UDF: write hangs w/ certain applications (2.6.38...Git)

UDF: write hangs w/ certain applications (2.6.38...Git)

[Matthias Matiak]

Dear kernel hacker,
there is a problem while trying to write to an UDF filesystem with 
some userspace applications like "tar" or "dar" since linux 2.6.28 till currrent git
at least on x86/x86_64. The process who wants to write hangs at D state forever,
and no data were saved on the blockdev or image file actually. 
There is no chance of killing that prozess, unmount that UDF filesystem or 
reboot/shutdown the box in a clean fashion. 
Other tools like "cp" or piping stuff via shell works perfectly however. 

This problem does not occur with linux <= 2.6.37

No errors are shown by dmesg, except:
"INFO: task dar:$PID blocked for more than 120 seconds."
followed by a trace. Turning on udf debugging does not show any new infos
after mounting the filesystem. 

Steps to reproduce:
0) Fire up a virtual machine 
1) boot a (x86) linux kernel 2.6.38 till current GIT
2) create an image file or choose any block device, format it as UDF with mkudffs and mount somewhere.
3) install "dar", a UNIX backup tool ( http://dar.linux.free.fr/ ).
4) Try to create an archive. e.g.: 
	dar --verbose --create /path/to/testarchive_on_UDF --fs-root /sbin 
(replace /sbin with any path with some files within that you like)
5) dar will hang now almost instantly.

This behavior was reported by someone else already on debian bug tracking system
some weeks ago, but with no responses so far.
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=647204
You can find additional information there.

Would be great if someone could investigate this issue further. :)


Best regards
Matthias

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