Re: "bad tree block start" when trying to mount on ARM

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

[-- Attachment #1.1: Type: text/plain, Size: 3244 bytes --]



On 2019/6/28 下午4:00, Erik Jensen wrote:
>> So it's either the block layer reading some wrong from the disk or btrfs
>> layer doesn't do correct endian convert.
> 
> My ARM board is running in little endian mode, so it doesn't seem like
> endianness should be an issue. (It is 32-bits versus my desktop's 64,
> though.) I've also tried exporting the drives via NBD to my x86_64
> system, and that worked fine, so if the problem is under btrfs, it
> would have to be in the encryption layer, but fsck succeeding on the
> ARM board would seem to rule that out, as well.
> 
>> Would you dump the following data (X86 and ARM should output the same
>> content, thus one output is enough).
>> # btrfs ins dump-tree -b 17628726968320 /dev/dm-3
>> # btrfs ins dump-tree -b 17628727001088 /dev/dm-3
> 
> Attached, and also 17628705964032, since that's the block mentioned in
> my most recent mount attempt (see below).

The trees are completely fine.

So it should be something else causing the problem.

> 
>> And then, for the ARM system, please apply the following diff, and try
>> mount again.
>> The diff adds extra debug info, to exam the vital members of a tree block.
>>
>> Correct fs should output something like:
>>   BTRFS error (device dm-4): bad tree block start, want 30408704 have 0
>>   tree block gen=4 owner=5 nritems=2 level=0
>>   csum:
>> a304e483-0000-0000-0000-00000000000000000000-0000-0000-0000-000000000000
>>
>> The csum one is the most important one, if there aren't so many zeros,
>> it means at that timing, btrfs just got a bunch of garbage, thus we
>> could do further debug.
> 
> [  131.725573] BTRFS info (device dm-1): disk space caching is enabled
> [  131.731884] BTRFS info (device dm-1): has skinny extents
> [  133.046145] BTRFS error (device dm-1): bad tree block start, want
> 17628705964032 have 2807793151171243621
> [  133.055775] tree block gen=7888986126946982446
> owner=11331573954727661546 nritems=4191910623 level=112
> [  133.065661] csum:
> 416a456c-1e68-dbc3-185d-aaad410beaef5493ab3f-3cb9-4ba1-2214-b41cba9656fc

Completely garbage here, so I'd say the data we got isn't what we want.

> [  133.108383] BTRFS error (device dm-1): bad tree block start, want
> 17628705964032 have 2807793151171243621
> [  133.117999] tree block gen=7888986126946982446
> owner=11331573954727661546 nritems=4191910623 level=112
> [  133.127756] csum:
> 416a456c-1e68-dbc3-185d-aaad410beaef5493ab3f-3cb9-4ba1-2214-b41cba9656fc

But strangely, the 2nd try still gives us the same result, if it's
really some garbage, we should get some different result.

> [  133.136241] BTRFS error (device dm-1): failed to verify dev extents
> against chunks: -5

You can try to skip the dev extents verification by commenting out the
btrfs_verify_dev_extents() call in disk-io.c::open_ctree().

It may fail at another location though.

The more strange part is, we have the device tree root node read out
without problem.

Thanks,
Qu

> [  133.166165] BTRFS error (device dm-1): open_ctree failed
> 
> I copied some files over last time I had it mounted on my desktop,
> which may be why it's now failing at a different block.
> 
> Thanks!
> 


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]