Re: Trying to recover data from SSD

From: Konstantin Svist <fry.kun@gmail.com>
To: Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc: Btrfs BTRFS <linux-btrfs@vger.kernel.org>,
	Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Subject: Re: Trying to recover data from SSD
Date: Tue, 10 Aug 2021 22:22:05 -0700	[thread overview]
Message-ID: <544e3e73-5490-2cae-c889-88d80e583ac4@gmail.com> (raw)
In-Reply-To: <c7fed97e-d034-3af1-2072-65a9bb0e49ef@gmx.com>

On 8/10/21 16:54, Qu Wenruo wrote:
>
>
> On 2021/8/11 上午7:21, Konstantin Svist wrote:
>> On 8/10/21 15:24, Qu Wenruo wrote:
>>>
>>> On 2021/8/11 上午12:12, Konstantin Svist wrote:
>>>>
>>>>>> I don't know how to do that (corrupt the extent tree)
>>>>>
>>>>> There is the more detailed version:
>>>>> https://lore.kernel.org/linux-btrfs/744795fa-e45a-110a-103e-13caf597299a@gmx.com/
>>>>>
>>>>>
>>>>
>>>>
>>>> So, here's what I get:
>>>>
>>>>
>>>> # btrfs ins dump-tree -t root /dev/sdb3 |grep -A5 'item 0 key
>>>> (EXTENT_TREE'
>>>>
>>>>       item 0 key (EXTENT_TREE ROOT_ITEM 0) itemoff 15844 itemsize 439
>>>>           generation 166932 root_dirid 0 bytenr 786939904 level 2
>>>> refs 1
>>>>           lastsnap 0 byte_limit 0 bytes_used 50708480 flags 0x0(none)
>>>>           uuid 00000000-0000-0000-0000-000000000000
>>>>           drop key (0 UNKNOWN.0 0) level 0
>>>>       item 1 key (DEV_TREE ROOT_ITEM 0) itemoff 15405 itemsize 439
>>>>
>>>>
>>>> # btrfs-map-logical -l 786939904 /dev/sdb3
>>>>
>>>> checksum verify failed on 952483840 wanted 0x00000000 found 0xb6bde3e4
>>>> checksum verify failed on 952483840 wanted 0x00000000 found 0xb6bde3e4
>>>> checksum verify failed on 952483840 wanted 0x00000000 found 0xb6bde3e4
>>>> bad tree block 952483840, bytenr mismatch, want=952483840, have=0
>>>> ERROR: failed to read block groups: Input/output error
>>>> Open ctree failed
>>>>
>>>>
>>>>
>>>> Sooooo.. now what..?
>>>>
>>> With v5.11 or newer kernel, mount it with "-o rescue=all,ro".
>>
>>
>> Sorry, I guess that wasn't clear: that error above is what I get while
>> trying to corrupt the extent tree as per your guide.
>
> Oh, that btrfs-map-logical is requiring unnecessary trees to continue.
>
> Can you re-compile btrfs-progs with the attached patch?
> Then the re-compiled btrfs-map-logical should work without problem.

Awesome, that worked to map the sector & mount the partition.. but I
still can't access subvol_root, where the recent data is:

[root@fry ~]# mount -oro,rescue=all /dev/sdb3 /mnt/
[root@fry ~]# ll /mnt/
ls: cannot access '/mnt/subvol_root': Input/output error
total 0
d?????????? ? ?    ?     ?            ? subvol_root
drwxr-xr-x. 1 root root 12 Mar 18 20:55 subvol_snapshots

dmesg:

[532051.071515] BTRFS info (device sdb3): enabling all of the rescue options
[532051.071521] BTRFS info (device sdb3): ignoring data csums
[532051.071523] BTRFS info (device sdb3): ignoring bad roots
[532051.071524] BTRFS info (device sdb3): disabling log replay at mount time
[532051.071526] BTRFS info (device sdb3): disk space caching is enabled
[532051.071528] BTRFS info (device sdb3): has skinny extents
[532051.077018] BTRFS warning (device sdb3): sdb3 checksum verify failed
on 786939904 wanted 0xcdcdcdcd found 0xc375d6b6 level 2
[532051.077710] BTRFS warning (device sdb3): sdb3 checksum verify failed
on 786939904 wanted 0xcdcdcdcd found 0xc375d6b6 level 2
[532052.705324] BTRFS error (device sdb3): bad tree block start, want
920748032 have 0
[532052.705934] BTRFS error (device sdb3): bad tree block start, want
920748032 have 0