Niklas Schnelle wrote:

On Tue, 2011-08-16 at 11:25 +0800, Li Zefan wrote:

quoted

krzf83@gmail.com wrote:

quoted

# uname -a
Linux dhcppc1 3.0.1-xxxx-std-ipv6-64 #1 SMP Sun Aug 14 17:06:21 CEST
2011 x86_64 x86_64 x86_64 GNU/Linux

mkdir test5
cd test5
dd if=/dev/null of=img5 bs=1 seek=2G
dd if=/dev/null of=img6 bs=1 seek=2G
losetup /dev/loop2 img5
losetup /dev/loop3 img6
mkfs.btrfs -d raid1 -m raid1 /dev/loop2 /dev/loop3
btrfs device scan
btrfs filesystem show

Label: none  uuid: d7ba6c4e-04ed-49f5-88cd-8432c948e822
        Total devices 2 FS bytes used 28.00KB
        devid    1 size 2.00GB used 437.50MB path /dev/loop4
        devid    2 size 2.00GB used 417.50MB path /dev/loop5

mkdir dir
mount -t btrfs /dev/loop2 dir
umount dir
losetup -d /dev/loop3
mount -t btrfs -o degraded /dev/loop2 dir

mount: wrong fs type, bad option, bad superblock on /dev/loop2,
       missing codepage or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

It works on latest kernel (3.1.0-rc2)

--
Li Zefan

Shouldn't we really really have some test case for this in the test
suite? I mean it's kinda uaccepabtle even for an experimental system to
brake this way in a release, also will there be backports? 
That would be helpful especially since some of the big distros will be
stuck with 3.0 for months to come and this will (rightfully so) make
btrfs look really bad!

The situation is being improved. We're adding btrfs-specific test cases
to xfstests. I'll consider adding new ones for degraded feature.

We rarely have btrfs patches backported. I think Chris has not enough
time to do this time-consuming work, and it's not considered very
important in the current status (under heavy development and not quite
production-ready).

But if you want a specific bug to be fixed in older kernels, I think
you can find out the git commit that fixes it and send it to -stable
mailing list? See Documentation/stable_kernel_rules.txt

--
Li Zefan