Re: Problems with btrfs

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

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On 2018年04月28日 22:06, David C. Partridge wrote:
> Here's the log you asked for ...
> 
> David

To dump the offending tree block, you could use the following command:

# dd if=/dev/mapper/Charon--vg-root of=copy1.dump bs=1 count=16k
skip=22919544832

# dd if=/dev/mapper/Charon--vg-root of=copy2.dump bs=1 count=16k
skip=23456415744

And attach copy1.img and copy2.img.

Thanks,
Qu

> 
> -----Original Message-----
> From: Qu Wenruo [mailto:quwenruo.btrfs@gmx.com] 
> Sent: 28 April 2018 14:54
> To: David C. Partridge
> Subject: Re: Problems with btrfs
> 
> 
> 
> On 2018年04月28日 21:38, David C. Partridge wrote:
>> Oh! doing a private build from source a bit beyond my skill level :(  Are there alternatives like climbing in with a disk editor or is there too much to change?
> 
> It's possible to only modify that offending tree block.
> But I can't ensure the safety, thus I recommend to use btrfs-corrupt-block.
> Since it's not convenient for you, then let's go that way.
> 
> Please provide the following dump:
> 
> # btrfs inspect dump-tree -t chunk <device>
> 
> Then I could calculate the offset on-disk for you to do a binary dump and send that tree block back to me to hand patch it.
> 
>>
>> I'm prepared to install a newer version of btrfs-progs if that will fix the problem (assuming I can find a suitable package file).
>>
>> I'm assuming that I'll likely also need to update the kernel?
> 
> Not exactly.
> If latest btrfs check gives no error after fix, even old kernel should handle it well without problem.
> 
> But as a generic advice, it's recommended to use latest kernel for btrfs if possible.
> 
> And currently there is nothing sensitive in the thread (btrfs-inspect.log could contain some filenames, but nothing sensitive right now), so it's better to CC the mail to mail list, just in case some other guy could provide extra help.
> 
> (Next mail may be after 8~10 hours, as it's bed time for my timezone)
> 
> Thanks,
> Qu
> 
>>
>> David
>>
>> -----Original Message-----
>> From: Qu Wenruo [mailto:quwenruo.btrfs@gmx.com]
>> Sent: 28 April 2018 14:25
>> To: David C. Partridge
>> Subject: Re: Problems with btrfs
>>
>>
>>
>> On 2018年04月28日 21:14, David C. Partridge wrote:
>>> Here's the output from
>>>
>>> # btrfs inspect dump-tree /dev/mapper/Charon--vg-root | grep -C 20
>>> 224304857088
>>
>> Located the problem:
>>
>> 	item 382 key (224304857088 EXTENT_ITEM 16384) itemoff 14495 itemsize 51
>> 		extent refs 1 gen 735989 flags TREE_BLOCK
>> 		tree block key (4401028 UNKNOWN.0 0) level 0
>>                                 ^^^^^^^^^^^^^^^^^^^
>> 		shared block backref parent 140827475968
>>
>> It could be fixed by special crafted btrfs-corrupt-block tool to handle it.
>> Although this means you need to compile btrfs-progs by yourself with special branch.
>>
>> Before patching btrfs-progs, I'd like to double check if other part is correct.
>>
>> Please execute the following command:
>> # btrfs inspect dump-tree -b 140827475968 /dev/mapper/Charon--vg-root
>>
>> If the output is correct, I could start patching btrfs-corrupt-block then.
>> But please be aware of that, this could only fix the problem found in extent tree, I'm not 100% sure if there will be other problems, as the btrfs-progs is pretty old.
>>
>> Thanks,
>> Qu
>>
>>>
>>> HtH
>>> David
>>>
>>
> 


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