RAID-1 and Reiser4 issue: umount hangs

[Arend Freije <afreije@inn.nl>]

Hi,

I'm using Reiser4 for my filesystems on disk (/dev/sda) , and it works
just fine. Recently I bought a second disk (/dev/sdb) for RAID-1
mirroring. With mdadm I created a degraded raid-1 array  on /dev/md/0,
devices missing,/dev/sdb1. After that I created a Reiser4 filesystem on
/dev/md/0 and mounted it at /mnt. Then I copied the data from /dev/sda1
to /mnt.
All goes well until I umount /mnt, umount simply hangs without any
error. Syslog doesn't report any error. In /proc/mdstat, the array
remains "active sync". Shutting down linux fails because the umount is
still waiting and seems to block other umounts. The umount process
cannot be killed by the root. A hard reset is the only resolution to get
my system functioning normally, but without the raid-1 of course.
The problem seems to emerge only with the combination of RAID and
Reiser4.  I've created an ext-2 filesystem on /dev/md/0, and after that
mount ; cp -ax ; umount works without  a problem, and the hanging umount
re-appears when using Reiser4 again.

My questions:
- how can I find the cause of the hanging umount?
- how can I fix it?

A few details of my linux-box:

Gentoo Linux, 2.6.16 kernel with Reiser4-for-2.6.16-2.patch.gz
i686 AMD Athlon(tm) XP 2400+
DC4300 SATA-II controller (Silicon Image 3124, libata + sata_sil24 drivers)
2 x Samsung SP2504C hard disk

Thanx in advance,

Arend