Re: Restoring a file from damaged btrfs raid1 shard

[Konstantin Svist <fry.kun@gmail.com>]

On 4/24/21 12:46, Chris Murphy wrote:
> On Wed, Apr 21, 2021 at 9:24 PM Konstantin Svist <fry.kun@gmail.com> wrote:
>
>> Superblock thinks the generation is 5857883
>> Superblock thinks the level is 1
>> Found tree root at 4883439714304 gen 5857883 level 1
>> Well block 4883437158400(gen: 5857882 level: 1) seems good, but
>> generation/level doesn't match, want gen: 5857883 level: 1
>> Well block 4883434635264(gen: 5857881 level: 1) seems good, but
>> generation/level doesn't match, want gen: 5857883 level: 1
>> Well block 4883426295808(gen: 5857880 level: 1) seems good, but
>> generation/level doesn't match, want gen: 5857883 level: 1
>> Well block 4883417972736(gen: 5857879 level: 1) seems good, but
>> generation/level doesn't match, want gen: 5857883 level: 1
>> Well block 4883409846272(gen: 5857878 level: 1) seems good, but
>> generation/level doesn't match, want gen: 5857883 level: 1
>> Well block 4883352633344(gen: 5857877 level: 1) seems good, but
>> generation/level doesn't match, want gen: 5857883 level: 1
>> ...
> You can try plugging these larger block values in, starting at the top
> (most recent) into 'btrfs restore -iv -D -t $BLOCKNUM' and see if
> it'll work.

# btrfs restore -iv -D -t 4883437158400 /dev/sdb3 -l
warning, device 3 is missing
warning, device 3 is missing
parent transid verify failed on 4883437158400 wanted 5857883 found 5857882
parent transid verify failed on 4883437158400 wanted 5857883 found 5857882
Ignoring transid failure
bad tree block 5246265278464, bytenr mismatch, want=5246265278464, have=0
Could not open root, trying backup super
warning, device 3 is missing
warning, device 3 is missing
parent transid verify failed on 4883437158400 wanted 5857883 found 5857882
parent transid verify failed on 4883437158400 wanted 5857883 found 5857882
Ignoring transid failure
bad tree block 5246265278464, bytenr mismatch, want=5246265278464, have=0
Could not open root, trying backup super
warning, device 3 is missing
warning, device 3 is missing
parent transid verify failed on 4883437158400 wanted 5857883 found 5857882
parent transid verify failed on 4883437158400 wanted 5857883 found 5857882
Ignoring transid failure
bad tree block 5246265278464, bytenr mismatch, want=5246265278464, have=0
Could not open root, trying backup super

From my very limited understanding, the older generation info should be
on the disk, even if the newer one is mangled somehow.

But also looks like this is not happening..?