how to repair a damaged filesystem with btrfs raid5

[Alexander Fieroch <alexander.fieroch@mpi-dortmund.mpg.de>]

[-- Attachment #1.1: Type: text/plain, Size: 4765 bytes --]

Hello,

I'm testing btrfs RAID5 on three encrypted hdds (dm-crypt) and I'm 
simulating a harddisk failure by unplugging one device while writing 
some files.
Now the filesystem is damaged. By now is there any chance to repair the 
filesystem?

My operating system is ubuntu server (vivid) with kernel 3.18 and btrfs 
3.18.1 (external PPA).
I've unplugged device sdb with UUID 65f62f63-6526-4d5e-82d4-adf6d7508092 
and crypt device name /dev/mapper/crypt-1. This one should be repaired.
Attached is the dmesg log file with corresponding errors.

btrfs check do not seem to work.

# btrfs check --repair /dev/mapper/crypt-1 enabling repair mode
Checking filesystem on /dev/mapper/crypt-1
UUID: 504c2850-3977-4340-8849-18dd3ac2e5e4
checking extents
Check tree block failed, want=165396480, have=5385177728513973313
Check tree block failed, want=165396480, have=5385177728513973313
Check tree block failed, want=165396480, have=65536
Check tree block failed, want=165396480, have=5385177728513973313
Check tree block failed, want=165396480, have=5385177728513973313
read block failed check_tree_block
Check tree block failed, want=165740544, have=6895225932619678086
Check tree block failed, want=165740544, have=6895225932619678086
Check tree block failed, want=165740544, have=65536
Check tree block failed, want=165740544, have=6895225932619678086
Check tree block failed, want=165740544, have=6895225932619678086
read block failed check_tree_block
Check tree block failed, want=165756928, have=13399486021073017810
Check tree block failed, want=165756928, have=13399486021073017810
Check tree block failed, want=165756928, have=65536
Check tree block failed, want=165756928, have=13399486021073017810
Check tree block failed, want=165756928, have=13399486021073017810
read block failed check_tree_block
Check tree block failed, want=165773312, have=12571697019259051064
Check tree block failed, want=165773312, have=12571697019259051064
Check tree block failed, want=165773312, have=65536
Check tree block failed, want=165773312, have=12571697019259051064
Check tree block failed, want=165773312, have=12571697019259051064
read block failed check_tree_block
Check tree block failed, want=165789696, have=4069002570438424782
Check tree block failed, want=165789696, have=4069002570438424782
Check tree block failed, want=165789696, have=65536
Check tree block failed, want=165789696, have=4069002570438424782
Check tree block failed, want=165789696, have=4069002570438424782
read block failed check_tree_block
Check tree block failed, want=165838848, have=9612508092910615774
Check tree block failed, want=165838848, have=9612508092910615774
Check tree block failed, want=165838848, have=65536
Check tree block failed, want=165838848, have=9612508092910615774
Check tree block failed, want=165838848, have=9612508092910615774
read block failed check_tree_block
ref mismatch on [99516416 16384] extent item 1, found 0
failed to repair damaged filesystem, aborting



Trying a btrfs scrub is finishing with uncorrectable errors:
# btrfs scrub start -d /dev/mapper/crypt-1 scrub started on 
/dev/mapper/crypt-1, fsid 504c2850-3977-4340-8849-18dd3ac2e5e4 (pid=2014)
# btrfs scrub status -d /mnt/data/
scrub status for 504c2850-3977-4340-8849-18dd3ac2e5e4
scrub device /dev/mapper/crypt-1 (id 1) history
         scrub started at Mon Jan 26 14:36:57 2015 and finished after 
617 seconds
         total bytes scrubbed: 29.78GiB with 10906 errors
         error details: csum=10906
         corrected errors: 0, uncorrectable errors: 10906, unverified 
errors: 0
scrub device /dev/mapper/crypt-2 (id 2)         no stats available
scrub device /dev/mapper/crypt-3 (id 3)         no stats available


Any chance to fix the errors or do I have to wait for the next btrfs 
version?
Thank you very much,
Alexander


# uname -a
Linux antares 3.18.0-9-generic #10-Ubuntu SMP Mon Jan 12 21:41:54 UTC 
2015 x86_64 x86_64 x86_64 GNU/Linux

# btrfs --version
Btrfs v3.18.1

# btrfs fi show
Label: 'antares-data'  uuid: 504c2850-3977-4340-8849-18dd3ac2e5e4
           Total devices 3 FS bytes used 89.35GiB
           devid    1 size 698.63GiB used 47.03GiB path /dev/mapper/crypt-1
           devid    2 size 698.63GiB used 47.01GiB path /dev/mapper/crypt-2
           devid    3 size 698.63GiB used 47.01GiB path /dev/mapper/crypt-3

# btrfs fi df /mnt/data/
Data, single: total=8.00MiB, used=0.00B
Data, RAID5: total=92.00GiB, used=89.25GiB
System, single: total=4.00MiB, used=0.00B
System, RAID5: total=16.00MiB, used=16.00KiB
Metadata, single: total=8.00MiB, used=0.00B
Metadata, RAID5: total=2.00GiB, used=100.44MiB
GlobalReserve, single: total=48.00MiB, used=0.00B





[-- Attachment #1.2: dmesg.log.gz --]
[-- Type: application/gzip, Size: 20290 bytes --]

[-- Attachment #2: S/MIME Cryptographic Signature --]
[-- Type: application/pkcs7-signature, Size: 4860 bytes --]