Re: interest in post-mortem examination of a BTRFS system and improving the btrfs-code?

["Nik." <btrfs@avgustinov.eu>]

2019-04-05 02:47, Qu Wenruo:
> 
> 
> On 2019/4/4 下午11:27, Nik. wrote:
>>
>>
>> 2019-04-03 03:04, Qu Wenruo:
>>>
>>
>> [snip]
>> ...
>>
>>>>> In your case, you just need latest btrfs-progs and re-run "btrfs check
>>>>> --readonly" on it.
>>>>
>>>> Will try this, but have no time before tomorrow evening.
>>>>
>>>>
>>>>> If it just shows the same result, meaning I can't get the info about
>>>>> which tree block is corrupted, then you could try to mount it with
>>>>> -o ro
>>>>> using *LATEST* kernel.
>>>>
>>>> I tried this before with the 4.15.0-46 kernel, it was impossible. Will
>>>> try again with newer one as soon as possible (in best case tomorrow
>>>> evening); I will post the results.
>>
>> Sorry for the delay, compiling the btrfs-progs took much more time than
>> expected (had to install new packages again and again). Finally had to
>> give up the conversion ("make" could not find reiserfs/misc.h, although
>> both libreiserfscore and reiser4fs are installed).
>> Output of the commands:
>> # uname -r
>> 5.0.6-050006-generic
>> #btrfs --version
>> btrfs-progs v4.20.2
>> # btrfs check --readonly /dev/md0
>> Opening filesystem to check...
>> incorrect offsets 15003 146075
>> ERROR: cannot open file system
>>
>> It seems that I will wait until 5.2 is out...
>> (the answer to Jeff Mahoney is coming with separate e-mail!)
> 
> OK, then you can try mount it with 5.0 with -o ro.

# mount -t btrfs -o ro /dev/md0 /mnt/md0/
mount: /mnt/md0: wrong fs type, bad option, bad superblock on /dev/md0, 
missing codepage or helper program, or other error.

> The objective is not to make it work, but to get the dmesg, which should

# dmesg|tail
[65283.442278] audit: type=1107 audit(1554438151.396:115): pid=1 uid=0 
auid=4294967295 ses=4294967295 subj=kernel msg='Unknown class service 
exe="/lib/systemd/systemd" sauid=0 hostname=? addr=? terminal=?'
[72504.975359] audit: type=1107 audit(1554445372.928:116): pid=1 uid=0 
auid=4294967295 ses=4294967295 subj=kernel msg='Unknown class service 
exe="/lib/systemd/systemd" sauid=0 hostname=? addr=? terminal=?'
[72535.214394] audit: type=1107 audit(1554445403.166:117): pid=1 uid=0 
auid=4294967295 ses=4294967295 subj=kernel msg='Unknown class service 
exe="/lib/systemd/systemd" sauid=0 hostname=? addr=? terminal=?'
[72535.257571] audit: type=1107 audit(1554445403.210:118): pid=1 uid=0 
auid=4294967295 ses=4294967295 subj=kernel msg='Unknown class system 
exe="/lib/systemd/systemd" sauid=0 hostname=? addr=? terminal=?'
[73427.486853] BTRFS info (device md0): disk space caching is enabled
[73427.938260] BTRFS info (device md0): bdev /dev/md0 errs: wr 0, rd 0, 
flush 0, corrupt 2181, gen 0
[73429.172707] BTRFS critical (device md0): corrupt leaf: root=2 
block=1894009225216 slot=30, unexpected item end, have 146075 expect 15003
[73429.176628] BTRFS critical (device md0): corrupt leaf: root=2 
block=1894009225216 slot=30, unexpected item end, have 146075 expect 15003
[73429.177153] BTRFS error (device md0): failed to read block groups: -5
[73429.197019] BTRFS error (device md0): open_ctree failed


> contain the tree block bytenr, so that we can try to fix that offending
> tree block manually.
> 
> Thanks,
> Qu

Should I try something alse?
Thank you!
Nik.
--
> 
>>
>>>>> Latest kernel will report anything wrong pretty vocally, in that case,
>>>>> dmesg would include the bytenr of corrupted tree block.
>>>>>
>>>>> Then I could craft needed commands to further debug the fs.
>>>>
>>>> Ok, I will try to post more info tomorrow about this time.
>>>>
>>>> Nik.
>>>> -- 
>>>>
>>>>> Thanks,
>>>>> Qu
>>>>>
>>>>>>
>>>>>> Thank you for trying to improve btrfs!
>>>>>>
>>>>>> Nik.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Qu
>>>>>>
>>>>>> You are not from the 007 - lab, are you? ;-)
>>>>>>
>>>>>>>>
>>>>>>>> Kind regards,
>>>>>>>>
>>>>>>>> Nik.
>>>>>>>
>>>>>
>>>
>