Re: BTRFS error (device sda4): failed to read chunk tree: -5

[Zirconium Hacker <jared.e.vb@gmail.com>]

I hope "Reply All" is the right option here.  Again, first time
interacting with a mailing list.  Google said that was what to do.

I have found no I/O errors in dmesg -- at least, none mentioning
'I/O', 'IO', or anything triggered by mount besides BTRFS's
complaints.

$ sudo btrfs rescue chunk -v /dev/sda4
(See https://pastebin.com/YaRHuKeT -- the output hasn't visibly
changed since I tried this around a week ago, but this output is
recent)
$ man btrfs | grep show-super -A1
       btrfs-show-super
           moved to btrfs inspect-internal dump-super
$ sudo btrfs inspect-internal dump-super -fa /dev/sda4
(See https://pastebin.com/DbABqXGQ)
$ sudo btrfs-find-root -o 5 /dev/sda4
(See https://zerobin.net/?496ed00aed01ab0c#Kvp+FqrF6mfqQLZvUYJ1ODWYIzGayJbdyuMXc9RTauA=
   -- Pastebin wouldn't let me paste that much)

I hope the way I'm organizing the output is OK.

On Thu, Aug 17, 2017 at 6:42 PM, Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>
>
> On 2017年08月18日 00:53, Chris Murphy wrote:
>>
>> Readding Btrfslist, and adding Qu:
>>
>>
>> On Thu, Aug 17, 2017 at 12:48 AM, Zirconium Hacker <jared.e.vb@gmail.com>
>> wrote:
>>>
>>> Oh, sorry, I guess the output of the command I ran wasn't clear -- it
>>> was collecting the output of running the debug command on all 1,084
>>> and showing that it was the same.  Here's specifically what you asked
>>> for:
>>>
>>> $ sudo btrfs-debug-tree -b 61809344512 /dev/sda4
>>> btrfs-progs v4.12
>>> bytenr mismatch, want=61809344512, have=0
>>> Couldn't read tree root
>>> ERROR: unable to open /dev/sda4
>>> $ sudo btrfs-debug-tree -b 1085440000 /dev/sda4
>>> btrfs-progs v4.12
>>> bytenr mismatch, want=61809344512, have=0
>
>
> This means either chunk root is corrupted, or system chunk array in
> superblock is corrupted.
> Bytenr mismatch is normally impossible for normal operation.
>
> BTW are you using discard mount option? Sometimes it can cause problem.
>
> And please also paste the following output:
>
> # btrfs-show-super -fa /dev/sda4
> # btrfs-find-root -o 5 /dev/sda4
>
> The first is to output the full backup roots and current chunk root for us
> to debug.
> The second one will try to iterate your whole disk to find a valid but old
> chunk root.
> If we could find one (even a little old), it may make it possible to mount
> the fs.
>
> Thanks,
> Qu
>
>>> Couldn't read tree root
>>> ERROR: unable to open /dev/sda4
>>>
>>> I'm using GMail, and it's confusing me by trimming off quotes and
>>> stuff, so sorry if I miss something.
>>>
>>
>> OK well now we're in the bad part of Btrfs repair where the error
>> messages don't help. > It's one thing for it to complain about
>> 1085440000 being invalid, because by now it might have been
>> overwritten, but to say it wants some other root that we already know
>> it can't read, and then fail reading that root is not helpful
>> information.
>> Maybe Qu has an idea. But it does sound like something really
>> catastrophic happened to blow away all of the backup root trees.
>>
>> Going back to your first email, -o ro,usebackuproot failed with a
>> chunk tree error. I wonder if 'rescue chunk' might help.
>>
>> Try 'btrfs rescue chunk -v' and see what you get.
>>
>>
>