Re: Recover btrfs volume which can only be mounded in read-only mode

[Dmitry Katsubo <dmitry.katsubo@gmail.com>]

On 14/10/2015 16:40, Anand Jain wrote:
>> # mount -o degraded /var
>> Oct 11 18:20:15 kernel: BTRFS: too many missing devices, writeable
>> mount is not allowed
>>
>> # mount -o degraded,ro /var
>> # btrfs device add /dev/sdd1 /var
>> ERROR: error adding the device '/dev/sdd1' - Read-only file system
>>
>> Now I am stuck: I cannot add device to the volume to satisfy raid
>> pre-requisite.
> 
>  This is a known issue. Would you be able to test below set of patches
>  and update us..
> 
>    [PATCH 0/5] Btrfs: Per-chunk degradable check

Many thanks for the reply. Unfortunately I have no environment to
recompile the kernel, and setting it up will perhaps take a day. Can the
latest kernel be pushed to Debian sid?

1. Is there any way to recover btrfs at the moment? Or the easiest I can
do is to mount ro, copy all data to another drive, re-create btrfs
volume and copy back?

2. How to avoid such a trap in the future?

3. How can I know what version of kernel the patch "Per-chunk degradable
check" is targeting?

4. What is the best way to express/vote for new features or suggestions
(wikipage "Project_ideas" / bugzilla)?

Thanks!

-- 
With best regards,
Dmitry