On 09/15/2012 10:17 PM, Antoine Sirinelli wrote:

Hi,

I have experienced a very reproducible Oops within the btrfs driver. On
a linux 3.5.4, if I mount a volume with the option "degraded" because
one of the device is missing, I would get an Oops when I unmount it (or
even before). You can see attached the kernel log.

Thanks for the report.  And this has been fixed by

commit 99f5944b8477914406173b47b4f261356286730b
    Btrfs: do not strdup non existent strings

You can find this commit in 3.6.0-rc5. :)

thanks,
liubo

Here is how I create my btrfs volume:

# mkfs.btrfs /dev/vdb /dev/vdc
# mount /dev/vdb /mnt
# dd if=/dev/zero of=/mnt/zeros count=1M
# umount /mnt
# shutdown -h now

I am then wiping one volume (/dev/vdc) and restarting the system. To
get a crash, here is what I am doing:

# mount -o degraded /dev/vdb /mnt
# umount /mnt

I recognise the volume is not usable after having erased one drive but I
would expect no to crash the kernel in such circumstances. I am not an
expert, I am just reporting a crash from an user point of view.

Antoine