Frozen transaction

[Olivier Bonvalet <btrfs.list@daevel.fr>]

Hi,

on one system I have a "frozen transaction" since more than 24 hours, 
without any IO.
I can't umount the partition, delete a snapshot or write anything.
I try to reboot the system, but the problem is still present.

Here the "frozen transaction" :
$ ps auxw | grep btrfs | grep D
root      1835  0.0  0.0      0     0 ?        D    Oct08   0:13 
[btrfs-cleaner]
root      1836  0.0  0.0      0     0 ?        D    Oct08   0:01 
[btrfs-transacti]
root      2633  0.0  0.0      0     0 ?        D    Oct08   0:00 
[flush-btrfs-1]


The partition is mounted with this options :
# mount | grep btrfs
/dev/mapper/vg--sofia-backup on /backup type btrfs 
(rw,noatime,compress-force=zlib,nossd)


The disk is near full :
# btrfs fi df /backup/
Data: total=482.68GB, used=480.89GB
System, DUP: total=32.00MB, used=72.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=10.12GB, used=8.82GB

But one of the last actions was the removing of some big subvolumes 
(near 50GB).

There is no error in logs, the frozen transaction was started from a 
3.5* kernel (from GIT), and the system is now running on a 3.6.1 kernel 
(vanilla).

Is there something I can do to solve that problem ?

Thanks,
Olivier