable handles for inode
Aug 1 23:06:46 dreadnought kernel: CIFS VFS: close with pending writes
Aug 1 23:07:02 dreadnought kernel: CIFS VFS: close with pending writes
Aug 1 23:07:46 dreadnought kernel: CIFS VFS: server not responding

I found a workaround which involves disabling Opportunistic Locking. This will have a small performance impact, but at least the thing wont hang up and use 100% CPU for no goddamn reason. Yes, this article has an angry tone, because this issue has eaten way too much of my time today. http://blog.dhampir.no/content/cifs-vfs-no-response-for-cmd-n-mid

To disable Opportunistic Locking, you have to set the contents of the file “/proc/fs/cifs/OplockEnabled” to 0. This file only exists after the cifs module has been loaded, and will be replaced if the module is unloaded and reloaded. Thus, I configured my /etc/rc.local script (use whatever equivalent your distro has to a startup script) to both load the cifs module and set the contents of said file:

# cifs client workaround
modprobe cifs
echo 0 > /proc/fs/cifs/OplockEnabled