Re: Filesystem won't mount (open_ctree failed) or repair (BUG_ON)

[Koen Kooi <koen@dominion.thruhere.net>]

Op 09-06-17 om 21:57 schreef Hugo Mills:
> On Fri, Jun 09, 2017 at 09:12:16PM +0200, Koen Kooi wrote:
>> Hi,
>>
>> Today the kernel got wedged during shutdown (4.11.x tends to do that, haven't
>> debugged) and I pressed the reset button. The next boot btrfs won't mount:
>>
>> [Fri Jun  9 20:46:07 2017] BTRFS error (device md0): parent transid verify failed on 5840011722752 wanted 170755 found 170832
>> [Fri Jun  9 20:46:07 2017] BTRFS error (device md0): parent transid verify failed on 5840011722752 wanted 170755 found 170832
>> [Fri Jun  9 20:46:07 2017] BTRFS error (device md0): failed to read block groups: -5
>> [Fri Jun  9 20:46:08 2017] BTRFS error (device md0): open_ctree failed
> 
>    With a transid failure on mount, about the only thing that's likely
> to work is mounting with -o usebackuproot. If that doesn't work, then
> a rebuild of the FS is almost certainly needed.

Hrm, that is also a no-go:

# mount /dev/md0 /media/data/  -o usebackuproot

[  740.294141] BTRFS info (device md0): trying to use backup root at mount time
[  740.294145] BTRFS info (device md0): using free space tree
[  740.294146] BTRFS info (device md0): has skinny extents
[  754.248228] BTRFS error (device md0): parent transid verify failed on 5840011722752 wanted 170755 found 170832
[  754.449435] BTRFS error (device md0): parent transid verify failed on 5840011722752 wanted 170755 found 170832
[  754.449527] BTRFS error (device md0): failed to read block groups: -5
[  754.609960] BTRFS error (device md0): open_ctree failed

So, any more suggestions of things to try?

regards,

Koen

> 
>    Hugo.
> 
>> I tried repair, but that didn't work either:
>>
>> # btrfsck --repair /dev/md0
>> enabling repair mode
>> couldn't open RDWR because of unsupported option features (3).
>> ERROR: cannot open file system
>> enabling repair mode
>>
>> Googling around it was suggested clearing the v2 space cache:
>>
>> # btrfsck --mode=lowmem --clear-space-cache v2 /dev/md0
>> parent transid verify failed on 5840011722752 wanted 170755 found 170832
>> parent transid verify failed on 5840011722752 wanted 170755 found 170832
>> parent transid verify failed on 5840011722752 wanted 170755 found 170832
>> parent transid verify failed on 5840011722752 wanted 170755 found 170832
>> Ignoring transid failure
>> leaf parent key incorrect 5840011722752
>> parent transid verify failed on 5367057465344 wanted 170755 found 170828
>> parent transid verify failed on 5367057465344 wanted 170755 found 170828
>> parent transid verify failed on 5367057465344 wanted 170755 found 170828
>> parent transid verify failed on 5367057465344 wanted 170755 found 170828
>> Ignoring transid failure
>> leaf parent key incorrect 72105984
>> btrfs unable to find ref byte nr 4628577484800 parent 0 root 10  owner 0 offset 1
>> parent transid verify failed on 5366993256448 wanted 170755 found 170827
>> parent transid verify failed on 5366993256448 wanted 170755 found 170827
>> parent transid verify failed on 5366993256448 wanted 170755 found 170827
>> parent transid verify failed on 5366993256448 wanted 170755 found 170827
>> Ignoring transid failure
>> leaf parent key incorrect 41287680
>> ERROR: failed to clear free space cache v2: -1
>> transaction.h:41: btrfs_start_transaction: BUG_ON `root->commit_root` triggered, value 22938400
>> btrfs check[0x411674]
>> btrfs check(close_ctree_fs_info+0x125)[0x41368c]
>> btrfs check(cmd_check+0x36d8)[0x45e8e8]
>> btrfs check(main+0x15d)[0x40ac5c]
>> /lib/libc.so.6(__libc_start_main+0xf0)[0x7f9b4cb060d0]
>> btrfs check[0x40a729]
>> Clear free space cache v2
>>
>> The underlying md0 (raid6) doesn't report any errors, trying different kernels makes no difference, 4.10.17, 4.11.4 and 4.12.0-rc4 all give the same errors. Everything above was
>> done with btrfs-progs 4.11.
>>
>> Any hints on how I can fix the errors in the filesystem? I don't mind loosing todays changes, but I would like to keep all the older data :)
>>
>> regards,
>>
>> Koen
>>
>